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Weekly Field Crops Pest Report 2011

May 4, 2011, Volume 10 Number 1

  1. Welcome Back to Another Growing Season!
  2. Weather and Crop Highlights
  3. View from the Field
  4. Some Plant Disease Management Considerations in this Cool, Wet Spring
  5. Alfalfa Weevil—Now's the Time
  6. Black Cutworm and True Armyworm—Be on the lookout
  7. The Lady Beetle Challenge
  8. Growing Degree Days
  9. Clipboard Checklist
  10. Contact Information

Welcome Back to Another Growing Season!

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This issue marks the beginning of our tenth season for the Weekly Field Crop Pest Report.  We look forward to another exciting year sharing pest observations and information to help keep you informed of current pest conditions and management of field crop pests.  As always we appreciate hearing from you regarding your pest observations.

This year's newsletter almost did not happen… As most of you know, the existence of the New York State IPM Program was threatened during the most recent state budget process. During January, we learned that the Program would be forced to close as of March 31. However, during budget negotiations, some funding for the NYS IPM Program was restored. We are absolutely certain this would not have occurred without the tremendous support expressed by you, our stakeholders!! We are most grateful for all of your efforts. Although it is unlikely that this is the end of our IPM funding challenge, we do know that the Program is safe until the next state budget process. Thank you again. It is a pleasure to work with you all! We are looking forward to a great 2011 season.

Weather and Crop Highlights

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Highlights from: WEATHER AND CROPS, May 2, 2011. (Source: United States Department of Agriculture, National Agricultural Statistics Service, NY Field Office)

WEATHER: A mild, stormy and very wet week occurred across New York State. Severe thunderstorms produced damaging winds and tornadoes across the state during the mid week period and the heavy rain resulted in record flooding in some areas. Only the southeast corner of the state escaped the heavy rain and rainfall totals in those areas were generally under half an inch. Temperatures for the week averaged around 10 degrees above normal while precipitation averaged 2 to 4 times the normal rainfall for the week with the greatest amounts falling from the Great Lakes, Mohawk Valley and upper Hudson Valley Climatic Divisions northward.

CROPS: Another rainy week resulted in very little progress in fields across the state. There were 1.3 days suitable for fieldwork. Soil moisture was rated as 19 percent adequate and 81 percent surplus. Winter wheat condition was 4 percent poor, 42 percent fair, 52 percent good, and 2 percent excellent. Oat seedings were 7 percent completed compared to 79 percent last year and a 5-year average of 60 percent.

View from the Field

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Rain, Rain, Rain is the theme so far this spring. Wet soil and cool temperatures are keeping us out of the fields. So while it is raining we can gear up for dealing with the pests that plague us each year. On Friday April 22, I scouted the Cornell Research Farm in Valatie, NY. Tom Kilcer has a lot of active research going on at the farm this summer. The triticale plots looked very good and had little to no sign of diseases. The triticale that bordered the research plots had a lot of snow mold as seen in the photos below. A fungal mass can appear on the leaves. The colors of the masses are pinkish, whitish or even gray. If the fungus just infects the leaves the plant should recover. If the disease infects the crown then most likely the plant will die. Selecting the proper snow mold resistant varieties is very important when growing small grains. I have seen whole fields triticale and wheat (20 acres plus) lost to snow mold. Take a little time and research what varieties are resistant to specific diseases to small grains in NY.

Snow Mold (April 22)

snow moldsnow mold

While sweeping an alfalfa trial at the Cornell Farm in Valatie. I came across a lone alfalfa weevil adult. Alfalfa weevil adults migrate from the edges of the fields, hedge rows and under debris to feed on alfalfa. The females lay eggs inside alfalfa stems, eggs hatch and the larvae move up the plant to leaf buds to feed. Alfalfa weevil populations can build-up in alfalfa fields from year to year. In a wet spring like this one they can catch you off guard. Their threshold temperature for activity is about is 480F. If the first cutting is delayed due to factors like wet weather, alfalfa weevil may continue to feed cause significant crop injury.

I observed a lot of winter kill in alfalfa and clover at the Cornell Research Farm in Valatie on April 22. Sometimes when a field has a lot of winterkill growers think it is just a cold bad winter causing frost heaving. In fact, most of the time the alfalfa has been weakened by root diseases as viewed below. If the plant has a crown or root rot it cannot hold itself in the soil as a healthy plant. So in a winter like the last one we get a lot of diseased plants pushed out of the soil. The problem after that is that the open space left by the dead plant allows a gap for invasion by weeds.

