Science

Agricultural products

Alfalfa Weevil Advisor

The Oklahoma Alfalfa Weevil Advisor is based on three factors:

The growth stage of the alfalfa weevil (modeled via degree days),
The growth stage of the alfalfa plant (obtained through scouting), and
The population levels of weevil larvae (also obtained through scouting).

Insect development can be predicted based on degree-day heat units. Each insect species has lower and upper temperature thresholds. These are the minimum and maximum temperatures required for growth and development. For the alfalfa weevil, the minimum temperature is 48°F. Degree-day heat units are calculated for each day and the daily units added together to give degree-day heat unit accumulation from a “Planting Date.” This is done by taking the average temperature for a single day and subtracting the 48°F minimum temperature. For example, if your average day’s temperature is 58°F, then 58°F - 48°F = 10 degree-day heat units for that day.

The Alfalfa Weevil Advisor logs the degree-day heat units accumulated since January 1 above a 48°F base.

Scouting is recommended for alfalfa fields once 150 degree-day heat units have accumulated. To assess alfalfa weevil activity, collect a 30-stem sample, from 30 evenly-spaced spots across the dry interior portions of the field. Place the collected stems in a 2-3 gallon container and beat vigorously against the inside of the container for 10-20 seconds. Count and record the number of larvae that fall out.

To determine alfalfa height, select 10 stems and record their average length to the nearest inch.

Consult the Spraying Recommendation Table to determine whether spraying is necessary, or when the fields should be scouted again.

Note that the advisor calculates two sets of variables that relate to the temperature thresholds associated with mortality of alfalfa weevil eggs (10°F) and larvae (20°F). Beginning in December, the advisor shows the number of hours since December 1 that temperatures were at or below 10°F, the last date on which such temperatures occurred, and the number of hours of such temperatures occurring on that date. Beginning in February, the advisor also shows the number of hours since February 1 that temperatures were at or below 20°F, the last date on which such temperatures occurred, and the number of hours of such temperatures occurring on that date.

For additional information on controlling alfalfa weevil refer to:
- Alfalfa Weevil and Its Management in Oklahoma, OSU Extension Fact Sheet PSS-2097
- Scouting for the Alfalfa Weevil in Oklahoma, OSU Extension publication CR-7177

Cattle Stress Advisor

Oklahoma’s weather extremes can have a direct and dramatic impact on grazing livestock. When weather conditions are ideal and livestock are “comfortable”, their performance and nutritional requirements are not affected. However, extreme weather conditions can dramatically alter feed intake, reduce daily weight gain, and increase nutritional requirements.

The Oklahoma Mesonet Cattle Stress Advisor is a tool to assist cattle producers in identifying stress periods, caused by extreme weather conditions. This index provides an indication of the level of stress outdoor cattle may experience from either heat or cold temperatures. This measure of cattle stress allows producers to know when to take appropriate action to reduce cattle stress. Both cold and heat stress indexes are run on a continuous basis.

HEAT STRESS
When ambient temperature and thermal radiation exceed the temperature of the animal’s skin surface, the animal’s body gains heat. Cattle shed heat primarily through evaporation from the skin and through respiration (breathing). As relative humidity increases, the effectiveness of evaporative heat loss diminishes. In fact, when relative humidity reaches 100 percent, evaporative heat loss is totally ineffective. The heat stress index is based on air temperature and relative humidity. The cattle heat stress index values are not the same as the human heat index or air temperature. The cattle heat stress index numbers are unique to outdoor cattle and cannot be used without additional interpretation for dairy cows or other livestock.

Heat stress can cause reduced productivity in beef and dairy cattle herds. The effects of severe heat stress are often seen in the form of reduced reproductive performance, reduced daily weight gain of growing cattle and reduced milk production. Cattle are more sensitive to heat stress than humans, although cattle do seem to have a wide range of heat tolerance. From an environmental perspective, heat stress is a combination of temperature, relative humidity, and wind speed. However, animal factors, such as age, hair coat length, hair coat color, and nutrition status, interact with these environmental factors to determine the severity of heat stress.

The Mesonet Cattle Stress Advisor index is a calculated value that is unique for livestock. The calculated value is not the same as the air temperature or human heat index.

When cattle heat stress is at 71 or lower, cattle are in the thermal neutral zone, meaning that they are comfortable and production will not be sacrificed due to severe environmental conditions. Values ranging from 72-79 indicate “Mild Stress.” This is often when cattle will move to shade to cool themselves. Livestock managers should monitor the weather and prepare to take action if conditions worsen. Cattle heat stress values ranging from 80-89 indicate a “Moderate Stress.” This is the time to implement management strategies to help reduce cattle stress. Values above 90 indicate “Severe Stress.”

The cattle heat stress index formula is -

THI = tair - [0.55-(0.55*relh/100)]*(tairf-58.8)

where:

THI = Temperature-Humidity Index
tair = air temperature in Fahrenheit
relh = percent relative humidity

What can be done in a heat stress situation?

Provide ample water.

On days when the index is 72 or higher the cattle may need more than 2 gallons of water per 100 pounds of body weight. Provide enough tanks for cattle to be able to get the water they need. If possible, water should be cooled. Tanks should be cleaned weekly to encourage water consumption. Making water available under a shaded area will increase cattle water consumption.

Avoid handling cattle:
Handling cattle can elevate their body temperature by as much as 3.5°F. If cattle must be worked on days when the Cattle Stress Index is likely to go over 80, try to do the work before 8:00 AM and keep the maximum time in the holding facilities to no more than 30 minutes. On days when the index will be 80 or above, do not work cattle after 10:00 AM. The 60-hour forecast component of the cattle stress index, will allow you to schedule management practices to best maintain cattle health.

Change feeding patterns:
Shift the feeding schedule toward evening on days when the Cattle Stress Index is above 72. Try to deliver 70 percent of the daily scheduled feed two to four hours after the peak air temperature. Providing only small amounts of feed during the heat of the day, will decrease the metabolic heat of digestion.

Provide shade:
A shade tree is just as welcome a relief for cattle as humans on a hot summer day. Shade can also be constructed. Shade height should be 8-14 feet tall and should be large enough to provide 20-40 square feet per animal. The most effective shade is a solid reflective roof constructed of white colored, galvanized, or aluminum materials. Shading with wooden slats, plastic fencing, or other materials that allow flecks of sunlight to hit the animals are less effective. If possible two shaded areas are recommended, one over the feed area to increase feeding time, and another away from the feed area to encourage the cattle to rest. Water should be made available under both shaded areas, to increase the water consumption during heat stress period. If the structure is left up year-round, construct a frame adequate for snow load. Shade is insurance against mortality loss. Any performance benefits are a bonus.

