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Weekly Field Crops Pest Report 2012

April 19, 2012, Volume 11 Number 1

  1. View from the Field
  2. Reports of Large Numbers of Black Cutworm Moths
  3. A Mild Winter and Insect Pests in Field Crops
  4. Alfalfa Weevils on the Move
  5. Clipboard Checklist
  6. Contact Information

View from the Field

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It is that time of year again when we pull out the sweep nets, pocket our 20x hand lens, throw collection vials, shovels, soil probes, soil thermometers, tape measures, and pest related resources into the vehicle and head to the field.  The question will be what will we find this season? Soybean aphids, gray leaf spot, western bean cutworm, common ragweed, Asian soybean rust, brown root rot, brown marmorated stink bug, potato leafhopper ... and so on? This means it is time to start the NYS IPM Weekly Field Crops Pest Report. As you may already know this is the 11th year of the publication. This publication would not exist without your help and observations from the field. When we all share information it strengthens our pest related alerts and efforts statewide. Besides being published here at this website, this publication will be sent to the field crop list serves at Cornell University each week. In addition, an announcement regarding each issue will be posted on the  field crop extension blog at the field crop extension home page. Again welcome back and happy scouting!
On April 10 I found an alfalfa weevil adult in an alfalfa field at the Cornell Research Farm in Valatie. As it warms up again we will start to see more adult alfalfa weevils entering fields.
While scouting alfalfa at the Cornell Research Farm in Valatie, NY I came across an unfamiliar weed in the field. It is European Field pansy, Viola arvensis. This is a winter annual. Field pansy is normally 4 to 12 inches tall and have a white/yellow flower. It is considered an invasive species in the US.

field pansy
Field pansy, Viola arvensi

Nathan Herendeen reports finding cereal leaf beetle eggs on winter wheat this week. The eggs can be found on the upper surface of the leaves near the midrib. Eggs are elongate, yellow to brown and about 1/16 inch long and are laid in chains of two or three.
Keith Waldron reports finding alfalfa weevil adults in alfalfa in Geneva, NY. He also observed several species of winter annuals in alfalfa.

Reports of Large Numbers of Black Cutworm Moths

Ken Wise, NYS IPM

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There have been reports of large numbers of black cutworms caught in pheromone traps in states to the south and south west of New York. Some of them are the highest initial captures on record. The question is will this cause New York growers problems? Even when you have a large flight of moths does not always mean you will have damage in your fields. Black cutworm moths have to travel on weather fronts from the south and southwest to find their way here to NY. Then they have to find grasses to lay their eggs on. If you have controlled your weeds early in the season you have greatly reduced the risk of black cutworm damage. If there are no winter annuals like chickweed and mustards in the field there is no habitat for them to lay eggs on. We will discuss more on black cutworm in the next issue. For more information on black cutworm please refer to our brochure: Black cutworm in field corn Management Guide.