Crown and Root Rot/Winter Kill (April 22)

crown & root rotcrown & root rot


Some Plant Disease Management Considerations in this Cool, Wet Spring

Gary C. Bergstrom
Cornell University

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Fungicidal seed treatment a must!
Seeds planted into cool, moist soil are at greater risk of seed rot, damping-off, and seedling blights.  All field crop seeds planted this spring should be protected with a broad-spectrum fungicidal seed treatment product, preferably one applied by your seed supplier to certified seed.   Planter box fungicides are also available.

Winter wheat
Prolonged cool soil temperatures this spring have been highly conducive for development of symptoms of soilborne virus diseases, Wheat spindle streak mosaic and Soilborne wheat mosaic.  Now is the time to assess soilborne virus diseases on varieties you grow and to consider planting resistant varieties this September.  [See What's Cropping Up? 2009. Vol 19 No. 3 Pages 1-2.]

Established alfalfa and spring seedings
High soil moisture, even in well-drained soils, is conducive for development of Phytophthora root rot.  For new seedings, it will be important to plant varieties with resistance to Phytophthora root rot.  Seed treatment with fungicides with water mold activity (those with metalaxyl or mefanoxam as active ingredients) provide protection against Pythium and Phytophthora at the seedling stage.  

Late-planted corn
There is a somewhat greater risk of foliar fungal diseases especially those such as common rust and northern leaf blight initiated by spores that may carried into fields by air currents from more distant sources.  Fields should be assessed for foliar fungal diseases at late vegetative stages prior to a fungicide application decision at tassel to silk emergence.

Alfalfa Weevil—Now's the Time

Keith Waldron

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Alfalfa weevil damage can vary year to year but one thing remains constant – early field monitoring helps head off weevil surprises before crop losses occur. Pre-first cutting is the time to watch for alfalfa weevil (AW). The larvae of this insect feed on alfalfa foliage leaving them stripped and in tatters. Fields with heavy infestations of alfalfa weevil can have a grayish appearance when seen from a distance. Weevil larvae range in size from 1/16 inch to 3/8 inch and initially are a yellow to green in color becoming greener as they increase in size. Weevil head capsules are black and the larvae have a distinct white stripe down the middle of their back.

alfalfa weevil

Monitoring for weevil is very simple. Walk through the alfalfa field, collecting 25 - 50 stems at random – taking care not to bias your sampling. Avoid sampling border areas. Check upper leaves of selected alfalfa stems for a tattered, shot-hole appearance that indicates weevil feeding. If one leaf in the top inch shows signs of AW feeding, that stem should be considered "positive" for AW. A decision to act is based on the percentage of affected stems. Before the first alfalfa cutting, control measures are recommended when 40% or more of the stems are positive for AW feeding. Base your decision to manage alfalfa weevil on the quality of the stand (% alfalfa), cost of treatment, and the number of days until cutting. Note that early cutting, if within seven to ten days of harvest will manage alfalfa weevil effectively and is the preferred option. If alfalfa is harvested early, examine stubble (particularly on plants in the windrow) for signs of weevil feeding four to six days later.
If fields had high infestation levels of AW larvae before the first cutting larvae may carry over into alfalfa re-growth and cause damaged. The ratio of observed cocoons to larvae indicates the relative age of the population. If more than 50% of the AW are in the cocoon stage, the population is maturing to a non-feeding stage and will no longer be a problem for this year. If the larvae are predominantly young, however, damage may be expected, especially if the weather is cool and dry. When assessing alfalfa weevil damage on stubble, check areas within and outside the windrows. Consider the presence of AW cocoons, the ratio of cocoons to larvae, and the number of parasitized cocoons found when making management decisions.

When to monitor for alfalfa weevil?
Alfalfa Weevil Stage (Degree Days*) for Peak (50%) Occurrence of Stage:
eggs hatch (280); instar (315); instar 2 (395); instar 3 (470); instar 4 (550); cocooning (600); pupa (725); adult emergence (815); * 48 F Base temperature.

Alfalfa weevil populations can be affected by several natural enemies including at least two parasitic wasps (Bathyplectes spp) and a fungal pathogen (Zoopthora phytonomi). Our wet weather and high relative humidity conditions are quite favorable for the Zoopthora fungus to develop an epizootic capable of significantly reducing alfalfa weevil populations. While monitoring fields, check for brown and shriveled infected larvae on tops of leaves or curled around the tops of alfalfa plants. Alfalfa harvest will concentrate larvae, including the infected ones, in the windrow where environmental conditions will continue to favor the development and spread of the fungus.
An interactive alfalfa weevil growth stage prediction model for a location near you may be found at NEWA Alfalfa Weevil.