Improve airflow:
Consider where the cattle are located and if there is any air restriction. Buildings, high fences, or vegetation can block airflow. A 6-foot high windbreak can obstruct airflow for 60 feet downwind.

Provide water mist:
Providing a spray of water will help to cool the animals down. However it is important to place misters over a clean, concrete area. Running misters over dirt creates mud and increases the potential for mastitis or other bacterial diseases. A timer should be used to run the mister long enough to cool, but not wet the cattle. Do not allow mist to wet nearby feed. Wet feed spoils rapidly with Oklahoma’s summer heat.

Control biting flies:
Stable flies cause cattle to bunch and disrupt cooling. Monitor the situation and control the flies as needed. Eliminate any shallow pools or muddy areas nearby, since they are common breeding areas for flies.

COLD STRESS
Experienced livestock producers are well aware of the toll severe winter weather can have on animal health and performance. The Oklahoma Mesonet Cattle Stress Advisor provides livestock producers a measure of cold stress conditions.

Research indicates that the effects of cold, wind, wet hair coat and muddy pastures and pens are additive. These stresses can be managed to a limited degree. Beef cattle can be comfortable within a wide range of temperatures; from 20 to 70°F, depending largely on hair coat length and hair coat condition (dry, wet, muddy etc.). The lower critical temperature is defined as the effective ambient temperature at which energy intake must increase in order to minimize reduction in weight gain, in the case of growing cattle, or to prevent weight loss in mature cattle.

Calculation of cattle stress levels is complicated by cattle coat changes as they are exposed to seasonal temperature variations. As temperatures cool down in the fall cattle coat hair thickens to offer the animal more protection. The following table suggests guidelines for lower critical temperature for various hair coat conditions.

Estimated lower critical temperatures for beef cattle.

Coat Description	Lower Critical Temperature
Wet or summer coat	60°F
Dry fall coat	45°F
Dry winter coat	32°F
Dry heavy winter coat	19°F

Another factor that contributes to animal stress is rainfall. A wet cattle coat loses its insulative properties. In terms of stress, a wet coat is the same as a summer coat.

The cold stress experienced by outdoor cattle is based on air temperature, wind speed, and the presence of rain or snow. The Cattle Cold Stress Index numbers are based on human wind chill calculations developed using the 1945 Siple and Passel Index. As of November 2001, the National Weather Service is using a new human wind chill formula that will undergo additional refinement in 2002. The new human wind chill values are warmer than the values based on the 1945 Siple and Passel Index. Thus, the Cattle Cold Stress Index numbers are lower than the current human wind chill values. Since cattle management recommendations are based on the older wind chill formula, it will continue to be used until a more accurate formula is created, based on new cattle research.

The following is the basic formula used to calculate the Cattle Cold Stress Index when temperatures fall below 45°F.

WCT = 0.0817*[(3.71*wind0.5)+(5.81-0.25 wind)]*[(tair-91.4)+91.4]

where:

WCT = Wind Chill Temperature (traditional formula) tair = air temperature in Fahrenheit wind = wind speed in miles per hour

When temperatures are between 59°F and 46°F, the following formula is used.

CSI = [(tair-45F/14)] x tair + [(59F tair)/14] x WCT

where:

CSI = Cold Stress Index tair = air temperature in Fahrenheit WCT = Wind Chill Temperature (traditional formula)

The following table shows the Wind Chill Temperature ranges in Fahrenheit where “Mild, Moderate, and Severe” cold stress is likely. Actual cattle stress will vary with location, cattle breed, stage of hair growth, and wind exposure.

Cattle Coat Impact on Wind Chill Temperature Stress Levels

Cattle Coat	Dates	Mild	Moderate	Severe
Dry heavy winter	January 1 - March 31	19-10	9-0	<0
Dry spring	April 1 - April 30	45-32	31-18	<18
Dry summer	May 1 - October 15	59-46	45-32	<32
Dry fall	October 16 - November 30	45-32	31-18	<18
Dry winter	December 1 - December 30	32-20	19-7	<7
Wet	Year-round	59-46	45-32	<32

Whenever 0.1 of an inch of rain occurs in the last hour, the calculated cold stress is the same as if the animal had a summer dry coat.

The forecast advisor will indicate an alert if 0.1 of an inch of rain is forecast during the 6-hour period covered by the forecast advisor.

What can you do in a cold stress situation?
The combined effects of temperature and wind are often expressed as a wind chill index. The wind chill index, rather than ambient temperature, is used to estimate effective temperature when considering the severity of cold stress. For example, when the temperature is 20°F with no wind, the wind chill index is 20°. At the same ambient temperature, 5, 15 and 25 mph winds would result in a wind chill index (or effective temperature) of 13°, 4° and -7°F, respectively. Obviously, anything that can be done to reduce exposure to wind will dramatically reduce cold stress.

In general, a cow’s energy requirements increase 1 percent for each degree the wind chill is below 32°F. For a wet cow, the increased energy requirement begins at 59°F and increases 2 percent for each degree drop.

In cold wet conditions, this increased energy need is often virtually impossible to accomplish with feedstuffs available on ranches. In addition, this amount of energy change in the diet of cows accustomed to a high roughage diet, must be made very gradually to avoid severe digestive disorders. Therefore, the more common-sense approach is a smaller increase in energy fed during wet cold weather, and extending the increase into more pleasant weather to help regain energy lost during the storm.

For example, a cow consuming 16 pounds of grass hay per day and 5 pounds of 20 percent range cubes under mild weather, could have its feed in increased to 20 pounds of grass hay per day (also possibly offering a better quality hay) plus 6 to 7 pounds of range cubes during a severe weather event. This is not a doubling of the energy intake but extending this amount for a day or two after a storm may help overcome the energy loss during the storm and is done in a manner that does not cause digestive disorders.

A second approach that is often used is to reserve the highest quality hay for feeding during stressful cold periods.

Degree-day Heat Unit Calculator

Degree-day heat units provide agricultural producers and crop consultants a way to estimate the changes in crop growth and pest development, based on recent weather conditions. Degree-day heat unit indexes were developed as a tool to measure the heat units that drive plant growth and insect development.

Each crop or insect has a unique lower and upper air temperature threshold. It is assumed that little or no growth occurs outside of this range. The temperature range is lower for crops or insects that develop best in cool air temperatures and higher for those needing more heat for growth. For example, wheat has a lower temperature threshold of 32°F and an upper temperature threshold of 86°F. Cotton, a crop that needs warmer weather for plant growth, has a lower temperature threshold of 60°F and an upper temperature threshold of 100°F.

Degree-day heat units are calculated each day and the daily units added together to give a degree-day heat unit accumulation from a “Planting Date.”

