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Sweet Corn Pheromone Trap Network

for Western NY - 2007

This is a seasonal scouting report giving growers in the Western New York area information on the presence of sweet corn pests and recommendations on scouting and thresholds. The report is written by Abby Seaman, NYS IPM's Area Extension Educator for Vegetables.

For 6/12/07

ECB catches decreased at many locations this week.  Egg masses and newly hatched larvae were found in the field.  Growers using the recommendations outlined below for fields started under plastic or row cover should have applied an insecticide by now in areas where the flight peaked last week.  Continue scouting fields for new egg masses and newly hatched larvae to determine the need for additional sprays.  The threshold in silk stage fields is 5% infested plants.  No CEW or FAW were caught at the few locations where traps have been set up.

For fields in the early tassel-silk stage when the moth flight peaks:

Fields started under plastic or row cover will be very attractive to egg-laying moths because the plants are larger than those in bare ground fields.  We have found that using the usual tassel emergence scouting and thresholds do not work in corn started under plastic or row cover.  John Mishanec has had good results in trials in which pheromone trap catches were used to time sprays in row cover or plastic corn. Growers waited until there was a significant increase in the ECB trap catches in their area and then timed sprays to coincide with egg hatch.  ECB eggs require 100 degree days (base 50) from oviposition to hatch.  Degree day accumulations for many locations may be found on the NEWA web site.

Or to calculate base 50 degree days, add the daily maximum temperature and the daily minimum temperature, divide by 2, and subtract 50.  For example, if the maximum temperature for a day is 85 and the minimum is 60, (85+60)/2 = 72.5 - 50 = 22.5 degree days.  At that rate of accumulation, eggs would hatch about 5 days after oviposition.

For fields in the whorl stage when the moths are laying eggs:

Split field demonstrations have shown that applying insecticides to sweet corn for worm control before tassel emergence does not produce better results than waiting until the recommended tassel-emergence spray timing.

In fields still in the whorl stage when eggs are deposited, larvae move to the whorl, feed on the foliage and un-emerged tassel, and are found feeding on the tassel when it emerges.

Larvae feeding in the whorl are protected from insecticide applications and mortality will not be as high as at tassel emergence, when larvae feeding in the emerging tassel are exposed to the spray.  Fields should be first scouted for ECB and FAW larvae at early tassel emergence.  For corn borers, look down into emerging tassels for tiny larvae or frass (white to brown material about the size of fine sand).  For armyworms look for ragged feeding holes and frass pellets the texture of coarse sawdust.

The threshold for ECB and armyworms at tassel emergence is 15% infested plants.

Before any insecticides have been applied, scouting is fast and easy because any sign of feeding is an almost sure sign of live larvae, so it's not necessary to spend time finding the larvae.  After the initial insecticide application, feeding damage may be from a larva that has already been killed, so finding the critter is more important for an accurate estimate of the number of infested plants.

Larvae will leave the tassel as it opens up and no longer provides a moist, protected feeding environment, and move down the plant looking for protected places to feed.  Insecticide applications need to be timed to kill larvae before they bore into a new feeding location where they will be again protected from sprays.  In fields with very uneven development, two applications may be necessary, one when approximately 25-50% if the tassels have emerged, and again after 75-100% of the tassels have emerged, if the field is still over threshold.

Location

ECB-E

ECB-Z

CEW

FAW

Baldwinsville (Onondaga Co.)

7

6

0

NA

Batavia (Genesee Co.)

1

4

NA

NA

Bellona (Yates Co.)

74

1

NA

NA

Eden Z (Erie Co.)

0

28

NA

NA

Farmington (Ontario Co.)

5

0

NA

NA

Hamlin (Monroe Co.)

0

1

NA

NA

Kennedy (Chautauqua Co.)

1

13

0

NA

King Ferry (Cayuga Co.)

0

0

0

0

Kirkville (Madison Co.)

NA

NA

NA

NA

LeRoy (Genesee Co.)

0

4

0

0

Lockport (Niagara Co.)

0

41

NA

NA

Medina (Orleans Co.)

0

0

0

0

Olean (Cattaraugus Co.)

0

0

0

0

Owego (Tioga Co.)

4

3

NA

NA

Penn Yan (Yates Co.)

16

5

NA

NA

Spencerport (Monroe Co.)

0

34

NA

NA

Williamson (Wayne Co.)

0

0

0

0