UMass Extension Landscape Message May 3, 2013

"Winter Moth - In Southeastern MA, all winter moth eggs have now all hatched and the caterpillars are either in the first or second instar larvae stage. Most of the susceptible host plants have experienced bud-break and are pushing out new foliage, with the exception of the oaks, which are always later. Deborah Swanson of Plymouth County reports that the overall numbers of larvae this year is low and damage to host plants, thus far at least, is minimal. Fine silken webbing can be now found on many maple species, which is typical for winter moth once the caterpillars have become settled on a host plant. The caterpillars are still very tiny in physical size and close inspection is required when monitoring. Any insecticide that contains Spinosad works well. Bacillus thuringiensis Kurstaki (B.t.K.) also works well but must be ingested by the young caterpillar in order to be effective. Leaves that are not yet fully expanded but treated with a spray of B.t.K. will quickly continue to produce more leaf tissue daily that is not covered by the spray and therefore allowing caterpillars to potentially consume more foliage before ingesting the bacterium. Many pyrethroid insecticides are also labeled for this pest but tend to be harsher on foraging pollinators, such as bees, and other beneficial insects and predatory mites. Monitor host plants now and treat where necessary.

Lily Leaf Beetle adults are active and seeking newly emerging Asiatic lily foliage as a food source and eventual site for laying their eggs. This bright red beetle is quite obvious at this time. In small plantings, one can monitor every 1-2 days and hand-remove adult beetles. Sprays for the adult beetles usually require a chemical such as one of the pyrethroids, if deemed necessary. Eggs will be deposited on the undersides of Asiatic lily foliage beginning within the next few weeks. Larvae, when active, are easily treated with a product that contains Spinosad."

Claire