Crumbly Berries: Information And Reasons For Raspberries Falling Apart


By: Bonnie L. Grant, Certified Urban Agriculturist

If you find malformed berries on your canes that have only a couple of drupes and fall apart at a touch, you have crumbly berries. What is crumbly berry? We’ve all seen the fruits that failed to live up to their promised splendor. A fungal disease usually causes this. Crumbly raspberry fruit may also be the result of poor pollination, sneaky little mites, or even overeager hoeing and trimming. Find out reasons for berries falling apart and how to ensure gorgeous, full berries on your plants.

What is Crumbly Berry?

Raspberries are actually a fruit composed of numerous clustered smaller fruits called drupes and include blackberry plants as well. When your berry has only a portion of the usual number, it is misshapen and devoid of juice and flavor. This is usually because the plant has contracted tomato ring spot or raspberry bushy dwarf viruses. As soon as you try to pick the affected fruits, they break apart. The virus is wind borne and has numerous hosts. Signs of bramble problems may include yellow streaked and stunted older leaves. New leaves rarely show any signs of infection.

Other Reasons for Berries Falling Apart

Another simple cause for crumby berries is mechanical injury. Broken canes and damaged stems cannot feed the forming fruit adequately, resulting in diminished raspberries.

Areas with extremes of wind, heat, and cold, or overuse of pesticides can limit the ability of bees and other pollinators to do their job. The flowers do not fully get pollinated and produce partial fruits.

One of the hardest to identify causes of crumbly berries is the dry berry mite. Crumbly raspberry fruit is the result of this tiny insect’s feeding. The sucking causes some parts of the forming berry to ripen early and become swollen in spots. The other areas fall inward and create a lumpy berry that is smaller than it would otherwise grow. Fruits affected by the mites are not as crumbly as those with the virus, but boast large seeds.

Raspberry leaf curl virus is another raspberry problem caused by an insect. Raspberry aphids transmit the disease when they feed on the berries. The overall effect is stunted plants, poor winter hardiness and small malformed berries.

Crumbly Raspberry Fruit Cures

The wind borne method of spread makes it difficult to prevent the viral spread. Remove excess vegetation from the raspberry bed and ensure that wild brambles are not located near your plants. You can also try moving newer plants to unaffected areas of the garden. This may limit the spread of the disease to the new plants.

There are no recommended domestic sprays for control of these viral bramble problems. Your best bet is to choose plants that are virus free, such as Esta and Heritage.

Combat aphids and mites with a horticultural soap and blasts of water to rinse off the pests. Provide superior care for healthy plants that are better able to withstand injury and recover from pest infections.

This article was last updated on

Read more about Raspberries


How to Identify Elderberry Problems

Part of the honeysuckle family, the elderberry (Sambucus spp.) is a deciduous shrub-like tree that produce edible berry-like fruits. Elderberries are usually pest- and disease-free, rarely succumbing to debilitating infestations. However, sometimes elderberries can suffer from diseases like cankers, leaf and stem spots, and heart rots, as well as from pests like soft scales, borers and aphids. Elderberry shrubs can also be affected by nutritional deficiencies and excesses, as well as under- and over-watering.

Identify nitrogen and iron deficiencies in your elderberry plants by looking for stunted growth, yellowing leaves, and leaves, flowers and fruits that are undersized and develop later than normal.

Look for wilted foliage, leaf drop and leaf discoloration to diagnose under-watering. Identify over-watering problems by looking for root rots, unusually small leaves, as well as twig and limb dieback.

  • Part of the honeysuckle family, the elderberry (Sambucus spp.)
  • However, sometimes elderberries can suffer from diseases like cankers, leaf and stem spots, and heart rots, as well as from pests like soft scales, borers and aphids.

Identify canker diseases in your elderberries by looking for discolored sunken or callused woody tissues, as well as yellowed or browning wilted foliage on infected branches.

Diagnose wood-rot fungal diseases in your elderberries by looking for mushroom-like growths at the base of the shrub and on bark wounds. Feel the wood around these areas, which may be crumbly and decayed.

Look for discolored spots or blotches on the elderberry leaves to diagnose leaf and stem spots. Caused by a fungus, leaf and stem spots produce irregular patches that are usually yellowish or brown.

Spot the symptoms of aphid infestations by looking for yellowed, curled and distorted leaves. Aphids also secrete a sticky liquid substance called honeydew, which can induce sooty mold growth on the foliage.

  • Identify canker diseases in your elderberries by looking for discolored sunken or callused woody tissues, as well as yellowed or browning wilted foliage on infected branches.

Identify a soft scale infestation, particularly by the European fruit lecanium. Both aphids and soft scales produce honeydew and can cause yellowed or curled leaves, but soft scales also can cause the bark to crack and seep a gum-like substance, as well as cause reduced plant growth, discolored rings in fruit, leaves or stems and premature leaf drop.

