UMASS Update

Pioneer Valley (Amherst)

General Conditions: 

There was another round of heavy rain to start this past reporting period (5/8–5/9) with nearly 2” of precipitation recorded at the Easthampton gauge. From 5/1 through 5/9, total rainfall across the tri-counties spanned from 3.5” to >8”. The long-term forecast at the time of writing indicates more wet weather but in between were some exceptional spring days (5/11–5/13), with bright sun and highs in the 70s. Low temperatures dropped into the middle and lower 30s on the morning of 5/12, but associated frost injury appears to be minimal and scattered.

Lawns are vibrant green and turfgrasses are growing at a fast rate. Oak pollen is abundant right now and branches are draped in dangling catkins. Black flies have emerged and at higher elevations are aggressively swarming. Mosquito populations continue to build as well. The recent rains have been good for gray tree frogs (Dryophytes versicolor) and their distinctive mating calls have been common. Red maple (Acer rubrum) samaras are falling in huge numbers, and we’ll soon be weeding the seedlings. For plant lovers, May is arguably the choice month of the year with a cascade of new growth and colors throughout the landscape.

Pests/Problems:

Pest and pathogen activity is ramping up. Scattered leaf chewing by unknown insects can be found on various hardwoods like Japanese maple (Acer palmatum), red oak (Quercus rubra), and black birch (Betula lenta), among many others. Oak leaf blister (Taphrina caerulescens) is appearing on various oaks (Quercus spp.). Lily leaf beetle adults (Lilioceris lilii) are active and relatively easy to hand pick. Larvae of the non-native columbine sawfly (Pristiphora rufipes) are locally abundant and can quickly defoliate columbines (Aquilegia canadensis). Azalea sawfly (Amauronematus azaleae) larvae are actively feeding on deciduous azaleas (Rhododendron spp.) and when abundant, are capable of defoliating plants. Hydrangea leafier (Olethreutes ferriferana) is active on smooth hydrangea (Hydrangea arborescens) sealing together pairs of leaves. European pine sawfly (Neodiprion sertifer) larvae were observed feeding on older needles of mugo pine (Pinus mugo) on the UMass campus.

Continue to scout for bagworm (Thyridopteryx) cocoons on arborvitae (Thuja) and juniper (Juniperus). Individuals not familiar with these pests can confuse the cocoons for seed cones. With eastern hemlock (Tsuga canadensis) pushing new growth, now is the time to apply dinotefuran to control both the hemlock woolly adelgid (Adelges tsugae) and the elongate hemlock scale (Fiorinia externa). A single application, made as a lower trunk spray, will penetrate into the vascular tissue and move to the canopy, providing multiple years of control against these two non-native pests.

We are entering the peak period of needle browning and shedding for diseased eastern white pines (Pinus strobus). White pine needle damage (WPND) is caused by several native fungal pathogens. An increase in disease severity has been linked to an increase in seasonal rainfall in the region. Various other two-, three-, and five-needle pines are also affected.

Nick Brazee, Plant Pathologist, UMass Extension Plant Diagnostic Lab, reporting from Amherst.