Army Worm infestations have been reported in small grains crops late last week. The recent ideal growing conditions for wheat and oats have also been great for the worms. Producers should be scouting their crops and improved forages such as Coastal Bermudagrass to ensure early detection and control. Armyworms should be controlled when they occur in large numbers or plant damage is becoming excessive.
Fall armyworms feed any time of the day or night, but are most active early in the morning or late in the evening. Susceptible fields or lawns should be scouted by counting the number of armyworms in a square foot area in 8 different sites. Divide the total worm count by 8 to find the average number of armyworms per square foot. Be sure to take samples in the interior of the field because this pest is often heaviest near the field margins. Sometimes, only the field margins require treatment
The threshold level ranges from two to three larvae per square foot for seedling wheat. For older plants, three to four larvae and obvious foliage loss justify control measures. Thresholds in improved pastures and lawns vary with conditions but treatment should be considered when counts average three or more worms per square foot.
Insecticide choices vary with the crop but the following (with product names and grazing restrictions in parentheses) are labeled for use in pastures, including carbaryl (SevinÒ) (14 days), malathion (0 days), methomyl (LannateÒ) (7 days), methyl parathion (PenncapÒ-M) (15 days) and various biologicals such a DipelÒ (0 days). Insecticide labeled in lawns and turf include halofenozide (MachÒ 2), bifenthrin (TalstarÒ), cyfluthrin (TempoÒ, Bayer AdvancedÒ), carbaryl (SevinÒ) permethrin (multiple brands) and spinosad (Conserve Ò and others).
For more information about armyworms refer to Extension publications “Managing Insect and Mite Pests of Small Grains”(B-1220), “Integrated Pest Management Guide for Texas Forage Crops” (B-1401); and “Managing Insect and Mite Pests of Cotton”(E-5, E-6 and E-7).