References and Suggested Readings
This field guide provides information on the common pests (insects, mites, and diseases) of strawberry in Minnesota. It is designed to help strawberry growers, researchers, and others professionals associated with strawberry production and pest management to identify common pests (insects, mites, and diseases), pest damage, and beneficial organisms in Minnesota strawberry plantings. The ability to correctly identify pests and beneficial organisms in strawberry plantings is crucial to the adoption of integrated pest management (IPM) by growers.
The 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.
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 twin publication "Integrated Pest Management Manual for Minnesota Strawberry Fields". The manual, also published by the Minnesota Department of Agriculture, contains information on monitoring techniques, thresholds, and managements options for each key pest.
Various pest organisms, primarily arthropods (insects and mites), diseases, and weeds can cause significant economic losses to commercial strawberry growers in Minnesota. The focus of this guide is on arthropod pests and diseases of strawberry. Arthropod pests found in strawberry plantings attack the fruit, leaves, buds, flowers, and other parts of the plant. Their feeding activities can also increase the susceptibility of the plant to diseases and other pests. Tarnished plant bug, sap beetles, thrips, and strawberry bud weevil (clipper) are examples of insects that can damage the strawberry fruit. Insect pests like leafrollers, leafhoppers, aphids, spittlebug, and mites attack the leaves and other vegetative parts of the plant. A third category of insects will attack and damage strawberry roots. They include strawberry rootworm, root weevils, and white grubs. Although foliage and root feeders do not directly injure the fruit, they may sharply reduce yield if present in large numbers.
Not all insects and mites in the strawberry planting 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 are also beneficial arthropods that aid strawberry pollination.
Just like arthropod pests, strawberry diseases can be classified according to the part of the plant affected. Gray mold, anthracnose, and leather rot are examples of diseases that directly affect the fruit. Leaf spot, leaf scorch, and leaf blight are restricted to strawberry leaves, while diseases such as red stele, root rot, and Verticillium wilt attack the root.
Not all insects found in a strawberry planting are pests. Many organisms benefit the grower by eating or parasitizing strawberry pests. These organisms are known as beneficials, natural enemies, or biological control agents. They may be native or introduced from other areas.
Beneficial organisms (insects and mites) that may occur in a strawberry field could be classified as predators or parasitoids. Predators are those that attack, kill, and feed directly on a pest (prey). Examples of predators of insects are lady beetles, flies, lacewings, wasps, bugs, ants, spiders. Predator mites also prey on pest mites. Parasitoids are insects that lay their eggs on or in a pest (host). The developing larvae lives and feeds on the host, parasitizing and eventually killing it. Example is Peristenus digoneutis, a parasitoid of tarnished plant bug nymphs.
Bees are a different class of beneficial insects in the field in that they benefit the grower by aiding strawberry pollination. It is important that growers are able to recognize, identify, and conserve beneficials in their fields. 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 selection of pesticides that are least toxic to beneficials.
Prepared and Edited by:
Henry Y. Fadamiro, formerly Minnesota Department of Agriculture
With Contributions from:
Suzanne Wold, University of Minnesota
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 Minnesota Fruit & Vegetable Growers Association.
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