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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 3, 2004

FIELD CORN

Stop! Check for Corn Ear Rot

Are you ready with the chopper or combine! STOP; check for corn ear rots first! Some kinds of fungi can create mycotoxins that are toxic to livestock. The cool and wet conditions we have had most of the summer have been good for certain ear rots to establish. Taking a few minutes to check a field for certain ear rots can help you determine if you want to feed your field of corn to livestock. Pull back the husks on several plants and look for the presence mold growing on the ear of corn. The following are specific symptoms of certain ear rot diseases that can be found in NYS:

Fusarium ear rot appears as a white-to-pink or salmon-colored mold. This mold can begin with birds, deer or insect-damaged kernels. Fusarium ear rot may contain fumonisins which are mycotoxins that can be toxic to livestock.

Gibberella ear rot symptoms are pink to reddish colored mold. This disease starts near the tip of the ear and progressing down toward base of the ear. Gibberella can produce vomitoxin and zearalenone which is toxic to many kinds of livestock.

Diplodia ear rot symptoms appear as a thick white mold that usually starts near the base of the ear. This disease can also appear on the plant as raised black fruiting bodies on moldy husks or kernels.

Diplodia does not produce any known toxins.

Cladosporium ear and kernel rot symptoms appear as greenish black, blotched or streaked kernels scattered over the ear. This disease can also infect kernels that have been damaged by insects, birds, deer, hail, or frost. The disease can progress after the grain is harvested and stored.

Penicillium ear rot or blue eye symptoms range from a powder-like green or blue-green mold that is on and between the kernels and normally on the tip of the ear. If this disease progress in storage it is referred to as blue eye because the germ is a bluish-green color. Penicillium ear rot can produce a mycotoxin called ďochratoxinĒ.

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

               Resistant Crop Rotation  Clean Plow          

Corn Disease   Variety   Rotation       Down of Residues      Fungicides

Ear Rots       2     2                 2              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

Remember if you can reduce stress on the plants with proper fertilization, timely weed control, and reductions in insect pest pressure, the disease risk will be reduced. For example: European corn borer (ECB) resistant Bt corn has lower risk of insect injury to the corn. This means there is less potential for fungi to infect through wounds caused by ECB tunneling. Also avoid continuous planting of corn under conservation tillage where stalk rot can be prevalent. If you are harvesting corn grain make sure you clean the grain bins. Keeping the proper temperature, moisture content and good aeration in the grain bin can reduce storage molds from developing. It is important to have regular inspections of the stored grain. This is essential to minimize risk of developing insect and mold associated storage problems. Harvest silage at recommended maturity and moisture level, and pack silage tightly and exclude air rapidly. Consider using organic acid preservatives if you can't exclude air or reduce moisture. If you had a lot of stalk rot and were growing for grain consider chopping earlier for silage to minimize lodging and combine losses. There are kits you can purchase to test your corn for different toxins on your own farm. The following are places where you can also test your corn:

Dairy One Forage Lab in Ithaca: For more information, call the lab at 1-800-496-3344 extension 172.

The Cornell College of Veterinary Medicine's Nutritional and Environmental Analytical Services Lab: More information is available on the web (www.vet.cornell.edu/public/neas/) or from lab manager Joe Hillebrandt at 607-257-2345.

SOYBEANS

Soybean aphid update

Written By Julie Stavisky

Now that it is September, the soybean aphid story should be nearly over for the year. But recent observations in Northwest New York by Mike Stanyard have indicated that we need to keep watching! A late-season surge in populations of soybean aphids has been seen in several fields, and few natural enemies are still on-scene.

Letís review thresholds and plant growth stages. Yield loss from soybean aphid damage may be prevented when the plant is still in the early reproductive stages (flowering to pod-set). Threats to yield loss are reduced during beginning seed and full seed (R5 and R6) growth stages. In western New York, some late-planted beans (planted about June 6 ≠ 16) are still in the early reproductive stages (pre-pod fill). Spray treatments are not warranted unless there are 250 aphids per plant. When 250 aphids are seen per plant, there is still a several-day window to plan the spray. If many natural enemies are observed (ladybug adults and larvae, parasitized aphids, or fungal pathogens), treatment with an insecticide is probably not justified. Additionally, if many of the aphids are winged, they may soon be ready to move out of the field.

Keep watching for soybean aphid, and stay tuned next week for information about where soybean aphids go for the winter, and when they start making their move out of soybean fields.

WHEAT

Certified seed and fungicide seed treatment are good insurance for winter wheat

Written By Julie Stavisky

Soilborne fungal disease occurrence on roots, stems, and crowns of winter wheat are generally not severe when wheat growers rotate with non-cereal crops. However, low levels of soilborne and seedborne fungal diseases can cause problems with stand establishment. A stand that is not well established in the fall will have a harder time making it through the winter.

Seedling disease threats can largely be prevented with the use of fungicide-treated seed. These threats include the smut diseases that may be present on the surface of the seed or deep inside the embryo of the seed. Also, several soil-dwelling disease agents can cause plant roots and/or crowns to rot before the plant becomes established. In addition, seed fungicide treatments can aid in the suppression of early foliar diseases such as powdery mildew in the fall.

Fungicide-treated seed is widely available commercially, or treatments of fungicides can be made on-farm. The most effective treatments combine a systemic fungicide and a protectant fungicide. For specific reference to chemicals, please visit the Cornell Guide for Integrated Field Crop Management online at: http://ipm.cornell.edu/guidelines/fieldcrops.asp

ALFALFA

Fall Weed Survey for Alfalfa

In the fall as your alfalfa is putting energy back into their roots for the winter it is a good idea to go and look at what weeds might be in the alfalfa stand. This can help you make decisions about what to do with your alfalfa fields the next season. You will want to conduct a weed survey. Observe weed infestations in at least 5 locations chosen at random in a 40-acre field. Divide fields larger than 40 acres into equal parts for scouting. Keep a record of significant weed infestations by drawing their location and logging predominant species composition on a map of the field. Check unique features such as droughty slopes, poorly drained areas, field borders, and fence rows for weed infestations. These areas can be major sources of weed contamination. Visually estimate significant weed infestations (by individual species) using the following Weed Rating Scale:

Determine the severity of the most common weeds observed.

Few: Weeds present, but very few plants in the field. There are enough to produce seed but   not enough to cause significant loss

Common: Weeds are dispersed throughout the field. There are up to 5 grass or 3 broadleaf annual weeds per sq. ft. or 0.3 perennial or biennial weeds per sq. ft. (3 per sq. yd.) or scattered spots of severe infestation.

Abundant: Fairly uniform concentrations of 6 to 20 grass or 4 to 10 broadleaf annual weeds per sq. ft. or 0.5 to 1.0 perennial or biennial weeds per sq. ft. (6 to 20 per sq. yd.).

Extreme:  Concentrations of more than 2 grass or 1 perennial or biennial weeds per sq. ft. (20 grassy or 10 perennial or biennial plant sq. yd.). Large areas of severe weed infestation.

Clear stands of alfalfa should have at least 5 healthy crowns per sq. ft. but grasses can be important in maintaining quality and quantity of forage in thinning alfalfa stands. Consider crop rotation for alfalfa stands with less than 4 vigorous alfalfa crowns per sq. ft. Donít forget to check areas with lotís of weeds for diseases which may have thinned the stand. If the field needs to be rotated this information will be very helpful in future selection of appropriate disease resistant varieties.

Thanks to: Keith Waldron, Julie Stavisky (NYS IPM) and Gary C. Bergstrom, (Professor-Department of Plant Pathology) for contributing to this week's report.

Cheers,
Ken Wise