Tent Caterpillar

Tachinid flies and ichneumonid wasps parasitize tent caterpillar larvae -- they are already present in most landscapes and provide significant suppression in undisturbed areas. Cuckoos, orioles, and other birds rip tent colonies open and consume larvae actively -- habitat for these species near orchards and gardens provides real population pressure. Leaving low-level tents on wild host trees at field edges provides a reservoir of parasitoids that move into orchards. Bacillus thuringiensis kurstaki specifically kills tent caterpillar larvae that eat treated foliage without harming parasitoid wasps.

Tent caterpillars build distinctive silken tents in branch crotches in early spring -- unlike fall webworm which builds tents at branch tips, tent caterpillar tents are at crotches and forks. Eggs overwinter as shiny brown masses around small twigs -- a single egg mass contains 150-350 eggs wrapped in a foam-like cover. Removing egg masses during dormant season (fall through early spring) is the highest-return preventive activity. Scout preferred hosts -- wild cherry, apple, and crabapple -- in winter for egg masses.

Prune out egg masses during winter dormancy on young trees and orchard trees -- each mass removed eliminates up to 350 larvae. Mature established trees tolerate tent caterpillar defoliation and refoliate within weeks -- young trees and those already stressed need protection. Accept some webbing on wild host trees at property edges as parasitoid reservoirs. Avoid planting large monocultures of highly favored hosts like wild cherry without planning for cyclical outbreaks.

Remove tents on reachable limbs in early morning when larvae are clustered inside for warmth -- drop into soapy water. A pole with a rough surface (wrapped with burlap) can twist and remove high tents. Pruning out egg masses in winter from young trees is faster and more cost-effective than spray programs on small plantings.

Bt kurstaki on small larvae feeding outside tight silk gives strong targeted control -- apply in the evening coating all foliage thoroughly. Spot applications to tents and adjacent foliage are more effective than whole-tree sprays. Apply before larvae are half-grown for best results. Spinosad for larger larvae where Bt timing was missed. Neem oil deters adult egg-laying when applied to preferred host trees in late summer during moth flight.