Berry’s Picks

Armyworms, Grasshoppers and Bermudagrass Stem Maggots

With all the moisture and green grass, we have had it has become banner year for forage feeders. There has been a steady increase in the numbers of all 3 above mentioned pest.

Grasshoppers have gotten large enough that they can really do some damage to everything from grass to leaves on trees. Armyworms are very widespread and are eating untreated fields at a fast rate.

If those two are not enough, I have found Bermudagrass Stem Maggots (BGSM) in most fields I have checked. I will discuss BGSM’s in next week’s article.

The larvae of the fall armyworm are green, brown or black with white to yellowish lines running from head to tail.

There will be a white line between the eyes that forms a “Y” pattern on the face.

At first the fall armyworm caterpillar or larvae are very small about 1/8”, at this stage they cause very little damage and usually go unnoticed. The larve will feed for 2 to 3 weeks growing to 1 to 1.5”. Once the armyworm reach ¾” in length they quantity of forage they eat increases dramatically.

During the final 2-3 days of feeding, armyworms consume 80% of the total forage during their entire development. Once the armyworm completes feeding it tunnels into the soil and enters the pupal stage. The moth emerges from the pupa in about 10 days and repeats the lifecycle.

Scouting is the key to controlling damage associated with the fall armyworm. It is best to check fields late in the evening or early in the morning; this is when they will be feeding in the upper canopy. Damage from the small larvae will leave a clearing or windowpane effect on the leaf, as the larvae grow, they will begin eating on the edges of the leaves.

There are several products that will work on both grasshoppers and armyworms but may have different requirements for stage of treatment and different residual times. Though it is more expensive, I think Prevathon or Vantacor are going to be two of the better products to use this year, they have up to a 6-week residual and work on mature grasshoppers and armyworms. If you just need a quick knockdown and do not require a long residual any of the lambda cyhalothrin products are less expensive and will work well at killing mature worms and grasshoppers but offer only about a 7-day residual.

The following is a list of insecticides for fall armyworm control, I encourage you to check with your good local pesticide dealers and applicators to see what is working best in your area.

Insecticides Labeled for Armyworm and Grasshopper Control in Pastures and Hayfields.

Always read and follow all label instructions on pesticide use and restrictions. Information below is provided for educational purposes only. Read current label before use.

Karate Z. 13.1% lambda cyhalothrin. Fall armyworm and grasshoppers. Pasture and rangeland grass, grass grown for hay and silage and grass grown for seed. Pasture and rangeland grass may be used for used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide.

Lambda-Cy. 11.4% lambda cyhalothrin. Fall armyworm and grasshoppers. Pasture and rangeland grass, grass grown for hay and silage and grass grown for seed. Pasture and rangeland grass may be used for used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide.

Mustang Max. 9.6% zeta-cypermethrin. Fall armyworm and grasshoppers. Applications may be made up to 0 days for forage and hay, 7 days for straw and seed screenings. Restricted use insecticide.

Tombstone Helios. 25% cyfluthrin. Fall armyworm and grasshoppers. Pasture, rangeland, grass grown for hay and seed. Zero days to grazing or harvesting hay. Restricted use insecticide.

Warrior II. 22.8% lambda cyhalothrin. Fall armyworm and grasshoppers. Pasture and rangeland grass, grass grown for hay and silage and grass grown for seed. Pasture and rangeland grass may be used for used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide.

Baythroid XL. 12.07% cyfluthrin. Fall armyworm and grasshoppers. Pasture, rangeland, grass grown for hay and seed. Zero days to grazing or harvesting hay. Restricted use insecticide.

Dimilin 2L. 22% diflubenzuron. Fall armyworm and immature grasshoppers. Dimilin must be applied before armyworm larvae reach ½ inch or larger. Provides residual control for up to 2-3 weeks, as long as forage is not removed from the field. Label does not list a restriction on grazing.

Prevathon or Vantacor. 5% chlorantraniliprole. Fall armyworm and grasshoppers. Prevathon has a 0-day waiting period for harvest or grazing and is not a restricted use insecticide. Up to 6 weeks of residual control.

Besiege. 9.26% chlorantraniliprole and 4.63% lambda cyhalothrin. Fall armyworm and grasshoppers. Pasture and rangeland grass may be used for grazing or cut for forage 0 days after application. Do not cut grass to be dried and harvested for hay until 7 days after the last application. Restricted use insecticide. Sevin 4F, Sevin XLR,

Sevin 80S, Generic Carbaryl. Fall armyworm and grasshoppers. When applied to pastures, there is a 14 day waiting period before grazing or harvesting.

Malathion 57% and Malathion ULV. Fall armyworm and grasshoppers. Zero days to harvest or grazing.

Intrepid 2F. Fall armyworm (not grasshoppers). Begin applications when first signs of armyworm feedings appear. Use higher rates for heavier infestations. Do not harvest hay within 7 days of application. No preharvest interval for forage. 0 days to grazing.

Tracer. Treat when armyworm eggs hatch or when larvae are small. Use higher rates for larger larvae. Do not graze until spray is dry. Do not harvest hay or fodder for 3 days after treatment. Do not allow cattle to graze until spray has dried.