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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.

For 4/30/04:

Hello Field Croppers:

I am starting the Field Crops Pest Report earlier this year. Well, here we go. 2004!

Note: You are welcome to use any of this report in your own newsletters!

Alfalfa

General Crop Condition: Alfalfa (April 27) at the SUNY Cobleskill farm was 4 to 6 inches tall and in good condition.

Alfalfa Weevil have Awakened! They have awakened from a long winters nap to feed on alfalfa fields. Alfalfa weevils were discovered April 22 at the SUNY Cobleskill Farm in the Schoharie Valley. Alfalfa weevil populations can build up over the life of the alfalfa stand. The longer an alfalfa field is in production the more likely the risk of alfalfa weevil damage. Adult weevils that enter fields in the spring are light brown and 3/16" long. They have a band of darker brown down the center of their back and a long snout. You may ask what do they do to alfalfa fields? (Check next week for the answer or go to our web-site on alfalfa weevil management: IPM for Alfalfa Weevil.

Clover-root curculio: In the same sweep net on April 22 with alfalfa weevils were clover-root curculio adults. Adult clover-root curculio weevils are 1/8 inch long and 1/16 inch wide with short, broad snouts. The adult weevil is brownish-black and covered with grayish hair and scales. Adult curculios chew the margins of leaves leaving C shaped notches. Clover-root curculio larvae feed on nodules, small rootlets, and chew out portions of the main root. Root feeding by larvae can provide opportunities for diseases to enter the plant.

Alfalfa Winter Kill, Root Diseases and Frost Heaving: There have been reports of alfalfa fields suffering winterkill. There are many potential causes of alfalfa winter kill often involving some type of root disease. Crown rot, one of the possible problems can occur in older fields with a history of stress, heavy traffic or grazing, poor drainage, fertility and pH problems, previous insect damage, etc. Plants exhibiting crown rot appear stunted and have few stems. Crown rot progresses slowly in the crown and taproot area of the plant. In many situations, crown rot cannot be attributed to a single pathogen. Several fungi (Fusarium spp., Phoma, Pythium, Rhizoctonia) as well as some bacteria, have been implicated in the disease. Often, a complex consisting of several of the pathogens attacks the plant. The way to tell if a plant has the disease is to dig up (not pull up) a plant showing symptoms. Then use a knife to split open the crowns and roots. Healthy tissue should be white, moist, and firm. Rotted tissue usually has a black or brownish- red color, but the color may vary from yellowish to pinkish or gray.

Another common alfalfa problem observed this time of year is frost heaved crowns. Low areas of the field that tend to accumulate water are sites worth checking for this ailment. Frost heaving may indicate potential disease problems such as Pythium or Phytopthora root rot which attack lateral and main root systems leaving plants with limited holding power for staying in the ground. The photos shown came from a field in Freeville NY which was poorly drained and had a history of Phytopthora root rot.

Question for Next Week: What alfalfa insect pest displays damage similar to winter kill?

Field Corn

Insecticide Seed Treatments for Seed Corn Maggot: Last growing season I was in a few corn fields where seed corn maggot infestations reduced plant populations by 5,000 to 6,000 plants per acre. This reduction can translate to a loss of 1 to 2 tons of corn silage per acre. This pest is, however, easily and inexpensively controlled by using an insecticide planter box seed treatment or insecticide pretreated seed. Prevention is the key to controlling seed corn maggot!

Seed corn maggot (SCM) is an insect pest that feeds on large seeded crops like corn and soybean. In the early spring, the female SCM fly searches fields with high organic matter (decomposing plant material, fields with manure, etc.) for soil cracks and germinating seeds in which to lay their eggs. Maggots hatch from the eggs and feed by burrowing into germinating seeds. These maggots are tapered, legless, appear to be headless, pale yellowish-white, and reach a length of about a 1/4 inch long. Symptoms of SCM damage may show as skips in the corn rows. In bean crops, such as soybeans and drybeans, SCM damaged seedlings may appear as "snake heads" i.e. seedlings without cotyledons. Proper diagnosis requires some digging in the gaps within a row to check for seeds and on seed health. For more information on SCM management check out Early Season Insect Pests of Corn, 1Mb pdf file

Be Ready to Prevent Early Season Corn Diseases

Prevention is the key to control early season corn diseases! By using a fungicide planter box treatment will help prevent corn seed from many different early season diseases. Sound planting practices, such as use of certified seed, good seed bed preparation, good seed soil contact, and appropriate planting depth, help promote stand establishment and help avoid seedling blights and emergence diseases. Watch for foliar diseases in continuous corn fields if contaminated residue from last season is present. For more information on early season disease management visit our web page on Field Corn Diseases.

Small Grains

Wheat

Septoria tritici blotch

During a TAg meeting last week in Oneida County we discovered Septoria tritici blotch on the lowest leaves of wheat plants. This disease is detected in the fall or early spring. As temperatures rise as summer progresses the disease decreases. The first symptoms are yellowish or chlorotic flecks on the lowermost leaves. The flecks increase in irregular lesions and are brown-to-reddish brown. When the lesions develop, the centers become bleached with gray or ash-white centers. At this time, small, dark brown to black specks appear in the center of the lesion. This tiny black dot is a pycnidia or spore producing body. The presence of small, black pycnidia in lesions is the most reliable character for identifying the disease.

File written by Adobe PhotoshopĀ 4.0

Thanks to: Jeff Miller (Oneida County), Julie Stavisky (NYS IPM) and Keith Waldron (NYS IPM) for helping with this weeks report!

Cheers,

Ken Wise