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What to do this week –
By Mark Govan, Host “Florida Gardening“
Army and Sod Web Worms
The afternoon rains we have been receiving are a great change over last year. Normally, we have to wait until summer officially begins in order for our rainy season to bring us the precipitation necessary to keep our lawns and plants from drying out. The abundance of rain we have been so fortunate to receive, has allowed us to cut back on the amount of time our sprinklers have had to work and the amount of money we pay for our watering bills. Although these times of plenty may be great for our plants, there are pests who are also taking advantage of this too. Army and Sod Web Worms are out in full force damaging our lawns. In this article, I would like to share my experience in detecting these insect pests and controlling them in your turf grass. Let’s get started!
Turf destroying caterpillars have a life cycle which is called a complete metamorphosis. Metamorphosis means change and this particular pest starts out as an egg, which develops into a larva or caterpillar in about three days. Larvae start feeding immediately upon hatching from their egg capsule and molt up to six times as they grow. During this growth stage, which lasts approximately eighteen days, the foliage of turf grass is consumed. This feeding stage is the destructive stage of this pest.
Once the larval stage is complete, the caterpillar enters its third stage of development, the pupa stage. To enter the pupa stage, the larvae will burrow into the soil a short distance and will spin a silken cocoon around itself. The pupa stage of the life cycle is where the transformation to adult occurs. This process can take as little as five days in warm weather and up to a month in cooler locations. Once the pupa has matured, the adult stage or moth will emerge from the soil, mate, and then start her egg-laying cycle all over again. On average, the adult Army-Worm will lay over one-thousand eggs. During periods of warm weather and ample food sources, the entire life-cycle can take place in as little as two to three weeks with multiple generations overlapping themselves.
Both the army and sod web worms feed on turf grass, but most people will not see the damage until after it occurs. This is because the heaviest damage occurs during the night when they are most active. Even though the army worm is much larger than the sod web worm, they are rarely seen. Army worms can grow up to an inch and a half long, while the sod web worm grows to a maximum of three-quarters of an inch. You may think this size difference will give the army worm the dominance in the damage they can do, but I have seen more damage to lawns caused by sod web worms than by army worms. There are several things you can look for that may indicate you may have a problem developing in your yard.
One of the first indications you may observe is the presence of the adult moths fluttering above your lawn. Merely walking over the grass will disturb the moths, forcing them to fly up and away from the lawn. Heaviest populations of the moths are found in areas shaded during the afternoon. In severe infestations, there could be hundreds of moths in a fairly small area. Just because you have moths in your yard does not mean you have the damaging worms. However, they are there for a reason, to lay eggs.
During the egg-laying process, the moths will travel freely from yard to yard. Trying to establish a control factor to eliminate the adult stage of this pest would prove ineffective as they can disappear to the neighbor’s lawn today and then fly back again tomorrow. The best measure for control is to treat your lawn with a residual insecticide when you spot the moths or when you see the actual damage.
Damage occurs when the larvae feed on the blades of grass. If you can picture an ear of corn with several bites taken out of it, then this is how the damage will appear in the first stages of an infestation. As the worms grow, and their appetite increases, you will notice small areas of your lawn which appear to have been mowed while other areas do not. This difference in blade height of your grass will become more pronounced as the worms continue to feed. In just a few days, large areas of your lawn will be eaten down to the base of the crown. Turf that is diseased or stressed and areas suffering from drought damage will compound the effects of the feeding. Major areas of turf can be severely damaged if left untreated.
The best way to control an infestation is to monitor your lawn for the winged moths. Once you know they are in your lawn, you will need to apply an insecticide such as Bifenthrin. Bifenthrin will kill the young larvae as they begin to feed. By using a liquid product, you can treat all of the blades of grass, giving you better control of the larvae as they feed on the turf during the night. A second application may be necessary in fifteen to thirty days to break the life cycle and kill any additional eggs that have hatched. The best time to make your application is late afternoon to early evening. Although Bifenthrin is one of the products I like to use, there are other choices you can use to control them.
Dipel, Thuricide, and BT are organic products, which contain the active ingredient, Bacillus thuringiensis. This active ingredient is a naturally-occurring soil borne organism which only kills caterpillars. Many organic gardeners prefer these types of products, which are selective in the insects they kill. Because these products will only kill caterpillars, natural predators and other insects will be unaffected. Once the caterpillar ingests one of these products, the spores begin to reproduce very rapidly in the caterpillar’s digestive system. The spores release a crystalline toxin paralyzing the caterpillar’s digestive tract which causes the caterpillar to quit feeding. Death of the caterpillar occurs within one to five days.
If you choose to use one of these products, then you need to be aware that they must be ingested by the caterpillar in order to work, and they must be re-applied to the turf grass if rainfall occurs. Having to re-apply the product and the fact that these products only kill caterpillars, is the main reason I prefer to use the Bifenthrin I mentioned above, however; the choice is yours.
Army and Sod Web Worms can be devastating to areas of turf grass, especially if your lawn is suffering from drought, pest, or fungal problems. All cultivars of turf grass are vulnerable to their attack. Make sure you monitor your lawn for moth activity and pay special attention to the shady areas of your landscape. Treat your lawn accordingly when these pests are spotted with products you feel comfortable using. Be sure to read the label of any product you purchase and mix accordingly. Re-apply as necessary and remember, without plants, we would not be here!