Eastern New York Field Crops Pest Report, 2004

This is a seasonal scouting report giving growers in the Eastern New York area information on the presence of agricultural pests. The report is written by Ken Wise, IPM Extension Area Educator for Livestock and Field Crops.

July 26, 2004

Alfalfa

Potato Leafhopper
Populations of potato leafhoppers were moderate to low this last week at the SUNY Cobleskill farm. The continued thunderstorms and heavy rain might be keeping infestations low. Be sure to scout fields to make sure populations are below threshold. For management information check our on-line IPM guides: IPM for Potato Leafhopper in Alfalfa.

Syrphid Flies Munch On a Few Aphids

While monitoring crops this week I saw many syrphid flies in alfalfa and soybeans. Adult syrphid flies like to feed on nectar and pollen of several kinds of flowers. Many species of adult syrphid flies look like bees. After the adults feed they lay 100‚s of white 1mm long eggs in the mist of aphid colonies. Syrphid fly larvae are good predators of aphids and other soft-bodied insects. Larvae are legless maggots that are green, yellow or gray with a yellow or white stripe down their back. For pictures of syrphid flies view this website: Syrphid Flies

Field Corn
Common Rust

I have observed common rust in several corn fields over the last 2 weeks. The conditions that favor this rust are warm and moist weather. Common rust appears as small, round to elongate, golden to cinnamon-brown pustules that form on leaf surfaces and other above ground parts of the plant. The pustules become brown to black as the plant matures. When the disease becomes severe, the leaves turn yellow, wither and die early. Common rust rarely causes significant yield reduction in field corn. Most commercial corn hybrids have good tolerance to this disease. For pictures of common rust view this website: Common Rust

Corn Rootworm Scouting Tip
Remember, when taking beetle counts you are monitoring to assess the potential that CRW's will lay enough eggs in the field to cause damage to next year's corn crop. Taking beetle counts is important but make sure you stop to check a portion of the female western CRW's for the actual presence of eggs. Squeeze the abdomens of the yellow and black striped CRWs and look for the small yellow - white eggs. It takes CRW about three weeks from the time the adult beetles emerge from the soil and mate until the time the females are gravid. In this time period you may find high CRW numbers in a field but since the females are not yet capable of laying eggs they are not causing an economic problem. This is the reasoning behind sampling the same field 2-3 times before making the management decision. Being pollen feeders and highly mobile, CRW's may relocate to another pollinating field during the 3 week period. Comparing the two types of fields, the second field is at greater risk from subsequent CRW damage since females (and their eggs) will have matured and are ready for deposit. For more information on corn rootworm checkout our online publication: IPM for Corn Rootworm

Weed concept of the week: How many seeds can a weed produce?

Have you ever thought about how many seeds a weed can produce? Here is a flavor of what some weeds can produce and how many years seed can survive to grow later.

Reference: Field Crops Pest Management Manual ­Purdue University

Do you think certain soil conditions favor certain weeds? See next week’s report to find out!

SOYBEANS

Soybean Rust - It's not here now but.....

By Julie Stavisky

Many fungal diseases love the wet weather we have been experiencing this growing season. Leaves in the soybean canopy are likely to be infected with some of the common diseases. It is more important than ever to be able to confidently identify the foliar soybean diseases common in NY because of the possibility of being confronted with the new threat of soybean rust. While soybean rust has not yet been detected in the US, it is likely to show up in the next few years. Preparation may be the key to preventing devastating losses. This is what different stages of the disease look like on the lower surface of soybean leaves:

(Photo courtesy of the Soybean Rust National Pest Alert) Pictures of the disease can be viewed on the following website:  Soybean Rust Pest Alert.

See next week’s report on how to identify other “Soybean Foliar Fungal Diseases.”

Thanks to: Jennifer Beckman (Lewis County), Keith Waldron and Julie Stavisky (NYS IPM) for contributing to this week's report.

Cheers
Ken Wise