Eastern New York Field Crops Pest Report, 2002

For 8/30/02:

Alfalfa

General: Alfalfa stands ranged between 8 and 15 inches tall this week at the SUNY Cobleskill farm (August 27).

Potato Leafhopper: Leafhopper infestations have dramatically declined in alfalfa fields this week at SUNY Cobleskill (August 27).

Where did all the potato leafhoppers go? If you want to know see next weeks report!

Check out our on-line publication, Potato Leafhopper Management in Alfalfa

Field Corn

General: No-till corn faired the drought much better than the conventional corn on the SUNY Cobleskill farm. The no-till corn was fairly uniform and about 8 feet tall, while the conventional cropping system had plants ranging from 3 to 12 feet tall (August 27).

Corn Rootworm: There were 3 of 6 fields over threshold for corn rootworm on the SUNY Cobleskill farm this season (August 27).

Kevin Ganoe reports extremely high infestation levels of corn rootworm in three fields in Herkimer County. The levels reached as high as 54 corn rootworm beetles in 8 samples. Many of the plants exhibited the classic ìgoose necking.î Lodging of corn is a symptom of excessive corn rootworm feeding on roots. This type of lodging is sometimes called goose-necking. Goose-necking is an attempt by the plant to straighten up again after it has begun to lean or lodge.

What do you do if you had fields over threshold for corn rootworm this year?
The best option for control of corn rootworm is to rotate the field. Corn after corn is prime habitat for corn rootworm and will increase infestations from year to year. A three to four year rotation is suggested for most field corn operations. Be aware that even in a three to four year rotation you still have to scout for corn rootworm. Adult corn rootworm beetles will travel from other fields in search of pollen. The second option is the use of a soil-applied insecticide at planting. In selecting a corn rootworm registered insecticide consult the Cornell Guide for Integrated Field Crop Management. We will have seed treatment and transgenic resistant hybrid corn management options in the near future to control corn rootworm.

For more information on How to Monitor for Corn Rootworm check out our online publications:

• Corn Rootworm Management in Field Corn.

• Sampling and Management of Corn Rootworm in New York

In the fall, weeds are fully-grown and easily identified. Correctly identifying and recording weeds helps you select the most economical method of control. Knowing whether the weed is a broadleaf, grass, sedge, summer or winter annual, biennial, or perennial is critical in selecting the right weed control measures. Remember, while herbicides are widely used for weed control other methods like crop rotation, cultivation, proper fertilization, planting dates, banding pre-emergence herbicides, crop spacing, plant populations, cover crops and combinations of these techniques should also be part of an integrated weed control program.

Conduct your fall weed surveys from late August through October. Sketch out a map, walk each 1/4 of the field, and record the weeds you observe. While no economic thresholds have been developed for weeds in New York, we recommend using a weed rating scale. The following scale can help you determine the severity of weed infestations in cornfields.

Evaluating Weed Presence- Weed Rating Scale:
Determine the intensity of each weed species as follows:

None:
No weeds present

Few:
Weeds present but very few plants within the field. Enough plants to produce seed but not enough to cause significant economic loss in the current year.

Common:
Plants dispersed throughout the field, an average of no more than 1 plant per 3 feet (.91m)
of row, or scattered spots of moderate infestation.

Abundant:
Fairly uniform concentrations across field. Average concentrations of no more than 1 plant per foot (.30m) of row or scattered spots of severe infestations.

Extreme:
More than 1 plant per foot (.30m) of row for broadleaf weeds and 3 plants per foot of row for grasses, or large areas of severe infestations.

So take a few minutes and encourage growers to look at their fields---it will help save on weed control costs and increase crop production. Remember, if you don't look, you will never know.

Check out our on-line publication: Weed Management in Field Corn

Do weeds indicate what insect pests may infest a cornfield next year? See the next exciting issue of Eastern New York Field Crops Pest Report!

Happy scouting!