The blooming of dogwood and redbud means it’s the beginning of spring here in Tennessee. Daytime temperatures are on the rise, and it finally feels like there’s enough time in the day to actually do something. The trees around us are feeling the same way as they come out of their winter dormancy. Unfortunately, so do the pests that stress them every spring.
Healthy trees can usually tolerate mild to moderate pest pressure throughout the year, but trees in our landscapes can experience near-constant hostility from the urban environment. This can make an attack from native or non-native pests devastating for them when energy reserves are low after winter. This is by no means a rallying cry to grab our systemics and pretreat every tree for every pest; but maybe, for us to focus our eyes and check out degree days to catch pest pressures before the damage becomes unacceptable.
Defoliators – Several native species of caterpillar and inchworm become active in spring and early summer to gorge themselves on fresh new foliage. The Eastern Tent Caterpillar (Malacosoma americanum) is a common pest in the southeast. Egg masses laid on branches begin hatching with instars around the time that cherry blossoms start to wane. Large portions of ornamental trees can be defoliated within a few weeks, exposing the distinctive large silken tent in the fork of the tree’s inner branches. This wriggling mass of protected caterpillars can be unsettling and unsightly for homeowners, but usually the foliage is quickly replaced, and your local birds help to keep the population in check from year to year. A simple stick can be used to extract and dispose of the tent early in the morning before the caterpillars venture out to feed.
Borers – Wood boring insects can be one of the most destructive pests to urban trees, even becoming the final nail in the coffin for struggling trees. In this region, cultivated flowering dogwood (Cornus florida) are particularly susceptible to the dogwood borer (Synanthedon scitula). Larva feeding on the cambium leave behind galleries of destroyed wood tissue just under the bark. Infestations left untreated can lead to girdling of the trunk and leave the door wide open to wood decay Fungi. Graft swellings on the trunk of young trees, areas damaged by string trimmers, and clustered branch unions of older trees are ideal spots for the wasp-like adult moths to lay their eggs throughout the summer. Several systemic and contact insecticides labeled for this flatheaded borer are highly effective when treated within the first year of the infestation.
It’s important to remember that pests and diseases require a vulnerable host to be successful, so cultivation of healthy trees in a diverse landscape is the first line of defense for our urban forests. Beyond that, utilizing your local phenology (seasonal cycles) when developing a monitoring schedule can give a leg up to your integrated pest management plan. (Written by the UT Institute of Agriculture Residential & Community Forestry Workgroup)
