Resource Guide for Organic Insect and Disease ... - Cornell University

Materials Approved for Organic Production:
None currently available.
SEEDCORN MAGGOT (Delia platura)
Seedcorn maggots (Photo 8.11) can greatly reduce stands of untreated seed in cold, wet soils.
They are particularly attracted to decomposing organic matter, so corn planted in fields where
manure or cover crops have been recently incorporated is especially susceptible to infestation.
The female flies lay eggs near germinating seeds, and the larvae feed inside the sprouting
seeds. Feeding damage also leads to rot.
Cultural Control:
1. Create conditions for rapid germination, including use of ridges and waiting until the
soil has warmed.
2. In cold climates, consider row covers or transplants for the earliest sweet corn.
3. Be sure that raw manure and green plant residues are well incorporated and have time
to decompose prior to seeding.
Materials Approved for Organic Production:
None currently available.
WESTERN BEAN CUTWORM (Striacosta albicosta)
Western bean cutworm (WBC) is a new pest of sweet corn that has been moving eastward from
its historical range in the west. Field corn and dry beans are also hosts. This insect has one
generation per year in late July to early August, and egg-laying females are most attracted to
late whorl to tassel emergence stage fields. Masses of 50-200 eggs (Photo 8.12) are laid on the
upper leaf surface near the emerging tassel, and larvae feed on the tassel and surrounding tissue
for a short time before moving to the ear. Multiple larvae may infest the same ear (Photo
8.13). Adults overwinter in the soil, and overwintering may be more successful in light, sandy
soils. Moths may be monitored using pheromone traps, and fields in an attractive stage should
be scouted for egg masses and newly hatched larvae after the flight peak. Check with the local
extension program to see if WBC is being monitored in a given area.
Cultural Control:
Because moths are strong flyers, rotation may reduce, but not eliminate infestations.
Materials Approved for Organic Production:
Spinosad and Bt products are labeled for western bean cutworm, but efficacy information is
not available. Spray timing is crucial; target newly hatched larvae before the bore into the ear,
where they are protected from the insecticide.
BROWN MARMORATED STINK BUG (Halyomorpha halys)
Brown marmorated stink bug (BMSB) is an exotic, introduced pest with a wide host range that
includes sweet corn. It was first confirmed as an agricultural pest in 2010. Adults are shieldshaped
and mottled brown, with distinctive white bands on the antennae and markings at the
edge of the abdomen (Photo 8.14). Adults emit a distinctive odor when disturbed. Eggs are
round and light green and are laid in clusters of 20-30 on the undersides of leaves. Immediately
after hatching, nymphs are reddish orange with black markings, legs, and antennae; over time,
they become mottled brown with white banding on the antennae and legs, resembling adults,
but without wings (Photo 8.15). BMSB damages sweet corn by feeding on kernels through
the husks, causing incomplete kernel fill, kernel collapse, and discoloration. Information about
BMSB can be found at: http://www.northeastipm.org/index.cfm/working-groups/bmsb-working-group/bmsb-information/.
Cultural Control:
Because of its wide host range, crop rotation is not a viable option. As more is learned about its
biology and host preference, biological control or trap cropping may become useful.
Organic Resource Guide 69