A Mild Winter and Insect Pests in Field Crops

Ken Wise, NYS IPM

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A mild winter and record breaking early spring temperatures stirs the question "How does this affect insect pest issues in field crops?" I have been asked often how a mild winter or early spring will affect an insect pest population. Many speculate that because we have had mild winter conditions suggests that insect pest pressure will be higher this growing season.  There are a few other factors to consider when looking at an insect pest population than just mild winter conditions.
Spring and summer weather patterns, natural enemy populations and crop development can also affect a pest population.  Even if you have a high population of a certain pest the conditions may not be good for its continued development. It is important to remember that scouting and IPM leads to correct informed decisions in regard to a pest. 
We have two kinds of insect pests that can affect field crops in New York. There are those that overwinter here and those that migrate on weather patterns from the south or southwest. Let's start with the insect pests that overwinter in New York. It is important to know how certain insect pest may overwinter. An example is that insect pests that overwinter in the soil are less affected by any extreme conditions whether it is mild or very cold. These insect pests include corn rootworm (eggs in soil), western bean cutworm (pre-pupa in the soil) wireworms (larvae in soil) or white grubs (larvae in soil). Being under the soil surface protects these insects from the above ground environmental conditions.
Alfalfa weevil overwinters in hedgerows and field margins as an adult. A mild winter might help more of the adults to survive. The areas in the fields that warm earlier are the places to check. South facing slopes and hill tops are a good place to look for early weevil activity.
One insect pest that might benefit from a warmer winter is corn flea beetle. Corn flea beetle overwinters as an adult in grasses near fields. Research has shown that this pest does survive better with mild winter conditions. Corn flea beetle is the vector for a bacterial disease called Stewarts wilt in both field corn and sweet corn. The good thing is that most field corn hybrids have resistance to Stewarts wilt.
European corn borer (ECB) overwinters as a larva in corn stubble from the previous season. While they are larvae in stubble on the soil surface ECB are very adapted for surviving either very cold or mild winters.  Spring and summer weather conditions and natural enemies can affect ECB populations. Weather must be favorable for emerging ECB adult moths to fly from the field to find corn and oviposite eggs.  Research suggests that ECB larvae hatching on corn in the early whorl stage do not survive as well as later. This is because there is higher concentration of a natural feeding deterrent called "DIMBOA."
Soybean aphids overwinter as eggs on buckthorn. A mild winter might help their survival, although they are well adapted to surviving very cold winters. If spring conditions also favor the development and distribution of natural enemies this could help maintain a lower population.
Insect pests like black cutworm, true armyworm, and potato leafhopper all have to migrate to New York via weather fronts from the south and southwest. Migratory insect pests have several factors affecting their development. First they must have favorable conditions for overwintering in the Southern United States. Next are there natural enemies helping control the insect pest population? The pest must have weather fronts to migrate north and find their host plants. After taking a long journey from the south they have to have conditions and crops favorable for their development. Currently, many of the corn hybrids and alfalfa have resistance to these migratory insect pests. Much of the corn is genetically modified (Bt gene) for resistant to black cutworm and armyworm.  Many cultivars of alfalfa are highly resistant to potato leafhopper.  (On a side note I was reading that the University of Kentucky caught 49 true armyworm moths for the week ending on Friday March 9th. They state that this was the largest initial capture of moths in pheromone baited traps in 19 years of monitoring. ) What does this mean to us? It means that there may be an early jump in the population to armyworms in Kentucky. It may or may not mean anything to us…. You need to get out in the fields and LOOK for the pest!  Remember both armyworm and black cutworm like grassy weeds in fields to lay eggs on.  Fields with good early weed control reduces the risk of moths laying eggs in them.
It is very difficult to predict what a mild winter and early spring can do for an insect pest population.  Spring and summer weather conditions have just as much to do with insect survival as a mild winter. Planting dates and crop development also play a large role in an insect pest population. The best thing to do is to be out there monitoring your crops for pests.  Use the principles of IPM so you can make well-informed decisions on management issues over the coming growing season.

Alfalfa Weevils on the Move

Ken Wise, NYS IPM

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There have been reports of early sightings of alfalfa weevil in alfalfa fields this season. Alfalfa weevils over winter as an adult. When the weather gets warmer in the spring they start to move back into the alfalfa fields. If you do not know what they look like they are light brown weevils that are 3/16" long They have a band of darker brown down the center of their back with a long snout as seen in the photo below:
alfalfa weevil adult

Adult Alfalfa Weevil

The adults will feed on alfalfa leaflets and lay eggs into new stem tissue in the plant. The eggs are hard to find. Look for tiny pinholes in the stem. These are where the female weevil has chewed a small hole and lay her eggs in the hollow stem cavity. These eggs are bright yellow but very small. As the eggs mature they start to darken. Each female can lay up to 25 eggs/stem and as many as 500 to 2000 eggs per season.  Depending on the temperature the eggs generally hatch in one to two weeks.
Calculating alfalfa weevil activity. By calculating the number of alfalfa weevil heat units you can predict the different life stages of the weevil.
Things you will have to know are the maximum and minimum temperature data from March 1 through the current day. Take the high and low temperature of each day and divide it by 2 and subtract 48 degrees F. This will give you the number of heat units for an individual day. If it is a negative number then there were no heat units that day for alfalfa weevil to develop.
(High Temperature + Low Temperature / 2) – 48 F = AW heat units.
Keep a running tally of the accumulated heat units from day to day. Compare the total GDD's and compare this number against the expected alfalfa weevil growth stage from the following table.

Instead of doing all those long drawn out calculations let NEWA do it for you! NEWA is short for Network for Environment and Weather Applications. This website has a function that will calculate the alfalfa weevil heat units for your region or area of the state. NEWA's page for Alfalfa Weevil GDD Reports.

CURRENT Accumulated Growing degree days (48F Base):

March 1 - May 2, 2011

Base 48 F
Base 50 F
*Indicates missing data
source: NEWA's Degree Day data page

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, purple deadnettle, 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 adjust crop plans if necessary
*Monitor alfalfa for alfalfa weevil
*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, weed issues, 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

*Prepare land and plant corn as soon as conditions allow
*Pre-plant weed evaluation, timing cultivation and/or pre-plant weed management

*Check and mend fences as needed.
*Check crop growth
*Invasive species, plants harmful to livestock
*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 stored grain bins for temperature, moisture and signs of mold and insects. Aerate, core, transfer grain or treat as necessary
*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