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Sweet Corn Pheromone Trap Network for Western New York, 2006

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 9/19/06

For the locations reporting this week, ECB counts for both races are in the single digits, with the exception on Penn Yan.  Corn earworm catches are also zero or in the single digits this week  Fall armyworm catches are high at several locations.  Late sweet corn fields are very attractive to egg-laying moths because they are islands of fresh vegetation in a sea of mature, dry, or senescent crops and wild plants.  Infestation levels at harvest can be very high in these fields, so insecticide applications are needed, especially while the silks are fresh and green.  Insecticides are no longer warranted when the field is within one week of harvest.

The spray threshold in silk stage fields is 5% infested plants.  Scout the ear zone (roughly from two leaves above and one leaf below the ears) for ECB egg masses and ECB or FAW larvae.  Egg masses are found most frequently on the underside of leaves near the midrib, and consist of approximately 10-20 flattened eggs overlapping like fish scales. Eggs are white when first laid, turning cream colored after a couple of days, and show the black head capsules of the tiny larvae through the surface of the eggs when within 1 day of hatching (the "black head" stage).  Egg masses can also sometimes be found on the flag leaves of the ears or on the husk itself.  Eggs take approximately 100 base 50 degree days to hatch.   When temperatures are in the 70's during the day and the 50's at night egg masses will take about a week to hatch.  When temperatures are in the 80's during the day and the 60's at night, they could hatch in only 4 days.

Look down into the tops of the silks for newly hatched larvae, and pull the ear away from the stalk slightly to look for larvae feeding between the stalk and the ear.

Once CEW are being caught in higher numbers, insecticide applications in silk stage fields should be determined by CEW trap catches.  The recommended spray intervals for CEW should be adequate for ECB and FAW control.  Because CEW lay their eggs directly on the silk, and eggs are difficult to find in the field unless the population is VERY high, we rely on pheromone trap catches rather than scouting to make CEW management decisions.  It is most important to adhere to the recommended spray intervals when the field is in the green silk stage.  The chart below indicates recommended spray intervals during the silk stage for a range of trap catches:

Average CEW Pheromone Trap Catches

Per Day

Per Five Days

Per Week

Days Between Sprays

<0.2

<1.0

<1.4

No Spray (for CEW)

0.2-0.5

1.0-2.5

1.4-3.5

6 days

0.5-1.0

2.5-5.0

3.5-7.0

5 days

1-13

5-65

7-91

4 days

over 13

over 65

over 91

3 days

Add one day to the recommended spray interval if daily maximum temperatures
are less than 80 F for the previous 2-3 days.

Location

ECB-E

ECB-Z

CEW

FAW

Baldwinsville (Onondaga Co.)

NA

NA

NA

NA

Batavia (Genesee Co.)

NA

NA

NA

NA

Eden Z (Erie Co.)

NA

NA

NA

NA

Farmington (Ontario Co.)

5

0

2

0

Hall (Ontario Co.)

1

2

0

31

Hamlin (Monroe Co.)

0

3

0

10

Kennedy (Chautauqua Co.)

0

3

4

40

King Ferry (Cayuga Co.)

NA

NA

NA

NA

Kirkville (Madison Co.)

NA

NA

NA

NA

LeRoy (Genesee Co.)

0

2

0

82

Lockport (Niagara Co.)

NA

NA

NA

NA

Medina (Orleans Co.)

NA

NA

NA

NA

Olean (Cattaraugus Co.)

0

3

0

6

Owego (Tioga Co.)

0

1

1

NA

Penn Yan (Yates Co.)

2

18

5

19

Spencerport (Monroe Co.)

NA

NA

NA

NA

Williamson (Wayne Co.)

NA

NA

NA

NA