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NY Weekly Field Crop Pest Report, 2005

May 12, 2005 Volume 4 Number 4

1. View from the Field

2. Alfalfa Weevil Management: Beneficial Insects on Our Side

3. Powdery Mildew on Wheat

4. Black Cutworm Management-Field Corn

5. 2005 Asian Soybean Rust Status

6. Spotted Lady Beetle a Native Predator

7. Early Season Leaf Spots on Alfalfa

8. Potato Leafhopper Challenge -Alfalfa

9. Accumulated Growing Degree Day-NYS

10. Clipboard Checklist

11. Contact Information

View from the Field

Julie Stavisky, NYS IPM

Ken Wise, NYS IPM

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Western NY and Finger Lakes:

Winter wheat fields observed this week are on the verge of reaching the jointing stage.

Alfalfa fields planted during our warm spell in April are peeking through the ground.

Established stands of alfalfa are teeming with alfalfa weevil adults. I observed mating adults, but have yet to see eggs or larvae. Pepperweed and chickweed are very abundant.

I went in search of hatching soybean aphids on buckthorn, but no aphids were evident. Nearby states are reporting that soybean aphid eggs have begun tohatch over the past couple of weeks, so I’ll keep searching.

Organic Wheat and Soybeans in Essex County

Anita Deming and I are going to be working with organic field crop producers relative to wheat and soybeans. We plan to have a meeting a month to cover specific pest and crop management issues organic producers face with their field crops.

Alfalfa in Eastern NYS

Alfalfa is looking good and is 5 to 10 inches tall depending on the field. I have not seen too much alfalfa weevil activity yet. I have only caught a few adults. I did see clover leaf weevil larvae. They look very similar to alfalfa weevil larvae. The clover leaf weevil larvae are green with a white strip bordered by pink or red down the center of their backs. Alfalfa weevil does not have the bordered pink of red along the white strip. This larvae has a brown head while alfalfa weevil has a black head. Clover leaf weevil larvae are larger at about ý inch long.

Alfalfa Weevil Management: Beneficial Insects on our Side

Julie Stavisky, NYS IPM

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Within 10 years of the arrival of the invasive alfalfa weevil in the US in the late ‘40s, USDA scientists began releases of parasitic wasps to combat alfalfa weevil. We can generally count on these tiny wasps to help keep alfalfa weevil populations in check. But how do we know if they are really here? One of the easier times to look for alfalfa weevil parasitoids is when they are in the pupal stage. While searching for alfalfa weevil pupae on the ground below the alfalfa canopy later this month, keep your eye out for the parasitoid pupae, too. The alfalfa weevil pupa is withina white to tan web cocoon. A weevil larva parasitized bya wasp is instead surrounded by a hard brown 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 with cocoons

Pupae of parasitic wasps of Alfalfa Weevil, (Photo from Univ. of Nebraska)

For alfalfa weevil scouting guidelines, see our online publication: Alfalfa Weevil Management Guide

Powdery Mildew on Wheat

Julie Stavisky, NYS IPM

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It’s about the time of season when powdery mildew can really take off in wheat fields, now that the canopy is nice and dense. If powdery mildew shows up, the first symptoms include white powdery patches on upper surfaces of lower leaves. With continued moderate temperatures and wet conditions, the white powdery patches can spread to stems and upper leaves. Patches may turn to a dull gray color, peppered with tiny black specks as the disease continues to develop. A dense, lush stand that does not dry from dew and rain is at the highest risk from powdery mildew. The greatest chance for yield loss occurs when the flag leaf is infected. Follow this link for photos of powdery mildew symptoms.

Management of powdery mildew depends on planning ahead. Varieties that are moderately resistant are recommended, as are systemic seed fungicides. Avoiding excess nitrogen will prevent the growth of an excessively dense stand. Foliar fungicide sprays are generally not economical, though many factors must be considered. When should fungicides be considered? Take a look at the Guidelines for Wheat Fungicide Decisions in the online version of The 2005 Integrated Guide for Field Crop Management. (www.fieldcrops.org)

Black Cutworm Management-Field Corn

Ken Wise, NYS IPM

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There have been signs of migrating cutworm moths to the south in Pennsylvania. Since they ride storms that bring the adult moths from the south to the Northeast we should watch our corn for signs of feeding. Weedy grasses, winter annual broadleaves, and chickweed are favorite targets. If cutworm moths lay eggs in the field and the field is treated with an herbicide, hatching cutworm larvae bail off the dying weeds and look for greener food sources such as emerging corn seedlings. Cutworms can be an annual problem in some fields; particularly those with a history of poor weed control or have low wet areas in the field. Field margins, especially those next to ditch banks, grassy lanes, and hay fields are potential sites for infestation. Doing an early season plant population count is a good way to check corn fields for cutworm damage and other corn emergence problems.