Study your elderberry plant for stains and holes in the bark that seep a liquid substance to identify longhorned borer infestations. Longhorned borers tend to attack damaged or weakened shrubs and trees, causing branch dieback and discolored, wilted foliage.

Identify nutrient excesses in your elderberry plants by looking for leaf-tip dieback, branch dieback and discoloration of the leaf edges.

Don’t confuse soft scale insects with aphids. Both may appear to have a waxy or wool-like white coating, but aphids have long legs and antennae with tube-like projections growing from their hind ends. Aphids are pear-shaped, while the European fruit lecanium type of soft scales is convex and ¼-inch long or smaller.


Blackcap Brambles

Early in this century, black raspberries were just as popular as red raspberries. And no wonder! This jet black bramble, sometimes called a blackcap, has a rich, sweet taste. The berries are firm and not overly juicy. When you eat them fresh, their texture is a little thicker than red raspberries or blackberries. Their firmness also helps the fruit resist rotting better than other brambles, either on the plant or in your refrigerator.

Despite the black raspberry's past popularity and the fact that it will grow well from zone 4 south through zone 8, today the blackcap is mostly a regional favorite. The middle Atlantic region and Ohio are traditional hotbeds of black raspberry enthusiasm. There are a few commercial growers of black raspberries in the East, all with small plantings. The state that grows the most black raspberries is Oregon, with about 1,000 acres planted. Most of these berries are mechanically harvested for processing into jams, dessert flavorings and even a natural dye for meat. You may already enjoy black raspberries, but if you don't yet know them, you've got a real treat in store.

The black raspberry is a native fruit, growing wild along the edges of woods from Quebec to North Dakota, and south to Arkansas and Georgia. The first variety, Ohio Everbearing (small and not very tasty), was named in 1832. By the end of the 19th century, thousands of acres of black raspberries were being planted in western New York alone. In his 1925 classic, The Small Fruits of New York, Ulysses Prentiss Hedrick described almost 200 varieties of black raspberry, most of them selections from the wild. Today, however, only a handful of black raspberry cultivars are readily available.

Although named varieties of black raspberries do differ from one another in fruit size, firmness and flavor, the differences are not all that great. Nor are named varieties very different from good wild ones, with one important exception. Wild black raspberries are very lely to carry diseases. Nurseries, on the other hand, work diligently to produce plants that are close to disease-free.

Here are some of the best named blackcap varieties available today. Expect to pick between three and four pints per plant over the 10- to 14-day ripening period. Blackcap harvest starts at the very end of the strawberry season and a few days earlier than the first red raspberries. You'll get to taste your first berries a year after planting.

'Allen'. Bred in New York in 1947 and named in 1963, it ripens in a concentrated period, so nearly all the fruit can be picked at once. Bristol is one of its parents.

'Blackhawk'. Bred in Iowa and introduced in 1953, it is one of the hardiest varieties available and ripens about five days later than most blackcaps.

'Bristol'. Bred in New York in 1921 and named in 1963, it has become the most widely planted blackcap in the East.

'Haut'. Bred in Maryland by Harry Swartz, currently the most active blackcap breeder, and released in 1984, Haut ripens three to five days later and has a longer picking season than most blackcaps.

'Jewel'. Bred in New York and named in 1973, it is slightly late in ripening and is one of the most disease-resistant varieties. Bristol is one of its parents.

'Munger'. Developed in Ohio and introduced in 1897, it is still the leading variety for machine harvesting in Oregon.

Among the varieties listed in 1925, quite a few were everbearing or bore white fruits. In years to come, look for both of these traits to be reintroduced. Also look for complex hybrids of black raspberries and various species of other raspberries and blackberries, including some that are tropical and Asiatic.

Rule number one in growing black raspberries is: Don't do what I did! When I put in my first planting, I dug nearby wild blackcaps, then set them in a row with my collection of red raspberries. Not only are wild blackcap likely carriers of disease, but the red raspberries may be symptomless carriers of mosaic virus, which aphids can spread to nearby black raspberries.

Instead, purchase nursery-grown plants -- they're much less likely to carry diseases than wild plants are. Few nurseries can officially certify their plants to be virus-free because symptoms are not always obvious and there is not yet a convenient test that determines whether or not plants are infected with mosaic. But researchers are developing a virus test, so that in the future, virus indexing and tissue culture propagation can ensure disease-free nursery plants.

Plant blackcaps as far away as possible from red raspberries or other cultivated brambles, and remove existing wild berries if practical, or your new plants may soon pick up diseases. Black raspberries are susceptible to Verticillium wilt, so also avoid planting where other hosts of this soilborne disease -- such as brambles, tomatoes, peppers, potatoes or eggplants -- recently grew.

