UMASS Landscaping Update

General Conditions:

We endured our first heat wave of the summer season, and it was a rough one in the Pioneer Valley. Heat index values repeatedly peaked over 100ºF with thick, swampy humidity. Rainfall was recorded five days in a row (6/19–6/23) as a barrage of powerful thunderstorms continued to develop across the Northeast. Accumulations over this stretch ranged from 1.5–2.5” in Hampden County, 2–4” in Hampshire County, and 2.5–5.5” in Franklin County. Some of the western hill towns were repeatedly hit with damaging winds and pounding rainfall from the storms. On the bright side, we received some needed moisture and soils are holding it well right now. Plant growth continues to be strong among herbaceous perennials and woody plants. Blue lacecap hydrangeas are having a year and it’s hard to remember the last time these plants flowered so well. Overall, it’s been a good growing season, but with July on the horizon, there’s a lot of summer left to go.

Pests/Problems:

While the rain is good for plants, it’s also good for plant pathogens. An assortment of minor to serious diseases can be encountered in the landscape, ranging from anthracnose, foliar blotches/ blights, and stem/ branch cankering diseases. Brown rot of cherry, caused by Monilinia, is abundant this year. Many mature flowering cherries are still suffering the fallout from the February 2023 freeze. In the aftermath of this damaging event, opportunistic cankering fungi have established or caused further dieback on stressed trees.

Apple scab is quite serious on scattered crabapples but fortunately these trees continue to produce new growth. Verticillium wilt is starting to appear on sugar maple, redbud and other susceptible hardwoods. Foliage often develops a diffuse bronzing to browning that is distinct from the symptoms produced by foliar pathogens. Given the regular moisture most landscapes have experienced, water starvation from drought is highly unlikely if these symptoms are present.

Slug damage is high in scattered landscapes and trapping may be necessary to save some herbaceous plants from destruction.

Japanese knotweed continues to appear in upland sites, away from streams and rivers. Every effort should be made to eliminate populations while they’re small in scale as this scourge of the valley rapidly expands once established.

Non-native scarab beetles (e.g. Oriental, Japanese and Asiatic garden) continue to appear as we approach their peak season.