Army and Sod Web Worms are tearing through our lawns in Central Florida

Army and Sod Web Worms are tearing through our lawns in Central Florida by - Mark Govan, Host of “Florida Gardening” heard on 970WFLA

Army and Sod Web worms are out in full force right now. Even a short walk around your home will disturb the adult moths and send them fluttering around the landscape. These moths seem to be more prevalent in the shady areas of the lawn, but you can see them almost anywhere you walk. Just like other lawn pests, healthy lawns attract these insects. Adult army and sod web worms lay their eggs on the grass and in a short time, their young hatch out and begin to feed. Before you lose your lawn to these unwanted visitors, I would like to share my experience in detecting and controlling them. Let’s get started!  

Do not let their size stop you from taking them seriously. Even though they are barely one-half to one-inch in length, they are congregating by the hundreds in your turf. Their single mission is to lay eggs on your grass blades for the next generation to feed upon. On average, the adult army-worm can lay several hundred eggs. In four to five days, these eggs will hatch and a small caterpillar will emerge. These caterpillars start feeding immediately on the edges and midrib of your turf grass blades. During the day, they rest in the thatch, which keeps them moist. At dusk, they climb the grass blades and feed. Over the next two weeks, the turf grass is consumed as the caterpillar grows larger. This feeding stage is the destructive stage of this pest. During periods of warm weather and ample food sources, the entire life-cycle can take place in as little as three to four weeks with multiple generations overlapping themselves.  

Both the army and sod web worms feed primarily on turf grass, but most people will not see the damage until after it has occurred. 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 too 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 can help you find them in your lawn.  

 The first indicator you will find are the moths that when disturbed, fly up and away from the turf. 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. The second way to spot an active infestation is to look at the blades of grass. If you can picture an ear of corn with several bites taken out of it, then this is what you should look for on the blades of grass in the first stages of an infestation. As the worms grow and their appetite increases, you will notice small areas of your lawn will appear to have been mowed, while other areas do not. This difference in blade height 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 leaf. Turf that is suffering from additional problems such as fungus or drought can compound the effects of the caterpillars feeding leading to severely damaged or dead turf grass.

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 control measure you can take is to treat your lawn with a residual insecticide like bifenthrin or Talstar once you spot the moths or see the actual damage.

Bifenthrin will kill the young larvae as they begin to feed. By using a liquid product, you can treat all the blades of grass, giving you better control of the caterpillars as they feed on the turf during the night. A second application will be necessary in ten to fifteen days to break the life cycle and kill any additional larvae 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 at your local garden center.  

Army and Sod Web Worms can be devastating to turf especially if your lawn is suffering from drought, pests, or fungal problems. Replacing turf is expensive and laborious. All cultivars of turf grasses 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. Look closely at the blades of grass for signs of feeding by the caterpillars. 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!                                               

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