University of Maryland Extension

Fruit Disease and Insect Pest Control

To grow any type of fruit successfully, you must grow healthy plants and anticipate and prevent problems. The appearance and severity of pest problems varies between neighborhoods, areas of the state, and growing seasons. When symptoms of a problem are noticed, accurately identify the problem (weed, insect, disease, cultural/environmental), monitor for changes (increasing severity), and be prepared to act. Prevention and control measures at your disposal may be physical (e.g., handpicking Japanese beetles, removing diseased plants), cultural (e.g. pruning brambles to improve air circulation), or chemical (e.g. spraying horticultural oil to smother San Jose scale.)

Do not assume that plant problems are caused by insects and diseases. A large number of problems are caused by cultural and environmental factors. These include insufficient water, nutrients, space, sunlight and support, poor soil, low pH, temperature extremes, and root damage from cultivation. In addition, the severity of some common problems is closely related to weather (some diseases are worse in wet years) and to gardening decisions (choosing inappropriate varieties, purchasing low-quality plants, incorrect spacing, etc.).

The integrated pest management (IPM) approach to preventing or managing pest problems is highly recommended and can be summarized as follows:

1. Correctly identify the problem—if it is caused by insect or disease, learn about the life cycle and habits.
2. Learn to anticipate and prevent problems.
3. Monitor the problem for worsening symptoms.
4. If level of pest damage becomes unacceptable, choose the least-toxic control.

The IPM approach used by organic growers should be nearly identical to the one employed by conventional growers. The difference is that the organic grower needs to monitor more closely and rely more heavily on cultural and physical techniques for preventing and managing problems and use only acceptable organic sprays. Keep in mind that organic pesticides are not generally as effective as chemical pesticides. And they still can negatively impact the pollinator population. 

Cultural Control Practices - the following should be part of regular maintenance practices to reduce insect and disease problems. 

  • Remove; rake up from the ground and dispose of any infested or diseased fruit. 
  • Handpull or gently cultivate around plants to control weeds which can harbor insect populations. 
  • Prune properly to improve spray coverage, encourage air circulation and sunlight penetration. Prune out dead, damaged or decaying branches, canes or stems. 
  • Keep plants vigorously growing by fertilizing according to our recommendations and keeping plants watered during dry periods. 

Pesticides as Part of the IPM Approach

The use of pesticides is meant to keep pest populations below levels that might result in moderate to severe damage, rather than to eradicate all pest organisms. The kinds of pesticides needed and the frequency of their application varies greatly in each home garden and depends on many factors. Pesticides should be used only when needed, and then in strict accordance with label directions.

Although this fruit section lists many major pests, not all plantings will require treatment for all of these pests every year. These recommendations are guidelines not magic formulas for fruit production. Let experience be your guide. Learn to recognize the symptoms caused by the major pests so that the most effective control measures can be taken.

If you have never seen a particular pest, then that pest may not be a problem in your planting. New plantings, especially where isolated from other similar fruit crops, often seem nearly pest free, and pesticide treatments may not be necessary for some time. Blueberries, for example, can often be grown for 6 to 8 years before pest populations develop to damaging levels.

If you have a current problem with a particular pest or disease, you should plan preventative treatments accordingly. This is particularly true for specific diseases such as brown rot of peaches, black rot of grapes, and apple scab. These diseases can only be controlled with scheduled, preventative sprays early in the growing season (see spray schedule link below).

Pest populations are seldom static. They increase and decrease at different rates as a result of changes in the weather, plant and fruit maturity, and the management practices followed by the grower. Careful management of fruit crops early in the growing season can prevent certain pests from causing damage that warrants chemical treatments later.

Home Fruit Preventative Spray Schedule and Management of Common Problems

Fungicides (Organic and Chemical)

Insecticides (Organic and Chemical)

If you need assistance diagnosing a fruit problem send us a question along with digital photos of the problem.

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