UMASS Update

Pioneer Valley (Amherst)

General Conditions: 

April is wrapping up, and we’re settling into the heart of spring here in the Pioneer Valley. The UMass campus is humming with activity as classes wind down and graduation approaches. After the unseasonably warm stretch in mid-April, the pace of new plant growth has slowed down significantly with a return to more seasonable conditions. This past week has provided some peak spring weather with bright sun and high temperatures in the 60s to 70s, but low temperatures continue to bottom out in the 30s.

Many redbuds and cherries are still in full flower and the mobs of bees attracted to their canopies are one of the sights of spring. Native wildflowers like red trillium (Trillium erectum), wild ginger (Asarum canadense), bloodroot (Sanguinaria canadensis), violets (Viola), and Anenome are in bloom.

Precipitation was minimal over this past week and with the bright sun, low humidity, and lack of shade, the uppermost soil layer may be dry. However, deeper horizons still have good moisture, so spot watering is all that’s currently required. Mass DEP will update outdoor water use restrictions on May 1.

During the winter, mulch and organic matter may build up over the root flare of smaller trees and shrubs. Ensure the root flare is exposed to avoid the development of girdling roots.

Pollen levels are building now that oak catkins are fully developed.

Pests/Problems:

As feared, the freeze on April 21 was very damaging to certain plants with tender new growth. The injury is highly scattered across the landscape, and it appears that most woody and non-woody plants fared well despite temperatures plunging into the lower and middle 20s. Regrettably, damage to Japanese maple (Acer palmatum), fragrant snowbell (Styrax obassia), Hick’s yew (Taxus × media), spirea (Spirea), katsura (Cercidiphyllum japonicum), and numerous herbaceous perennials and annuals (e.g. toad lily) has been observed. The UMass fruit team reports minor to serious freeze injury on apples (Malus domestica) at the Cold Spring Orchard. The damage varied by elevation and stage of development, with bud mortality ranging from 10% to possibly 90%.

Pine candles are elongating, and this remains a good time to scout for white pine weevil (Pissodes strobi) and the European pine sawfly (Neodiprion sertifer). Larvae of the sawfly can be highly camouflaged against the dark green needles of two- and three-needle pines. Recent scouting on Japanese white pines (Pinus parviflora) revealed an adult white pine weevil on the terminal shoot and larvae of some type of pine shoot moth (possibly Rhyacionia buoliana) inside developing candles that were distorted and growing at an odd angle.

Scout deciduous hardwoods like cherry (Prunus), and apple/crabapple (Malus) for eastern tent caterpillars (Malacosoma americanum). This native pest is capable of significant early season defoliation on infested trees.

Voles (Microtus spp.) can be a destructive nuisance in the garden but poisoning these rodents can kill wildlife and pets higher on the food chain. Instead, use castor oil pellets or granules to drive them away. When applied thoroughly to an area, inside their tunnels and the surrounding area, they can be very effective.

Nick Brazee, Plant Pathologist, 

UMass Extension Plant Diagnostic Lab

, reporting from Amherst.