When choosing a site, pay attention to sunlight and soil. A sunny site promotes sweeter fruit and quicker drying of leaves, canes and fruits, which helps thwart fungal disease. The soil itself must be rich in humus and well drained, with a pH of about 6. One quarter pound of 10-10-10 (or another fertilizer with an equivalent amount of nitrogen) per plant will get young blackcaps off to a good start. A third of a pound of soybean meal is a good organic alternative. Spread the fertilizer evenly over the surface of the planting bed and work it in shallowly. Most of the roots of black raspberries grow in the surface layers of the soil, so blanket the ground with a thick organic mulch such as leaves or straw.

Space plants three feet apart in the row, with eight feet between the rows. Right after you plant, lop all canes back to the ground, just in case they have any diseases on them. You don't have to worry about plants spreading underground like red raspberries, because most nblack raspberry shoots arise right at the base of the plant. Black raspberries do spread in their own way, however. They take root wherever the tips of arching canes reach down and touch the ground. Don't allow those tips to root unless you want to propagate new plants.

Pruning Black Raspberries

1. Raspberry canes are biennial, growing stems the first season, then fruiting and dying in the second season. So the first step in pruning is to cut the canes to the ground right after they finish fruiting. They'll soon die anyway, and removing them admits more sunshine to the new canes growing from the base of the plant. Finish pruning old canes before plants leaf out in spring.

2. In the summer, when the new canes reach about 20 inches tall, pinch out the top two inches to keep them at 18 inches. Do this weekly for several weeks until all the new canes (primocanes) have reached the desired height and been pinched back.

3. The summer topping described in step 2 stimulates growth of side branches, which will fruit the following season. Pinching back at 18 inches keeps the plants stocky enough that you won't need a trellis. (Alternatively, you could run a single wire above the row at about three feet. Delay pinching until the canes are tall enough to be tied to the wire.)

4. In the dormant season, preferably just before growth begins in spring, thin out canes, removing any that are diseased, damaged or spindly. On remaining canes, shorten the side branches proportionally to their vigor. The largest side shoots can be 18 inches long, and the thinnest about six inches long.

Black raspberries fall prey to a number of diseases. Orange rust is a fungus that produces decorative but deadly splotches of orange spores on the leaves. Anthracnose fungus can also be debilitating, attacking black raspberries more readily than red raspberries. The weakened canes, spotted with purple-margined gray lesions, are susc to winter cold damage and produce dried-up fruits. Black raspberries also are very susceptible to mosaic virus. In its advanced stages, mosaic causes mottled leaves as well as stunting, and even death, of a plant.

Disease problems of black raspberries vary from site to site. "Some plantings get rust, while others do not," says Dr. Harry Swartz, a breeder of black raspberries at the University of Maryland. "I could not get infection in my test plots on young or old plants even after dusting them with the contents of a one-ounce bottle of spores that I had collected."

In a test planting of black and red raspberries during two wet years, Pennsylvania State University's Dr. Barbara Goulart found that the blacks outyielded the reds, in spite of the blacks' higher susceptibility to anthracnose. Even mosaic infection is unpredictable. Some commercial plantings in New York become unproductive within three years because of mosaic virus while other plantings seem unaffected. Farther south and in the Pacific Northwest, mosaic is less common. The Pacific Northwest does have its share of Verticillium, though.

The first line of defense is to obtain clean plants from a nursery. Then select a site with the good drainage and the ample sunlight that raspberries like. Prune to encourage air circulation and remove diseased canes.

If anthracnose becomes a problem, spray the plants with lime-sulfur solution at budbreak and, if needed, during the growing season. Always keep an eye out for orange rust and mosaic virus. Pull up and burn any plants you suspect carry either disease. Even with clean plants and a clean site, a black raspberry planting will eventually decline from a buildup of pests, so don't be surprised if you need to replant at a new site in 5 to 10 years.


Fall Bearing

Fall bearing raspberry primocanes emerge from the soil in early spring, but stop terminal growth and begin flowering in mid-summer, with fruit harvest beginning in late summer or early fall and continuing until the first fall freeze causes the plants to stop bearing fruit and begin dormancy. The height at which fruiting begins depends on the cultivar and the vigor of the plant. As shown in Figure 3, if canes are not completely removed during winter pruning, the lower portion of the remaining cane will produce a summer floricane crop the following season. The yields for the primocane crop depend on earliness and when the first fall freeze comes. In areas with a growing season less than 125 freeze-free days, primocane yields may not be sufficient to justify planting these cultivars.

Figure 3. Fall-bearing raspberry lifecycle.

