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Eastern New York Field Crops Pest Report, 2003

For 6/13/03:


General Crop Condition
Alfalfa at the SUNY Cobleskill farm was harvested this week (June 2). The alfalfa at the Cornell Research Farm in Valatia (June 3) was 30 inches tall but has lodged due to heavy rain and wind (June 11).

Increases in Alfalfa Weevil Damage in Eastern New York
Alfalfa weevil damage is rising in Eastern New York. Many counties are reporting 10 to 60 percent tip feeding. Larval development within the same field is mixed with 1st to 4th instar larvae present. This could pose a problem after the first cutting because sometimes harvesting alfalfa will not completely control alfalfa weevil and can still cause economic damage on re-growth. Insecticide use may be necessary after the first cutting if small larvae are still present and damaging re-growth of at least 50% of the new buds. Watch windrows for signs of weevil feeding on re-growth. Recent rains may have helped us a bit by fostering conditions favorable to epidemics of a fungal disease (Zoopthora spp.) which attacks alfalfa weevil - and other insects. If you see shriveled up, brown colored, or dead weevil larvae you know fungal diseases are at work keeping alfalfa weevil populations low.

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:
Beth Spaugh (Clinton County)
Jeff Miller (Oneida County)
Kathryn Evans (Madison County)
Kevin Ganoe (Chenango, Montgomery, Herkimer, Otsego Counties)
Richard Gast (Franklin County)
Ken Wise (Eastern New York)

Potato Leafhopper
I found potato leafhopper in several fields this week at the SUNY Cobleskill farm (June 12). While currently the infestation levels are low, they can increase rapidly as daily temperatures start to increase. New seedings and short alfalfa can be particularly at risk for potato leafhopper. Even in a new seeding that is resistant to potato leafhopper can be at risk. An alfalfa variety may be resistant but not immune to potato leafhopper. So, scout all alfalfa fields even the resistant ones.

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

Picture of potato leafhopper

Verticillium wilt
Verticillium wilt can be a serious disease limiting yield and the number of productive years of an alfalfa stand. An early symptom includes V-shaped discoloration at the tip of a leaflet. As the disease progresses, leaflets wilt, turn yellow or pink, and often curl or twist. The curl and twisting of leaflets is the most characteristic symptoms of Verticillium wilt. Taproots appear healthy and sound, but have a dark ring (the water-conducting tissues) which is evident when the taproot is cut in cross section. Verticillium wilt symptoms may be more obvious in the second cutting.

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 development varies in many parts of Eastern New York. I have seen corn being planted and as tall as 8 inches this week across the region (June 11).

I observed slug damage on several corn plants at the SUNY Cobleskill farm (June 12). Slugs can be a minor problem in cool wet springs like we have been having this year. Slugs do windowing type damage (leaf tissue eaten with one clear layer of cells left, that looks like a window), and leave a slime trail (a shiny trail near its feeding damage).

Here is a picture of SLUG damage on corn.

Maize Billbug damage
Have you ever seen 2 or 3 identical holes side by side across a leaf when the corn is 2 to 6 inches tall? This minor insect pest (maize billbug) drills through the main stem of the plant. When the plant grows and the leaf unrolls it leaves 2 or 3 holes side by side. Maize billbug rarely causes economic damage to the corn crop.

There were many weed seedlings emerging in corn fields at the SUNY Cobleskill farm this week (June 12). There were 1000s of common lambsquarters, common ragweed, velvetleaf and crabgrass in large patches in all the corn fields.

Which of these weeds have developed resistant populations to triazine type herbicides in New York?

See next weeks report for the correct answer!

For more information, see Weeds in Corn Management Guide 1Mb pdf file

IPM Question of the Week!
We all know that seed corn maggot will attack corn seed, but what other field crop is grown in New York that these fly larvae will seek out and feed on? See next week's report for enlightenment!

Birdsfoot Trefoil

General Crop Condition
Birdsfoot Trefoil was harvested this week at the SUNY Cobleskill farm (June12).

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

Happy Scouting!
Ken Wise