Black Cutworm and True Armyworm—Be on the lookout

Ken Wise

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Indiana is reporting higher than ever levels of black cutworm adult moths captured in light traps over the past 2 weeks. Pennsylvania has also reported significant flights of black cutworm moths. Kentucky also reports very high levels of adult true armyworm moths captures. While we have not heard reports of these two pests in NY so far this season, it would be prudent to keep on the lookout for them. Both of these insect pests migrate on storms from southern regions to the northeast. We have certainly had our share of storms already this season. This means there is a good chance that adult moths may already be here. Both of these pests prefer grasses like small grains, pasture, grass hay, and corn. Corn fields with grass weeds can be at particular risk because the moths will lay eggs on the weeds. Black cutworm moths are attracted to chickweed as egg laying sites. Be attentive to potential armyworm problems in wheat and corn, especially when the latter is adjacent to wheat or planted into a rye cover crop, a preferred egg laying site. Once the larvae hatch and weeds are sprayed the larvae will turn their attention to the corn. Our delayed planting season will shorten the interval between herbicide applications and corn planting / emergence creating the opportunity for larvae attracted to weeds to bridge over to young corn plants.

Black Cutworm larvae vary in color from light gray to black with a pale brown to black head. Larvae have a greasy, shiny appearance with coarse granules present over their body. During the day larvae burrow into the soil next to the corn plant. These larvae curl into a "C" shape when disturbed.

black cutworm

True armyworm larvae appear smooth, cylindrical, and pale green to brownish when they are still small. Mature larvae are smooth and marked with two orange, white-bordered strips on each side. True armyworm ranges in size from 1/8 inch to 1.5 inches long. There is a website with a photo of armyworm: Armyworm photo.

Early detection is the key to avoiding crop losses. Both armyworm and black cutworm feed at night. Signs of armyworm feeding are chewed leaves, cut stems, lodged plants, pellet-like frass on the ground, and larvae hidden under plant canopy and surface residue. Black cutworm symptoms of damage are leaf feeding, irregular holes in stem, notched and cut or missing plants. Black cutworm will bury itself in the soil directly next to the plant during the day. They can also be found under crop residue on the soil surface.

You should start scouting small grains now and corn when it starts to emerge every 3 days to 5 days. Scout for larvae when they are less than 1/2 inch long. If there is at least 5 to 10% damage an insecticide could be justified. The distribution of armyworm and cutworm in fields is often patchy. Many times they infest the edges of fields. Treat only the affected area and a 20 to 40-foot border around the infestation. Rarely does a whole field need to be treated. Larger larvae, greater than 1/2 inch long, are much more difficult to control. These large larvae are also more tolerant of insecticides, reducing the effectiveness and economic viability of this option.

The Lady Beetle Challenge

Ken Wise

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Many of you know I like to monitor lady beetles in my weekly scouting efforts. I like to take photos of any species I find. You many know our state insect the 9-spotted ladybeetle has seemed to become extinct in NY. Some think that species of lady beetles that have been released in the NE from other parts of the world may have replaced it in the environment. I am looking to be the first to find this insect in NY since it disappeared. You want to try to find it before me…. Join Dr. John Losey (Cornell University) "Lost Lady Bug Project". This project documents species of ladybeetles across the country.

multicolored asian ladybird beetle

Multicolored Asian Lady Beetle (Harmonia axyridis) eating soybean aphids

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

Clipboard Checklist

Keith Waldron

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*Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks
*Note and record location of wet areas on field maps or aerial photo for future tiling considerations and crop decisions, check for areas of soil erosion
*Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
*Minimize field to field movement of soil and crop debris on equipment, particularly from field with known pest problems such as white mold and Phytophthora.
*Watch for early season weeds: winter annuals, chickweed, henbit, field penny cress, shepherd's purse, giant and common ragweed, lambsquarters, redroot pigweed, velvet leaf, Pennsylvania smartweed, common sunflower, quackgrass, foxtail

*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 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

*Prepare land and plant corn as soon as conditions allow
*Pre-plant weed evaluation, timing cultivation and/or pre-plant weed management
*Monitor for slugs, seed corn maggot, black cutworm, common armyworm, seedling blights, foliar diseases, nutrient deficiencies

*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