UMASS Landscape Updates

Pioneer Valley (Amherst)

General Conditions:

If plants are a big part of your life, then May is the prime month of the year. New growth and endless colors are covering the landscape right now. Changes are happening daily, and it’s dizzying to take it all in. Azaleas and rhododendrons that were devoid of flowers last year, due to the early February freeze, are blanketed in blooms this spring. Redbuds have also had a fantastic flowering period. Most trees and shrubs are really filling out, so shade is increasing dramatically. The shade is good for retaining soil moisture as humidity levels are still generally low and winds have been strong. Despite the wet spring, upper surface soils are drying out in exposed settings. Cloudy skies and light rain at the time of writing should help, but carefully monitor soil moisture levels for new transplants. At deeper horizons, soil moisture is plentiful and after last year’s excessive rainfall, it’s important not to overwater established plants that often don’t require supplemental irrigation, like rhododendron and yew. As we mark the anniversary of last year’s damaging frost on 5/18, we can be thankful that a repeat event did not take place this year.

Pests/Problems:

Scouting for disease and insect pests from a distance is often not effective. Only close examination can detect an insect infestation or disease outbreak so that appropriate treatment can commence. For example, a Fraser fir on the UMass campus appeared relatively healthy from 40’ away, perhaps a bit thin in the canopy with some scattered branch dieback. But when carefully examined, a severe spider mite and elongate hemlock scale infestation was obvious, with chlorotic flecking symptoms abundant on the upper side of the needles. Beech leaf disease (BLD) symptoms are present and detectable as new leaves develop. However, the interveinal banding and cupping may be a bit nuanced on immature leaves when disease severity is low. When BLD cases are more serious, meaning that the nematode populations were high within the infested buds, the newly emerging leaves appear undersized, distorted and possibly thickened. Phosphite applications, as a soil drench around the root flare, may help to slow disease development. Fluopyram foliar sprays can also be performed but this treatment is generally recommended for later in the season and may not be effective if the entire canopy can’t be treated. For trees with high cultural and historical value, injections with Arbotect 20-S are now labeled for use against BLD. Pine candles continue to elongate and needles are starting to form. Symptoms of needle blight on eastern white pine can quickly develop from mid- to late May, peaking in early June. Older needles turn brown and are prematurely shed from the canopy. Symptoms of needle blight on two- and three-needle pines are clearly visible right now and many of the same fungi that attack eastern white pine also occur on hard pines.