Warm weather means that turf is currently in active growth. So is the hatching of caterpillars. Armyworms and Sod Webworms. Each of them causes damage to turf and ornamental plants.

Armyworms: These worms can be found year-round in central Florida and feed 24/7, 365 in packs or a small army, hints the name. They will feed on turf, ornamental flowers, lettuce, corn, cabbage, peppers, potatoes, ornamental shrubs, and over 350 species of plants. They aren’t picky eaters, to say the least. The lifecycle starts when the adult, a moth, lays clusters of around 2,000 eggs on the leaves of an older plant. Soon after hatching they grow into a larvae that begins eating where it was placed. The adult caterpillar has a greenish to tan with black stripes/dots, and a white ‘Y’ shape in between the eyes. These caterpillars have a fast lifecycle and cause damage rather quickly if not taken care of at first sight, they can cause large patches of yellowing in the lawn.

Sod Webworms: Light green to brown colored with lined rows of spots. They are the larvae of a moth that lays around 200 eggs on the leaves of grass in early summer. Known to tunnel and leave a web-like substance behind in the turf, giving them the name sod webworm. They have a preference for St. Augustine grass but will also feed on Centipede, Bahia, Bermuda, and Zoysia grasses. They can be found year-round here in central and southern Florida. They feed mostly at night, early morning, and dusk when the temperatures are cooler. Signs are seeing blades of grass that appear that the chlorophyll is missing in areas of the blade, this is called ‘window feeding’. The surface of the leaf has been eaten away giving a clear appearance. As damage worsens, blades will appear roughly cut or bitten with eventually the entire lawn looks thinned and patchy.

Control: to control these caterpillars you want to approach them using Integrated pest management (IPM). The first step in an IPM program is doing the best management practices for the type of turf you have; a healthy turf will be able to withstand a few pests and not suffer drastically. This can be done with proper mowing, irrigation, and appropriate fertilization. If done correctly natural predators/ beneficials will be present to help mitigate the impact of damage. If the caterpillars are beyond this point it may be time to intervene with pesticides. This is when making a proper identification is critical. Once you’ve identified the pest find a pesticide with the insect listed on the label, follow the instructions, and treat only the areas where the infestation is present. If you need help identifying a pest check out your local extension office’s plant clinic.


Reference 

Plant Biosecurity and Product Integrity. “Fall Armyworm.” NSW Department of Primary Industries, 25 Feb. 2022, www.dpi.nsw.gov.au/biosecurity/plant/insect-pests-and-plant-diseases/fall-armyworm#:~:text=The%20fall%20armyworm%20life%20cycle,damage%20to%20crops%20through%20feeding.

2