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Weekly Field Crops Pest Report 2007

May 23, 2007                Volume 6 Number 6

1. View from the Field

2. Where are the Alfalfa Weevils? The Role of Biological Control

3. Russ’s Weed Alert - Impact Herbicide

4. Seed Corn Maggot the Invisible Thief of Corn Seed!

5. Growing Degree Days and Alfalfa Weevil Development in NYS

6. Clipboard Checklist

7. Upcoming Events

8. Contact Information

View from the Field


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Western NY and Finger Lakes
Julie Dennis, NYS IPM

Wheat fields that I have walked this week are pretty short.  Thanks to the recent dry weather, diseases are hard to find, even on the lower leaves.  Generally, the upper 3 leaves of wheat that I’ve observed are very clean and healthy.  I did see a few plants with yellow dwarf (see photograph). Yellow dwarf symptoms include yellowing of leaf tips, sometimes progressing to red or purple colors. Several species of aphids common in New York transmit yellow dwarf. If winter wheat was planted early in the fall, aphids may have had time to infest and infect plants.

Cereal leaf beetles are few and far between.  I observed one adult, but no eggs or larvae.  The ground is getting pretty dry. One field had abundant chickweed and corn cockle. 

Eastern NYS

Ken Wise

At a recent organic field crop TAg meeting in Essex county a grower asked, “Why is my alfalfa getting field pennycress?” As we dug into the issue it appeared that the pennycress was only in areas where seeding errors had apparently been made. Meaning the weeds established where there was open ground and did not have to compete with the alfalfa. This is true for most weeds that start to grow in alfalfa fields.  I have also seen a lot of white cockle in the fields where openings have occurred this year. The picture below was taken at the Cornell Research Farm at Valatie where an opening was left between to two clover varieties. The strip has a lot of field pennycress and some white cockle.

I am starting to see more alfalfa weevil larvae at the Cornell Research Farm at Valatie. There is still less than 10% tip feeding by larvae. There were 1st, 2nd and 3rd instar larvae in the fields. Remember, it is the 4th instar of alfalfa weevil larvae that does most of the damage to alfalfa. A 4th instar larva consumes 80% of all the forage the developing alfalfa weevil will consume over the course of it's lifespan.

Where are the Alfalfa Weevils? The Role of Biological Control

Julie Dennis

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Reports of alfalfa weevil (AW) adults and larvae have been slow to roll in this year.  Growing degree day accumulations are still lower than usual for this time of May, but other factors contribute to low numbers of AW, too. Biological control is a major factor. Several parasitic wasps and fungal pathogens are responsible for keeping AW numbers in check every year in NY.

Within 10 years of the arrival of the invasive alfalfa weevil in the US in the late 1940s, USDA scientists began releases of parasitic wasps to combat this pest.  A parasitic wasp lays an egg in an AW larva, thus killing the larva of the pest insect and providing the food source for a growing parasitic wasp. How do we know if these wasps are helping us out in our fields? One of the revealing times to look for alfalfa weevil parasitoids is when they are in the pupal stage. While searching for alfalfa weevil pupae later this month or in early June, keep your eyes out for the parasitoid pupae, too. Alfalfa weevil pupae can be found inside small net-like, pea-sized cocoons generally found in lower regions of the plant on or 2-3 inches above the soil surface. The alfalfa weevil pupa is surrounded in a white to tan webbing, often associated with a leaf, and a wasp pupa is instead surrounded by a small hard brown capsule-shaped pupal case (see photos). Enclosed in the brown case is the wasp pupa, which has grown up using the alfalfa weevil larva as its food source.

Alfalfa weevil pupae

Pupae of parasitic wasps of Alfalfa Weevil

Don’t forget to review the NY alfalfa weevil scouting guidelines in our online publication: Alfalfa Weevil Management Guide

Russ’s Weed Alert - Impact Herbicide

Julie Dennis

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This week, Russ Hahn, Weed Scientist with the Cornell Department of Crop and Soil Sciences, provides us with an update on a new herbicide available for the 2007 season.  “NY State Department of Environmental Conservation recently approved the registration of Impact Herbicide for use on field and sweet corn,” says Russ. “Many NY corn growers are familiar with another herbicide, mesotrione, with the same site of action” as Impact.  “Mesotrione is the active ingredient in Callisto and a component in Lumax and Lexar,” explains Russ.  Both of these herbicides turn susceptible weeds white, and then tissue necrosis and death follow. 

Where will Impact fit in to corn production in NY?  Russ tells us that “While Callisto can be used both pre-emergence (PRE) and post-emergence (POST) in corn, Impact is registered for POST use only.  Impact is a 2.8 lb/gal suspension concentration (SC) with a normal use rate of 0.75 fluid oz/A.  For best performance, Impact should be tank-mixed with atrazine at 0.25 to 1.0 lb ai/A.  It can be applied from the spike stage of corn up to 45 days prior to harvest.  Applications should be made in a minimum of 10 gallons per acre of water and must include a methylated seed oil (MSO) or crop oil concentrate (COC) and a nitrogen fertilizer source such as urea ammonium nitrate (UAN) or ammonium sulfate (AMS).