Agweather uses the following formula to calculate degree-day values:

Degree-days = (Maximum Daily Air Temp + Minimum Daily Air Temp) - Base Temp

where:

Minimum Daily Air Temp Base Temp = specific crop lower temperature threshold. Maximum Daily Air Temp = specific crop upper temperature threshold

When the maximum daily air temperature is above a crop’s upper temperature threshold, the maximum daily air temperature is set to the upper temperature threshold. When the degree-day heat unit value is negative, the degree-day value is set to zero.

The following are the lower and upper temperature thresholds for agronomic crops used on the Agweather Web site.

Crop	Lower Temperature Threshold	Upper Temperature Threshold
Alfalfa	41°F (5°C)	86°F (30°C)
Corn	50°F (10°C)	86°F (30°C)
Cotton	60°F (15.6°C)	100°F (37.8°C)
Peanut	55°F (12.8°C)	95°F (35°C)
Sorghum	55°F (12.8°C)	95°F (35°C)
Soybean	50°F (10°C)	95°F (35°C)
Wheat	32°F (0°C)	86°F (30°C)

Dispersion Advisor

The Oklahoma Dispersion Advisor is a tool developed to aid in decision-making with respect to the near-surface release of gases and small particulates (airborne particles with diameters less than 20 microns). Examples include pesticides released by surface or aerial spraying, odors associated with land application of animal waste, and smoke generated by fire. In such practices, it is important to know both (1) the ability of the atmosphere to disperse the material and (2) the direction the material will be transported.

The Oklahoma Dispersion Advisor features both graphical and textual output that depict current and future conditions for atmospheric dispersion. The focus of the advisor is the evaluation of dispersion conditions with respect to downwind concentrations at distances of one-quarter mile to several miles. Thus, the advisor is a useful tool for assessing appropriate times to minimize downwind pollutant concentrations resulting from the near-surface release of gases and particulates.

In addition to dispersion conditions, it is also important to know the transport direction of such material. Interpretation of the Dispersion Advisor is discussed below, with dispersion conditions and transport direction described separately.

With respect to dispersion conditions, the Oklahoma Dispersion Advisor is used in conjunction with weather conditions reported by the Oklahoma Mesonet to produce a map of current dispersion conditions across Oklahoma. The Dispersion Advisor is also used in conjunction with the latest National Weather Service 84-hour North American Model (NAM) forecast to produce tables of forecast dispersion conditions at 1-hour or 3-hour intervals into the future. With respect to transport direction, the Mesonet wind maps can be used to view current wind conditions, while the forecast and past dispersion tables list wind direction for 1- or 3-hour intervals. These tables show a multitude of variables including future dispersion conditions and wind directions, and are available for specific Mesonet locations across Oklahoma.

Dispersion Conditions
Based on the current or forecasted weather conditions, the Oklahoma Dispersion Advisor assigns a “Dispersion Conditions” category, which is reflective of concentrations at downwind distances of one-quarter mile to several miles. There are six categories:

Dispersion Condition

Color of Map

Fire Danger Advisor

The Oklahoma Fire Danger Advisor (OFDA) produces 1-km resolution colored maps of four U.S. Forest Service National Fire Danger Rating System (NFDRS) fire danger indices (dimensionless): Spread Component (SC), Energy Release Component (ERC), Burning Index (BI), and Ignition Component (IC). Colored maps of 1-hr dead fuel moisture and the Keetch-Byram Drought Index (KBDI) are also produced, the latter map once per day. In addition, for each model run, a table of fire danger indices, fuel moistures, KBDI, and selected weather variables is produced for each Mesonet site.

The Oklahoma Fire Danger Advisor utilizes weekly 1-km resolution AVHRR satellite data for NDVI (Normalized Difference Vegetative Index) to estimate the “relative greenness” of the earth’s surface, which is directly related to live fuel moisture. One kilometer resolution colored maps of both “relative” and “visual” greenness are available.

Limitations of the Oklahoma Fire Danger Advisor include:

Every 1-km “grid” square of Oklahoma has been assigned one of five surface fuel models (so many tons/acre of 1-hr, 10-hr, 100-hr dead fuels, herbaceous and woody live fuels, etc.). If the particular fuel model of concern (e.g, an open grassy area) within a given grid square is not the same as the assigned fuel model (e.g., a deciduous forest), then the OFDA results for that 1-km square can be expected to be different from what they would be for your fuel model of concern.
The OFDA, like the NFDRS, is a surface-fuel based model and does not apply to crown fires.
The OFDA assumes an NFDRS Slope Class of 1 (terrain of 0-25% slope), so actual upslope conditions over steep terrain will be amplified over OFDA predictions.
As can be inferred from the above, the OFDA is not designed for specific fire behavior predictions for a given field, fuel type, slope, etc., but rather for the predominant vegetative fuel type over a 1-km square, mainly flat region.
The fuel models utilized are for native vegetation and each 1-km square of land is assigned one of these five fuel models. Accordingly, for 1-km grid squares of primarily agricultural land (e.g., fields of bare soil or green wheat fields - what the satellite ÒseesÓ), the OFDA model predictions will not be accurate. The live fuel moisture assessment with respect to the agricultural vegetative cover will be reliable, but it may not be similar to native vegetation in that pixel; in addition, other aspects important to the model, such as fuel types and loads will be in error.
The OFDA output will be unreliable for locations having a snow cover (covering the fuels) and should be ignored. After the snow cover melts, model output will become valid once again.

Fire Behavior and the Weather
In Oklahoma, as mentioned earlier, the Oklahoma Fire Danger Advisor uses one of five surface fuel models (NFDRS Model A for shortgrass prairie; L for mixed prairie and western cropland; T for tallgrass prairie and eastern/central cropland; R for deciduous forests; and P for pine forests). These models consist of so many tons/acre of 1-hr, 10-hr, and 100-hr dead fuels and live herbaceous and woody fuels. Grassy fuel models, such as predominate in the panhandle and western Oklahoma, contain only “fine” 1-hr dead (and live) fuels, while forest fuel models such as are in eastern Oklahoma have equal amounts of 1- and 10-hr fuels and a lesser amount of 100-hr fuels. In addition, the 1988 revisions to the NFDRS include a “drought dead fuel load” in the subsurface - increasing amounts of this fuel become available (in the same proportions as the “non-drought” dead fuels) to burn as the KBDI value increases above 100.

It is important to realize that fire initiation and behavior are primarily determined by the current weather conditions, of which solar radiation, temperature, relative humidity, and wind speed are most important. Fine fuels (1-hr dead class) respond quickly to changing weather conditions - the subsurface can be completely saturated from a recent rain, but the surface fine fuels can have very low fuel moisture and carry a fire. The fire danger indices (especially SC and BI) are primarily a function of the current weather conditions, even though fuel types with 10-hr and 100-hr components are taken into account.

