Pioneer Valley (Amherst)

General Conditions: 

Spring is in full force across the Pioneer Valley with new growth and flowering advancing at a rapid pace. After the cool, cloudy and rainy start to April, capped off by a mixture of snow and rain on 4/11–12, the second half of the month has been mild, sunny and dry. There was widespread frost on the morning of 4/21 and hopefully this is our last experience with sub-freezing temperatures until autumn. The long-term forecast does not indicate any low temperatures dropping beyond the lower 40s. However, it was only two years ago (5/18/23) that we suffered a late and damaging spring frost, so we’re not out of the woods yet. The cool temperatures this April have prolonged the flowering of Cornelian cherry dogwood, forsythia and star magnolias. The latter are having an excellent year. Turfgrasses are rapidly greening up and the first mowing has commenced in scattered locations.

Pests/Problems:

As we watch deciduous flowering trees and shrubs put on a fantastic floral display, it provides a clue to explain the devastating levels of winter injury on broadleaf and needled evergreens. While there were certainly bitter cold temperatures across southern New England this past winter, there seemed to be an unusually large number of storms and fronts delivering strong and relentless winds. These drying, desiccating winds may be largely responsible for the serious damage that occurred on rhododendron, hollies, and arborvitae, among many others. If the cold temperatures were the driving force of the injury, we would expect to see damage on deciduous trees and shrubs. Yet, magnolia, redbud and flowering cherry appear to have avoided any major injury. Given the extreme autumn drought in 2024, winter injury was expected but the severity is still surprising. For rhododendrons, if flower and vegetative buds appear healthy, then prune all blighted foliage from the canopy. Once new growth flushes, the plants will fill back in over time.

Given the cool and wet start of the month, foliar anthracnose may be locally abundant as deciduous trees start to leaf out. Hemlock woolly adelgid mortality was high over the winter (≥90%), so keep that in mind when scouting trees. Orange spore masses produced by Gymnosporangium rust fungi are behind schedule across the UMass campus. The galls and pads that produce these spore masses are visible, and once wetted by rain, will swell dramatically to disperse spores to infect rosaceous hosts.