Recent Frost: Low temperatures from May 14- 17 have caused some concern about frost injury to corn. Frost damage to corn can appear serious initially. Full recovery is expected if the growing points are not damaged. Sometimes growing points are damaged when cold air gets below the soil surface.

Corn plants should show new leaf tissue from the whorls 3 to 5 days after the frost. Dead plants will still look dead after 3-5 days. Yield damage to corn from frost is usually related to the amount of stand loss that occurs and not the amount of leaf damage.

Corn Replant Decisions: Stand reductions can occur from a number of reasons. Plant populations of about 20,000 would be expected to yield about 89% of normal. Corn replanted on May 20 is expected to yield about 87% of normal. Therefore a stand below 20,000 may be a candidate for replanting. Use this checklist to help make replant decisions.

Black Cutworm: Black cutworm larvae will likely be large enough to damage corn on May 27/28 for northwest/north central Iowa. No large problems are expected. However, check fields for leaf feeding and/or cut plants at or before May 27/28.

Thresholds follow for different growth stages:

Stage               Cut plants/100 plants

Seedling                    2

V2                             3

V3                             5

V4                             7

Alfalfa Quality: Alfalfa quality can be tracked using PEAQ (predictive equation of alfalfa quality). The method uses alfalfa stand height and maturity stage to estimate the relative feed value (RFV). The PEAQ measurements will be posted on the ISU Extension Dairy Team page.

Prepared by Paul Kassel, Extension Field Agronomist

Phone: (712) 262-2264, Email: kassel@iastate.edu