On the other hand, the Keetch-Byram Drought Index (KBDI) relates to the moisture levels in the subsurface (litter, duff, and upper soil layers). Increasing KBDI values add extra amounts of fuel to the fuel load, but the moisture content of the 1-hr fuels is still determined by current weather conditions. Thus, one can have extremely high KBDI values, but if wind speeds are low and relative humidities are high, there will be low fire danger. Conversely, one can have very low KBDI values, but if wind speeds are high and relative humidities low, there will be high fire danger. KBDI, because it is based on the subsoil moisture profile, is also a fairly reliable indicator of live fuel moisture. High KBDI values means the understory vegetation is low in water content and susceptible to ignition with a minimum of preheating.

Descriptions of SC, ERC, BI, IC, and KBDI
With these thoughts in mind, we now present some descriptions and interpretations of the four fire danger indices (SC, ERC, BI, IC) and of KBDI:

Spread Component
For fire control planning, the first consideration is the rate of spread. The Spread Component (SC) is numerically equal to the predicted rate of spread ?of the headfire in feet/minute. It is the most variable of the indices, with daily variations being caused by changes in wind speed and in the dead and live fuel moisture contents.

SC = (1 min/ft)*(Rate of Spread in ft/min)

[MPH=0.0114*SC]

Energy Release Component
ERC is a measure of the heat released per unit area in the flaming zone of the fire. It is the least variable index on a day-to-day basis. Variations are caused by varying fuel moistures in the fuel bed.

ERC = (0.04 ft**2/Btu) * (Heat Release in Btu/ft**2)

Burning Index
The fireline intensity, given by I, in Btu/ft-min is given by:

I = SC * ERC * (25 Btu/ft-min)

The larger this number, which is based on both SC and ERC, the greater the difficulty of containment of the fire.

From this variable, a flame length (FL) relationship has been developed:

FL (ft) = j(I/60)**0.46

Finally, the burning index (BI) is related to the flame length as follows:

BI = k (FL), where k = 10/ft.

Or,

Flame Length (ft) = BI/10

Thus, the burning index contains information related to both the fireline intensity and flame length. It is the most important single fire danger index (besides fireline intensity I).

Ignition Component
The ignition component is the probability (0-100%) that a reportable fire requiring suppression action will result from a firebrand. It says nothing about the intensity of the fire.

Keetch-Byram Drought Index
Drought, as defined by the KBDI, is a condition of dryness in the litter, duff, and upper soil layers that progresses from saturation to an absence of available moisture. The KBDI is based on an arbitrary 8 inches of water in the litter/duff/soil column. When the full 8” of water are available, KBDI = 0. As water is removed from the column by evapotranspiration, the KBDI increases in value. When KBDI = 800, all the water has been removed.

As a drought proceeds, the upper soil layers dry and the amount of dead fuel available for consumption increases. During combustion some of this fuel contributes directly to fireline intensity (BI), but most increases total heat release (ERC) and contributes to burn severity through smoldering combustion with its resulting smoke. The interpretations below are based on experience within forested areas in the southeastern United States.

KBDI Value	Interpretations
0 - 200	Nearly all soil organic matter, duff, and litter are left intact after a burn. Once the fire passes, remaining embers extinguish quickly and, within a few minutes, the area is completely extinguished and smoke free.
200 - 400	At these levels, litter and duff layers begin to contribute to fire intensity. Heavier fuel classes can become involved in the burn. Soil exposure is minimal. Smoke management can become a real hazard, especially if there are larger fuel classes available. Smoldering with resulting smoke can carry into the night.
400 - 600	These levels represent the upper range at which most understory type burning should be conducted. Most of the duff and organic layers will ignite and actively burn. The intensity can be expected to increase almost exponentially from the lower to upper ends of this range. Considerable soil exposure occurs. Complete consumption of all but the largest dead fuels can be expected, and larger fuels not consumed may smolder for several days, leading to smoke and possible fire control problems.
600 - 800	These levels represent the most severe drought conditions, and many states issue burning bans at these levels. Prescribed fires should not even be attempted at levels over 700. Fires that do occur will be intense and deep-burning. Live understory vegetation (2-3” range) should be considered part of the fuel complex due to its low fuel moisture. Most subsurface soil organic material will be consumed; great soil exposure will occur with great future erosion potential. Smoldering may occur for many days, with smoke and fire control problems.

Fire Suppression Interpretations

CAUTION: These are not guides to personal safety. Fires can be dangerous at any intensity.

Flame Length (ft)	Fireline Intensity (Btu/ft/s)	Interpretations
<4 (BI <40)	<100	Fires can generally be attacked at the head or flanks by persons using handtools. Hand line should hold the fire.
4-8 (BI=40-80)	100-500	Fires are too intense for direct attack on the head by persons using handtools. Hand line cannot be relied on to hold fire. Equipment such as dozers, pumpers, and retardant aircraft can be effective.
8-11 (BI=80-110)	500-1,000	Fires may present serious control problems--torching out, crowning, and spotting. Control efforts at the fire head will probably be ineffective.
<11 (BI > 110)	< 1,000	Crowning, spotting, and major fire runs are probable. Control efforts at head of fire are ineffective

Peanut Leaf Spot Advisor

The Oklahoma Peanut Leaf Spot Advisor is a tool that has been developed to aid growers in proper timing of fungicide application for early leaf spot, a foliar disease of peanuts. Using the Oklahoma Mesonet, the state’s automated weather station network, the advisor calculates daily “leaf spot&rdquo hours for each Mesonet site. A leaf spot hour is defined as one hour with relative humidity greater than or equal to 90% and temperature between 60.5 and 86F. Beginning 30 days after planting or ten days since the last spray (whichever is later), the advisor accumulates leaf spot hours and recommends a fungicide application when 36 such hours are met or exceeded.

Growers are encouraged to use the Site-Specific Interactive Advisor, which gives a spray or no spray recommendation. After the user clicks on a nearby Mesonet site, the advisor asks for the peanut plant date as well as the date of the last fungicide application for early leaf spot (if one has occurred). This information is then entered and the advisor comes back with the recommendation (including the number of leaf spot hours that have occurred since 30 days after planting or since 10 days after the last fungicide application, whichever is later). If a number of peanut fields are involved, each with various plant dates or fungicide application dates, the advisor should be run separately for each field. The grower can try various nearby Mesonet sites as well, as a conservative approach.

