1. Advances in Management of Corn Earworm in Sweet Corn Rick Foster Purdue University and Rick Weinzierl University of Illinois

2. Corn Earworm Pest of sweet corn, seed corn, tomato and other crops Two generations per year

3. Corn Earworm Biology Females prefer to lay eggs on green silks

4. Corn Earworm Biology Females prefer to lay eggs on green silks When larvae hatch, they move directly into the ear tip Once inside the ear, the larvae are protected from insecticides

5. Corn Earworm Population Dynamics Climate in northern 2/3 of Indiana is generally too cold for earworms to overwinter in appreciable numbers There may be a small first generation The second generation is larger but much of the later season moths move northward on storm fronts

6. Week Ending Moths per Week 2009 Threshold 2 nd Generation

7. 2008 Moths per Week Week Ending

8. Corn Earworm Management Treat when fresh, green silks are present (start at 70%) Threshold is 10 moths per trap per night

9. Week Ending Moths per Week 2009 Threshold 2 nd Generation

10. 2008 Moths per Week Week Ending

11. NCRIPM Funded Study Four locations in Indiana and Illinois 9-10 plantings per location – start mid-March and plant every 2 weeks 2 varieties with 7 days difference in maturity Bagged 500 ears per subplot and exposed 50 ears to CEW each night for 10 nights Collected silks and counted eggs Compared egg numbers to pheromone trap catch

12. Relationship Between Pheromone Trap Catch and Egg Laying

13. Nightly Relationship Between Trap Catch and Egg Laying

14. What’s Going On? The use of pheromone traps and the economic threshold of 10 moth/trap/night has been used effectively for several decades and yet we can’t show a relationship between nightly trap catch and oviposition.

15. How Do Pest Managers Make Decisions? Growers must take all available information into consideration, not just last night’s pheromone trap catch. Most growers will take into account the general trend in trap catches when making a spray decision. So, we decided to look at how trap catch and egg deposition were related when we looked at 10 days of silking for each of our plantings.

17. Why? Later in the season, sweet corn is an island in an ocean of field corn that may be equally attractive for oviposition Sweet corn that silks before any field corn in the area is very attractive for oviposition so many of the moths will go to those small fields to lay eggs

18. So, what should our threshold be? In general, we should continue to use 10 moths per night as the threshold for the main season For early season sweet corn (before nearby field corn in silking, use a threshold of 1.

19. Future Work This year I will be testing the two thresholds (1 and 10 moths per night) at 5 different plantings time during the season

20. Questions?