“Impact has excellent activity against many summer annual broadleaf weeds such as velvetleaf, pigweed, common ragweed, common lambsquarters, and wild mustard.  It also provides significant burndown activity against giant foxtail and crabgrass and should provide partial control of other summer annual grasses like green and yellow foxtail and fall panicum. Experiments conducted the past two growing seasons suggest that Impact should improve the annual grass activity of residual premix or tank-mix combinations (ie. Bicep Lite II Magnum, Prowl H2O + AAtrex, etc.) that are applied early POST rather than PRE.  Impact might also prove beneficial in total POST weed control programs when Steadfast products are used with conventional hybrids or in Roundup Ready or Liberty Link corn weed control programs,” says Russ.

Understanding the site of action of Impact herbicide has important implications for resistance management.  Russ explains, “The 4-HPPD site of action (Group 27 Herbicides) is only one of two new target sites for herbicides introduced since 1991.  During this period, about two-thirds of herbicide introductions have been either PPO inhibitors (Group 14 Herbicides like Reflex, Resource, etc.) or ALS inhibitors (Group 2 Herbicides like Steadfast, Permit, Python, etc.).  While only three weeds have developed resistance to PPO inhibitors, 93 weeds have developed ALS-resistant populations.  To date, there are no confirmed cases of resistance to the new 4-HPPD inhibitors and lab studies indicate that the likelihood of developing 4-HPPD resistance is low.”  For more information about herbicides and site of action Groups, see Table 8.5 in the Cornell Field Crop Guidelines

For more information on Impact and other herbicide research results, mark your calendar to attend the Aurora Weed Field Day on July 11th.

Seed Corn Maggot the Invisible Thief of Corn Seed!

Ken Wise

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Seed corn maggot (SCM) is an insect pest that feeds on large seeded crops like corn and soybean. An adult female fly searches for moist soil cracks, high organic matter, decomposing plant material, fields with manure and germinating seeds in which to lay their eggs early in the spring. Maggots hatch from the eggs and feed by burrowing into germinating seeds. These maggots are tapered, legless, appear to be headless, pale yellowish-white, and reach a length of about a 1/4 inch long. Symptoms of SCM damage may show as skips in the corn rows or as "snake heads" i.e. seedlings without cotyledons. Proper diagnosis requires some digging in the gaps within a row to check for seeds and on seed health. Prevention is the key to control this insect pest by using an insecticide planter box seed treatment or pretreated seed. For more information checkout Early Season Insect Pests of Corn (1016k pdf file).

Growing Degree Days and Alfalfa Weevil Development in NYS

Ken Wise

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Growing degree Days for peak (50%) Occurrence of Alfalfa Weevil growth stage:

Stage or Event

Accumulated growing degree days (48F base temperature)

Eggs hatch


Instar 1


Instar 2


Instar 3


Instar 4






Adult Emergence


(Note: for alfalfa weevil predictions use Base Temp of 48F)


Base 48

Base 50







Clifton Springs












Clipboard Checklist

Keith Waldron

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• Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.

• Watch for early season weeds, any patches of herbicide resistant weeds?

• Storage areas cleaned and ready to accept upcoming hay harvest?


• Determine plant populations, make notes on germination problems

• Gaps in row? Check for seed corn maggot, wireworm, seedling blights, birds, seed placement issues?

• Monitor for weeds, note presence of “who”, “how many” and “where”

• Adjust post emergence weed control actions

Small Grains:

• Monitor winter grains for crop stage, insect and disease problems

      - evaluate crop for adequate stand and plant vigor

Alfalfa & Hay:

• Monitor alfalfa seedings for weeds, insects & diseases.

• Check established alfalfa stands for alfalfa weevil, weed and disease problems.

• Timothy stands: check fields for symptoms of cereal rust mite

• Storage areas cleaned and ready to accept upcoming harvest?


• Field preparations, planter ready, Rhizobium inoculum?

Dairy Livestock Barn Fly Management:

• Sanitation, sanitation, sanitation – clean animal resting areas, feed troughs, minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard

• Check waterers, drainage, roof gutters for leaks and potential overspill

• Begin fly monitoring: install “3X5” index card fly speck monitoring cards through out barn

• Order fly management materials: fly tapes, insecticide baits, natural enemies (parasitoids)


• Note any repairs needed for recently used equipment: tractors, tillage implements, planters, etc. as they are cleaned and serviced.

• Service corn planter as needed. alfalfa harvesting equipment, and tillage implements

• Soybean planter and alfalfa harvesting equipment ready?

• Calibrate manure spreaders - maintain records on amount spread per field

Upcoming Events


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Poplar Ridge Road, Aurora, NY
Thursday, June 7, 2007
Coffee at 9:30 AM
Program 10 AM to Noon

-2007 Crop Development/Management/Pest Overview
-Planting Rate Recommendations
-View Winter Wheat Variety, Fungicide, Seed Treatment, and Seed Rate x Planting Date Plots
-Small Grain Varieties for New York
-Introduction of New Soft White Wheat with Scab- and Sprout-Resistance
-Integrated Management of Fusarium Head Blight (Varieties, Fungicide, Biological Control)
-A Farmer's Tools for Early Harvest and Minimizing Sprout Damage and Mycotoxins
Stored Grain Pest Management Update
-Perspectives of Growers, Extension Educators, Consultants, Seedsmen, Agrichemical Co. Reps, and others

Contact Information


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Julie Dennis: IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411

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