Pine Webworm

Found in the Eastern US from Maine to Florida, the pine webworm

Pine webworm
Pine webworm  Credit: J. Daugherty UF/IFAS

(Pococera robustella) impacts several species of pines in the first year or two of growth. While less common, older saplings and branches of larger trees can also be impacted by these unsightly larval nests.  While this can be a worry to see, they are often of little concern for the long-term health of the infected plants.

The pine webworm is the larval stage of the pine webworm moth. Females lay eggs in masses of 1-10 on the flat surface of the pine needles from about April-October. The youngest larvae feed by mining into the needles (1st-3rd instar stages). As the larvae grow, they no longer fit inside the needle, causing them to move outside for the final instar stages (4th-6th instar stages). It is as this time that they become more obvious on the plant. These older larvae work together to build a nest using fecal matter, pine needles, and silk. This is referred to as a frass nest and can be found on the main stem of young plants.

Frass-evidence of pine webworm.
Frass-evidence of pine webworm.                Credit: J. Daugherty UF/IFAS

Management of the pest is usually not warranted as natural predators keep populations in check. If you notice them in your landscape, you can handpick the nests and larvae for removal. If your property is too large to manage in this way, you can apply Bt (Bacillus thuringiensis). This is a bacterium that infects any caterpillar larvae once ingested. It can take a few days to see the results. These management methods are not practical for larger plants, or forested areas. In those cases, it is best to let the natural predators manage the population.

Common Florida pines that can be impacted include loblolly (Pinus taeda), longleaf (Pinus palustris), sand (Pinus clausa), and slash (Pinus elliotii).


Pine webworm with its frass habitat.
Pine webworm with its frass habitat.           Credit: J. Daugherty


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Posted: June 5, 2023

Category: Forests, HOME LANDSCAPES, Pests & Disease,
Tags: Entomoogy, Gardening, Horticulture, Pest Management, Pine Tree Pest, Pine Webworm, Residential Horticulture, Yard Pest

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