Table 2 lists fall-bearing raspberry cultivars that grow well in Utah. For more detailed information on fallbearing cultivars in Utah see USU fact sheet Horticulture_Fruit_2013n-01pr.

Table 2. Fall-bearing raspberry cultivar recommendations.
Cultivar Size Flavor Yield Season
Caroline Large Good Med. Mid
Josephine Med. Excellent Med. Late
Polana Med. Good Med. Early
Joan J Large Excellent High Early
Polka Large Excellent Med. Very Early


Lack of Roots Cause Raspberries to Wither

Donald D. Tapio

WSU Extension Regional Specialist

A common complaint from home gardeners with raspberry plants this time of year is when fruit shrivels. In most cases, plants suddenly wilt, the leaves turn yellow, then brown and eventually die. In many cases gardeners assume the plants are not getting enough water and turn on the sprinklers which never seems to help. Despite the decline of the fruit bearing canes, new canes almost always remain healthy.

WSU plant pathologists have identified over thirty different root rot fungi that can infect raspberries in our coastal area. Plants infected with rot fungi not only have rotted roots, but also lack fibrous roots. After hot, dry periods older leaves may wither or become bronzed or scorched. Attached leaves droop. Fruit stems usually are shortened and berries, if formed, remain small and often wither before ripening. Once the root system begins deteriorating, new roots may arise from above decayed ones in summer.

Although this makes plants look as though they have recovered, the new roots are often weak and lack lateral development. The new roots in turn will become infected during the cold, wet weather this fall and winter so that the plant progressively declines and is unproductive. No Pacific Northwest raspberry varieties are very resistant to the problem however, Chilliwack, Meeker, Sumner and Summit are moderately resistant. Young Meeker plants are very susceptible, while mature plants seem to have some tolerance.

Home gardeners can reduce root rot problems by using certified planting stock and setting plants in fertile, well-drained soil which has a 3 to 4 foot deep water table in winter. Select a site which has not grown raspberries or other bramble fruit for several years. Place plants in beds that are raised so that the top of the bed is at least 12 inches above the surrounding soil. Slope soil away from the center of the planning bed to the alleyway between rows.

The fungicides Aliette, Agri-Fos, Fosphite, Phostrol and Ridomil Gold SL are all registered for use to prevent raspberry root rot. Most require multiple applications and must be used well in advance of harvest.

What Causes my Raspberries to Crumble?

Anyone who’s ever grown raspberries knows that fruit with only a few druplets tends to crumble when it’s picked. This is the result of abnormal fruit development. Normal flowers on a raspberry plant have between 100 to 125 pistils. Each is able to produce a seed and a druplet. In normal berries, from 75 to 85 druplets usually develop. If appreciably fewer than 75 druplets develop, the berry does not hold together and crumbles as it’s pulled from the plant.

Crumbly berries have a number of possible causes:

Lack of nutrients: Anything that seriously interferes with plant nutrition –such as drought, extremely low fertility, or damage to roots or crowns from nematodes, symphylans, root rots, crown gall, crown borer, flooding in winter, or cultivating too deep may bring about crumble. If plants with crumbly berries also have cane buds that fail to grow or short, stiff laterals with odd-shaped leaves, boron may be lacking. Taking a soil test will validate if Boron is needed and how much is needed to correct the deficiency. Some varieties tend to crumble more than others. The Tahoma and Latham varieties often bear crumbly fruit. Some seedling and some clones of the Sumner variety produce crumbly fruit. Occasional plants of most varieties apparently mutate to a crumbly condition.

Diseases: Viruses may cause failure of flowers to function or seeds to develop abnormally even though growth appears to be normal. The raspberry mosaic complex has been associated with crumble, but specific varieties associated with raspberry crumble have not been identified. In certain instances, bacterial and fungus diseases have been suspected of contributing to crumble.

Lack of bee activity and lack of pollination may result in crumbly berries.

Chemical damage to flowers from in-bloom applications of insecticides or fungicides could damage anthers, pistils, or pollen.

Our raspberries have finished producing fruit for the year. When and how should we prune them back?

Caneberries, like raspberries, loganberries, blackberries, and blackcaps need care after they are harvested. Three things need to be done to keep your plants healthy and ready for next year’s crop.

The first thing to do is prune. Remove all the canes which bore fruit this season. This pruning exposes the new canes (those that will bear fruit next year) to the light and gives them a chance to develop.

Retain 10 to 12 of the healthiest canes for the next year’s crop. Remove the top half of the cane from fall-bearing cultivars after fruiting is over, or remove the entire cane at ground level. Leave the lower half of the cane for a summer crop the following June, or remove the cane entirely for only a fall crop each year. Because the fall crop on fall fruiting varieties is superior to the summer crop, WSU horticulturists advise cutting all canes to the ground in mid-October.

