Insect Management

Key Species to Scout for in Pastures and Hayfields

The species listed here are the most common insects that will injure established pastures and hayfields in Georgia. This list is not all-inclusive, and you may encounter insect species beyond this list in your perennial grasses. There are three major insect species that are likely to cause damage in bermudagrass annually. There are two key species to scout for in tall fescue and bahiagrass. If you need help identifying these pests, please contact your local county Extension office.

Bermudagrass Stem Maggot (Atherigona reversura Villeneuve)

The bermudagrass stem maggot (BSM) reaches treatable thresholds in Middle and South Georgia each year. The BSM will reach North Georgia in years with good forage production (i.e. not drought years). Damage is most severe in late June to early September depending on the year and location within the state. The top 2-3 leaves of an infected stem will turn brown or yellow after the BSM larva has moved inside the stem. The damage most closely resembles drought damage. The BSM only affects bermudagrass.

The adult BSM flies are the easiest stage to identify. They have transparent wings, a gray thorax, and a yellow abdomen with at least one pair of black spots. The adult flies are around 1/8 inch big or just smaller than a pencil eraser. This is the only fly with this coloration and size, making them easy to identify once you know what you are looking for.

For more detailed information on the BSM, please refer to University of Georgia Extension publication B1484, Managing Bermudagrass Stem Maggots and Improved Management of the Bermudagrass Stem Maggot.

Fall Armyworms (Spodoptera frugiperda)

Fall armyworms (FAW) will cause thin and brown spots across the field. Small caterpillars feed low in the grass canopy, skeletonizing the leaves. As the caterpillars grow, they consume the entire leaf.  In severe infestations, all green materials may be removed, leaving just the stems. The FAW can cause significant damage to bermudagrass, bahiagrass, and tall fescue.

Most FAW are identified at the fully grown larva stage. They can be up to 1.5 inches long and are light green to nearly black with light and dark stripes that stretch horizontally along the body of the worm. One of their most distinct characteristics is an inverted Y-shape on the head of the worm and four black dots at the upper end of the abdomen.

For more detailed information on the FAW, please refer to University of Georgia Extension publication B1583, Fall Armyworm Management in Pastures and Hayfields.

Fire ants (Solenopsis invicta)

Fire ants (Solenopsis invicta) build mounds throughout the field and can be a nuisance to grazing livestock and for hay equipment operators. Fire ants can be found in bermudagrass, bahiagrass, and tall fescue. The mounds will look like loose soil mounds and are most common in open, sunny areas.

Fire ants are very aggressive and may be difficult to identify safely in the field if you disturb their mound. The ants are relatively small at less than ¼ inch long. Most will have a reddish-brown body with darker abdomen. There are also black fire ants, but those are less common than the red ones. 

Minor Species to Scout for in Pastures and Hayfields

The species in this list can occasionally cause severe damage, but severe infestations are much less likely to occur in pastures and hayfields compared to those listed as major species. Each insect listed here has the potential to cause damage to bermudagrass, bahiagrass, and tall fescue.

True Armyworms (Pseudaletia unipuncta)

True armyworms do not tolerate hot summers and typically fade away before causing significant damage. Their feeding is similar to fall armyworms in that they remove the tender, green portions of the plant. Most true armyworms are identified at the fully grown larva stage. They can be up to 1.5 inches long and are dark green to black with lateral stripes.

Striped grass looper (Mocis latipes)

Striped grass looper is active throughout the season but is rarely a cause of concern in forage grasses. They chew through leaves and create holes in the plant material. This pest is most identified in the larval phase. In this phase the larva is up to 2 inches long and striped with dull brown, gray, or black colors.

Green June beetle (Cotinis mutabilis)

Green June beetles feed on decaying organic matter. They do not actively feed on the roots but their tunnelling in the soil can cause the grass to be dislodged and pulled up by grazing livestock. The populations are higher where chicken litter is used. Damage symptoms include loosened soil and mounds of dirt where the larvae tunnel up to the surface to feed. The adult beetle is large at over an inch long. It has a metallic green color and is oval-shaped. Furthermore, it will stay on its back when it moves around, unlike other white colored grubs.

