Trees will always contain insects of different kinds. Sometimes these insects are opportunistic and may take advantage of the tree either by using it as a place to lay eggs and feed its larvae, or consume its leaves as adults. Honey locust trees are susceptible to attack from a few such insects.
Plant Bugs – are green and may infest your honey locust late in the spring, with damage peaking in May – June. Signs of infestation include leaf yellowing or browning. They can twist, and entire twigs may start dying. To treat infestations, chemical pesticides may be used, but these are recommended only under the heaviest infestations. The tree will re-grow any damaged leaves in June, when infestations are over anyways.
Pod Gall Midge – this insect lays eggs on the leaves of the honey locust in order to provide food for its larvae when they hatch. Leaflets that are infested form “pod galls”, where they thicken and curl together instead of expanding and growing normally. Leaflets that are already formed are not affected. After the adult midges emerge from the galls, the galls fall from the twigs, leaving them absolutely bare. There are natural controls to midge growth, and this includes parasitic wasps, predatory plant bugs (above), and severe weather. Pesticides can be used, but they have proven to be only moderately effective, reducing only portions of the galls.
Cankers – A fungus that manifests itself as sunken areas around the base of branches and trunks, and the bark of the tree can have a reddish-yellow discoloration. Cankers at the base of the tree usually signify that it is too late, and the tree will die. Healthy trees may be able to recover, but previously stressed trees will usually perish. Pruning infected parts or entire trees will help prevent spreading.
Root Collar Rot – This disease can quickly kill trees if not identified and treated promptly. Infection is indicated by loose bark, with healthy (although discolored yellow) wood underneath. It is like an open wound on the tree that spreads over several months. To treat it, the tree’s surface should be dried out to prevent further fungal growth.