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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.

August 20, 2004

WHEAT

What pest problems to consider when planting winter wheat.

There are several factors to consider when planting winter wheat. The first is to never plant wheat in the same field two years in a row. By rotating you reduce the risk of several diseases like eyespot foot rot, powdery mildew, leaf rust, stagonospora nodorum blotch, glume blotch and more. The second item to consider is what winter wheat variety to plant. Of course you will look at potential grain yield, grain test weight and straw quality. It is also important to consider resistance to diseases in the varieties you select. Diseases of particular concern are wheat spindle streak mosaic virus, soil borne mosaic virus, yellow dwarf virus (formally called “barley yellow dwarf virus”), powdery mildew, leaf & stem rust and/or other disease problems your farm has had in previous years? For a list of potential wheat varieties consult your Cornell Guide for Integrated Field Crop Management. Next remember to plant AFTER the Hessian fly free date. By doing so, not only are you avoiding infestations of Hessian fly but also certain aphids that can transmit yellow dwarf virus. The following figure shows the “Hessian Fly Free Dates” in NYS:

File written by Adobe Photoshop¨ 4.0

The use of certified wheat seed should be considered. When seed is certified you can be confident of the quality and it is void of diseases and weed seed. Next is to remember to always use a fungicide seed treatment to protect the crop from certain seed and seedling related diseases. Another core consideration is having a sound fertility program. When a plant is healthy it can complete with weeds and may tolerate more insect pest pressure and still maintain good yields.

SOYBEANS

White Mold Conditions are High!

It’s here now - at least it has been reported recently in central NY. While mold (Sclerotinia Stem Rot) sometimes is over looked as just a minor pest of soybeans. When conditions are wet, moist and cool and the soybean canopy starts to close is ideal for the development of Sclerotinia. Extended periods of wet, moist and cool conditions when soybeans are flowering under the canopy is very favorable for the development of the disease. Field symptoms include isolated patches of stunted, yellow or lodged plants. A fluffy white mycelium can be found on the lower stem and surrounding ground. Small black pellet-like "sclerotia" may also be present on or in affected stems or on the mycelium. These sclerotia can survive winters to produce apothecia the next season. These apothecia can produce thousands of microspores. These microspores are disseminated into the air and land on the soybean plants. If sclerotia are plowed under the surface they can survive as long as 7 years. One way to limit the disease’s ability to infect the lower canopy is to increase the row spacing to greater than 15 inches. This allows air to circulate under the canopy and reduce the humidity thus, limiting the disease progression. You may also plant cultivars resistant to Sclerotinia stem rot. While these cultivars help reduce infection there are no varieties that show complete resistance. The disease can also be transmitted with the seed you plant in the field. Be sure to use certified seed because it is guaranteed not have any diseases.

FIELD CORN
Do weeds indicate what insect pests may infest a cornfield next year?
Conducting a weed survey (see last week’s report on how to conduct a weed survey) may identify conditions attractive to certain insect pests. Some weeds serve as over-wintering sites for common stalk borer, hop-vine borer, and potato stem borer. Black cutworm lays eggs on several species of weeds in the spring. Larvae of these insects migrate from weeds to emerging corn in the spring. Here are some weeds that attract these insect pests:

Insect Pest

Weeds

Common stalk borer

ragweed and other large stemmed broadleaf weeds

Potato stem borer

quackgrass, green foxtail, barnyard grass, and dock

Hopvine borer

quackgrass and other grasses

Black cutworm

grasses, annual broadleaves such as common chickweed

Common billbug

yellow nutsedge

ALFALFA

Fall IPM Alfalfa Assessment
Fall stand counts provide an indication of the relative health of your alfalfa crop. There are a number of pests and crop management issues that can reduce a stand count in alfalfa. The following are guidelines for stand counts in NYS:

 

Crowns per square foot

Harvest Year

Optimum Stand

Adequate Stand

New Spring Seeding

25-40

12-20

1st hay year

12-20

6-10

2nd hay year

8-12

4-6

3rd and older

4-8

2-5

Fall scouting before the first hard frost can also reveal pest problems. If you find yellow to brown plants it may indicate several different disease problems. These could range from a wide variety of disease problems including, verticillum wilt, leaf spots, fusarium wilt, anthracnose and more. An inspection of the root system can also indicate disease problems. Yellow, reddish-brown to black discolored or damaged roots may indicate disease problems such as phytopthora root rot or verticillium wilt. One very damaging pest in Cayuga, Oswego, Jefferson, Lewis, St. Lawrence and Franklin and Clinton Counties is alfalfa snout beetle. Symptoms of alfalfa snout beetle larval feeding in late summer appear as yellow and often leafless plants.

Watch for next week’s report on more specific information about alfalfa snout beetle!

Thanks to: Keith Waldron (NYS IPM) for contributing to this week's report.

Cheers,
Ken Wise