Clint Perkins

Lookout for armyworms after recent rains

If you are in the forage business whether it is the hay business or forage to feed beef, dairy cattle, horses, sheep or goats, then you need to be on the watch for armyworms. With the recent rain, producers need to be diligent in watching their pastures and fields.

Armyworms attack many different kinds of plants. When food is scarce, they will move to plants that are not normally attacked. Thus, armyworms can be found on nearly any plant as they migrate in search of edible foliage. Plants attacked by armyworms include: Bermuda grass, grain and forage sorghum, corn, small grains, sweet potato, beans, turnip, clover, spinach, cucumber, potatoes, tomatoes, and many more.

Armyworms should be controlled when they occur in large numbers or plant damage is becoming excessive. Preventive treatments normally are not justified because attacks are sporadic and egg mortality is usually high. During favorable seasons, a number of parasitic enemies keep fall armyworm larvae down to moderate numbers.

Early detection works best and is achieved by frequent, thorough inspection of plants. Outbreaks seem to occur shortly after a rain or supplemental irrigation. Armyworms feed any time and 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 eight 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.

The threshold level ranges from two to three larvae per square foot for young tender growth. 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 small worms per square foot.

Insecticide choices have changed. Recommended applications for pastures and hay fields are:

Malathion (57% and Malathion ULV): Zero days to harvest or grazing.

Mustang Max (9.6 percent zeta-cypermethrin): The first pyrethroid insecticide labeled on pastures and hay fields. Applications may be made up to 0 days for forage and hay and seven days for straw and seed screenings.

Tracer: Do not allow cattle to graze until spray has dried or harvest hay or fodder for three days after treatment. There is no pre-harvest interval for forage. Treat when eggs hatch or when larvae are small.

Sevin 4F, Sevin XLR, Sevin 80S or Generic Carbaryl: When applied to pastures, there is a 14 day waiting period before grazing or harvesting.

Dimilin 2L: Wait one day until harvest. Label does not list a restriction on grazing and can provide residual control for up to 2-3 weeks as long as forage is not removed from field. Dimilin acts as an insect growth regulator.

Intrepid 2F: Do not harvest hay within seven days of application. There is no pre-harvest interval for forage but application must begin when first signs of feeding damage appear. Use higher rates for heavier infestations. Intrepid is an insect growth regulator.

Lannate (Bermuda grass only): Do not apply within seven days of feeding forage or allowing livestock to graze. Do not apply within three days of cutting for hay. Lannate is a highly toxic poison and all label precautions must be carefully followed.

Karate, Warrior, Lambda Cy and other lambda cyhalothrin products: These are used for pasture and rangeland grass, grass grown for hay and silage and grass grown for seed. Pasture and rangeland grass may be used for grazing or cut for forage immediately after application. Do not cut grass to be dried and harvested for hay until seven days after the last application.

Baythroid XL. Applications include pasture, rangeland and grass grown for hay and seed. It is labeled for control of small army worms in the fall. Zero days to grazing or harvesting hay.

Prevathon: No grazing restrictions or harvesting restrictions on hay crop. Sevens day must pass between treatments.

Be sure and follow label directions when using any pesticide. The label is the law when dealing with any pesticide. For more information, contact the Wood County Extension Office in Quitman or call 903-763-2924.