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Weekly Field Crops Pest Report 2011

May 12, 2011, Volume 10 Number 2

  1. View from the Field
  2. Crop and Weather Update
  3. Biological Control with Parasitoids on Alfalfa Weevil
  4. Wet Spring Season Corn Pests: Diseases, Slugs and Maggots
  5. Growing Degree Days
  6. Clipboard Checklist
  7. Contact Information

View from the Field

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Since we have had few warm dry days the soil has dried enough to let growers plant some of their corn acreage.
Pest reports from the field have been light this week. A few sightings of alfalfa weevil, some wheat fields with signs of wheat spindle streak mosaic virus, others with cereal leaf beetle and Canada geese in wheat. Some alfalfa snout beetle activity reported in Lewis and Jefferson counties.

Our cool wet spring conditions suggest several pest issues should be on our watch list once corn and soybeans are planted. Seedling diseases, slugs and seed corn maggot can all cause some problems with corn and soybeans. The weather forecast calls for more storms and rain over the next week that can potentially bring certain pests to the area like: black cutworm, armyworm, and potato leafhopper. States to our south and southwest are reporting high catch counts of black cutworm and armyworm moths. These two pests can ride weather fronts to the NE. Once here, they lay their eggs in weedy fields. Wet conditions have delayed much field activity and weeds are actively growing. Potentially, armyworms and black cutworms lay their eggs on these weeds. Once the weeds are controlled and the corn is planted these pest switch over to feeding on the corn.

Field monitoring will be important over the next several weeks. If black cutworm and armyworm are found early control, if needed, can be limited to spot treatments, heading off potential impacts. We'll provide pest updates as we hear them! Stay tuned!

Weather Outlook

May 12, 2011

Jessica Rennells, Northeast Region Climate Center, Cornell University

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A very wet month! Some stations had a record breaking April. The entire state had above normal precipitation, up to 6 inches above normal in some areas. The past week has been much closer to normal. Most of the state ranged from 0 to half an inch. Clinton and Franklin counties saw up to an inch. Our temperatures have been more seasonable but the week as a whole was 0 to 6 degrees below normal for the state. Overnight temperatures have been cool with some areas getting frost. The average date of last frost is approaching, ranging from the end of April to the end of May. Check out our home page for a graph of normal last frost.

Almost the entire state has had less than 25 growing degree days this week. Today's highs will range from the upper 60's to near 80. Tonight's temperatures will range from the upper 30's in northern NY to the low 50's. Friday will again be in the upper 60's to upper 70's but with showers and thunderstorms for western NY and moving into central and northern NY in the afternoon. Friday night will be in the 40's with a chance of light showers for all of the state. Saturday will be cooler but seasonable with highs in the upper 50's to near 70 with rain likely as a low pressure system tracks northeastward from the Ohio Valley. Lows will be in the 50's. Sunday highs will be in the mid 50's to mid 60's with rain likely again. Overnight temperatures will be in the mid 40's to low 50's. Monday will be in the mid to upper 50's and low 60's with a chance for showers. Lows will be in the upper 40's and low 50's. Tuesday's temperatures will be in the mid 50's to mid 60's with a continued chance for showers. Lows will be in the mid 40's to low 50's. Wednesday's highs will be in the upper 50's to mid 60's with a lingering chance of precipitation. Lows will be in the upper 40's to low 50's.

The five day precipitation amounts will range from 1 to 2.5 inches. The 8-14 day outlook is showing above normal temperatures and normal precipitation. Heavy rain in expected this weekend with widespread flooding in the Champlain Valley.

Biological Control with Parasitoids on Alfalfa Weevil

Ken Wise

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Several decades ago alfalfa weevil used to be the most damaging insect pest of alfalfa in the US. There are three different strains of alfalfa weevil in the US. The western strain introduced into Utah (1904), the Egyptian strain introduced into Arizona (1939) and the eastern strain introduced into Maryland (1951). In NY, we have the eastern strain of the alfalfa weevil (AW). A pest introduced to a new location that has no natural controls is considered an exotic or invasive species. USDA determined to help to manage alfalfa weevil in the long term they would need to find and release natural enemies from their native habitat in the Near East and Central Asia. In 1957, the USDA released several species of parasitoids in the US to control AW. Of the original releases Bathyplectes curculionis was the only one to effectively establish and parasitize AW. The USDA made a second release in 1980 and several more species established. We have 2 species common to controlling AW in NY. These are Bathyplectes curculionis and Bathyplectes anurus. Both are minute sized parasitic wasps that lay eggs in the prepupa of AW. The releases of parasitoids in North America were able to take a very serious pest and reduce its damaging impacts on alfalfa. While you can still have damage from AW weevil it is far less that before the parasitoid releases. You can see the biological control in action by looking at several of the pupa. At about 600 AW degree days look for the cocoons and alfalfa leaflets as in the photo below:

alfalfa weevil coccoon

Alfalfa weevil cocoon

Open the cocoon and if the weevil is healthy you will find a nice green colored soft-bodied alfalfa weevil. If parasitized, you will only find a small (1/8 inch long) mahogany colored pupa cocoon of the wasp that parasitized the weevil. Bathyplectes cocoons may or may not have a white line around the circumference of the cocoon. You can distinguish between Bathyplectes curculionis and Bathyplectes anurus species inside the pupa. Bathepletes anurus has a raised white band while B. curculionis is not raised.

