Most insects are herbivores that live off of plants. While fruit trees want animals to eat their nectar and their fruit in order to help them pollinate and distribute their seeds, some bugs do damage to the flowers, leaves, stems and roots of fruit trees, causing the flowers to drop early, weakening the tree by preventing photosynthesis and the absorption of nutrients in the soil and even killing the tree.
You can identify the type of pest infecting a tree by the kinds of wounds a tree bears. The plum curculio, for example, creates crescent-shaped scars in the trunk. Two-spotted spider mites can cause brown or bronze foliage. Wooly apple aphids may cause swollen roots. Pear slugs, according to the University of Arizona, will consume a leaf but leave the veins intact. Pear blister mites will leave brown blisters on a pear. When parts of the tree start to die, determining the cause of the dieback can be tricky because in a weakened state, the fruit tree can be vulnerable to diseases, fungi and malnutrition.
Fruit trees can become more resistant to bugs when they are otherwise very healthy. Fruit trees should only be grown in areas to which they are adapted. Also, fruit tries should be protected from injury whenever possible because harmful pests can enter inside the fruit trees through these openings. Newly planted trees, old trees and trees that are crowded together are also vulnerable to pests, according to the University of California, Davis.
Some bugs such as the plum curculio can cause fruit to drop before it has ripened, while other pests can cause fruit to become deformed, such as with the pear blister mites. Peach twig borers can kill new stems that are growing on fruit trees, according to the University of Arizona. Thrips can prevent fruit trees from developing new leaves. San Jose scales can kill young fruit trees that are 2 or 3 years old.
Insecticides can kill many of the harmful bugs on trees, but some bugs develop a resistance to the insecticides. Also, many insecticides can contaminate the fruit trees and can also harm wildlife. Fortunately, organic alternatives exist that can kill pests. Some naturally occurring substances are poisonous to some insects and bugs can also be fought by introducing their predators to the trees.
There are specific remedies for some pest species such as destroying infected fruits, directly capturing larger bugs and washing the leaves with soapy water. Some services are available that specialize in trapping pests and removing them from fruit trees, according to the University of Rhode Island.