Organic Pest and Disease Management in Home Fruit Trees and Berry Bushes

Organic Pest and Disease Management in Home Fruit Trees and Berry Bushes

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Charles Brun, Ph.D., Horticulture Advisor, Washington State University, Michael Bush, Ph.D., Extension Entomologist, Washington State University
The goal of this publication is to provide gardeners in the Pacific Northwest with an organic approach to keep their home grown tree fruit and berries pest free. This approach begins with proper plant selection and placement within the home landscape. It will rely on frequent monitoring of plant health and proper identification of any emerging pest problems. Finally, integrated pest management based on a combination of cultural, physical, biological and organically-approved chemical strategies will be used to manage fruit pests.
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The goal of this publication is to provide gardeners in the Pacific Northwest with an organic approach for reducing pests and plant diseases on their homegrown tree fruit and berries. After properly selecting and placing plants in the home landscape, gardeners need to periodically monitor plant health for any emerging pest or disease problems. Home gardeners should use a combination of cultural, physical, biological, and organically-approved chemical integrated pest man­agement (IPM) strategies to manage these problems.

Plant Selection for the Home Landscape

Home gardeners throughout Washington State can enjoy raising their own fruit for fresh consumption and preservation. Homeowners in western Washing­ton may have an advantage over residents on the east side of the state in raising strawberries, raspber­ries, blackberries, and blueberries, as the west side climate is relatively mild year-round. If one selects a well-drained site that receives a minimum of six hours of sun, all berry crops generally grow well on either side of the state.

Homeowners in eastern Washington generally have a climate more suitable for growing apples, pears, peaches, plums, nectarines, and apricots rather than berries. Tree fruits exhibit fewer diseases when they are grown in areas where the spring and summer months are drier. Regardless of which side of the state you reside, when disease-resistant cultivars of fruit trees are selected along with easily-managed dwarfing rootstocks, gardeners can achieve bountiful crops.

Figure 1. The symptoms of European canker (Nectria galligena) on apple include swollen, ring-shaped cracks forming along the bark of the trunk and twigs. Photo courtesy of Bruce Watt, University of Maine,

Monitoring and Scouting

One key to proper management of berries and fruit trees in the home landscape is frequent monitor­ing and scouting. Monitoring involves spending time walking through the garden and familiarizing yourself with the normal growth and development of plants as they mature and as fruit ripen. Scouting involves early detection of signs and symptoms that indicate the health of your fruit plants may become compromised by a pest. Scientists use the terms “signs” and “symptoms” to help describe and diag­nose diseases, pests and disorders (problems caused by non-living factors).

Signs of a disease are the direct evidence of the disease on the plant, such as the presence of fungal fruiting bodies, fungal growth, or bacterial exudates. Similarly, signs of an insect pest include the presence of insect eggs, larvae, cast skins, or even catching the pest in the act of feeding on the plant. In contrast, symptoms are the physical characteristics of diseases or disorders. Symptoms of a plant disease may include wilting, cankers (Figure 1), rots, necrosis (death of plant parts), chlorosis (yellowing of plant parts), and a general stunting or reduction in plant growth. Symptoms of insect pests may be indicated by missing plant tissue (holes, tunnels, leaf notches, etc.) (Figure 2), abnormal growth in plant tissues (galls, blisters, etc.), or other damage such as plant wilting or dieback resulting from insect feeding at the roots or in the plant tissues just below the damaged tissues.

Biotic Versus Abiotic Plant Problems

Biotic plant problems are caused by living organisms like insects and plant diseases, while abiotic plant problems are the result of non-living factors. Biotic plant problems may resemble abiotic problems in ap­pearance; if a similar problem occurs among multiple plant species, be sure to consider an abiotic plant problem first. Note that more than 70 percent of the plant problems examined by university diagnosti­cians, or trained Master Gardeners, fall under the non-living, or abiotic designation.

Abiotic plant problems may be caused by physical, chemical, or environmental factors. Physical factors may include air and water barriers such as compacted soil, pavement, or weed barrier fabric that inhibit normal plant growth. Physical damage can also oc­cur from human activities, such as mowing or using string trimmers too close to the trunk of fruit trees or canes. Chemical factors may include herbicide drift,



Copyright 2013 Washington State University

Published December, 2013

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