By: Amy Grant
It looks like there’s a problem with your raspberry patch. Rust has appeared on the raspberry leaves. What causes rust on raspberries? Raspberries are susceptible to a number of fungal diseases which result in leaf rust on raspberries. Read on to find out about treating rust on raspberries and if there are any rust resistant raspberry cultivars.
Leaf rust on raspberries is a disease that attacks the foliage of raspberries. It may be caused by the fungus Phragmidium rubi-idaei. It appears as yellow pustules on the upper side of leaves in the early summer or in the spring. As the disease progresses, orange pustules appear on the underside of the foliage. Further into the disease, the orange pustules turn black. These black pustules contain overwintering spores. Severe infection results in premature leaf drop.
Arthuriomyces peckianus and Gymnoconia nitens are two additional fungi that may cause rust on raspberry leaves. In this case, the fungi appear to only attack black raspberries as well as blackberries and dewberries. Symptoms appear in the early spring as new shoots begin to emerge. New leaves become stunted and deformed and a pale, sickly, green or yellow. Waxy blisters dot the underside of the foliage. The blisters eventually turn a bright, powdery orange lending the disease the name “orange rust.” Infected plants become bushy rather than caning.
As with P. rubi-idaei, orange rust overwinters in diseased roots and canes. All three are fostered by cool, wet conditions. The spores mature and break open around June and are spread to other plants by the wind.
No chemical control is known to be effective in treating rust on raspberries. If the disease becomes evident in only a few leaves, remove them. If the plant appears to be fully disease involved, however, remove the entire plant.
The best practice is to plant more rust resistant raspberries. Rust resistant raspberries include ‘Glen Prosen’, ‘Julia’, and ‘Malling Admiral.’
Starting the berry plot properly will go a long way in the prevention of fungal diseases. Keep the planting area weeded and the rows cut back to facilitate leaf drying. The disease needs a fairly lengthy period of leaf wetness to germinate and penetrate foliage in the spring. Allow plenty of air circulation amongst the canes; do not crowd the plants. Feed the plants when necessary to ensure vigorous raspberries.
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Rust diseases affect a plethora of fruit, nut and ornamental trees and shrubs. Rust is often a problem with roses but can also attack carnations, sunflowers and other flowering plants. Rust may cause leaf spots or turn the entire leaf yellow or brown. Rust also causes premature leaf drop, curling and withering of foliage. Cankers, galls and stunted growth can also be a result of rust disease. Fungicides may be used during the plant's dormant period, when no foliage is present, or in early spring, to help prevent rust diseases from developing. Preformulated fungicides are readily available commercially, but you can also purchase the basic ingredients and make fungicide sprays at home.
Since orange rust can’t be cured, plants infected with orange rust should be dug up or killed.
Plant leaves can sometimes change colour or produce unusual marks, blotches or even weird-looking structures on them. Here are some of the more common leaf problems.
In some cases, you may need to identify pest and disease problems on plant leaves. Click on the links where appropriate to find out even more about prevention and control.
The most common of all pests and almost every plant from the smallest shrub to the tallest oak tree can be infested. They tend to feed on the underside of leaves and you'll often see the white shed skins. Some produce specific leaf problems - such as leaf-curling aphids and blister aphids. Further details on aphids
These insects are about 6mm long with six long legs and antennae. They love the tips of young shoots and have wide tastes - roses, fuchsias, hydrangeas, forsythia, chrysanthemums and currant bushes. They make small holes that get bigger as the leaf grows and expands and often cause the leaf to distort in shape.
Not all of them are particularly harmful. Some will eat through leaves, stems, flower, fruit and even roots. Some curl up the leaves to give them protection from predators
Sometimes, plant leaves change colour during the growing seasons – spring and summer. There are numerous reasons for this, so you'll have to become a plant detective, to see what has caused it.
Downy mildew thrives in moist damp conditions and loves young plants. The upper leaf surfaces develop yellowy discoloured patches that can extend across large areas of the leaf and sometimes a white/grey 'downy' coating.
Certain species of the adult flea beetle are fond of cabbages, Brussels sprouts, swede and other brassicas some like potatoes others are equally fond of wallflowers, alyssum, aubrieta and nasturtiums. They swarm all over the leaves.
The spots can be of various colours - grey, brown or black (roses in particular). The spots are in fact dead leaf tissue caused by the fungus that spreads the disease.
Although a trace element, iron can be locked up in the soil so roots of rhododendrons, azaleas, camellias and other ericaceous plants cannot absorb any reserves. Raspberries can also show similar signs of deficiency. Leaves start to turn yellow between the veins.
