UMASS Update

As we round out the final days of August, it’s been another strong growing season in the Pioneer Valley. The sheer volume of vegetation produced annually across forests and the managed landscape is truly impressive. Two major rain events bookended this reporting period with combined accumulations ranging from 3–5” across the tri-counties. Soil moisture remains high as it has for most of the summer and conditions remain ideal for transplanting certain woody plants. Temperatures have taken a nosedive at the time of writing (high temps near 70ºF with lows near 50ºF on 8/20 to 8/22), but the long-term forecast calls for a return to more seasonable temperatures.

By late summer, the landscape is no longer looking its best. While some plants still appear quite vigorous, others are showing the rigors of a very hot and humid summer. As such, it’s easy to encounter plants with scattered twig and branch dieback, premature leaf shedding, and a general chlorotic appearance. As mentioned previously, crabapples and apples (Malus) are nearly devoid of foliage due to apple scab and other foliar pathogens. Many sugar maples (Acer saccharum) have been observed with pale green to yellow canopies. Leaf reddening is developing on certain plants, especially Viburnum, due to the changing sun angle and an increase in the production of anthocyanins to prevent sunburn as chlorophyll production wanes.

Pests/Problems:

Feeding injury from the elm zigzag sawfly (Aproceros leucopoda) has been observed on several Princeton elms (Ulmus americana ‘Princeton’) on the UMass campus. This non-native insect pest, which originates from parts of China and Japan, is capable of severe defoliation when populations are high. Widespread planting of DED-resistant American elms has occurred on campus in recent years, including a long allée of Valley Forge elms (U. americana ‘Valley Forge’). Currently, the symptoms are nuanced, and the damage is very minor (see photo). However, it seems that the early stages of infestation will be challenging to detect in many cases. Elms should be carefully scouted for evidence of the serpentine (or zigzag) pattern of feeding so that management efforts can be targeted in the future.

The combined effects of Tubakia leaf blotch (Tubakia spp.) and oak anthracnose (Apiognomonia errabunda) has some oak canopies looking brown and ragged. Annual and perennial mushrooms and conks of wood-rotting fungal pathogens continue to appear on or near the base of infected trees. Document the number of fruiting bodies and their location to include in risk assessments.