Fruit growers can use many methods to control bramble diseases. summarizes disease control strategies, and Table 7.2 summarizes disease control strategies, and Table 7-5 lists some fungicides for some of the important diseases. Fungicides, however, are only one of the control options and are not always successful on brambles. Table 7.3 describes the occurrence of insects and mites on brambles, and Table 7.4 and Table 7.5 provide information about pesticide use. A general discussion of insect management appears in Pest and Pesticides. The following practices will help in both insect and disease control.
Good Air/Water Drainage
Good air drainage and circulation within the planting speeds the drying off of plants and reduces the potential for infection. Many disease organisms require wet foliage or fruit for infection to take place. Similarly, it is important that the soil dries out quickly after rain. Waterlogged soil increases the likelihood of disease infection in the root system. Several important disease organisms on brambles will infect the root system in wet soil.
Plant Brambles More Than 500 Feet from Existing Brambles
This control is aimed primarily at reducing the spread of viruses from existing brambles to young healthy plants. Because of the widespread occurrence of virus-infected wild brambles in Pennsylvania, it generally is assumed that older domestic plantings or wild brambles all contain viruses, and that new plantings should be placed well away from the area. Sometimes planting new brambles 500 feet from older or wild brambles is not possible. In that case, the next best option is to put the new planting upwind. Viruses are spread primarily by aphids, so planting upwind will reduce the potential for virus spread since flying against the wind will be more difficult for the aphids.
Some crops can build disease organisms in the soil, which can devastate the next crop if it is susceptible to the disease. Brambles should not follow tomatoes, potatoes, eggplants, peppers, strawberries, raspberries, or stone fruits for 5 years since these crops may harbor the Verticillium fungus, which is very severe on brambles. Avoid an area with a history of verticillium problems. Grass crops or corn are recommended before red raspberries are planted since nematodes will lose the crumbly berry virus once they feed on corn or grasses.
Tolerance or Resistance
Some plants are not susceptible to some diseases or are less susceptible than other varieties. Resistance or tolerance to diseases will eliminate or greatly reduce the need for disease control.
Avoid Adjacent Plantings
Keep black and purple raspberries away from red raspberries because mosaic virus can spread from red raspberries and is more severe on black and purple raspberries. Keep all red raspberries away from blackberries because blackberries can be a symptomless carrier of curl virus.
Eliminate Wild Brambles
Wild raspberries serve as a host for many insect and disease problems that spread to domestic plantings. Removing wild brambles will reduce the need for insect and disease control. Remember, many virus-infected plants may not show symptoms.
Disease-Free Planting Stock
Use only disease-free planting material. Since viruses and bacteria cannot be seen at the time of planting, the grower must rely on good propagation and methods used by the nursery. Virus-infected plants are infected for life, and bacteria-infected plants will contaminate the site for many years. Buy only healthy plants from reputable nurseries.
Aphids are vectors of viruses and must be controlled if virus diseases are to be managed.
Rogue Diseased Plants
Pulling out diseased plants helps to reduce the amount of disease in a planting. This is an especially important control tactic for orange rust and verticillium wilt.
Most disease organisms that cause foliage or fruit diseases require wet surface areas for infection to take place. By speeding the drying time after rain or heavy dew, the potential for disease development can be greatly reduced. Two important methods for accomplishing this in a bramble planting are good weed control and adequate pruning to allow good air circulation within the canopy.
Prune Three Days before Rain
Cane blight can be a serious problem on black raspberries. The fungus requires a fresh pruning wound and wet surface for infection to take place. If it is possible to time pruning so that these do not occur at the same time, no disease will develop.
Dispose of Pruned Canes
Anthracnose, a serious problem on brambles, can survive on dead canes that have been pruned off. If pruned canes are left in or near the planting, the disease can spread back into the planting. Removing the pruned canes reduces the potential for disease development.
Maintain Plant Vigor
Some diseases, like cane blight, can more easily infect weak canes than healthy ones. Maintain plant vigor through a good nutritional program to reduce the potential for cane blight development.
Fungicide applications should be used only if other control strategies are not adequate to control the disease. Fungicide sprays will help in the control of cane blight, powdery mildew, and fruit rots.
Harvest before Fruit Becomes Overripe
The fruit rots will spread more quickly on overripe fruit. Overripe fruit will also allow a disease to build up in the planting, making control more difficult.
Fruit Storage Conditions
Fruit rots will develop more slowly or not at all if the fruit is cooled rapidly (to 40°F) after picking.
Groundcover Management and Weed Control
It is best to grow sod between bramble rows. This prevents soil erosion and allows the home gardener to easily walk between rows. The grass should be mowed regularly to discourage rodents from nesting near the planting. Weeds, especially dandelion, can serve as hosts for viruses. Weeds adjacent to or between plants should be removed mechanically by hoeing, hand pulling, or shallow cultivation.