UMass Extension Landscape Message April 26, 2013
Temperatures have been on the cooler side for the past week thus keeping plant growth and insect activity at a slow pace. However, mid to late week this week, temperatures will be in the 60s with at least one day reaching into the 70s in more central parts of the state. We will see an almost Ã¢ÂÂsuddenÃ¢ÂÂ burst of plant growth and insect activity.
Winter Moth. The majority of winter moth eggs have hatched. Oak buds still remain fairly tight and this will force ballooning for those caterpillars on species of oak. Crabapple, apple, blueberry, birches and maples, however, are susceptible to attack now by being farther along in their bud-break phenology. Winter moth is a problem in Massachusetts on many different deciduous hosts but it is important to note that it does not attack conifers nor evergreens here. Once the caterpillars are within the buds, they are virtually impossible to treat until the leaf tissue fully expands from the bud. At that point, 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. Overall, winter moth populations are lower in many MA areas this season than in recent years but damaging population levels most likely still exist in random areas of eastern MA. Monitor host plants now and treat where necessary.