Cover Crops

Agronomy News is a statewide newsletter for farmers, consultants, researchers, and educators interested in grain and row crop forage production systems. The topic for this edition is Preemergence Herbicides, Mowing Pastures: To Mow or Not to Mow, Checking Vegetative Growth Stages, Summer Nutrient Management Tips, Wheat Yields & Double-Crops—Time is Important to Maximize Yield, New Extension Agent, 2021-2022 Cover Crop Sign-Up, LEAD Maryland Fellowship Applications, MDA Pesticide Exams, MDA Pesticide Disposal Program, Weather Outlook, and Regional Crop Reports.

A common question asked by farmers dealing with herbicide resistant Palmer amaranth is, “What are the most effective burndown options in situations where Palmer amaranth is larger then the ideal 3-4 inch control range?”

It’s that time of year when growers are considering which herbicides to include in their burndown programs. Utilizing effective herbicides will help to ensure less weed competition at planting. However, growers should consider not only what herbicides they plan to use in their burndown programs, but also the weed species present in the field.

Last season, aphids transmitted an unusual amount of barley yellow dwarf virus (BYDV) to wheat and barley across the Delmarva Peninsula. BYDV is particularly important when it infects plants in the fall. Fall BYDV infections can stunt plants (noticed as early as green-up, Figure 1) and cause more serious yield loss than spring infections. Our most common small grain aphid species are bird cherry oat aphid (Figure 2) and English grain aphid, although bird cherry oat aphid are associated with greater and more severe incidence of BYDV.

Although sorghum faces relatively few pests compared to our other grain crops, it is not a “plant and forget” crop. Sorghum is often grown on marginal ground, in areas with greater deer pressure, dryland fields, and as a rotational component for managing weed and disease pressure. Sorghum is generally a minor component of a farming operation, and as such is easy to overlook during the season, especially now as other pests are requiring more attention and corn is nearing harvest. However, there are two significant insect pests that need to be scouted for to avoid potential losses and both are active right now on Delmarva. 

IPM Threshold Guide for Agronomic Field Crops

Reports of slug damage to emerging soybean seedlings (Glycine max) have increased in recent years, though their activity is highly variable from field to field, and within a field from year to year. Spring, 2021 weather was both cool and wet, conditions that many slug species find ideal. Slug eggs overwinter in the soil, hatch in the spring, and the juvenile slugs can begin causing damage to crops in just a week’s time after hatching (Hammond et al. 2009).

August IPM insect scouting tips on soybean, field corn, and sorghum.

Soybeans: Continue scouting for corn earworm, stink bugs, and soybean looper in double-crop fields. Defoliation thresholds at R5 are 15% and between 20 and 30% at R6. Corn earworm pheromone trapping information for Maryland can be found at https://extension.umd.edu/resource/corn-earworm-pheromone-trapping. NC State Extension has a good CEW threshold calculator can be used to help decide if it is worth treating: https://www.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html. Stink bug thresholds are 5 bugs per 15 sweeps until the soybeans reach the R7 stage, after which treatment for stink bugs is not necessary.