This is another poem in my sugar maple cycle, which deals with a pest – pear thrips – which can pose a real threat to sugar maple trees as they leave ‘Budbreak‘. Pear thrips (Taeniothrips inconsequens) are very tiny, around 1.5 mm, thin, striped brown bugs with a hairy fringe that are invasive to the United States and damage the leaves of sugar maple (and other) trees. Sugar maples are noted to be attacked most frequently and severely. Pear thrips were introduced to the US sometime before 1904, when they were documented in CA, and defoliated 1.3 million acres in PA during 1988 alone.
Adult female thrips live in the soil during the winter before emerging as air temperatures warm during early spring; they fly through the air to find suitable hosts, then crawl through the scales of the trees’ buds to lay eggs and feed on the delicate leaf/flower tissues underneath. Adults feeding on this delicate tissue, and possibly also oviposition of eggs itself, can cause heavy damage where leaves are crinkled, yellowed, and/or 1/4 normal size – trees can sometimes look yellow or thin from quite a distance. Reduction of foliage can cause an individual tree to produce less seeds, likely since they have less photosynthetic capacity and produce less sugars.
After the buds break, releasing their damaged leaves, small white eggs can sometimes still be seen clinging to the veins of the leaves where larvae will hatch and feed on the fluid from the leaves themselves. Adults die relatively shortly after oviposition, with few surviving past late May; the larvae stick around to feed before taking to the soil for another cycle.
Budbreak and pear thrip emergence from the soil occur nearly simultaneously; thus the timing actually plays a big role in how much damage the thrips can do to their hosts. Should buds break and leaves expand prior to thrips emerging from the soil, the thrips are highly susceptible to predators and the environment and will have a far smaller effect on tree health. However, should buds begin to leave dormancy and swell later than thrips emerge from the soil, the thrips have a dry, safe environment to feed and lay eggs inside the bud, wrecking havoc on the slowly developing leaves within; thus a late budbreak can spell disaster for maple trees in the northeast.