Farm News
05-19-06
Holmes: Scout for black cutworms
By KRISTIN GREINER- Farm News staff
Producers should be scouting now for the pesky black cutworm (BCW) as
projected based on 300 degree days from moth arrival, especially since reports
received this week identified black cutworms west of Scranton.
John Holmes, an Iowa State University (ISU) Extension crops field
specialist, said that West Central Cooperative Agronomist Bill Heaning reported
finding black cutworm (BCW) larvae feeding on corn west of Scranton on May
12. Heaning reported that BCW larvae were feeding on V1-V2 stage both above
and below the soil surface with fields showing 10 to 15 percent damage.
Holmes said that ISU Extension Entomologist Marlin Rice predicted black
cutworm feeding would begin on May 11.
“It appears that the predictions were pretty accurate,î” Holmes said, advising
producers to “scout fields” for cutworm feeding and watch for leaf feeding initially
followed by plant cutting and stand reductions. Insecticide treatments should be
considered if cutworms are 3/4 inches or less in length and 2 to 3 percent of the
plants are wilted or cut.î
Rich Pope, an entomologist at ISU, said he has received some “anecdotal
commentsӔ about pinhole feeding, but no confirmed instances of BCW.
“If they do happen, infestations are typically sporadic anyway, varying from field
to field,î” he said.
Pope and Rice said in a report that while the insect is an occasionalî pest of
seedling corn, it deserves attention because of its potential for causing economic
damage. If leaf feeding is detected, producers should determine if it’s being
caused by black or dingy cutworms. Very large cutworms found during the
earliest black cutworm cutting dates are often dingy cutworms, they wrote,
because dingys overwinter in Iowa as partially grown larvae. Also, fields with
winter annual weeds are more likely to have cutworms than clean fields, and
soybean stubble is more attractive to the moths than corn stubble.
If producers find leaf feeding and only black cutworms, they should mark off 100
plants in a row with stakes or flags, and scout these same plants for cutting over
a period of several days at several locations across the field, Rice and Pope said
in their report. Then, monitor the cutworm activity and determine whether they
are cutting plants and the percent cut plants.
Producers can stop scouting when infected fields are sprayed or when plants
have five fully developed leaves (stage V5).