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Eastern New York Field Crops Pest Report, 2003

For 7/14/03:

Alfalfa

General Crop Condition
Alfalfa at the Cornell/Valatie Research Farm was lodged over (July 8).

Potato Leafhopper infestation high!
Potato leafhopper infestations are at moderate to very high levels across Eastern New York (July 14). Several reports suggest that many fields were over threshold this last week. I had several questions about spraying mixed stands recently. A mixed stand if defined as alfalfa, grass and or clover planted together in a field at the same time. New York State has approved the use of Warrior as a section 18 for use in grass/clover/alfalfa mixtures on potato leafhopper. For clear seeded alfalfa stands there are several more options to select from: Baythroid, Lorsban 4E, Dimethoate, Warrior T and Ambush or Pounce. Remember, if you are within a week of cutting the field, harvesting early is a viable control measure.

For more information, see Potato Leafhopper on Alfalfa Management Guide, 302k pdf file

Picture of potato leafhopper

Field Corn

General Crop Condition
Field corn this week was between the 4 and 8 leaf stage across many regions of Eastern New York (July 14). I also saw a few fields in the North Country that were just planted about two weeks ago (July 10).

When can you expect to find adult corn rootworm beetles in the field?
The speed beetles develop is affected by heat units. With corn rootworms their development is also aligned with corn development. Over time the beetles have evolved to synchronize their emergence to correspond with the availability of corn pollen (silking time) the preferred food source of adult corn rootworm beetles. To estimated what stage of development corn rootworm beetles are at and when would be a good time to scout for CRW beetle adults check out the corn rootworm prediction map on the Livestock and Field Crops IPM Home page. Go to the alfalfa weevil prediction map and reset the model for corn rootworm. You'll find it under the "Reference Corner" section of our new and improved Livestock and Field Crop IPM web site. As of today (7/14/03) the map predicts first, second, and third instars of CRW are occurring across the state.

What are the other species of corn rootworm in New York?

Northern Corn Rootworm

  • Northern corn rootworm is a Generalist which means they have several hosts

  • Eggs are laid in corn, other crops, and borders

  • Relatively fewer eggs per female than compared to Western Corn Rootworm

  • Adults tend to stay in or around same field

  • Emerge later than Western Corn Rootworm

  • Shorter adult time in field than compared to Western Corn Rootworm

  • Larvae less competitive than Western Corn Rootworm

  • Threshold: 2 beetles / plant

Western Corn Rootworm

  • Western corn rootworm is a Specialist which means they prefer corn

  • Corn is preferred for egg laying

  • Relatively more eggs per female than compared to Northern Corn Rootworm

  • Adults more prone to migrate to new fields in search of corn pollen.

  • Emerge earlier than Northern Corn Rootworm

  • Longer adult time in field than compared to Northern Corn Rootworm

  • Larvae are more competitive than Northern Corn Rootworm

  • Threshold: 1 beetle / plant

How to Monitor for Corn Rootworm

Soybeans

Soybean Aphids
For those producing soybeans reports from central and western NY indicate that the soybean aphid (SBA), a pest recently introduced into the US, is now being found. This is the only aphid found on soybeans. High populations of these aphids can stress plants and cause stunting, reduced yield, and are potential vectors of virus diseases. Checking fields for soybean aphids is easy. Check border areas walking in about 50 feet from the edge of the field.

If present aphids can be found on the lower sides of leaves in the top 3-6 inches of the plant. The top two or three trifoliates are prime real estate for the aphid populations. Large numbers of lady bird beetles, other insect predators, or ants in tops of soybean plants may indicate that SBAs are present.

Interested in participating in a research project? Keith Waldron (NYSIPM), John Losey and Anne Hajek from Cornell Entomology are collaborating this summer to detect and identify naturally occurring predators, parasites and pathogens found attacking soybean aphids in soybean fields. In the past two years they have sampled fields for biological control organisms and found at least 8 species of lady bird beetles (Coccinellids) aka lady bugs and predaceous heteropterans such as damsel bugs, big eyed bugs, and parasitoids that are known to prey on aphids in other systems. This summer they hope to detect entompathogenic organisms too. If you find SBAs and they appear to be sick discolored brown, shrunken in size, they would be interested in obtaining samples for further study.

Please see the Soybean Pests (Insects) Management Guide (140k pdf file) for more information.

Grass Hays and Pastures

This week there was a report of horses in the north country region suffering from toxicity from eating hay from a bale harvested earlier this season containing the weed, "Hoary Alyssum" (aka Berteroa incana) which is known to be poisonous to livestock. This observation serves as a reminder for us to monitor for poisonous weed species in pastured systems and hay being sold off the farm. Information on plants affecting livestock can be found at the following websites:

Hoary Alyssum: Toxicity to Horses, Forage Quality, and Control

Field Guide to Noxious and Other Selected Weeds of British Columbia

University of Pennsylvania's Poisonous Plants Home Page

Cornell University Poisonous Plants Informational Database

Last week's IPM Question!

Why is it important to change the families of herbicides used on fields from year to year?

By using different families of herbicides from year to year helps prevent specific weeds from developing resistance.

Do you know the number of growing degree-days in your region today?

Check this website: NEW YORK GROWING DEGREE-DAY TRACKER
(Base Temp. 50F)

Contributors to this week's pest report
Beth Spaugh (Clinton County)
Jeff Miller (Oneida County)
David Norton (TAg Scout: Chenango, Fulton, Montgomery, Herkimer, Otsego, Madison, Oneida Counties)
Kathryn Evans (Madison County)
Kevin Ganoe (Chenango, Fulton, Montgomery, Herkimer, Otsego Counties)
Richard Gast (TAg Scout: Franklin County)
Keith Waldron (NYS Field Crops and Livestock IPM Coordinator)
Ken Wise (Eastern New York)

Happy Scouting!
Ken Wise