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Eastern New York Field Crops Pest Report, 2003

For 5/27/03:


General Crop Condition
Alfalfa at the SUNY Cobleskill farm was 18 to 24 inches tall (May 22) and is in excellent condition. The alfalfa at the Cornell Research Farm in Valatie (May 22) was about 18 to 22 inches and mixed with other grasses.

Alfalfa Weevil
Jeff Miller (Oneida County) and Kevin Ganoe (Chenango, Otsego, Herkimer, Fulton & Montgomery Counties) are reporting 5 to 16% tip feeding and very few larvae present in the fields (May 22). 

There were 1st instar larvae at the SUNY Cobleskill Farm and 2nd instar Cornell Research Farm in Valatie (May 22). Tip feeding ranged from 5% to 20% in the 8 fields scouted. Alfalfa weevil larvae leave a little SHOT HOLE in the leaflets that is called "tip feeding". The percent of tip feeding is how we determine the action threshold for alfalfa weevil. 

  • Pick 50 alfalfa stems at random throughout the field.

  • Look for the small "shot holes" in the leaves that indicate that larvae are feeding.

  • Record the percentage of alfalfa stems that show at least one "shot hole" feeding damage in the top 3 inches of the canopy.

Before the first cutting, if 40% of the stem tips show feeding damage, you are at the "action threshold". It's time to do something!

The good thing is that alfalfa weevil can generally be controlled by harvesting. If you reach an action threshold within a week of your normal 1st cutting date, early harvesting will help avoid economic, yield, and forage quality losses. Alfalfa weevils only have one generation per year and are typically not a problem after first harvest. Occasionally, weevil can damage alfalfa re-growth after harvest. This damage may be more evident in the windrow areas, and can be more noticeable under cool or droughty weather conditions. If you find that 50 percent of the new growth is damaged, with many small larvae present, a chemical control may be warranted.

Alfalfa Weevil Adult & Larvae

Check out our on-line publication, IPM for Alfalfa Weevil. 1.2 Mb pdf file

Field Corn

General Crop Condition
Tillage, seedbed preparation and planting have been occurring throughout eastern New York.

True Armyworm
Lisa Fields and I did not catch any true armyworm moths this week (May 15).

Have you seen fireflies?
What do fireflies and corn rootworm have in common?

See next week's report to be enlightened!

Small Grains

Cereal Leaf Beetle
Cereal leaf beetle can be an occasional problem in small grains. Some years they do reach action thresholds and need to be controlled. Eggs can be found on the upper surface of the leaves near the midrib. Eggs are elongate, yellow to brown about 1/16 inch long, and are laid in chains of two or three. Small black slug-like larvae emerge from the egg and reach about a inch long. Larvae feed on the leaf surface, leaving long narrow white strips between the veins. The adults are 3/16 inch long with metallic bluish-black head and wing covers. Cereal leaf beetle is more of a problem in oats but can occasionally reach threshold levels in wheat.

The threshold for cereal leaf beetle is three or more eggs and larvae per stem before the boot stage of oats or one or more larvae per flag leaf after the boot stage. Check 30 stems distributed throughout a field to determine if the field are at an action threshold.

Cereal leaf Beetle eggs

Cereal Leaf Beetle larvae

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 12 to 16 inches tall (May 22).

(Base Temp. 50F)

Have a good week!
Ken Wise