Controlling Diseases and Insects in Home Fruit Plantings

Bulletin 780-01

Introduction

Growing fruit crops in the home garden can be a rewarding experience and a source of enjoyment for many years. It can also be a disappointing venture and a source of frustration. The difference is most often due to the many diseases and insect pests that attack fruit crops and in understanding how to best avoid or reduce the damage they cause. Some problems are minor, but others have the potential to destroy the entire crop or to kill the plants. Resistant cultivars reduce some losses and good cultural practices reduce others, but some use of chemical pesticides may also be necessary to ensure an abundant crop of wholesome fruit.

The pesticide issue is important to everyone. Pesticides are used to kill pests such as insects, fungi and weeds, and as such are poisons. However, it is important to recognize that many common household products such as bleach, ammonia and drain cleaner are very poisonous to humans, but are safe when used properly and help improve our quality of life. When chosen carefully, used only when needed and, then, only in strict accordance with the label instructions, pesticides can provide excellent control of insects and diseases with only minimal and short-term effects on the environment. If you choose to use pesticides, you must also accept the responsibility for their proper use, storage and disposal. If you choose not to use pesticides, more attention must be paid to the choice of crops, disease-resistant cultivars and good cultural management tactics. As a rule, pesticides are generally less effective when used to eradicate pest populations that have become a serious problem. However, they have proven very effective when used selectively as part of an overall pest management program.

This bulletin details the kinds of decisions that must be made for successful pest control in home fruit production with and without pesticides and the decisions that apply to each approach. These decisions fall into five general areas:

1. Identifying and Understanding the Major Fruit Diseases and Insect Pests. It is important for growers to be able to recognize the major diseases and insect pests of the fruit crops they wish to grow. Proper disease and insect identification is critical to making the correct management decisions. In addition, growers should develop a basic understanding of the pathogen or insect's biology and life cycle. The more you know about the disease or insect pest, the better equipped you will be to make sound and effective management decisions. Maintaining a good library is an extremely important part of successful disease and insect management. The following literature contains photographs of fruit diseases and insect pests, as well as information on their biology, development and control.

   Growing and Using Fruit at Home, Bulletin 591

   This is a publication of Ohio State University Extension and should be considered as a sister publication to this disease and insect control guide for home fruit growers. It provides information on cultural production practices and variety selection as well as disease and insect identification and control. It can be obtained from your county office of The Ohio State University Extension.

   The following literature also contains information about specific diseases and insects, varietal susceptibility to insects and diseases, and various aspects of fruit production in general. These publications are also available through your local county Extension office.

   Bulletin 861, Midwest Small Fruit Pest Management Handbook
   Bulletin 783, Brambles: Production, Management and Marketing
   Bulletin 436, Ohio Strawberry Manual
   Bulletin 758, Apple Rootstocks and Cultivars
   Bulletin 815, Grapes: Production, Management and Marketing
   North Central Regional Extension Publication No. 45, Diseases of Tree Fruits in the East
   North Central Regional Extension Publication No. 359, Insect Traps for Home Fruit Insect Control
   North Central Regional Extension Publication No. 63, Common Tree Fruit Pests

   The following publications should be useful for backyard fruit growers who desire more information about chemical control of diseases, insects and weeds or who require a more intensive spray program than is described in this bulletin:

   Bulletin 506 B2, Ohio Commercial Small Fruit and Grape Spray Guide
   Bulletin 506 A2, Ohio Commercial Tree Fruit Spray Guide

   Many of the above mentioned publications, as well as numerous Ohio State University fact sheets and other useful publications are currently available on the World Wide Web at the following address: http://ohioline.ag.ohio-state.edu.

2. Crop and variety selection. As a rule, tree fruits require more pesticides than most small fruits. However, some apple varieties are highly or moderately resistant to a number of important diseases. These can be grown using few if any fungicides, but may still require some use of insecticides. Similarly, nectarines are more likely than peaches to have more serious problems with brown rot disease. If pesticide use is not acceptable in the home garden, blueberries, raspberries, thornless blackberries, strawberries, and some grape cultivars (in that order) offer the greatest chance for success.
3. Sanitation methods. Sanitation means keeping the fruit planting cleaned up. Good sanitation should be followed regardless of whether conventional pesticide use is planned.

   Because fruit crops are perennial, many of the more serious disease and insect problems tend to overwinter in or near the planting. Good sanitation practice in and around the home garden reduces the risk of pest damage and can significantly reduce the need for pesticide treatments. Neglected fruit plants harbor many pests and should be eliminated. Good weed control in most small-fruit plantings not only reduces the competition for water and nutrients, but promotes rapid drying after a rain or dew and thus reduces the likelihood of infections by several important pathogens. Depending on the crop and the pests involved, sanitation measures can be as simple as a light raking in blueberries to more time-consuming pruning and leaf removal with apples. Specific measures needed in managing each crop are given later in this bulletin.

4. Experience. It is important to recognize or anticipate major pest problems early and to properly time specific cultural practices and any necessary pesticide treatments. A missed or poorly-timed pesticide application can result in lower fruit yields and quality. Additional treatments may later be necessary if the problem becomes worse. Similarly, sanitation methods designed to reduce the populations of overwintering pests are of little value if used too late. Diseases and insect pests are strongly affected by the weather, and so what seems to work best in one year may not be very effective in another. Similarly, a troublesome pest in one fruit planting may not be a problem in another. Thus, knowing when and how best to respond to these differences is an important part of any gardening experience; the solution is not always to use more pesticides. Some pests, such as peach leaf curl, peachtree borers and raspberry canker diseases attack plants during only a short time each season; knowing when this is likely to occur often means using a particular pesticide only once a season.
5. Expectations. For tree fruits in particular, if the primary goal is to produce a perfect, blemish-free crop, the need for pesticide sprays must also be accepted. This means additional time and expense and, in the long run, no assurance of a perfect crop, because of the limited number of pesticides available for home gardens. Some of the pests affecting a particular crop are relatively minor and present only a cosmetic or surface injury without affecting the basic fruit quality. Other pests may cause the entire fruit to rot or become infested with insect larvae (worms). Diseases such as apple scab may cause serious or minor damage depending on when fruit infection occurs; thus, the level of treatment required may vary. Early-season infections by the apple scab fungus, for example, can deform the fruit and cause it to crack or drop before ripening, while late season infections are usually only skin deep and easily removed in peeling. With this in mind, early-season fungicide applications may be necessary for scab control on susceptible varieties. Of course, by planting scab-resistant varieties, very little, if any, fungicide may be needed.

   Growers should expect some fruits of unsprayed strawberries, blackberries and raspberries to rot, mainly due to gray mold. Losses are greatest in wet seasons. In dry seasons, fruit rot may be minimal. Some home fruit growers are satisfied to produce a crop consisting of only 50 percent to 75 percent sound fruits. Be prepared to use fungicides if you expect a crop with few or no rotted fruit during wet growing seasons.