Yellowish and 2-3mm long. As their name suggests they (the adults) will jump off if the plant is disturbed. The immature nymphs are creamy-white and crawl. Both nymphs and adults feed on the sap of plants. They cause leaf yellowing and the overall weakening of the plant.
Leaf miners produce characteristic pale twisting tunnels (or mines) under the surface of affected leaves.
Discolouration of the leaves, turning them brown from the edges inwards. The leaves can dry and curl although in moist conditions a white fungal growth can occur around the edges.
Just as the name suggests, a white powdery fungus grows mostly on the upper surface of leaves. It will occasionally spread to the underside and other parts of the plant.
Perhaps the smallest of the common sap-feeding insects. Leaves first develop a pale mottling, but as the infestation progresses the leaves become increasingly yellowish white.
The spots can be of various colours - grey, brown or black (roses in particular).
The spores of these diseases need a moist environment in which to prosper. The fungus develops mostly on leaves but also on stems. In appearance, they can develop either as patches or as pustules (like septic spots), usually with a rusty-brown colour – but some are different, such as chrysanthemum white rust.
There’s no need to tell you what they look like. And the silvery trails (not always present or visible) will tell you where they came from and where they went on to after lunch.
Sooty moulds are spreading dark brown or black, superficial marks on the top part of the leaves of numerous plants – but particularly glossy-leaved evergreens. they are the result of sap-sucking insects feeding on the leaves above.
Thrips (sometimes called thunder flies or thunder bugs) are yellow-black, very thin and about 2mm long. The typical symptoms are mottled and discoloured leaves, with signs of bleaching.
Vine weevil adults feed on the leaves, making characteristic 'mouth-shaped' bites on the edges of the leaves. The grubs are far more destructive, as they eat the roots, causing the leaves and whole plant to wilt.
These little pests set up home and live out their lives on the underside of leaves. As adults, they are about 2mm long with white wings, which give them their name. When disturbed from feeding on the leaves, they produce an almost cloud-like eruption.
The main signs of rust typically appear on plant foliage. Common rust often starts out as raised spots, sometimes white in color. Eventually, the marks transition to a reddish hue – hence the name rust! Spots may turn black in some cases.
Another common symptom that appears on foliage is raised bumps. They appear in a variety of colors, including brown, yellow, or orange. The bumps usually appear on the underside of infected leaves.
In severe cases of rust, leaves crumple, wilt, and fall to the ground.
There are many possible reasons that your raspberry canes are dying. The first thing to consider is the age of the canes and the age of the plant itself. If the cane or plant is too old, then they will stop producing flowers and berries, and eventually die.
A single raspberry plant has multiple canes, and each cane only produces berries for a limited period of time. A primocane is a first-year raspberry cane, and a floricane is a second-year cane.
A summer-bearing variety of raspberry plant produces no fruit on its primocanes (first-year canes). Instead, it will only produce fruit on its floricanes (second-year canes).
After the second year, the canes will die and produce no more fruit. At this point, you should cut them off to make room for new growth.
On the other hand, an ever-bearing variety of raspberry plant produces fruit twice: in the late summer or early fall on its primocanes, and also in the summer of the second year on its floricanes.
As with summer-bearing varieties, the canes will die and produce no more fruit after the second year, so you should cut them back. For more information, check out this article from Iowa State University on pruning raspberry plants.
A raspberry plant will produce new primocanes (new growth) every year for some time. However, it will eventually slow down its growth, produce fewer berries, and then die at the end of its lifespan.
Many raspberry plants can live 15 to 20 years. However, if your raspberry plant is more than 10 years old, you should consider the possibility that it is dying due to age.As long as they have proper pollination and care, raspberry plants can produce fruit for over a decade!
At that point, it makes sense to replace older plants with new ones. I would suggest staggering the replacement over time. For example, if the raspberry variety you choose lasts 10 years and you want 50 plants, then you should replace 5 plants per year.
Most garden centers have raspberry plants available, but you can also order them online and get them delivered to your house.
If age is not a factor in the death of your raspberry canes, then there are several environmental conditions that can also kill your plants. The best place to start looking is the simplest one: watering.
Many beginner gardeners tend to “kill their plants with kindness” by over watering. Although your raspberry plants do need plenty of water, it is not always true that more is better!Make sure not to over water your raspberry plants – check the soil first!
Before you water, you should check the soil around your plants for moisture. Dig down a few inches with your fingers and feel the soil.
If the soil is dry, you can water right away. If the soil is wet and soggy, you should not water any more. The reason is that a plant can develop root rot if its roots sit in soggy soil for too long.
Over time, root rot will prevent a plant from absorbing water and nutrients through its roots. This will eventually kill the plant.Root rot causes roots to turn brown and mushy.
