UMass Extension Landscape Message May 30, 2014

"Winter Moth activity continues to move quickly. Not only is this a very early-season pest but it also goes through its destructive stage (feeding caterpillar) rather quickly and is capable of creating much defoliation when population numbers are high. While some infested areas in the state this year show limited effects of this pest, adjacent areas may harbor huge numbers of this insect and defoliation in these areas is now quite obvious. Reports of observed pupation for this pest began late last week in the warmer regions of the state where this pest exists. Within the next 1-2 weeks, all winter moth caterpillars will have entered into pupation and feeding injury will cease for this year. However, this caterpillar can be a voracious feeder just prior to pupation. Monitor closely for damage, numbers of caterpillars, and the current rate of pupation to best judge the need and potential efficacy for any treatments now. Mature caterpillars drop to the soil, burrow down about an inch and then quickly pupate. The insect will not be seen again until they emerge around mid-November as non-feeding but mating adults. When treatment is deemed necessary, a spray application of an insecticide that contains Spinosad can be very effective. Many pyrethroid insecticides are also labeled for this pest but tend to have a greater detrimental effect on beneficial organisms, such as parasitoids, predators, and pollinators. Do not apply Spinosad, Dinotefuran, Neonicotinoid or pyrethroid insecticides to plants that are in bloom."

"Lily Leaf Beetle adults remain active. The adult beetles continue to feed on the foliage of Asiatic lily. This pest can be found occasionally feeding on other hosts but Asiatic Lilies are the primary host. This beetle will cause ragged holes to appear in the foliage but this damage is often much less than the potential damage caused by the larvae, which will not begin to appear for about 2 more weeks. Monitor for the bright red beetles on host plant foliage. Mating pairs of this beetle continue to be observed. In small plantings, the beetles can be hand-picked and destroyed. When occurring in numbers that warrant controls, a contact chemical insecticide such as one of the pyrethhroid compounds may be necessary. Larvae, when they appear, are easily treated with a product that contains Spinosad. Adult female beetles lay their eggs on the undersides of leaves in jagged lines that are about one inch long. When monitoring for eggs, stand next to a plant and gently fan the foliage upwards to visually inspect the leaf undersides. Make note of small, irregular lines of tan eggs that will be quite apparent on the fresh new lush green foliage. In small planting, leaves with eggs can be physically removed and destroyed. In larger plantings, continue to monitor. The eggs will turn orange and then a deep shiny red just prior to hatching. Treat new larvae with a product that contains Spinosad."

Claire