Rules for the early leaf spot advisory are as follows:

It is recommended that growers wait until at least 30 days after planting before even considering spraying their peanuts for early leaf spot. If a grower wishes to apply a first fungicide at 35 days after planting and then follow the advisory, that is acceptable; otherwise, the advisor will not recommend a first spray until 36 leaf spot hours have accumulated since 30 days after planting.
Once the peanuts are 30 days old, the Oklahoma Peanut Leaf Spot Advisor should be consulted on a regular, if not daily, basis. In addition, after a fungicide application, the advisor should be consulted regularly beginning 10 days after the spray date.
If a given field cannot be sprayed within 3 days of an advisor spray recommendation, then spray on a 14-day schedule.
Use only highly effective fungicides (Bravo, Folicur, or Tilt/Bravo). If another fungicide is used, spray on a 14-day schedule.
If levels of early leaf spot exceed 25% infection (leaflets with spots or defoliated), revert to a 14-day schedule.
If late leaf spot, web blotch, or pepper spot are identified, revert to a 14-day schedule.
Be alert to weather forecasts. Spray if rain is in the forecast and a field is close to reaching 36 leaf spot hours.
Maintain the spray program until 14 days before the anticipated harvest.

The Oklahoma Peanut Leaf Spot Advisor web page features other products. The “Current Model Output” section includes a table of leaf spot hours for every Mesonet site, specific Mesonet site table and statewide map of season-long leaf spot hours.

The “last effective spray date (LSPDATE)” is an alternative method to determine fungicide application timing. Using the LSPDATE method, a grower applies a spray when (1) the LSPDATE first exceeds 20 days after planting, and, from then on, (2) once LSPDATE exceeds the date of the last fungicide application.

Pecan Scab Advisor

The Oklahoma Mesonet Pecan Scab Advisor is a weather-based tool to aid growers in the proper timing of fungicide application for pecan scab. The Pecan Scab Advisor runs from March 1 to August 31. Using data from the Oklahoma Mesonet, the state’s automated weather station network, the advisor calculates daily “scab hours” for all Mesonet sites. A scab hour is defined as one hour with relative humidity of 90 percent or higher, and an air temperature of 70°F or higher. Research at pecan orchard sites using Mesonet weather data has shown that only the total scab hours during the 14 days preceding a scab rating were critical in correlating disease development.

The advisor assumes that a correctly applied fungicide, labeled for pecan scab, protects the crop for two weeks following application. When the user clicks on a Mesonet site, the advisor calculates the number of scab hours at that site that have occurred in the unprotected part of the last 14 days. If no fungicide application date was entered, the model uses March 1 as a default. Knowing the pecan scab hours and the susceptibility of the pecan variety, the grower can decide whether to spray or not. The threshold for highly susceptible pecan varieties is 10 scab hours, for moderately susceptible varieties is 20 scab hours, and for natives and less susceptible varieties is 30 scab hours.

Pecan scab susceptibility for Oklahoma recommended pecan varieties

Highly susceptible

10 Scab Hours

Moderately susceptible

20 Scab Hours

Low susceptibility (resistant)

30 Scab Hours

Burkett

Caddo

* Native trees *

Squirrel’s Delight

Colby

Barton

Western

Creek

Choctaw

Wichita

Giles

Graking

Kiowa

Kanza

Maramec

Lakota

Mohawk

Mount

Oconee

Nacono

Shawnee

Osage

Pawnee

Peruque

Stuart

(from Damon Smith, OSU Pecan Pathology Specialist, and Michael Smith, OSU Pecan Researcher, on April 21, 2008.)

The Pecan Scab Advisor is updated hourly. The forecast of scab hours is based on the National Weather Service ETA Model. This NWS model is a numerical model for each 36 square mile area. The Pecan Scab Advisor is operational from March 1 through August 31. Outside of these dates the Fungicide Timing Decision Support graph will not provide reliable display data.

Pecan Scab advisor formula:

Scab hour = One hour with relative humidity at or above 90% and air temperature at or above 70° Fahrenheit.

Pecan Scab advisor rules:

The advisor runs from March 1 to August 31.
The interactive Fungicide Timing Decision Support module calculates scab hours from the end of a 14-day fungicide control window.
Only pecan scab hours during the last 14 days are considered in making fungicide application recommendations.
A fungicide application is recommended based on scab susceptibility of the pecan variety. For highly susceptible varieties, a fungicide application is recommended when 10 scab hours have occurred over the last 14 days. The scab hours that trigger an application recommendation are increased to 20 scab hours for moderately susceptible varieties. 30 scab hours are necessary before a fungicide application is recommended for resistant improved varieties and native pecans.

SITE-SPECIFIC PRODUCTS

Mesonet Site Selection
The Mesonet site location can be selected by clicking on the Oklahoma map or from the list that appears when the small “blue arrow box” to the right of the “SITE:___” box is selected. When a site is selected from the Oklahoma state map, the name of the selected Mesonet site will show up in the “SITE:___” menu. Weather data used in the model will be from the Mesonet tower selected.
Fungicide Timing Decision Support
The Fungicide Timing Decision Support product is an interactive graph and text that can be used to decide when to make a fungicide application. The graph is updated every hour. Hourly weather data recorded by the Oklahoma Mesonet replaces the forecast data. The forecast data is updated twice a day, in the morning and evening. When the graph is flat, no pecan scab hours are accumulating. When the graph rises, pecan scab hours are accumulating.
The graph times are shown in Central Daylight Time (CDT).
The Pecan Scab Decision Support page includes user selections for highly susceptible, moderately susceptible, and resistant pecan varieties.
The default for “Date of Last Fungicide Spray:” is March 1 of the current year.
Text for the Pecan Decision Support Page includes:
- A recommendation statement indicating whether a fungicide application is “Recommended” or “Not Recommended,” based on the scab susceptibility selected and the number of pecan scab hours over the last 14 days.
- “Today’s Date:”
- When the “Date of Last Fungicide Spray” is left on the default date of March 1, a “Season started on March 1” line is displayed.
- When a “Date of Last Fungicide Spray” is entered, the indented text shown below is displayed. This provides a check of the date entered and the important fungicide control window dates.
  
