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Eastern New York Field Crops Pest Report, 2002
Eastern New York Weed Day
Note: CCA and DEC Credits have been requested
General: The SUNY Cobleskill fields were 10 to 25 inches tall, but much of the alfalfa has lodged, due to thunderstorms and heavy rain.
Alfalfa Weevil: Alfalfa weevil tip feeding dramatically declined this week (June 27). I did not find any larvae in the 5 fields monitored this week, while last week there were 50 per 10 sweeps with the net. Where did they go? They all pupated! What does this mean? It means the potential for alfalfa weevil damage to occur this year is over.
Check out our on-line publication, IPM for Alfalfa Weevil. 1.2 Mb pdf file
Alfalfa Weevil and Parasitoids: Alfalfa weevils have many natural enemies. One group of these are tiny beneficial wasps called parasitoids. Some parasitoid species attack weevils in their egg stage, other types attack larvae, and still other types attack adults. A common weevil parasite (Bathyplectes spp) lays its eggs in late instar larvae just before they pupate. The parasitoid egg hatches and the young wasp feeds on the developing pupa effectively killing the weevil before it completes its development. If you find a weevil cocoon and instead of a healthy green to brown weevil pupa you find a small dark brown egg-shaped structure about 1/8 inch long you have found the cocoon of a Bathyplectes parasitoid. The natural predator has devoured the alfalfa weevil pupa. Biological control in action!
Potato Leafhopper: I found moderate levels of potato leafhopper in 5 alfalfa fields at the SUNY Cobleskill farm this week. While there were no fields over threshold the number of potato leafhoppers is increasing (June 27). Keep those nets sweeping fields!
Check out our on-line publication, Potato Leafhopper Management in Alfalfa
General: Corn growth ranged between the V1 and V4 stage at the SUNY Cobleskill farm this week (June 27). The latest herbicide application on cornfields controlled the weeds that were present last week.
Western Corn Rootworm Vs Striped Cucumber Beetle: Who knows the difference between corn rootworm and striped cucumber beetle?
Pete Carey (Sullivan County) pointed out to me that there is conflicting information about the difference between the two beetles on the World Wide Web. Striped Cucumber Beetle and Western Corn Rootworm look similar but are two different species of insects.
Striped Cucumber Beetle, Acalymma vittatum
Western Corn Rootworm, Diabrotica virgifera virgifera
Differences between the two insects:
Female Western Corn Rootworm:
Striped Cucumber Beetle:
Refer to the following website on differences between Western Corn Rootworm and Striped Cucumber Beetle: Cucumber Beetles, Corn Rootworms, and Bacterial Wilt in Cucurbits
Is the western corn rootworm the only corn rootworm in New York? See next week's report for the answer.
Black Cutworm: I saw minor patches of cutworm damage in a no-till field this week at the SUNY Cobleskill farm (June 27). Corn is vulnerable to cutworm feeding until about the V6 growth stage. Pay particular attention to no-till or reduced till fields and those fields with poor weed control. Cutworm moths are attracted to grasses and also seem to like laying their eggs on chickweed.
For more information on Black Cutworm in Field Corn, check out our on-line publication (912k pdf file).
Are there certain species of weeds resistant to triazine herbicides
in New York?
Grass and Pasture
True Armyworm: Lisa Fields, (Schoharie County) reports low captures of true armyworm moths (June 27).
General: Soybean growth ranged between the VE to V3 stage in central NY fields.
Slugs: Holes in soybean leaves? Slime trails may lead to culprit hiding in soil cracks or field residue. Slug damage to young soybean plants is easily found in 5-10% of plants in central NY. Economic impacts not generally expected at low levels observed.
Soybean aphids: Soybean aphids have recently been found in soybean fields in central NY. If soybeans are grown in your neighborhood, field Scouting is recommended. Read about the biology and life cycle of soybean aphids here.