Aloha! Hawaiian Beet Webworm in Celosia
Each year eastern Long Island, NY is inundated with exotic summer visitors, including some of the entomological persuasion. This past summer was notable for a few that arrived in levels far more damaging than usual. Hawaiian beet webworm (Spoladea recurvalis) bears mentioning for the trouble it caused in late celosia production. It sounds like something that wouldn’t be comfortable here (and it’s clearly a snowbird), but it finds our summers – and some of our crops – much to its liking. Probably not native to North America, it is established across the tropical areas of the world and southernmost portions of the US (including Hawaii) from whence it launches annual assaults northwards, arriving in our area by late summer in some years. We usually notice the pigweed (amaranth) getting defoliated as the first sign, then growers with beets and chard report problems. Favorite hosts are all members of the same plant family and also include spinach, lambsquarters, and the celosia noted earlier. The annual love-lies-bleeding would be another ornamental host. The caterpillars, initially pale translucent green with pale grayish spots, later develop white longitudinal bands and a darker central stripe as they feed under leaves. Foliage may be entirely consumed, or sometimes small ‘windowpane’ areas (just the upper surface) remains. The adult moth has a wingspan just under 1” (1.7-2.3 cm), chocolate-brown with bright white bands, and this year they were quite numerous, flitting low around fields and hedgerows and often stopping to rest on plants. Note other kinds of ‘beet webworms’ affect many of these same plants in the southern US, but Hawaiian beet webworm is the only one we ever regularly see in the north owing to its peripatetic nature. It’s not difficult to control and appears to be quite susceptible to Bacillus thuringiensis kurstaki, spinosad and other insecticides used for caterpillars.
Dan GilreinEntomologist, Cornell Cooperative Extension of Suffolk County
Dan Gilrein is the Extension Entomologist with Cornell Cooperative Extension of Suffolk County at the Long Island Horticultural Research and Extension Center, Riverhead, NY since 1995 and previously served there as IPM Specialist with Cornell from 1987. In his current position he conducts applied research on control of arthropod pests in food crops and on ornamental plants, provides diagnostic services to the horticultural industries, and conducts educational programs and presentations for industry, government officials, civic groups and the public on pests and pest management.