The last thing to do is very easy and also very important. Stop watering the new canes! This will allow growth to slow and the canes to harden up before the first frost. Do not fertilize canes at this time of the year. That will stimulate berries, from 75 to 85 druplets usually develop. If appreciably fewer than 75 druplets develop, the berry does not hold together and crumbles as it’s pulled from the plant.

Crumbly berries have a number of possible causes

Lack of nutrients: Anything that seriously interferes with plant nutrition –such as drought, extremely low fertility, or damage to roots or crowns from nematodes, symphylans, root rots, crown gall, crown borer, flooding in winter, or cultivating too deep may bring about crumble. If plants with crumbly berries also have cane buds that fail to grow or short, stiff laterals with odd-shaped leaves, boron may be lacking. Taking a soil test will validate if Boron is needed and how much is needed to correct the deficiency. Some varieties tend to crumble more than others. The Tahoma and Latham varieties often bear crumbly fruit. Some seedling and some clones of the Sumner variety produce crumbly fruit. Occasional plants of most varieties apparently mutate to a crumbly condition.

Viruses may cause failure of flowers to function or seeds to develop abnormally even though growth appears to be normal. The raspberry mosaic complex has been associated with crumble, but specific varieties associated with raspberry crumble have not been identified. In certain instances, bacterial and fungus diseases have been suspected of contributing to crumble.

Other Causes:

· Lack of bee activity and lack of pollination may result in crumbly berries.

· Chemical damage to flowers from in-bloom applications of insecticides or fungicides could damage anthers, pistils, or pollen.

Our raspberries have finished producing fruit for the year. When and how should we prune them back?

· Caneberries, like raspberries, loganberries, blackberries, and blackcaps need care after they are harvested. Three things need to be done to keep your plants healthy and ready for next year’s crop.

· The first thing to do is prune. Remove all the canes which bore fruit this season. This pruning exposes the new canes (those that will bear fruit next year) to the light and gives them a chance to develop.

· Retain 10 to 12 of the healthiest canes for the next year’s crop. Remove the top half of the cane from fall-bearing cultivars after fruiting is over, or remove the entire cane at ground level. Leave the lower half of the cane for a summer crop the following June, or remove the cane entirely for only a fall crop each year. Because the fall crop on fall fruiting varieties is superior to the summer crop, WSU horticulturists advise cutting all canes to the ground in mid-October.

The last thing to do is very easy and also very important. Stop watering the new canes! This will allow growth to slow and the canes to harden up before the first frost. Do not fertilize canes at this time of the year. That will stimulate unwanted growth.


Reports on Plant Diseases

RASPBERRY LEAF CURL [ Disease Cycle ]

THE VIRUSES [ Disease Cycle ] BLACK RASPBERRY STREAK [ Symptoms ] [ Disease Cycle ]

RED RASPBERRY RINGSPOT [ Symptoms ] [ Disease Cycle ] RASPBERRY BUSHY DWARF [ Symptoms ] [ Disease Cycle ]

Raspberries probably suffer greater infection and more serious damage from virus diseases than any other fruit crop in the United States. Fruit yields may be reduced 50 to 70 percent, or more. Once infected, a plant remains diseased for life. Since all parts of an infected plant carries the virus, suckers or tips propagated from it are also diseased. All raspberry viruses in the Midwest, except black raspberry streak, are spread by the feeding activities of aphids. The viruses are not spread by pruning or otherwise mechanically injuring plants in the field.

Virus-like disorders of raspberries and blackberries may be produced by cool weather and late spring frosts, powdery mildew, mineral-element deficiencies (such as iron), pesticide injury, genetic disorders (yellowing of leaves and crumbly berries), or feeding by leafhoppers, aphids, and red spider mites.

Positive identification of the virus or viruses responsible for the disease syndrome cannot be based entirely on foliage symptoms. Greenhouse and laboratory tests using specific indicator plants and serology are required. Positive identification is necessary to facilitate appropriate control measures and to help detect possible new virus diseases of brambles in Illinois.

Figure 1. Leaf curl of red raspberry.

RASPBERRY LEAF CURL

Figure 2. Leaf curl on black raspberry. The tip leaves are round and a dark greasy green.

This important and easily recognized disease occurs on red, black, and purple raspberries and upright blackberries. The yield of infected red raspberries may be reduced 20 to 70 percent. Black raspberries may degenerate and die after two or three years.