Masked chafers (Cyclocephala spp.)

Masked chafers (Cyclocephala spp.) feed on plant roots and can cause irregular brown patches across the field. The larvae is a small, C-shaped grub with white body and dark brown head that resembles a mask. The adult is up to ½ inch long and has a light brown, oval body and dark head that looks like a mask.

May beetles (Phyllophaga spp.)

May beetles (Phyllophaga spp.) feed on plant roots and can cause yellowing of the grass and stand thinning. The larvae is a small, C-shaped grub with a white body and brown head. The adult is up to 1 inch long and has an oval body that is brown to black.

Mole crickets (Neoscapteriscus spp.)

Mole crickets (Neoscapteriscus spp.) tunnel through the soil and cause significant damage to the stand if they begin uprooting plants. They also may feed directly on the grass plants and can cause extensive loss of stand in a short time. Mole crickets are more common in the Coastal Plains than other parts of Georgia. The mole crickets are light brown and up to 1 ½ inches long. They are short and stout in their build. 

Control and Suppression Options

Insecticide options are limited for most pests found in a pasture or hayfield. Therefore, you should consider an integrated pest management (IPM) plan. A good IPM plan will incorporate two or more control strategies when possible. These strategies may include cultural, mechanical, biological, and chemical control depending on the crop and pest.

All insecticide recommendations may be found in the Georgia Pest Management Handbook. Specific recommendations are not provided here because they are updated annually in the Georgia Pest Management Handbook. It is important to always read any pesticide label before use. Use the product strictly according to the label directions. It is particularly important to follow all safety precautions. Trade and brand names are used only for information. The University of Georgia does not guarantee nor warrant published standards on any product mentioned; neither does the use of a trade or brand name imply approval of any product to the exclusion of others, which may also be suitable.

Bermudagrass Stem Maggot

Flies are not present early and late in the production season, so do not treat until evidence of the pest is observed and flies are identified in your sweep sample. If damage occurs close to the time of harvest, go ahead and harvest as planned and then begin treating with insecticides during the next regrowth cycle. If severe damage occurs when the grass is only 6-8” tall, mow or clip the forage to reset to field and then apply a pyrethroid insecticide.

Foliage Feeding Caterpillars

These include the true armyworm and fall armyworm. Textbook treatment thresholds are typically recommended at three fall armyworm larvae per square foot, but weather and forage demand may dictate a more conservative threshold. If insecticides are required, be sure to follow all label instructions. Insecticides are labeled for specific life stages of the fall armyworm. In general, small caterpillars are easier to control than larger ones, and insecticides are only recommended when the fall armyworms are less than 3/4 inch long. Routine scouting during the summer and fall growing season is key to catching the fall armyworms before significant damage occurs.

Fire Ants

Only baits are labeled for use in pastures and hayfields. Fire ant baits are slow-acting and take time to work since it relies on the foraging ants to take the bait inside of the mound. It can take two to four weeks to see suppression of the any colony. The most effective application time is in the spring (Easter) and fall (Labor Day) when the ants are foraging for food. Soil temperatures need to be at least 60°F for effective suppression. They will burrow deeper in the ground during the hot summers.  

Green June Beetle Larvae

Textbook treatment thresholds suggest treating with a labelled insecticide when populations average 1 larva per square yard.

Mole Cricket

There are no effective insecticides are labeled for control of mole crickets in perennial forage systems. Biocontrol agents are most effective including Steinernema scapterisci (nematode) and Larra bicolor (wasp). Both are present throughout the Coastal Plain region of GA and are not available commercially.

Grubs

These include masked chafers and may beetles. There are no effective insecticides are labeled for control of grubs in perennial forage systems. Rotate to a crop where pre-plant or at-planting insecticides can be used to control grubs.