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. Symptoms of damage are leaf feeding, irregular holes in stems, notched and cut or missing plants. No-till fields and those with a lot of grass weeds are at particular risk to black cutworm. Monitor fields to find cutworm larvae when they are less than 1/2 inch long. If there are sufficient numbers and damage present, an insecticide could be justified. Treat only the affected area and a 20 to 40-foot border around the infestation. Rarely does a whole field need to be treated for cutworm. Larger cutworm larvae, greater than 1/2 inch long, are much more difficult to control. If the majority of cutworm larvae are 1/2 inch long or larger their damage is already done. These large larvae are also more tolerant of insecticides, reducing the effectiveness and economic viability of this option. Check out our on-line publication, Black Cutworm Management in Field Corn

2005 Asian Soybean Rust (SBR) Status

Keith Waldron, NYS IPM

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What’s the latest on Soybean rust in NYS? So far no SBR sightings..... no soybean sightings either.
There is a lot of timely SBR information being generated on various national list serves and other publications. The following soybean rust information is from the New York State Soybean Rust Information Center: http://www.ppath.cornell.edu/soybeanrustny/default.htm

Soybean rust on volunteer soybeans has been recently reported in Seminole County in the southwestern part of Georgia. This is the first discovery of soybean rust on soybean in 2005. This is also the first county outside of Florida to report soybean rust in 2005. To date, there are now four counties in Florida that have reported soybean rust on non-soybean hosts. National activity has increased in terms of surveillance of rust on other crops as well as the planned/planted sentinel plots. Most states in the southern U.S. have planted at least a portion of their sentinel plots. Some have been planted as far north as Illinois. (last updated 5/10/05, Gary Bergstrom,Cornell University).

Spotted Lady Beetle A Native Predator

Ken Wise, NYS IPM

This week while using my sweep net in alfalfa looking for pests I caught several Spotted Lady Beetles (Coleomegilla maculata). As many of you know I am a lady beetle nut and I’m always looking in several habitats for different species. You find this excellent native predator in all field crops growing in NYS feeding on aphids. Adults can consume 50 aphids per day, while larvae can eat 10 to 25 per day. The spotted lady beetle will consume plant pollen that may constitute up to 50% of the diet. View a picture of Spotted Lady Beetle at the following website: Spotted Lady Beetle

Early Season Leaf Spots on Alfalfa

Ken Wise, NYS IPM

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Spring Black Stem: is favored by cool and moist weather in early spring. Symptoms appear as irregularly shaped brown to black spots that can merge to form a larger blotch. This disease can infect the petiole, form elongated blackened areas on the stems, and may be a contributor to a crown rot.

Common Leaf Spot: proliferates when the weather is cool and wet. This disease first develops on the lower leaves near the soil surface and then progresses upward through the canopy. Common leaf spot appears as small, circular, dark brown to black spots, about 1/16 inch in diameter. When observed through a hand lens, tiny raised, light brown disk-shaped fungal fruiting bodies are visible in the center of mature lesionsSee photo at: Common Leaf Spot

Leptosphaerulina Leaf Spot(aka “Lepto”): is also favored by cool and moist weather in early spring and late summer to early fall. The lesions usually start as small black spots and enlarge to oval or round “eyespots” 1/16 to 1/8 inch across. As lesions develop they become light brown or tan with dark brown borders; often surrounded by a chlorotic (yellow) area. This disease primarily attacks young leaflets but may also attack petioles and other plant parts. See photo at: Leptosphaerulina Leaf Spot

Downy Mildew: causes leaves to become blotched or chlorotic (light green or yellow). Many times young leaflets can become distorted. Often a dark purplish-gray fungal mat covers the underside of the leaves. This disease is common early in the spring.

While alfalfa leaf spots may be easily found in most stands the real impacts for this harvest would be if 30% or more of the leaves on plants were shed as the result of infection.

For more information view our on-line management guide: IPM for Alfalfa Diseases: Leaf Spots

Potato Leafhopper Challenge!

Ken Wise, NYS IPM

Every year it is fun to see who finds the first potato leafhopper in alfalfa. I have not yet found one which is late for me… so has anyone else discovered this pest yet this year or if not who will be the first?

Accumulated Growing Degree Days Across NYS

Keith Waldron, NYS IPM

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March 1 - May 10, 2005


Base 48 F

Base 50 F







Clifton Park















Clipboard Checklist

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Update field records: variety, planting date/rate, pesticides used, nutrient inputs including manure, other important field observations, etc.

Note wet spots in field for future drainage.

Corn planting should be finished by May 15

Pest Monitoring Priorities:

alfalfa weevil, alfalfa snout beetle, weeds, crown rot, leaf spot diseases

Small Grain Cereals:

Winter Wheat: Cereal leaf beetle, virus diseases, weeds, powdery mildew

Spring Grains: Cereal leaf beetle, seedling diseases, weeds

Field Corn:

Monitor corn for weeds, note presence of triazine resistant annual broadleaf weeds. Cultivate or treat if necessary. Pre-emergence herbicide applications by May 20 if conditions allow.

Review herbicide options for relative control of problem weeds. See Table 3.7.1 Herbicide Effectiveness on Weeds for effectiveness of selected corn herbicides on annual weeds (wild buckwheat, common lambsquarters and ragweed, wild mustard, redroot pigweed, velvetleaf, barnyard grass, crabgrass, foxtails, fall panicum, witchgrass)

Check for damping off / seedling blights, seed corn maggot

Contact Information

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Julie Stavisky:IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Email: js38@cornell.edu

Keith Waldron: NYS Livestock and Field Crops IPM Coordinator

Phone: (315) 787 - 2432

Fax: (315) 787-2360

Email: jkw5@cornell.edu

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock

Phone: (518) 434-1690

Fax: (518) 426-3316

Email: klw24@cornell.edu

NYS IPM Livestock and Field Crops Website