Archives for August 2019

Sweet Corn

European corn borer (ECB) moth captures have decreased somewhat over the past week, and no map will appear in this issue.  The second flight remains very spotty, as is consistent with recent years’ second flights.  Low level feeding has appeared in whorl and pre-tassel corn, but rarely rises to the 12% threshold by itself.  In combination with fall armyworm (FAW) feeding, action thresholds have been exceeded in all areas of the state.

Growers should continue to scout whorl and pre-tassel stage plantings weekly and consider treating when infested plants exceed 12% in a 50 plant sample.  As plantings proceed to the pre-tassel stage, ECB larvae may be found in emerging tassels.  It is a good idea to treat individual plantings as they move into the full tassel/first silk stage one time.  This eliminates any ECB larvae that have emerged with the tassels as they begin to move down the stalk to re-enter near developing ears.

Useful insecticides for this particular application include synthetic pyrethroids (IRAC Grp 3), spinosyns (including OMRI approved Entrust) IRAC Grp 5), and diamides such as Coragen (IRAC Grp 28) or materials such as Besiege which include the active ingredient in Coragen.  Synthetic pyrethroids alone should NOT be used for corn earworm (CEW) protection on silking corn.  Control with these materials is very inconsistent.

The highest nightly black light trap catches of ECB for the week ending 8/14/19 are as follows:

Corn earworm (CEW) moth catches increased late last week in both trap types, then declined somewhat with cooler evening temperatures over the weekend.  The return of warm nights may result in higher CEW activity again.   There were some exceptionally high catches in southern NJ pheromone traps this past week (see blacklight map at left, and pheromone trap map below at right).    There are now economically important populations of this pest throughout the state, and most areas are at extreme risk of crop injury if strict silk spray schedules are not observed.   Red areas on the on the pheromone trap map indicate a 3-day silk spray schedule, while green indicates a 4-5 day silk spray schedule. Blue areas represent a 5-6 day schedule, and white areas are 6-7 day.  There are far fewer CEW pheromone traps than blacklights, and the resulting map has much broader color bands as a result.  It should also be noted that the pheromone traps are much more sensitive than blacklights.  Therefore, the number of moths caught in pheromone traps required to generate a specific spray interval is much higher than the number caught in blacklight traps.   It must be stressed that there is high variability in these catches, and growers should consult with their IPM practitioner on recommended spray schedules.

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Sweet Corn

European corn borer (ECB) moth captures have increased slightly for a second week in parts of the state (see ECB map at left).  The second flight is very weak and spotty, as is consistent with recent years’ second flights.  Limited feeding has appeared in whorl and pre-tassel corn.

Growers should continue to scout whorl and pre-tassel stage plantings weekly and consider treating when infested plants exceed 12% in a 50 plant sample.  As plantings proceed to the pre-tassel stage, ECB larvae may be found in emerging tassels.  It is a good idea to treat individual plantings as they move into the full tassel/first silk stage one time.  This eliminates any ECB larvae that have emerged with the tassels as they begin to move down the stalk to re-enter near developing ears.

Useful insecticides for this particular application include synthetic pyrethroids (IRAC Grp 3), spinosyns (including OMRI approved Entrust) IRAC Grp 5), and diamides such as Coragen (IRAC Grp 28) or materials such as Besiege which include the active ingredient in Coragen.  Synthetic pyrethroids alone should NOT be used for corn earworm (CEW) protection on silking corn.  Control with these materials is very inconsistent.

The highest nightly black light trap catches of ECB for the week ending 8/07/19 are as follows:

Corn earworm (CEW) moth catches are increasing now in blacklight traps in southern and central portions of the state.  Pheromone trap catches have increased as well, with significantly higher catches in southwestern NJ.  There are now economically important populations of this pest throughout the state (see blacklight map at left, and pheromone trap map below at right).   CEW numbers are likely to continue to increase steadily throughout August, with the potential for a dramatic increase in the event of a strong storm system hitting our state.  Red areas on the on the pheromone trap map indicate a 3-day silk spray schedule, while green indicates a 4-5 day silk spray schedule. Blue areas represent a 5-6 day schedule, and white areas are 6-7 day.  There are far fewer CEW pheromone traps than blacklights, and the resulting map has much broader color bands as a result.  It should also be noted that the pheromone traps are much more sensitive than blacklights.  Therefore, the number of moths caught in pheromone traps required to generate a specific spray interval is much higher than the number caught in blacklight traps.   It must be stressed that there is high variability in these catches, and growers should consult with their IPM practitioner on recommended spray schedules.

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