Corn earworm larvae. Photo: Frank Peairs, Colorado State University, Bugwood.org

There was not much increase in corn earworm numbers this week and some sites even caught fewer than last week. Sites in Franklin and Mifflin counties are experiencing catches per night of 6–7 moths per night which means a spray interval of 4–5 days would be suggested for corn that’s tasseling or silking in those areas. As a reminder, corn that is tasseling or silking is very attractive to corn earworm, as eggs are laid on silks. Control must be achieved while larvae are recently hatched and before they’ve entered the ear.

Once the spray threshold is reached, you can consider products from the pyrethroid class, diamide class, or spinosyn class for effective control. We tend to see the best efficacy from non-pyrethroid products such as Coragen, Blackhawk, and Radiant, as pyrethroid resistance has increased in migrating corn earworm populations. However, we tend to see more resistance later in the season than now, as moths migrate from further south in the United States up to our region. Diamides and spinosyns do not provide effective control of other pests such as sap beetles, brown marmorated stink bug, Japanese beetles, or adult corn rootworms. If you’re seeing these pests as you scout your corn, consider adding a pyrethroid, or the premix Besiege to control those.

We’re still seeing very few fall armyworm caught for this season in Pennsylvania, though one site in Lycoming County averaged 0.8 moths caught per night this week. By managing for corn earworm, fall armyworm should be adequately controlled, as well.

Average weekly catch – 7-day moving average. The average catch per night (total catch, divided by the number of nights trapping), divided by the number of nights where data exist, multiplied by 7. If no data exist for that week, null is reported.

CEW	CEW	CEW	FAW	FAW	FAW
County	Site	13-Jun	21-Jun	27-Jun	13-Jun	21-Jun	27-Jun
Blair	Curryville	1.7	7	0.9	0	0	0
Blair	Sinking Valley	0.9	2.1	2.9	0	0	0
Bucks	Doylestown	0	0.6	0.4	0	0	0
Centre	Harner	0.3	2	6	0	0	0
Centre	Rock Springs	0.7	2.8	2.8	0	0	0
Clinton	Kaufman	Null	0.3	0.3	Null	0	0
Franklin	Shippensburg	0.3	9.1	7	Null	0.1	0
Franklin	Waynesboro	8	8.7	5	0	0	0
Indiana	Indiana	Null	2.7	0.5	Null	0	0
Lancaster	Landisville	0.1	0.7	0.4	0	Null	0
Lancaster	New Danville	0	0.6	0.1	0	Null	0
Lancaster	Neffsville	Null	0.4	0.6	Null	Null	0
Lehigh	Germansville	Null	5.8	Null	Null	0	Null
Lycoming	Linden	Null	Null	2	Null	Null	0
Lycoming	Montoursville	Null	Null	0.9	Null	Null	0.9
Mifflin	Streamside	Null	7.1	6	Null	0	0
Washington	Bebout	Null	5.4	2.3	Null	Null	0
York	York	0.3	0	1	0	0	0

Thresholds: Reproductive (tassel/silk) and late vegetative corn attract moths. Shorten spray schedules when populations increase.

Threshold based on CEW	Catch per week	Spray Frequency
Almost Absent	1–13	7+
Very low	14–35	5–6
Low	36–70	4–5
Moderate	71–349	3–4
High	>350	2–3