  Last Fungicide Application date entered was: ____date____
  Fourteen day Fungicide Control Window was:
  - Start of Fungicide Control Window: ____date____
  - End of Fungicide Control Window is: ____date____
  Pecan Scab Hours since end of Fungicide Control Window: _hours_
The pecan scab hours are shown as numbers on the left vertical axis, y-axis. The dates are shown on the bottom horizontal axis, x-axis.
Graph line key:
- Green solid line - the pecan scab hours for the last 14 days, based on Oklahoma Mesonet data.
- Blue solid line - the forecast scab hours, based on the National Weather Service NAM Model.
- Black line and diamonds - the previous year’s daily scab hours from Oklahoma Mesonet data.
- Red line and diamonds - the 10-year average of daily scab hours from Oklahoma Mesonet data.
Seasonal Scab Hours Table
Table Data for a single Mesonet site:
- Date: Calendar date from March 1 to the current date.
- Daily Scab Hours: Daily pecan scab hours for each calendar date from March 1 to the current date.
- Cumulative Scab Hours: Accumulation of pecan scab hours for each day from March 1 to the current date.
- Maximum Air Temperature: Highest air temperature in Fahrenheit (°F) for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
- Minimum Air Temperature: Lowest air temperature in Fahrenheit (°F) for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
- Maximum Relative Humidity: Highest relative humidity in percent for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
- Minimum Relative Humidity: Lowest relative humidity in percent for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
- Rainfall: Recorded rainfall in inches for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
Historical Daily Scab Hours Table
Table Data for a single Mesonet site:
- Day: Sequence of days from March 1 to the current date.
- Date: Calendar date from March 1 to the current date.
- Average Temperature: The 24-hour average air temperature in Fahrenheit (°F) for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
- Average Humidity: The 24-hour average relative humidity in percent for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
- Rainfall: The rainfall in inches for each 24-hour period ending at 1:00 am CDT from March 1 to the current date.
- Cumulative Scab Hours: The accumulation of pecan scab hours for each day from March 1 to the current date.
- Daily Scab Hours: The daily pecan scab hours for each calendar date from March 1 to the current date.
- Cumulative Scab Hours Last Year’s Season: Last year’s accumulation of pecan scab hours for each day from March 1 to the current date.
- Daily Scab Hours Last Year’s Season: Last year’s daily pecan scab hours for each calendar date from March 1 to the current date.
- Cumulative Scab Hours Season 2 Years Ago: The accumulation of pecan scab hours for each day from March 1 to the current date for the season 2 years ago.
- Daily Scab Hours Season 2 Years Ago: The daily pecan scab hours for each calendar date for the season 2 years ago from March 1 to the current date.
- Cumulative Scab Hours 10-Year Average: The 10-year average of the accumulation of pecan scab hours for each day from March 1 to the current date.
- Daily Scab Hours 10-Year Average: The 10-year average of the daily pecan scab hours for each calendar date from March 1 to the current date.

STATEWIDE DATA PRODUCTS

Statewide Cumulative Scab Hours Map
This is an interactive, zoomable, color-contoured statewide map of pecan scab hours accumulated from March 1 to the current date and time for all Oklahoma Mesonet sites. The values displayed are the accumulated pecan scab hours since March 1 for the Mesonet sites shown.
14-Day Statewide Cumulative Scab Hours Map
This is an interactive, zoomable, color-contoured statewide map of pecan scab hours accumulated over the previous 14 days for all Oklahoma Mesonet sites. The values displayed are the accumulated pecan scab hours for the last 14 days for the Mesonet sites shown.

DAILY REFERENCE DATA

Forecast Scab Hours Table
Table Data for a single Mesonet site:
- Time: In Central Daylight Time (CDT).
- Air Temperature: Forecast of air temperature in Fahrenheit (°F) for each hour.
- Relative Humidity: Forecast of relative humidity (%) for each hour.
- Wind Speed: Forecast of average wind speed in miles per hour for each hour.
- Wind Direction: Forecast of the prominent wind direction for each hour.
- Rainfall: Forecast amount of rainfall in inches for each hour.
- Scab Hours: Forecast of pecan scab hours for each hour.
- Cumulative Scab Hours: Forecast of the accumulating pecan scab hours over the time period of the forecast
Daily Table of All Mesonet Sites
Table Data for the Date selected:
- STID: Mesonet site identifier
- DINF: Pecan scab hours for each 24-hour period ending at 1:00 am CDT.
- TINF: Total pecan scab hours accumulated from March 1 of the season selected.
- TMAX: Maximum air temperature in Fahrenheit (°F) for each 24-hour period ending at 1:00 am CDT.
- TMIN: Minimum air temperature in Fahrenheit (°F) for each 24-hour period ending at 1:00 am CDT.
- HMAX: Maximum relative humidity in percent (%) for each 24-hour period ending at 1:00 am CDT.
- HMIN: Minimum relative humidity in percent (%) for each 24-hour period ending at 1:00 am CDT.
- RAIN: Recorded rainfall for each 24-hour period ending at 1:00 am CDT.
View Reference Data
This links to the reference data used by the Pecan Scab advisor for the current and last ten years. Only the data for the date selected will be shown.
- Date and Time Stamp:
  This is a table of all Mesonet locations for the date and time selected.
  
  Table Data:
  - STID: Mesonet site identifier
  - STNM: Count of days since March 1.
  - TAIR: Maximum air temperature in Fahrenheit (°F) for each time period.
  - RELH: Relative humidity in percent (%) for each time period.
  - INFH: Pecan scab hours for each time period.
  - TINF: Total pecan scab hours accumulated from March 1 of the year selected.
- Map:
  This is a color-contour map of the seasonal pecan scab hours accumulated from March 1 to the date and time selected.
- Graph:
  This is a graph of the air temperature, relative humidity and pecan scab hours for each hour over the time period selected.

Reference
Pecan Diseases: Prevention and Control, Fact Sheet F-7642, Oklahoma State University, Sharon von Broembsen, April 2005.

Pecan Casebearer Advisor

The Oklahoma Pecan Nut Casebearer Advisor is a tool that has been developed to aid growers in proper timing of scouting for pecan nut casebearer (PNC). The advisor calculates degree-day heat units based on a 38°F lower threshold from a start date that is unique to each location. The PNC model was originally developed by entomologists at Texas A&M University in 1983. It was field tested and verified under Oklahoma conditions during 1996-1997.

The daily PNC degree-days are calculated by:

(daily high temperature + daily low temperature) - 38

where, negative values are not allowed.

For each Oklahoma Mesonet site, degree-day heat units are accumulated from a unique date, based on the climatological (30-year) average of annual frost-free (32°F) days at that site. A degree-day heat unit total of 1,831 indicates the date of first significant entry by PNC into the nuts.

Based on field observations, the action recommendations are:

Degree-day Heat Units

Action

1,100

Start hanging pheromone traps and begin monitoring of pecan casebearer adults.

1,500

Start scouting for pecan casebearer eggs.

1,600

Start scouting for pecan casebearer larvae.

Spinach White Rust Advisor

The Spinach White Rust Advisor calculates spinach white rust sporangia infection hours based on Oklahoma Mesonet weather data. A spinach “white rust” hour is defined as one hour with relative humidity at or above 90% and an air temperature in the range of 52-68°F (11-20°Celsius) (Sullivan et al., 2003). When relative humidity is at or above 90% and the air temperature is above or below the range of 52-68°F (11-20°Celsius), the spinach white rust hours are weighted to account for slower fungal development. White rust hours begin to accumulate from the first true leaf stage or at the end of a 7-day fungicide control window. The model assumes that disease infection is controlled for 7 days after the application of a fungicide labeled for control of spinach white rust.

