Learn all about oriental fruit moths, a prime attacker of cherry and other trees. Stop grapholita molesta damage to your cherries.
What Is It?
Oriental fruit moths are dangerous to cherry trees in all stages of their existence, from larvae to full grown adult night-flying moth. They are very difficult to control and can quickly damage the twigs, leafs, fruits and eventually the entire cherry tree. If left untreated, oriental fruit moths, which are known as grapholita molesta, may cause such damage to your cherry tree that abnormal branching patterns occur on younger trees. Oriental fruit moths also attack other stone fruit trees such as apples and pears.
What Does It Look Like?
Oriental fruit moths in their adult stage are night-flying moths. The adult form is a light to tannish brown and can vary greatly in size depending on region, climate and food availability. However, most of these moths are the size of a small butterfly and are rather non-descript in appearance. In their larval form, oriental fruit moths appear as worms that look similar to pinkish grubs, but rather than being found in the soil you will find them infesting your cherry tree twigs, branches, trunks and leaves. Eventually they will also infest your cherry stone fruits as they commence feeding. Damage from oriental fruit moths in adult and larval form usually causes new growth at the tips and outermost branches of the trees to wilt and die. Often you can confirm the presence of oriental fruit moth larva by slicing a presumed infested twig lengthwise. If you indeed have oriental fruit moths, the slice will reveal worms that look like grubs but are more pinkish than whitish and are approximately 1/4 to ½ inch in length. As the season progresses toward harvest, you may also be able to confirm the presence of oriental fruit moth larvae by slicing an infected fruit, as they will feed on fruits later in the growing season.
How Does It Manifest?
Oriental fruit moths in their brown adult form lay eggs on young cherry tree twigs and on the cherry leaves. These eggs then hatch into the oriental fruit moth larvae which bore into the twigs, young buds, shoots and trunk of the cherry tree. This boring into tender areas of the cherry tree can cause generalized weakness in the structure of the tree, or can result in death of entire twigs and branches depending on the severity of the infestation and number of larval worms. When the larvae mature they leave the twigs which they have bored into and they pupate on the external portions of the tree, or in debris on the ground near the base of the tree. When the larvae pupate they do so in cocoons which they spin. Oriental fruit tree cocoons are often seen in the crotches of tree branches or adhered to the side of the trunk near the soil line. It takes several months in the cocoon before the oriental fruit moth emerges as a brown, night-flying adult and the females lay their eggs to begin the cycle of reproduction and feeding again. Damage to the cherry tree can occur all through the growing season as new generations emerge from eggs and cocoons laid earlier in the season. You will notice that in the later stages of the growing season you will find the most damage on your cherry trees from oriental fruit moths who are feeding on mature cherry fruits.
What Can I Do About It?
Unfortunately, oriental fruit moths can be hard to control because once these pesky insects have bored into the twigs and fruit they cannot be adequately reached by pesticides. However, spraying the infested trees with carbaryl containing insecticide or one which contains diazinon should kill the surrounding adult night-flying moths and prevent future worm damage. Other than this measure, the best bet to the cherry tree owner is to prune off infected twigs and branches as well as discarding infested fruits. You can also do regular checks on the cherry tree to look for the presence of cocoons as an indicator that you may have oriental fruit moths and need to take action to prevent further damage to your stone fruit trees.