Symptoms on Red and Yellow Raspberries. The symptoms of leaf curl vary according to the virus strain and the type of raspberry infected. During the initial year of infection, plants show no symptoms or perhaps only a mild down-curling of the leaf tips. The following spring, leaflets near the tips of the canes appear rounded, dwarfed, and crinkled with margins curled tightly downward and inward (Figure 1). Fruiting lateral are shortened and a proliferation of the shoots may produce a rosette. When diseased shoots first appear they are a pale yellowish green, soon turning dark green, becoming stiff and brittle, and usually do not branch. Each year the plant loses vigor, and new shoots are progressively more dwarfed until they are only a few inches tall. Infected plants produce little fruit and berries that do form are small, dry, seedy, and crumbly.

Symptoms on Black and Purple Raspberries.The symptoms are similar to those on red and yellow raspberries with tip leaves arched upward, stiff, dwarfed, and nearly round, becoming a dark, greasy green (Figure 2). Affected plants are dwarfed and bushy. The berries are small and dry. In following years, the young canes are severely dwarfed, rigid, brittle, lack side branches, and cannot bend to the ground to root at the tips.

Symptoms on Erect Blackberries. Leaf curl is rare and unimportant on blackberries. Some cultivars show curl symptoms similar to those on red and yellow raspberries (Figure 1). Other cultivars may be infected symptomless carriers of the virus.

Disease Cycle

Leaf curl viruses are commonly spread from plant to plant by the feeding of a small sluggish aphid (Aphis rubicola). Heavy populations of this aphid on young foliage can cause severe in-rolling of the leaves in the absence of the leaf curl virus(es). Winged forms of the aphid transmit the virus to healthy raspberries from nearby infected cultivated or wild brambles. Windborne aphids may spread the virus several miles. All commercial cultivars are susceptible.

COMMON RASPBERRY MOSAIC

The common raspberry mosaic complex is widespread and may cause the greatest reduction in growth, vigor, fruit yield, and quality of any of the bramble viruses. Fruit yield may be reduced 50 percent or more. No raspberries are immune, however, black and purple raspberries are damaged more severely than red varieties. The symptoms differ with the cultivar grown, the virus or viruses involved, geographical location, and seasonal growing conditions. Symptoms are most evident in the cooler weather of spring and fall, being masked (or disappearing) when temperatures are high in summer. Mosaic symptoms are sometimes confused with a late spring frost, powdery mildew, feeding by red spider mites and aphids, pesticide injury, or a soil deficiency of boron.

Symptoms on Red Raspberry. The canes are short, growth is weak, and leaves produced in cool weather are mottled and puckered with large, irregular, green blisters that arch upward. The leaf tissue around the blisters turns yellowish or yellowish green and severely blistered leaves curl downward (Figure 3). The leaves that develop in hot weather are symptomless, or show a faint mosaic pattern with yellow flecks. Leaves that form in late summer show a fine, yellowish, speckled mottling. Mosaic-affected plants are often progressively more stunted each year. The leaves are dwarfed, yellow mottled, sometimes deformed and fruit yield from such plants is reduced the berries are dry and seedy (often crumbly) and lack flavor.

Figure 3. Mosaic symptoms on red raspberry in the late spring, green and yellowish-green ottling appear along with blisters on a leaf of a new cane (USDA photo).

Figure 4. Young black raspberry cane affected with heat-labile component of raspberry mosaic.

Symptoms on Black and Purple Raspberries. The tips of young, black and purple raspberry canes, newly infected with mosaic, often curl downward, turn black (necrotic), and die (Figure 4). The fruit tends to be small, dry, and seedy. Leaves produced in hot weather are often nearly symptomless. Those formed in cool weather are faintly to severely mottled and puckered. Chronically infected plants become severely dwarfed and rosetted, with brittle cane tips and usually die in two or three years.

Symptoms on Erect Blackberries. Infection on cultivated or wild blackberries is uncommon. They may be symptomless or show severe mottling, similar to that described for raspberries.

THE VIRUSES

The raspberry mosaic virus complex is composed of at least two viruses, each containing numerous strains. One group survives three months or longer in infected plants at 100 F (37 C), the other does not. The heat stable group is called the rubus yellow-net (RYN) virus because of the distinctive netlike yellowing that develops along the veins of leaves on infected plants. The heat-labile virus (which can be eliminated experimentally by growing plants at 100 F or 37 C for a week or more) is named the black raspberry necrosis (BRN) virus because it causes a dieback (necrosis of the terminal leaves and cane tips of black raspberry seedlings followed by a mottling of the lower leaves). Common raspberry mosaic is usually caused by a virus complex composed of the RYN and the BRN viruses.

Many of the BRN virus strains produce no external symptoms of mosaic or only an obscure leaf mottling, especially in red raspberries. Infected plants are weaker, produce fewer canes, and have a reduced yield. Since these plants appear to be healthy in all other respects, they are seldom removed from the planting. In addition, numerous virus strains that are symptomless in red raspberries produce striking symptoms (stunted mottled leaves on dwarfed shots) when transferred to black or purple raspberries. The viruses are not soilborne nor seed transmitted.