Spinach White Rust Advisor Formula
A spinach “white rust hour” is defined as one hour with relative humidity at or above 90% and an air temperature in the range of 52-68°F (11-20°Celsius) (Sullivan et al., 2003). When relative humidity is at or above 90% and the air temperature is above or below the range of 52-68°F (11-20°Celsius), the white rust hours are weighted to account for slower fungal development. White rust hours are adjusted by multiplying the white rust hour by the following “infection hour” factors:

Air Temp Range	(In Fahrenheit)	Infection Hour Factor
<6°C	<43°F	0
6-<9°C	43-<48°F	0.5
9-<11°C	48-<52°F	0.75
11-20°C	52-68°F	1.0
>20-22°C	>68-72°F	0.75
>22-27°C	>72-81°F	0.5
>27°C	>81°F	0

White Rust Hour = Hours at or above 90% RH x Disease Hour Factor based on Celsius air temperature.

The Spinach White Rust Advisor runs each hour. New white rust hour values are added to the current day’s total.

Each day the accumulated white rust hours for the day are totaled and added to Spinach White Rust Advisor tables.

Spinach White Rust Advisor Rules:

The Spinach White Rust Advisor is operational from September 15 to May 15.
The interactive Fungicide Decision Support module calculates white rust hours from the end of a 7-day fungicide control window to the current date.
A fungicide application is recommended when 12 white rust hours have accumulated, since the date of the first true leaf or the end of the 7-day fungicide control window, regardless of the number of days it takes to accumulate 12 white rust hours (Sullivan et al., 2003).
The “Last Effective Spray Date (LSPDATE)” is calculated by subtracting 12 white rust hours from the accumulated white rust hours. Then from the date this occurred, counting back 7 days to account for the fungicide control window.

SITE-SPECIFIC PRODUCTS

Mesonet Site Selection
The Mesonet site location can be selected from the Oklahoma map or from a list under SITE: window. When a site is selected from the Oklahoma state map, the name of the Mesonet site will show up in the SITE: window.
Fungicide Timing Decision Support
This product is an interactive graph that shows the white rust hours for the last two weeks and a forecast of white rust hours for up to 84-hours into the future. The graph is updated every hour, with current Oklahoma Mesonet data replacing the forecast data. Graph output is based on either the date of the first true leaf stage or the date of the last fungicide application. When the “Date of Last Fungicide Application” option is selected, no white rust hours accumulate during a 7-day fungicide control window from the entered date.
The graph times are shown in Central Daylight Time (CDT).
When the “Date of First Leaf Stage” option is selected the text above the Fungicide Decision Support graph includes:
- A Fungicide Application for Spinach White Rust is “Recommended” or is “Not Recommended.”
- “Today’s Date:”___current date___
- Date of First True Leaf Stage entered was: ___date___
- White rust hours since the First True Leaf Stage: ____white rust hours____
- Last Effective Spray Date: ____date____
When the “Date of Last Fungicide Application” option is selected the text above the Fungicide Decision Support graph includes:
- A Fungicide Application for Spinach White Rust is “Recommended” or is “Not Recommended.”
- Today’s Date: ___current date___
- Date of Last Fungicide Application: ____date____
- Last Fungicide Application Date entered was: ____date____
- Seven day Fungicide Control Window was:
  - Start of Fungicide Control Window: ____date____
  - End of Fungicide Control Window: ____date____
- White rust hours since end of Fungicide Control Window: ____white rust hours____
The spinach white rust hours are shown on the left vertical axis, y-axis. The dates are shown on the bottom horizontal axis, x-axis.
The Fungicide Decision Support graph lines are:
- Solid green line - white rust hours based on Oklahoma Mesonet data.
- Solid blue line - white rust hour forecast based on National Weather Service ETA Model data.
- Black line and open circle - white rust hours based on Oklahoma Mesonet data for the same time period from the previous year.
- Red line and closed circle - 10-year average of white rust hours based on Oklahoma Mesonet data for the same time period.
Forecast Table
Table Columns:
- Time: In Central Daylight Time (CDT).
- Air Temperature: Hourly forecast of air temperature in Fahrenheit (°F).
- Relative Humidity: Hourly forecast of relative humidity (%).
- Wind Speed: Hourly forecast of average wind speed in miles per hour.
- Wind Direction: Hourly forecast of the prominent wind direction.
- Rainfall: Hourly forecast amount of rainfall in inches.
- White rust Hours: Hourly forecast of spinach white rust hours.
- Total White rust Hours: Forecast of the accumulating spinach white rust hours over the time period of the forecast.
Seasonal Table
Table Columns:
- Date: Calendar date based on CDT midnight.
- Daily White rust Hours: Daily spinach white rust hours for each calendar date.
- Total White rust Hours: Accumulation of spinach white rust hours for each day from September 15.
- Last Effective Spray Date: This date is calculated by determining the date from when 12 white rust hours have accumulated and then subtracting 7 calendar days for the 7-day fungicide control window period. If a fungicide has been applied since this date, another application is not necessary. If the last fungicide application was made prior to this date, a new application needs to be made.
- Maximum Air Temperature: Highest air temperature in Fahrenheit (°F) for each 24-hour period ending at CDT midnight.
- Minimum Air Temperature: Lowest air temperature in Fahrenheit (°F) for each 24-hour period ending at CDT midnight.
- Maximum Relative Humidity: Highest relative humidity in percent for each 24-hour period ending at CDT midnight.
- Minimum Relative Humidity: Lowest relative humidity in percent for each 24-hour period ending at CDT midnight.
- Rainfall: Recorded rainfall in inches for each 24-hour period ending at CDT midnight.
Statewide Accumulative White Rust Hours Map
This is an interactive, zoomable, color-contoured statewide map of spinach white rust hours accumulated from September 15 to the current date and hour for all Oklahoma Mesonet sites. The values displayed are the accumulated spinach white rust hours since September 15 for the Mesonet sites shown.
Historical Daily White Rust Hours Table
Table Columns:
- Day: Count of days from September 15.
- Date: Calendar date based on CDT midnight.
- Average Temperature: The current spinach season’s 24-hour average air temperature in Fahrenheit (°F) for each 24-hour period ending at CDT midnight.
- Average Humidity: The current spinach growing season’s 24-hour average relative humidity in percent for each 24-hour period ending at CDT midnight.
- Rainfall: The current season’s recorded rainfall in inches for each 24-hour period ending at CDT midnight.
- Total White Rust Hours: The current season’s accumulation of spinach white rust hours for each day from September 15.
- Daily White Rust Hours: The current season’s daily spinach white rust hours for each calendar date.
- Total White Rust Hours Last Year’s Season: The previous season’s accumulation of spinach white rust hours for each day from September 15.
- Daily White Rust Hours Last Year’s Season: The previous season’s daily spinach white rust hours for each calendar date.
- Total White Rust Hours 2 Years Ago Season: The season’s accumulation of spinach white rust hours for each day from September 15 from 2 years ago.
- Daily White Rust Hours 2 Years Ago Season: The season’s daily spinach white rust hours for each calendar date from 2 years ago.
- Total White Rust Hours 10 Year Average: The 10-year average of the season’s accumulation of spinach white rust hours for each day from September 15.
- Daily White rust Hours 10 Year Average: The 10-year average of the season’s daily spinach white rust hours for each calendar date.

