Ash Plant Bug

In most years, the ash plant bug (Tropidosteptes amoenus) is present on trees in Manitoba. In most years damage is minimal or hardly noticed, as has been the case for the last several years. In other years damage is more significant, often when the damage the bug causes is combined with diseases that also affect ash trees.  

Ash plant bugs are small (5 to 8 mm long), oval-shaped insects that vary from pale yellow to brownish to greenish in colour. They are very active on plants and the adults can fly easily. Nymphs do not have wings and cannot fly, but can more quite quickly. 

These insects feed by piercing leaf tissue and sucking plant juices from the leaves. In relatively minor cases, the leaves will have some white stippling on the surface of the leaves and the trees are otherwise unaffected. In more severe cases the leaves will turn brown and curl along the edges, sometimes resulting in significant leaf drop.  

Fortunately ash trees are very resilient and can withstand attack by the ash plant bug. Only when several years of repeated infestation occur are trees in danger of not surviving. Even in years of heavy infestation with significant leaf drop, the trees usually produce a second set of leaves.  The canopy won’t be as thick as it usually was and the tree may not grow as much as it otherwise would have, but it has not experienced any significant damage. Young ash trees are more susceptible to damage, but minor feeding damage (stippling) and even some leaf curl still isn’t a major cause of concern. If there is considerable leaf curling and abundant leaf loss, control measures may be required. The only currently registered products available are those containing carbaryl as the active ingredient. Remember to use proper safety precautions and read and follow label instructions before applying any pesticide.