What kind of insect was seen on the ash?
The insect is an ash plant bug. Both the young nymphs and adults use needle-like mouthparts to feed on plant sap from the underside of the leaves, resulting in the speckled discolorations. Early, heavy feeding can also cause browning.
How seriously can it affect ash trees?
Their feeding just affects the tree's appearance. Even when most of the leaves are infested, ash plant bugs do not injure the tree's health. Although ash plant bugs feed throughout the year, the majority of damage occurs right away in the spring when the insects first feed.
Is this likely to cause leaves to fall?
There are several factors that can cause premature leaf drop in ash. The most likely possibilities are a type of disease known as anthracnose or stress due to unfavorable environmental conditions (e.g. late frost, high winds). Ash plant bugs normally do not cause ash leaves to drop.
How can you treat the tree for this problem?
If you wish to protect the appearance of your ash, treat it when the insects are first active and damaging the leaves, which is sometime in May. There are a variety of residual insecticides that would effectively reduce plant bug numbers. However, if you do nothing, the tree will survive just fine.