Disease Cycle

The large, European raspberry aphid (Amophorophora idaei), which is widely distributed on the tips of wild and older cultivated raspberries and some blackberries throughout much of the growing season, is the most common carrier (vector) of raspberry mosaic viruses. These aphids acquire ("pick up") the mosaic viruses after feeding on an infected plant. Winged aphids may transmit the mosaic viruses from the source plant to a healthy plant a quarter of a mile or more away. Aphids transmit the viruses by feeding on healthy plants for a few minutes. Where black and purple raspberries are grown near aphid-infested red raspberries or other brambles that have mosaic, the aphids will colonize the black and purple raspberries and quickly inoculate them with the mosaic virus(es).

Mosaic spreads naturally by commercial propagation from infected plants and by movement of diseased nursery plants. It may also spread along a field row through the establishment of suckers or rooting tips from an infected plant.

BLACK RASPBERRY STREAK

This is presently a minor disease that is limited mostly to the Lake Erie fruit gelt in northern Ohio, western Pennsylvania, and western New York. Black raspberries, and possibly blackberries, are the only known hosts.

Symptoms

Numerous (often faint), blue-to-purplish or gray dots and narrow, water-soaked lines or streaks (usually less than an inch long) develop on and under the surface on the lower parts of young canes in warm weather, and sometimes, on fruiting canes at fruiting time (Figure 5). Infected plants do not always show streaks, especially if they are not growing vigorously. Diseased plants, however, are usually vigorous and propagate well. The severity of the symptoms may vary from season to season among cultivars, even on the same plant. Infected plants do not always show streaks, and in fact symptoms may vary from season to season among cultivars.

Tip leaflets on infected new canes are often hooked or recurved, spirally twisted or rolled, and a darker green than normal (Figure 6). Sometimes the lower leaves on such canes show yellowing along the veins (vein-clearing ) or mottling. Leaf symptoms are more consistent than cane streaks in field plantings.

Fruits on infected plants are about three-quarters of the normal size, dull, seedy, crumbly, and lacking in flavor. The individual drupelets often ripen unevenly, giving the fruit a blotched appearance.

Figure 5. Black raspberry streak A. normal cane B canes showing severe streak symptoms..

Disease Cycle

Figure 6. Black raspberry cane 'hooking' and recurving of leaves caused by streak virus.

RED RASPBERRY RINGSPOT

Laminated evidence suggests that red raspberry ringspot, caused by the tomato ringspot virus (TomRSV), is the most widespread and damaging virus disease of red raspberry in North America, yet it was not identified until 1962. However, "running out" or "decline" of raspberry plantings, characterized by the gradual loss of productivity, has been known for many years.

Symptoms

The symptoms in red raspberries vary depending to a large extent on the cultivar, the duration of the infection, and the time of year when plants are examined. Infected plants, which normally occur in patches, usually show no symptoms during the season in which they acquire the virus. In the spring of the following year, some leaves on the primocanes develop yellow rings, line patterns, or vein yellowing. These "shock reaction" symptoms are rare in subsequent years. Chronic symptoms are delayed foliation in the spring, a tendency for leaves on the fruiting canes to develop various degrees of chlorosis, and for diseased plants to produce a higher proportion of misformed or crumbly fruit than do healthy plants. These symptoms are all variable, unreliable, and can be missed in disease surveys based on field observations. Field surveys are of little value unless visual observations are supplemented by (1) mechanical inoculations to herbaceous indicator hosts, or (2) highly specific serological tests such as ELISA.

It is not unusual when examining plants in fields with a history of poor productivity, to have apparently healthy plants index positive for TomRSV using the ELISA technique.

Disease Cycle

Tomato ringspot virus is spread from plant to plant in the soil by the feeding of one or more species of dagger (Xiphinema) nematodes on the roots of red raspberry plants. Field spread is restricted to plantings where these very common nematodes occur. The nematodes by themselves cause little damage to red raspberry plants unless the virus is also present.

RASPBERRY BUSHY DWARF

Raspberry bushy dwarf, caused by the raspberry bushy dwarf virus (RBDV), infects red and black raspberries and blackberries. Not all red raspberry cultivars are susceptible to this vigor- and yield-reducing virus. When a planting becomes uneconomical, the planting can be replaced with a resistant cultivar. Some cultivars in Europe previously considered to be immune have become susceptible to few strains of RBDV. There is no evidence that any of these severe strains occur in North American cultivars.

Symptoms

The severity of symptoms of raspberry bushy dwarf vary with the cultivar and the season. Some cultivars produce leaves with varying degrees of interveinal chlorosis other leaves develop irregular line or "oak leaf" patterns. Plants that show symptoms one year do not necessarily develop symptoms in subsequent years. Variations in leaf symptoms are believed to be dependent on genetic resistance to symptom expression and on environmental factors.

