Watch out for CUTWORM…

By Robert Moloney, Syngenta Seeds

This spring is shaping up to give us some issues with cutworm this year and Tracey Baute, OMAF, is reporting some damage north of Guelph already.  Cutworm moth counts in the U.S. have been very high and since cutworm blow into Ontario each spring this is setting us up for a problem.  We are also at greater risk due to the late planting season that we’re getting into.  If we get planted early the corn plants may be large enough (>5 leaf) to grow through whatever damage the cutworm cause but that’s not likely to be the case this year.  With the rainy weather we’ve had a lot of winter annuals (especially chickweed) have had a chance to get large and form a thick and attractive mat on the ground before being burnt off.  Undisturbed soybean stubble is also quite attractive to cutworm.

Cutworm moths are spring immigrants into Ontario. These pests are carried to Ontario from the U.S. by wind.  Growers in Essex, Kent, Elgin and Norfolk counties (especially along the north shore of Lake Erie) are the most often affected, but cutworm can sporadically show up anywhere in the province.  The adult moths lay eggs on low lying/matted weeds on the ground.  The larva will often start on the weeds then move on to corn plants after the weeds are killed and start to die.  They will continue feeding on developing corn plants through June.  Since the larva will tend to spend the day just below the surface of the ground, often the first indication you have of cutworm damage is holes in the leaves of the plant, a suddenly wilting plant (where the larva have cut partway through it or tunneled into the plant) or plants cut off entirely and fallen over.

Bt EVENTS ARE NOT EQUAL IN BLACK CUTWORM CONTROL!!

 Many Bt events provide no control at all on Black Cutworm larva.  These include the Yieldgard VT Doubles and Triples, Pride G2 and G3 and Agrisure CB and Agrisure 3000GT.  Agrisure Viptera 3111 provides the highest level of control available while Herculex and SmartStax (which contain Herculex) events will provide suppression/control of small larva.  Under high pressure of cutworm or (as is likely this spring) with larger cutworm scouting of all corn fields (including with fields planted with Bt hybrids providing control) is recommended.  This is since control is not perfect and level of control drops as larva get larger.  Cruiser or Poncho seed treatments also provide some protection, but only against small larva.

THRESHOLDS

If you have feeding on 10% or more of plants, plants are <6 leaf stage and the larva are less than 1 inch long spraying is recommended.  Matador 120EC is registered for control of cutworms.  Spray should be applied in the evening or nighttime hours when the cutworms have emerged from the soil and are actively feeding.  Keep water application volumes up for good coverage.

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