Better Yields Through Science
Caneberries Diseases & Pests
|Disease||Symptoms, Life-cycle and Pest Management|
|Cane Blight||Pathogen: Leptosphaeria coniothyrium
The fungus overwinters on infected dead canes. In the spring spores are blown, splashed by rain, and carried by insects to nearby canes. Under moist conditions the spores germinate and enter the plant through pruning wounds, insect damage, fruit stem breaks and other wounds. The fungus can then rapidly kill bark and other cane tissue. Dark brown to purplish cankers form on the new canes near the end of the season. The cankers enlarge and extend down the cane or encircle it causing lateral shoots to wilt and eventually die. Infected canes commonly become cracked and brittle and break easily. This disease is usually most severe during wet seasons.
|Cane and Leaf Rust||Pathogen: Kuehneola uredinis
Cane and leaf rust occurs on some blackberry cultivars, especially trailing varieties. The first symptom of cane and leaf rust is lemon yellow pustules (uredinia) that split the bark of the fruiting canes of susceptible blackberries. Spores from these pustules (urediniospores) infect leaves and produce small yellow pustules (uredinia) on the underside of leaves during early summer. Defoliation can occur if infection is severe. Buff-colored telia develop among the uredinia on leaves in early fall.
It is important not to confuse this common blackberry disease with the less common but far more damaging orange rust, which causes plants to produce many small, weak shoots from the base of the plant.
On susceptible blackberry varieties leaf defoliation can be severe and result in the loss of plant vigor. Normally cane and leaf rust doesn’t infect the fruit but masses of spores falling on fruit can render it unmarketable. Raspberries are hosts, but occurrence of this disease on this crop is rare. Wet spring conditions will favor disease development. The fungus overwinters on canes as mycelium or latent uredinia. Cane and leaf rust can be distinguished from orange rust by the presence of yellow pustules (uredinia) on both the canes and leaves. Orange rust has orange pustules on leaves only.
Removal of fruited canes after harvest and sprays of lime sulfur or some fixed coppers are acceptable management tools in an organically certified crop. A recommended spray control program is a winter application of lime sulfur, followed by application at green tip stage and then a treatment at bloom.
|Spur Blight||Pathogen: Didymella applanata
This disease is more common and serious on red raspberries and to a lesser extent on black and purple raspberries and loganberries. Blackberries and dewberries are highly resistant to this disease. Spur blight can cause yield losses in several ways. It can blight the fruit bearing spurs, cause premature leaf drop, and kill buds on the canes that later develop into fruit bearing side branches. In addition, berries produced on diseased canes may be dry, small, and seedy. Affected canes may be more vulnerable to winter injury than uninfected ones.
Chocolate brown, dark blue or purplish spots with encircling bands form on the new canes and leaf petioles in the late spring or early summer, usually at a bud or leaf attachment. The infected areas, which vary from half an inch to several inches long, gradually enlarge until the cane is girdled.
The fungus survives on infected canes during winter. The following spring and summer, during wet and rainy periods, spores are released and carried by splashing rain and wind to nearby canes and leaves, where they germinate and penetrate plant tissue. Infections commonly occur where the leaf petiole is attached to the stem. Treat with lime sulfur when the buds show no more than 3\8 inch (1 cm) of green at the tips.
|Anthracnose||Pathogen: Elsinoe veneta
The fungus overwinters in the bark of within lesion on infected canes. In early spring the spores are rain-splashed, blown or carried by insects to young, succulent, rapidly growing plant parts that are susceptible to infection. The spores germinate in a film of water and penetrate into the plant tissue. Symptoms appear about a week later. Anthracnose can cause symptoms on canes, leaves, fruit and stems of berry clusters. The most striking symptoms appear on the canes.
Infected canes will first show small purplish spots that grow in diameter and become oval in shape. The centers become sunken and are lighter in color. The margins are raised and purple to purplish-brown. If numerous, the lesions may merge and cover large portions of the cane and the diseased tissue will extend down into the bark, partially girdling the cane. As the canes dry in late summer and early fall, diseased tissues often crack. In the following year, fruit produced on severely diseased canes may fail to develop to normal size. On leaves anthracnose first appears as small yellowish-white spots on the upper surface. The spots enlarge and develop darker margins. The light centers may drop out producing a “shot hole” effect.
|Dryberry Mite||Scientific Name: Phyllocoptes gracilis
Adult mites have an oval body. They lack antennae and body segmentation. They are found on ripe fruit, in cracks, and in crevices. Ripening berries with dryberry mite infestations become dry.
Prune out and destroy damaged fruit. Apply lime sulfur at the delayed-dormant stage, just before buds break.
|Oystershell Scale||Scientific Name: Lepidosaphes ulmi
The oyster shell scale belongs to a group of insects called the armored scales. There is one or two generations of oystershell scale each season. Oystershell scale feeding weakens the plant. Damage consists of small, dark brown scales cluster on bark or on fruit.
Scales overwinter as fertilized females with 40-150 egg masses under their scale. Eggs hatch in late spring, approximately two to three weeks after bloom, and young crawlers emerge. Crawlers are small white with six legs, moving to an appropriate site where to begin feeding. They insert their mouthparts into the plant, begin to suck sap and soon molt. From this point on, they will remain in the same spot for the rest of their lives. After a few hours of feeding, the scale begins to form. Mating occurs and females die shortly after they lay their last eggs.
Crawlers spread through orchards by wind, birds’ feet, workers’ clothing and on farm equipment.
