Blackberries and raspberries are both brambles from the Genus Rubus and related to the rose. Blackberries are ripe when they lose their shine and raspberries are ripe when they separate at the core.
Blackberries are drought tolerant once established but still require regular watering during fruit development. Raspberries are grown in many climates. Both should be fertilized with a complete fertilizer after harvest to ensure good growth and preparation for winter.
Issues that can occur with blackberry include crown gall, root rots or wilt, nematode, leaf curl, vein chlorosis or mosaic virus, spur blight, gray mold, anthracnose, rust and rosette. Insects that attack blackberry include fruit worm, spider mites, Japanese beetle, weevil, aphids and borers. Many of these attack raspberry as well but in our area the major concerns include mosaic virus, anthracnose, blight and gall. Insects that dine on some part of the raspberry plant include fruit worm, spider mites and Japanese beetle.
Crown gall is easily recognized on both berries as a large round ball that encircles the cane. It is a bacterial infection that occurs through wounds. If you wish to ensure it does not spread to other plants you can remove the infected plant and be careful not to damage or wound remaining plants. The bacteria can survive in soil for at least one year.
If blight is present the leaves will wilt and die. Cut the stem open and look for brown discoloration. If blight is present then remove the plant and burn it to prevent further spread to healthy plants.
Rust appears as an orange powder that can be rubbed off the leaf surface or orange-yellow spots on the upper and lower leaf. Control of rust involves removing and burning infected canes to prevent spread.
Anthracnose often attacks the canes causing lesions that may girdle the cane causing death or cracking. Anthracnose also attacks leaves showing as small purple- brown spots. Copper and sulfur based fungicides should be used for control and damaged canes should be removed and burned.
Grey mold usually infects flowers and moves to fruit. It may hide until the fruit is fully formed before appearing. When conditions are right (wet and cool) a grey or brown mold will appear causing the fruit to burst or rot. While high applications of nitrogen may help cause it, good air circulation helps prevent grey mold.
Scouting will help to find insect issues before populations get out of hand. Aphids are a concern as they are responsible for spreading mosaic virus and rosette. Once you have either you should remove the infected plant to prevent its spread to other plants nearby. By keeping aphids under control you may prevent these two diseases.
Spider mites symptoms include dense webbing, yellowing between leaf veins, wilting leaves and dead tissue. Chemical applications should be limited to allow natural predators to control the population. When you use a chemical to spray the mites it will also affect the predators and possibly lead to a larger outbreak of the mites when the predators that control the population are gone. A focused spray of water with a high pressure hose may help reduce a population surge long enough for predators to gain control.
Fruit worm can be an issue on both berries. The adult lays eggs in the buds which hatch into small worms in five weeks. These feed on the fruit causing the fruit to decay, drop or become unpalatable. The worms are ? inch long and can be controlled by cultivating soil in late summer or early fall to expose pupae in the soil. Chemical control can be done by using carbaryl when blossoms first open and again when blossoms fall.
Japanese beetles prefer to dine on plants from the rose family. They will defoliate a bramble quickly, reducing its ability to produce food. The way to control the adult beetle may be to focus on the larvae or grub in the soil. One organic method that does not target other beneficial organisms in the soil such as worms is to use Bacillus papillae-Dutky or Milky Spore powder. Full control may take up to three years but can be effective for up to 20 years once established in the lawn.
One problem that is neither disease nor insect related in our area is sunscald. On both raspberries and blackberries a white or cream colored area may be found on the fruit. This 'sunburn' area is believed to be from excessive heat damage. There is no clear method to prevent this issue although watering deeply each week and shade cloth may help.
Although many problems can hinder our efforts to obtain quality bramble berries, in any given year we may only see one issue. Don't give up. Scout your brambles regularly to determine if there is anything going on. If you had a problem this year, you should be prepared for that same issue to occur next year.
The University of Missouri Extension center is located in Kennett, Missouri at 101 South Main Street (the old bank) on the 2nd floor. Open Monday -- Friday. University of Missouri Extension programs are open to all.
Sarah Denkler is a horticulture specialist with University of Missouri Extension
in Dunklin County.