Bathepletes pupa

(Batheplectes species cocoon-white middle stripe on pupa compared to two alfalfa weevil larvae).

I did a small study 9 years ago on the percent the pupa that were parasitized. After collecting about 200 pupa 65% of them were parasitized by Batheplectes species. So biological control is at work on AW in NY.

Wet Spring Season Corn Pests: Diseases, Slugs and Maggots

Ken Wise

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Wet spring? According to the Climate Center at Cornell University in many areas of the state we are 6 inches above normal in precipitation. Wet cool springs have potential problems for corn planted into wet soil. Since the temperature is cool the soil temperature is also lower than normal. Once seed is planted it will not emerge quickly. The longer the seed stays in the ground the chance of getting seed decay or seedling diseases increases. Early season corn seed and seedling diseases can reduce plant populations, thus reducing yields. Some expected yield losses can range from about 5% to 10%. If your average silage harvest is 20 tons/acre, a 10% loss in yield would be 2 tons/acre. The following is how to identify early season seed and seedling diseases. Seed decay is caused by a number of soil-inhabiting fungi such as Pythium, Fusarium, Diplodia, Rhizoctonia and Penicillium. The fungi can infect seed before it germinates causing mortality. Seeds infected with decay fungi are discolored and soft. Many times fungal material may grow on the seed. Often when the seed has rotted it may be completely decomposed and cannot be found. Sometimes the seed may germinate and grow but will die as the plant emerges from the soil. Seeding blights are caused by many of the same fungi that cause seed decay. Seedling blight symptoms include discolored seedling coleoptiles and roots. Seedlings may have a wet, rotted appearance before they reach the soil surface. Above ground symptoms of blight may include seedlings that turn yellow, wilt and die.

We often forget about potential problems with slugs. In wet cool springs slugs can cause significant damage to corn and soybeans. Slugs thrive in wet cool weather that can cause damage to early season corn with stand reductions. Slugs over-winter as eggs. They like a cool wet habitat and habitats with crop residue. Conservation and no-tillage systems can be at particular risk from slug damage. Slugs attack seedling and the lower leaves of the young corn plants. They feed on the leaf leaving irregular holes and slime trails.

Seed corn maggot can be a problem in cool wet springs. If the seed sits in the ground and germination is slow the maggot can infect the seed. Small flies (much like a house fly) will lay eggs in fields that have received manure or have crop debris for the year. The eggs will hatch and the tiny maggot will find the seed and bore in. The maggot will eat the inside of the corn seed. These maggots are tapered, legless, appear headless, pale yellow-white and reach about a 1/4 inch long.

Growing Degree Days

Keith Waldron

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CURRENT Accumulated Growing degree days (48F Base):

March 1 - May 2, 2011

Base 48 F
Base 50 F
*Indicates missing data
Data from NEWA

Alfalfa Weevil Prediction Model: A website at NEWA can predict alfalfa weevil development in your area:NEWA Alfalfa Weevil. Just select a weather station near you and it will give you the AW degree days.

Clipboard Checklist

Keith Waldron

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*Emergency contact information ("911", local hospital, Chem. Spill emergency contact, other?) posted in central posting area
*Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks.
*Observe wet areas and plot on aerial photo of farm for future drainage considerations and crop decisions
*Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
*Watch for early season weeds: winter annuals: chickweed, henbit, purple deadnettle, field penny cress, shepherd's purse; annuals: giant ragweed, lambsquarters, Pennsylvania smartweed, common sunflower

*Evaluate stands for plant population (stand count)
*Evaluate established legume stands for winter damage (thinning stand, frost heave), determine average alfalfa stand count, flood damage adjust crop plans if necessary
*Monitor alfalfa for alfalfa weevil as weather continues to warm
*Monitor new seedings for Pythium blight and Phytopthora Rot Rot.
*Monitor alfalfa for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)

Small Grains:
*Monitor winter grain fields for over wintering survival, check growth stage, number of tillers,
*Check stands for soilborne virus diseases, Wheat spindle streak mosaic and Soilborne wheat mosaic and powdery mildew symptoms, cereal leaf beetle, weed escapes, goose damage

*Pre-plant weed evaluation
*Prepare land for corn if it is dry enough and begin planting this week if possible (even if it is cold!)
*Using a Bt hybrid? Have a refuge plan?
*Evaluate plant population, emergence

*Pre-plant field / weed evaluation
*Evaluate plant population, emergence

*Check and mend fences as needed.
*Check crop growth
*Invasive species, plants harmful to livestock, common armyworm
*Review/Plan rotation system

*Remove / clean soil and crop debris from equipment
*Arrange for custom weed control or check your own application or cultivator equipment for repairs.
*Check nozzles, pumps, etc., recalibrate pesticide application equipment before use.
*Carry appropriate / necessary NYS DEC and EPA required documents: (pesticide applicators license, pesticide labels, MSDS sheets, etc.) with application equipment
*Calibrate planting equipment - maintain records on crop planting rate per field
*Calibrate manure spreaders - maintain records on amount spread per field

*Check forage allocation and anticipate feed program adjustments as forages from previous year are used up
*Plan where forages should be stored for optimum allocation next feeding season

Contact Information

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Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316