Silk Stage Sweet Corn - Action Thresholds

Cooperative Extension

Action Thresholds for Silk Stage Sweet Corn

Based on Corn Earworm Blacklight Trap Catches (conservative system)

Number of Moths caught per Seven Days	Silk Spray Schedule
<1	No Spray
1	6 Day
2	5 Day
3	4 Day
4	3 Day
38	2 Day

Based on Corn Earworm Pheromone Trap Catches

Generally used as a guideline in combination with light trap catch information. Requires use of a wire mesh trap and Hercon CEW pheromone lure placed with the base of the trap at silk height in fresh silking corn. Check traps at 3 times per week throughout the growing season.

Number of Corn Earworm Moths Caught
Per Day	Per 5 Days	Per Week	Spray Interval
<0.2	<1	<1.4	No Spray
0.2 – 0.5	1.0 – 2.5	1.4 – 3.5	6 Day
0.5 – 1.0	2.5 – 5.0	3.5 – 7.0	5 Day
1.0 – 13.0	5.0 – 65.0	7.0 – 91.0	4 Day
>13.0	>65.0	>91.0	3 Day

In some cases corn earworm catches are very low; however, corn borer and fall armyworm pressure is high. If no sprays are called for CEW, the following spray schedule should be used:

European Corn Borer/Fall Armyworm/Sap beetle	Spray Schedule
ECB light trap catch is > 100 per 5 days	4 Day
ECB light trap catch is 51-100 per 5 days OR FAW infestations in whorl stage corn is >30% infestation OR Sap Beetle infestation is greater than 10%	5 Day
ECB light trap catch is 25 to 50 per 5 days & FAW infestations in whorl stage corn is < 30% infestation & Sap Beetle infestation is < 10%	6 Day
ECB light trap catch is < 25 per 5 days & FAW infestations in whorl stage corn is < 30% infestation & Sap Beetle infestation is < 10%	No Spray