Use lime sulfur during late dormancy just before bud break when scales have only a thin wax covering. Delaying application until green tissue is present often results in poor scale control, because scales have produced a larger protective wax coating making complete coverage of the insect more difficult.
|Purple Blotch||Pathogen: Septocyta ruborum
All blackberries and hybrid berries are affected by this disease. The causal organism is a fungus similar to Septoria rubi, which causes leaf and cane spot. Dark green irregularly shaped lesions form on canes late in the growing season. In winter and spring, the lesions turn purple with a red margin. Small black fruiting structures (pycnidia) are found in the center of mature lesions on floricanes, which only infect primocanes. Affected areas are ½ to 2 inches long and develop into cankers, which girdle the cane.
The fungus that causes purple blotch survives on infected canes. Spores are released and spread to primocanes from April to mid August. Spores are dispersed by splashing water or rain. Most spores are released when temperatures are near 70º F. Symptoms do not develop unless a chilling requirement is met.
Fungicide applications will not remove the disease once it has developed, but will prevent infection from spreading on young primocanes. For every-year (EY) producers, sprays usually occur after harvest, in October (before every rains begin), and at bud break in early March.
|Powdery Mildew||Pathogen: Sphaerotheca macularis
Caneberry leaves infected with powdery mildew develop light green (chlorotic) spots on the upper surface, often with white mycelial growth on the lower leaf surface. Upper surfaces of leaves have a mottled appearance similar to that caused by mosaic virus infection. Infected shoot tips and fruit may also become covered with white, mycelial growth. Severely infected shoots become long and spindly with dwarf leaves that curl upward. Severely diseased plants may be stunted. The disease overwinters as mycelium in buds or on the surface of canes, thus the need for early control by delayed dormant treatment.
The use of resistant varieties, maintaining good air circulation in the planting, and sprays of lime sulfur or potassium bicarbonate are acceptable for use in organically certified crops. Treat when disease is first evident in the growing season.
|Redberry Mite||Scientific Name: Acalitus essigi
The redberry mite is a perennial pest of both cultivated and wild blackberries but is not an economic pest of raspberries. These mites belong to a group of microscopic mites known as eriophyid mites. This eriophyid mite has two pairs of legs; it can be seen with a 10 to 20X hand lens but is best seen with a dissecting microscope. The adult is wormlike and translucent white.
Redberry mites overwinter in bud scales or deep in buds. As shoot growth develops in spring, the mites move onto the developing shoots. As flower buds appear, the mites work their way into the unfolding buds, into the flowers, and down among the developing druplets of the berries, especially near the bases and around the core of the fruit.
Fruit infested with redberry mites do not develop normally colored druplets. Affected druplets usually remain hard and have a green or bright red color. The fruit is unmarketable. Fruit partially affected may have some druplets remain red and hard with the remaining druplets developing proper ripening. If not controlled, redberry mite can spread from isolated infestations to sizable portions of a planting in the next season. Very high populations can result in significant crop loss. The pest is most damaging to late-maturing blackberry cultivars.
The best time to control redberry mite depends upon variety grown and miticide that will be used. Note that oil and sulfur products should never be tank-mixed because of the risk of phytotoxicity during the growing season.
Timing of lime sulfur applications depends upon variety grown and redberry mite severity. For blackberry varieties that retain a leaf canopy through the winter, begin lime sulfur applications at bud break and continue at 3-week intervals up to 12 days before the start of harvest. For blackberry varieties that naturally defoliate over the winter, apply lime sulfur before buds break dormancy and then not again until canes have a full leaf canopy and first bloom appears.
|Rose Scale||Scientific name: Aulacaspis rosae (Bouche)
It is generally distributed in the United States on raspberry, blackberry, dewberry, rose, pear and some other plants. Female scales are white with more or less yellow at margin; nearly circular, about one-tenth of an inch in diameter. Male scales are white, narrow, and very small.
Plants thickly infested appear as though sprayed with whitewash. It winters in various stages, so all may be present at almost any time.
|San Jose Scale||Scientific name: Diaspidiotus (= Quadraspidiotus) perniciosus
Female San Jose scales give birth to living young that emerge from under the edge of the scale covering. These tiny yellow crawlers wander in a random fashion until they find a suitable place to settle. Immediately upon settling, the crawlers insert their mouthparts into the host plant and begin feeding and secreting a white waxy material (white cap stage); eventually the waxy covering turns black and is known as the black cap stage. Later the covers turn various shades from gray to black. Dormant season treatments are the key to controlling this pest.
|Septoria Leaf Spot||Pathogen: Septoria rubi.
The fungus overwinters in dead plant debris and on infected canes. In the spring, large numbers of spores are released and carried to young susceptible leaves and canes by splashing or wind-driven rain. The fungus spores germinate in a film of moisture and penetrate the leaf. Infected leaves will develop lesions that have a whitish to gray center, surrounded by a brown to purple border. Leaves of severely infected plants become badly spotted. The disease can cause premature defoliation that will produce weak plants more susceptible to winter injury.
|Yellow Rust—Red Raspberry||Pathogen: Phragmidium rubi-idaei
Yellow rust infects only red raspberry and is not a systemic pathogen, meaning the pathogen does not spread internally through the plant. In spring, yellowish orange pustules (aecia) form on the tops of raspberry leaves close to the ground. Early season observation of aecia on the tops of leaves is a general way to distinguish this rust from late leaf rust, which also infects red raspberry.
Severely affected leaves can dry out and die. Later in June and July, orange to yellow pustules (uredinia) appear on the undersides of leaves; these structures later darken as black teliospores develop from the middle of July to fall. The yellow rust fungus overwinters as teliospores on the bark of remaining floricanes (fruiting canes). Such canes are the sources of inoculum that affect emerging leaves and primocanes (vegetative canes) the following spring.