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Eastern New York Field Crops Pest Report, 2003

For 6/4/03:


General Crop Condition
Alfalfa at the SUNY Cobleskill farm was 24 to 28 inches tall (June 2) and has lodged due to wind and heavy rain. The alfalfa at the Cornell Research Farm in Valatia (June 3) was 22 to 26 inches.

Varied Alfalfa Weevil Damage in Eastern New York
Alfalfa weevil damage appears to be quite variable in Eastern New York this season. Oneida, Madison, Fulton, Montgomery, Herkimer and Franklin Counties are reporting 0 to 10 percent tip feeding. The exception to these observations is at the Cornell Research Farm in Valatia where I found droves of 1st to 3rd instar larvae and tip feeding was at 50 percent which is over threshold. Last week, I did not see many larvae or damage on alfalfa at the research farm. This is a little wakeup call to how rapidly the population of alfalfa weevil can change. A good control measure for alfalfa weevil is the 1st cutting of alfalfa. Wet weather may delay harvest and this might allow alfalfa weevil to reach levels that can cause economic damage. It is still essential to scout for alfalfa weevil even if you can‚t get in the fields to harvest. The reason is when fields do become dry enough to harvest you can cut the alfalfa that is closest to the tip feeding threshold first, avoiding more yield losses. Alfalfa weevil threshold before first cutting is 40% tip feeding. Sometimes harvesting alfalfa will not totally control alfalfa weevil and you can still get economic damage on re-growth. Insecticide use may be necessary after the first cutting if small larvae are still present and damaging growth of at least 50% of the new buds. Watch windrows for signs of weevil feeding on re-growth.

Check out the New York State alfalfa weevil development predication map!

... and see our on-line publication, IPM for Alfalfa Weevil. 1.2 Mb pdf file

Contributors to this week's Alfalfa Weevil Scouting:
Jeff Miller (Oneida County)
Kevin Ganoe (Fulton, Montgomery, Herkimer, Otsego Counties)
Kathryn Evans (Madison County)
Richard Gast (Franklin County)

Potato Leafhopper
The season for potato leafhopper is closing in quickly. Already we have heard of an isolated few PLH being found in alfalfa. So, it is time to dust off that sweep net in the closet and start looking of potato leafhopper. If you can‚t remember what they look like, adults are bright lime green, 1/8 inch long and can fly. Potato leafhopper nymphs are yellowish-green and look similar to the adult but do not have wings.

For more information, see Potato Leafhopper on Alfalfa Management Guide, 302k pdf file

Alfalfa Crown Rot
Richard Gast (Franklin County) reports several areas in a field with alfalfa crown rot (May 30). Crown rot occurs in older fields where there has been 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.

Picture of Alfalfa Crown Rot

For more information, check out our NEW on-line publication, Diseases of Alfalfa (Wilts and Rots) Management Guide 216k pdf file


Field Corn

General Crop Condition
Corn is emerging and is 1 to 2 inches tall at the SUNY Cobleskill farm (June 2). Both no-till and conventional corn seems to be doing well.

Black cutworm Alert in other parts of the country
In other parts of the United State they have had economic damage from Black Cutworm this year in field corn. Cutworms can be an annual problem in some fields; particularly those with histories of poor weed control or have low, wet areas in the field. Field margins, especially those next to ditch banks, grassy lanes, and hay fields are potential sites for infestation. Doing an early season plant population count is a good way to check corn fields for cutworm damage and other corn emergence problems. Black Cutworm larvae vary in color from light gray to black and a pale brown head. Larvae have a greasy, shiny appearance with coarse granules present over their body. During the day larvae burrow into the soil next to the corn plant. These larvae curl into a „C‰ shape when disturbed. Symptoms of damage are leaf feeding, irregular holes in stem, notched and cut or missing plants.

For more information, see Black Cutworm in Field Corn Management Guide 912k pdf file

True Armyworm
Lisa Fields (Schoharie County) and I did not catch any armyworm moths this week (May 30 and June 2).

Birdsfoot Trefoil

General Crop Condition
The birdsfoot trefoil in the Cornell research plots at the SUNY Cobleskill farm appears to be in very good condition and is 18 to 22 inches tall.

Do you know the number of growing degree-days in your region today?
(Base Temp. 50F)

Have a good week!
Ken Wise