Cutworms Will Test New Technologies

Cutworms are showing up on corn and sunflower seedlings in central and southeastern SD.

Producers should scout now. It’s also a chance for producers to verify whether Bt-corn hybrids
or seed treatments that producers bought to control cutworms are working as promised.

Seed treatments such as Cruiser and Poncho claim on their labels that they suppress or control
cutworms on corn and sunflower.  Corn hybrids containing the Herculex I and Herculex XTRA
genes are claimed by their respective seed companies to be protected from cutworm attacks.

There may be several species of cutworms damaging to South Dakota crops, including dingy,
black and red-backed cutworms, and currently available products may not control them all.  I am
of the opinion that we spent a lot of time working on black cutworms that we forgot about the other
so-called "minor" cutworm species

Larvae of black cutworms can be very damaging because they cut the corn growing points from
under the soil.  Wilted seedlings, scattered pieces of leaves, and small holes on leaves are
common signs of black cutworm infestation.

Cutworms are active at night and hide under loose soil during the day.  Scouting during the day
involves scratching the soil surface to expose hidden larvae.

Producers should consider insecticide treatment if 5 percent (one in 20) of the corn or sunflower
seedlings show signs of cutting or leaf feeding, and if the larvae are still less than an inch long. 

Insecticides labeled for use against cutworm larvae on corn or sunflower as seedling foliar
sprays include Asana XL (5.8-9.6 fluid ounces per acre), Baythroid (0.8-1.6 fluid ounces per
acre), Decis (1.0-1.5 fluid ounces per acre), Lorsban 4E (1-4 pints per acre), and Warrior
(1.92-3.20 fluid ounces per acre). Always read and follow all directions on the label.

Dingy cutworms may be accounting for some of the damage in area fields. Dingy cutworms
overwinter as partially grown larvae in the soil then resume feeding in the spring.  Dingy
cutworms are not as damaging as black cutworms because they usually cut seedlings above
the growing point.

The redbacked cutworm, a species that has gained importance only in the last 3 years,
may be as damaging as the black cutworm.  Why has this species all of a sudden become
important in central SD?  I have my own hypothesis and it involves disturbance ecology.

Kindly report any “failures” by Bt-corn and seed treatments to control cutworms to me
at (605) 688-4603.

                                                        


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 Web Posted on Tuesday, May 23, 2006 by Mike Catangui. Last Updated on Wednesday, May 24, 2006.