Disease Cycle

Raspberry bushy dwarf virus is transmitted through pollen from which infection spreads to a high proportion of the seeds and to the pollinated plant. The virus is confined to species of brambles (Rubus) and natural spread only occurs through pollen or seeds.

Control of Virus Diseases

The cultural and chemical practices outlined below, if vigorously followed, will keep virus diseases in check. Remember: once infected, a plant remains diseased, it cannot be cured.

1. Select a planting site that is sunny and fertile and has good air and soil drainage. Where possible destroy all wild and neglected raspberries, blackberries, wineberries, and other brambles located within 600 to 1,000 feet. These plants are likely to harbor viruses, other bramble diseases or disorders, and insects.

2. If both black and red raspberries are to be grown, separate them by 150 feet or more to reduce virus cross infection. If possible, plant the blacks on the windward side which further decreases virus spread by windborne aphids.

3. Start new plantings with the best quality plants available. Avoid the illegal, neighborhood exchange of noninspected plants (many plants are protected by patents). The U.S. Department of Agriculture has developed virus indexed stocks of many desirable red, black, and purple raspberries, and blackberries that are true to cultivar and genetically equivalent to the best available stock. These are propagated under rigidly controlled conditions by growers in well designed programs certified by state authorities. Virus indexed plants sell at a premium, but are well worth the extra expense.

Certification schemes that involve only visual examination with approval based on the absence of symptoms, are next to worthless. Several of the raspberry and blackberry viruses induce either no symptoms or symptoms that are so vague and variable as to be unreliable indicators. Sap inoculation, graft inoculation, serology (e.g., ELISA), elegron microscopy, or combinations of these techniques are required to detect infections. Extensive indexing of an individual plant and then subdividing this plant to establish a certification block of "mother" plants is preferable to establishing a certification block from several mother plants.

4. After growth has begun, go through the planting several times each season and remove all visibly infected plants. The best time to detect virus symptoms is during cool, cloudy weather in the mid to late spring, early summer, and again in the early to mid fall. A day or two before removal, thoroughly spray affected plants with malathion (25 percent wettable powdery), using 2 tablespoons per gallon of water, or scorch the diseased plants with a weed burner. These treatments will kill any virus carrying aphids and prevent their migration to healthy plants. All plants showing even faint symptoms of leaf curl, mosaic, black raspberry streak, or other diseases should be removed. Bush removal or roguing is most effective during the first year, since this decreases the source of the virus(es) for the following season and also saves the work of digging out a much larger plant with an extensive, virus-infected root system. Removing or marking black raspberry plants that leaf out later than normal in the spring is advisable, as they are very likely to have mosaic. In established plantings, where more than 5 to 10 percent of the plants are visibly virus-infected, roguing will probably not pay. Maintain the fruit planting until the yield of fruit becomes unprofitable, then destroy it.

5. Maintain strict aphid control at all times, especially in late spring and early summer when aphid populations are likely to be high. Various insecticides can be used. Follow the cultural and chemical recommendations outlined by entomologists at the University of Illinois as given in the "Illinois Commercial Small Fruit and Grape Spray Guide" (updated annually) (website: http://www.ag.ohio-state.edu/

ohioline/b861/index.html), and "Compendium of Raspberry and Blackberry Diseases and Insects", published by the American Phytopathological Society, St. Paul, Minnesota. The pesticide manufacturer's directions concerning rates and time should be carefully followed. Because the harvest season and aphid buildup may coincide, pay careful attention to insecticide residues. Observe the recommended safe interval between application and harvest.

6. Fumigation of soil with methyl bromide, chloropicrin-methyl bromide mixtures, Vorlex, or D-D prior to planting to eradicate nematode (Xiphinema spp) vectors or red raspberry ringspot is necessary where these nematodes are present. The manufacturer's directions should be carefully followed when applying these highly toxic pesticides.

Genetic resistance to some bramble viruses and their aphid vectors is being incorporated in the development of new raspberry and blackberry cultivars with plant breeding a promising new method of controlling bramble viruses.

For further information concerning diseases of crucifers and other vegetables, contact Mohammad Babadoost, Extension Specialist in Fruit and Vegetable Diseases, Department of Crop Sciences, University of Illinois at Urbana-Champaign.

University of Illinois Extension provides equal opportunities in programs and employment.


Watch the video: Мне не подошло! Косметика в мусорку!


Previous Article

Aeonium 'Cyclops' (Giant Red Aeonium)

Next Article

Globe Amaranth Info: Learn How To Grow Globe Amaranth Plants