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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.

September 10, 2004

FIELD CORN

Check For Stalk Rots!

It is important to monitor your fields for stalk rots as you prepare for harvest. If you have an infection of stalk rot it can cause the plant to die early losing grain or silage yields. Stalk rots are caused by many different fungi that enter the plant. They occur when the plant is under stress or when it may be injured by insect pests, hail, deer and bird damages, drought or soil saturation, lack of sunlight, extended cool weather, and the lack of fertility. The following are symptoms of specific stalk rots:

Anthracnose stalk rot symptoms may appear after tasselling as vertical, tan to reddish brown, water-soaked lesions (streaks) in the stalk rind. Lesions become large, dark brown to shiny black. Fields with high amounts of anthracnose leaf blight (both diseases have the same causal agent) should be checked for indications of anthracnose stalk rot.

Diplodia stalk rot symptoms may appear as numerous black pycnidia in the lower internodes of the stalk. The black dots are the size of a pinhead or smaller. When conditions are wet a white mold may develop on the stalk surface.

Fusarium stalk rot normally starts just after pollination and symptoms appear later in the season. When you cut open the stalk, the pith appears as a whitish to pink (salmon) color. There are also distinctive brown streaks on the lower internodes.

The first symptom of gibberella stalk rot is the onset of grayish-green color of the leaves. The stalk will turn dark green to tan near the base of the plant. The pith of the stalk becomes soft and will appear as a red to pinkish color.

Pythium stalk rot normally appears as a decay of the first internode above the soil. The pith will become soft, turn brown and appear water-soaked. Many times the stalk can twist and/ or lodge. Even though it may have lodged the plant will stay green for several weeks because the vascular tissue is not destroyed.

If you discover certain stalk rot diseases make notes of the hybrid, tillage methods, rotation history, and planting date. By doing this you be able to avoid the disease occurrence in the future. The following is the effectiveness of specific management practices for stalk rots:

               Resistant Crop Rotation  Clean Plow          

Corn Disease   Variety   Rotation       Down of Residues      Fungicides

Stalk rots

Anthracnose    1     1                 1              4

     All other 2     3                 3              4

1= highly effective, 2= moderately effective, 3=slightly effective, 4= not effective, 5 = not usually economical,

Reference: Purdue University Field Crops Pest Management Manual

As with most diseases that attack corn, if you can reduce stress on the plants you most likely can reduce the occurrence of certain stalk rots. Having a sound fertility program based on soil testing is important for keeping a corn plant healthy. Select a hybrid with resistance to certain diseases and good standability that is adapted to your region. Some of these stalk rots can produce mycotoxins that can be toxic to livestock. You should consider having silage tested for certain mycotoxins if you had fields with stalk rots this season. For more information on corn diseases checkout our online publication: IPM for Corn Diseases

SOYBEANS

Soybean Aphid Overwintering

Written By Julie Stavisky

All through western New York, very few winged forms of the soybean aphid (SBA) are present yet! Usually by this time of year, winged forms of the SBA are common. In Steuben County last week, SBA were extremely numerous, but no winged adults were observed. The same is true in Genesee, Wayne, and Seneca counties, but I did see a few winged aphids in Ontario county.

What would the appearance of winged forms of SBA tell us? Winged forms, or “migrants” start to appear in the late summer or early fall when SBA are getting ready to move out of soybeans to their winter hide-outs. Migrants fly to find buckthorn plants, where they lay eggs in the protected areas around the buds.

By collecting SBA in suction traps in Illinois, researchers have successfully predicted whether it would be a bad SBA year or a not-so-bad SBA year in 2003 and 2004. In the fall of 2002, they collected many winged SBA moving to buckthorn. They predicted high SBA populations in 2003. Nearly every soybean field was infested in 2003. In the fall of 2003, they collected very few aphids in transit to winter homes. They speculated that SBA might be less numerous in 2004. Their speculation proved corrected. Another factor they considered was the numbers of predators, especially the multicolored Asian lady beetle. Large numbers of the lady beetle in the fall led to fewer SBA the following spring. Suction trap counts also are used to determine when SBA leave their winter hosts and head for soybeans in the spring. Stay tuned for more on that next spring.

For more information about the suction traps, you can visit:

http://www.ipm.uiuc.edu/fieldcrops/insects/soybean_aphids/suction_trap_network/index.html

Although information gathered in the Midwest may not prove to be a predictor for SBA outbreaks in New York, we may be able to learn from our neighbors to the west, and make observations of our own regarding movement of winged SBA from soybean to buckthorn.

GENERAL IPM

Keeping pest records

It is very important to keep records from year to year on certain pest problems that may have occurred. Write down observations that you made over the course of the summer. Did you see potato leafhoppers go over threshold? Were there certain corn diseases present? Did you have corn that had corn rootworm injury? Were there new weeds or weed escapes you did not expect this year? Pick up a pencil and write them down on a field to field basis to better select certain management practices the next season. For example, if you were hit with potato leafhoppers this season and you want to rotate your alfalfa, one management option is to use potato leafhopper resistant alfalfa. Other example might be to select wheat varieties that are resistant to certain diseases. If you had weed escapes you might reconsider your selection of weed control products. If you wait too long you may forget what happened in certain fields. So write them down!

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

Cheers,
Ken Wise