The worst part about root rot is that the plant will start to display symptoms that look like a lack of water, such as wilted or dry leaves. However, no amount of watering will save the plant once the roots have died.
When you water your plant, avoid watering from overhead. If you get the leaves wet, there is a much greater chance of fungus or other diseases infecting your raspberry plant.
Also, water deeply and less frequently to encourage a stronger root system. Finally, water your plants in the morning, so that the water can soak into the soil before being evaporated by the strong midday sun.
Your raspberry plants can also die from a lack of sunlight. This is possible if they are planted near a house, shed, or garage where they are mostly shaded for a good part of the day.Make sure your raspberry plants get plenty of sunlight.
It is also possible that nearby hedges or trees are shading the raspberry plants. Remember: just because your raspberry plants did well in one spot in prior years does not mean they will thrive there now.
If young trees grow taller with thicker foliage, they may eventually overshadow your berries enough that they don’t grow the way you want them to.
Poor soil conditions can also kill your raspberry plants, even if they are getting plenty of water and sunlight. The first thing to check is the pH of your soil.
One way to do this is with a do-it-yourself test kit, which you can buy online or at a garden center. Another way is to send a soil sample to your local agricultural extension. For more information, check out my article on how to do a soil test.
Raspberries prefer a soil pH between 5.6 and 6.2 (somewhat to slightly acidic). Outside of this range, raspberries will not grow as well. If the pH is extreme enough, your plants may not be able to absorb the nutrients they need from the soil, leading to nutrient deficiencies in the plant and possible death.
If your soil test reveals that your soil pH is too low (acidic), then you can raise the pH by adding lime (calcium carbonate) to your soil. If your soil pH is too high (basic), then you can lower the pH by adding lime.
Always do a soil test before adding anything to your soil, and only use the recommended amounts! If you send your soil to a local agricultural extension and tell them what you are planting, they will send recommendations for adjusting your soil pH.
Nutrient levels in your soil may also be to blame for dying raspberry canes, even if the pH is in the proper range. For instance, a lack of nitrogen will cause leaves to turn light green instead of deep green, and you will experience slow growth.
One good way to provide both nutrients and organic material for your soil is to add compost each year in the spring. If a soil test reveals nutrient deficiencies, then you can use fertilizers or other additives as a supplement to compost.
Diseases are another potential cause of death for your raspberry canes. Some of the more common diseases that affect raspberry plants include:
The best way to avoid diseases is to choose resistant varieties when cultivating new areas or when replacing aged raspberry plants. If you find diseased raspberry plants in your garden, remove them immediately. Don’t transplant any other plants into or out of that same area, or else you risk infecting other plants.
Pests could also be to blame for the death of your raspberry plants. Two common pests are aphids and cane borers.
Aphids are small insects that can be green, white, black, or even pink. They suck the sap out of leaves or stems, especially the soft primocanes when they first emerge.
Aphids leave behind a sticky, sweet excretion called honeydew. Ants love honeydew, and will act as “aphid ranchers”, protecting the aphids in exchange for honeydew. This is why you will sometimes see ants colonizing plants infected with aphids.
Cane borers leave telltale signs when they attack a raspberry cane. First, you will see the tops of raspberry primocanes (first-year canes) wilting. Second, you will see two brown rings on the cane, right below where the wilting occurred.
The rings are chewed by the female cane borer so that she can lay eggs between the two rings.
To treat this problem, cut off the top of the infected cane, just below the lower ring. Then, destroy the part you cut off. This ensures that the eggs will not hatch and infect the entire plant.
Rust disease on raspberry leaves
Rust is a fungal disease that attacks many vegetable and fruit crops and ornamental plants as well.
Rust fungal spores are commonly carried on moist winds until they land on plant leaves, stems, flowers, or fruits. The spore pustules multiply creating a rusty-colored coating of spores. The coating of spores can eventually cover leaves and stems inhibiting the plant’s ability to photosynthesize and go on living.
Vegetable and fruit crops at risk of rust disease are asparagus, beans (particularly pole beans), peas, corn, eggplant, Jerusalem artichoke, okra, onions, sweet potatoes, and berries—such as raspberries.
Symptoms of rust can vary by infected plant. Beans develop reddish brown blisters on the undersides of leaves the blisters can also appear on bean pods. Corn leaves and stalks get similar blisters—yellowish to reddish brown colored. Asparagus plants develop orange-red blisters on leaves and stems. Raspberry leaves get yellowish to reddish blisters.
The spots and blisters are fungal structures that release spores. If a rust infection becomes severe enough, leaves will turn yellow and drop the plant can become stunted and die.