European corn borer larvae (left) adults (right). Photo: ©Marlin E. Rice
Corn earworm (CEW) trap counts have decreased. It appears that we had an overwintered population resulting in some high counts in June/early July. I expect those adults to be in a larval or pupal stage now. Current counts are more like the summer lull we get before significant migration from the south. This year, we may see a combination of that migration plus a 2nd generation from the overwintered population, so trap counts could increase, but right now most sites are below threshold, or at a wide (5-6 day) threshold. Sites at that wide spray threshold level are in Centre, Lancaster, Lehigh, and Westmoreland County.
European corn borer
European corn borer (ECB) is starting to emerge as second generation adults. Infestations are spotty, but noticeably high in Clinton and York County.
Fall armyworm (FAW): We continue to see low rates of trap capture, with an increasing number of sites. Early immigration appears to be occurring now. It is not uncommon to find damage prior to trap capture at this time of year. Check for larval feeding in vegetative corn: large, ragged damage to leaves with lots of frass.
CEW are low in most locations, at no-spray of a wide (5-6 day) spray threshold. ECB infestations are spotty - 2nd generation adults are in sites at Clinton and York Counties. FAW immigration has started. Silking corn will be very attractive to early-season CEW moths.
|Bradford||Shores Sisters Produce||0||10||0||13||2||0|
|Fayette||Duda's Farm Inc.||20||0||8||0||0||5|
|Huntingdon||New Morning Farm||7||7||null||null||5.3||null|
|Westmoreland||Schramms Farms and Orchard||null||null||21.5||null||null||0.9|
Reproductive (tassel/silk) and late vegetative corn attracts moths. Shorten spray schedules when populations increase.
Thresholds Based on CEW Captures
|Levels||CEW catch / week||Spray frequency|
|almost absent||1-13||4 days to no spray|
|very low||14-35||5 to 6 day|
|low||36-70||4 to 5 day|
|moderate||71-349||3 to 4 day|
|high||> 350||2 to 3 day|
If CEW is low, then consider ECB
|Levels||ECB catch / week||Spray frequency|
|almost absent||< 14||no treatment|
|very low||15-35||6 day|
|moderate||> 70||4 day|