This publication is designed to help apple growers, researchers, and other professionals associated with apple production and pest management to identify common pests (insects, mites, and diseases), pest damage, and beneficial organisms in Minnesota orchards. The ability to correctly identify pests and beneficial organisms in apple orchards is crucial to the adoption of integrated pest management (IPM) by growers.
This guide provides easy-to-use field identification characters (distinguishing marks or colors) that can be used to diagnose key pest species from look-alikes (pests and non-pests) that may be confused with them in sticky traps.
Insect pests are a challenge to identify after being in a sticky trap for many days. It is sometimes difficult to identify pests in sticky traps using pictures of fresh specimens. The current guide will help growers to identify how a pest species looks as a fresh specimen compared to after several days in sticky traps.
Although this guide features specific pest phenology data (pest emergence dates, number of generations, etc.) from Minnesota, growers and researchers from other parts of the United States, in particular the upper Midwest region, should also find it useful.
This publication is primarily a pest identification guide, and does not provide information on pest management. For pest management decisions, this guide should be used in conjunction with the companion publication Integrated Pest Management Manual for Minnesota Apple Orchards. The manual is also published by the Minnesota Department of Agriculture and contains information on monitoring techniques, thresholds, and management options for each key pest.
Various pest organisms, primarily arthropods (insects and mites), diseases, weeds, and mammals are associated with apple production in Minnesota and cause significant economic losses to commercial fruit growers. The focus of this guide is on arthropod pests and diseases of apple. Insect pests found in apple orchards can be classified into two groups depending upon which plant part is attacked. Direct pests are those insects that feed on apple fruits, while indirect pests are those that attack leaves, trunk, and other parts of the tree. Examples of direct pests of apple in Minnesota are apple maggot, plum curculio, codling moth, and other internal fruit feeders. Pests like spotted tentiform leafminer, aphids, and mites may affect yield if present in large numbers, but they are indirect pests since they do not directly injure fruits.
Insect pests can also be classified in terms of the seriousness of their infestation and effect on orchard economics. Major pests are those that have the potential to cause major economic losses to the grower. Usually, most direct pests that feed on fruit are also considered major pests. Apple maggot, plum curculio, and codling moth constitute the "big three" pests of apple in Minnesota and the upper Midwest. Indirect pests usually do not feed on the fruit, and although their activities may limit fruit yield they are considered minor pests. A third category of pest insects is the quarantine pests. Quarantine pests are insects not known to be established in a given area. The flat scarlet mite and apple ermine moth are current examples of quarantine pests in Minnesota.
Not all insects and mites in apple orchards are harmful. Many arthropods, such as lady beetles, predaceous bugs, spiders, and predator mites benefit the grower by feeding on pest insects and mites. Bees also fall into this category of beneficial arthropods by aiding apple pollination.
Many diseases of apple are not restricted to one part of the tree. For example, apple scab attacks the fruit, leaves, and flowers. Powdery mildew can also infect many parts of the tree. Fire blight is a tree disease infecting leaves, shoots, limbs, and trunk, but it can infect fruit and root stock. The fungal disease complex known as sooty blotch and flyspeck is, however, restricted to the fruit.
Not all insects found in an apple orchard are pests. Many organisms benefit the grower by eating or parasitizing pests in the orchard. These organisms are known as beneficials, natural enemies, or biological control agents. They may be native or introduced from other areas.
Beneficial natural enemies (insects and mites) that may occur in an apple orchard could be classified as predators or parasitoids. Predators are those that attack, kill, and feed directly on a pest (prey). Examples of common orchard predators are ladybeetles, flies, lacewings, wasps, bugs, ants, spiders, and predator mites. Parasitoids are insects that lay eggs on or in a pest (host). The developing larva lives and feeds on the host, parasitizing and eventually killing it. Examples include parasitic wasps such as the egg parasite, Trichogramma sp.
Bees are a different class of beneficial insects in the orchard in that they benefit the grower by aiding pollination.
It is important that growers are able to recognize, identify, and conserve beneficials in their orchard. Conservation of beneficial organisms is a basic tenet of an ecologically sound pest management strategy. Conservation or enhancement of beneficials can be achieved through judicious use of pesticides such as spraying only when and where needed, accurate timing of sprays, and selecting pesticides that are least toxic to beneficials.
Prepared and Edited by:
Henry Y. Fadamiro, formerly Minnesota Department of Agriculture
With Contributions from:
Harry Hoch, IPM Consultant, La Crescent, MN
This guide was produced by the Minnesota Department of Agriculture. Funding was provided by the U.S. Environmental Protection Agency, Region 5, Chicago, IL. We would like to acknowledge the encouragement offered by the following groups:
The following persons have helped in the preparation, review, or publication of this guide:
Most of the pictures published in this guide were photographed by the editor (Henry Fadamiro) and other staff of the Minnesota Department of Agriculture, Plant Pest Survey & Biological Control Program. Additional pictures were obtained from the following sources:
Ag Marketing & Development Division
Minnesota Department of Agriculture (MDA), 625 Robert Street N, St. Paul, MN 55155-2538, firstname.lastname@example.org