DAILY REFERENCE DATA

Daily Table of All Mesonet Sites
Table Data for the Date selected (only dates from September 15 to May 15 are available):
- STID: Mesonet site identifier
- DINF: Spinach white rust hours for each 24-hour period ending at midnight CDT.
- TINF: Total spinach white rust hours accumulated from September 15 of the season selected.
- TMAX: Maximum air temperature in Fahrenheit (°F) for each 24-hour period ending at midnight CDT.
- TMIN: Minimum air temperature in Fahrenheit (°F) for each 24-hour period ending at midnight CDT.
- HMAX: Maximum relative humidity in percent (%) for each 24-hour period ending at midnight CDT.
- HMIN: Minimum relative humidity in percent (%) for each 24-hour period ending at midnight CDT.
- RAIN: Recorded rainfall for each 24-hour period ending at midnight CDT.
View Reference Data
This links to the reference data used by the spinach white rust model for the current and each of the previous ten years. Only the data for the date selected will be shown.
- Clicking on a “Date and Time” links to a table of all Mesonet locations for that date and time.
- Clicking on “Map” links to a color-contour map of accumulated spinach white rust hours for the date and time indicated.
- Clicking on “Graph” links to a graph of the air temperatures, relative humidity and white rust hours for each 15-minute period over the previous 18 days from the date and time selected.
  Table Data:
  - STID: Mesonet site identifier
  - STNM: Count of days since September 15.
  - TIME: Military time in CDT.
  - TAIR: Maximum air temperature in Fahrenheit (°F) for each time period.
  - RELH: Relative humidity in percent (%) for each time period.
  - INFH: Spinach white rust hours for each time period.
  - TINF: Total spinach white rust hours accumulated from September 15 of the season selected.

References
Sullivan, M.J., J.P. Damicone and M.E. Payton. 2003. Development of a Weather-Based Advisory Program for Scheduling Fungicide Applications for Control of White Rust of Spinach. Plant Disease, August 2003, 87:923-928.

Sullivan, M.J., J.P. Damicone and M.E. Payton. 2002. The Effects of Temperature and Wetness Period on the Development of Spinach White Rust. Plant Disease, July 2002, 86:753-758.

Trent, M.A. 2004. Etiology and Management of Spinach White Rust. Oklahoma State University Master of Science Thesis.

Watermelon Anthracnose Advisor

The Oklahoma Watermelon Anthracnose Advisor is a disease advisory that has been developed to aid growers in proper timing of fungicide applications for anthracnose. It runs from May 1 to October 31. Using the Oklahoma Mesonet, the state’s automated weather network, the model calculates daily “infection hours” for each Mesonet site. An infection hour is defined as one hour with relative humidity greater than or equal to 80% and air temperature between 68°F and 86°F. The advisory recommends a spray when 80 infection hours have accumulated since either the date of first male watermelon flowering or the last fungicide application.

The Site-Specific Interactive Advisor provides a spray or no spray recommendation. After selecting a Mesonet site, the advisory asks for the date of the last fungicide application or the date of the first male watermelon flowers. With this information the advisory makes a recommendation based on the number of infection hours that have occurred since the date of the first male flowers or last fungicide application.

Guidelines for using the Watermelon Anthracnose Advisor are:

Delay application of a first fungicide until symptoms of anthracnose appear or until the advisory recommends a first spray. Given no symptoms of anthracnose, the advisory does not recommend a spray until 80 infection hours after male flowers first appear.
If no anthracnose symptoms are present, once the watermelon plants have reached first flowering, the Oklahoma Watermelon Anthracnose Advisor should be checked on a regular basis. After any fungicide application, the advisory should be checked regularly beginning 5 days after the last spray date.
If a field cannot be sprayed within 3 days of advisory spray recommendations, then spray on a 14-day schedule.
Use an effective systemic fungicide (e.g., Benlate or Topsion) in combination with an effective protectant fungicide (such as Dithane, Pencozeb, or Bravo).
If more than 10% of leaves become diseased or defoliated, a more aggressive control strategy is needed. Apply fungicides every 7 days.
If downy mildew appears in the field, apply an effective fungicide (e.g., Bravo) every 7 days.
If more than 60 infection hours have occurred, apply a fungicide if rain is likely and no fungicide has been applied in the last 7 days.
Follow the instructions on all pesticide labels. Make special note of Òdays to harvestÓ spray restrictions.

The Oklahoma Watermelon Anthracnose Advisor has been designed to aid in scheduling fungicide applications. Other factors should also be considered in making such decisions, such as the market value of the crop, method of irrigation, growth stage of the crop, density of the foliage, history of anthracnose in the field, and time of year. The likelihood of an anthracnose outbreak may be higher when overhead irrigation is used or when foliage is dense. The Oklahoma Watermelon Anthracnose Advisor is a weather-based disease advisory to aid in making disease management decisions. It is not intended to replace the best judgment of the grower.

Wheat Growth Day Counter

The Wheat Growth Day Counter (previously Number of Days GDD>0) is a table that shows the number of days when wheat degree-day heat units were positive from a specified planting date. Degree-day heat units are based on a lower air temperature threshold of 40°F (4.4°C) and an upper air temperature threshold of 86°F (30°C).

The Oklahoma Mesonet uses the “Cutoff Method” to calculate degree-day values, based on the following formula:

Degree-days = (Maximum Daily Air Temp + Minimum Daily Air Temp)/2 - 40°F (4.4°C)

When the maximum daily air temperature is above wheat’s upper temperature threshold, the maximum daily air temperature is set to 86°F (30°C). Negative degree-day heat unit values are set to zero.

The Wheat Growth Day Count table shows the count of days with positive degree-day heat units accumulated from a specified planting date for a single Mesonet site. The fourth column shows the count of “Wheat Growth Days” for the Mesonet site selected for any corresponding “Date” in the first column.

For additional information on the OSU Nitrogen Use Efficiency, click the “OSU Nitrogen Use Efficiency” Agweather menu item in the “Wheat Fertilization” section.