Raspberries are usually straightforward to grow in home gardens. Nonetheless, they can sometimes be prone to a few pests and plant disease issues. Keep reading to learn about practical solutions for some of the most common raspberry problems.
In general, plants are considerably more resilient against attacks from pathogens and insects when healthy. Therefore, the best way to prevent raspberry plant diseases and severe pest infestations is to give them the correct amounts of nutrients, water, and sunlight.
The best practice is to employ cultural controls in your garden that help prevent pest and disease problems whenever possible. Crop rotation and companion planting effectively reduce the likelihood of raspberry plant disease and pest problems.
When complications arise in your garden, it’s always best to try natural remedies before resorting to harsh chemicals. Doing so helps to protect the populations of beneficial insects and soil microbes that keep your garden and the surrounding environment healthy and thriving. Here’s what to do if your raspberry plants start showing signs of distress or aren’t producing fruit.
Practical Solutions for Prevalent Raspberry Problems
Understanding how raspberries grow is essential to providing them with proper care. To begin with, plant raspberries in a location with full sun and rich, well-draining soil. The plants need plenty of water, especially in their peak fruiting period.
On average, give your raspberries one to two inches of water per week throughout the growing season and up to four inches per week during the harvest period. Since raspberry plants have relatively shallow roots that primarily grow in the top two feet of soil, regular watering is generally better than deep, infrequent watering. You’ll likely get a disappointing crop of dry, overly seedy berries if they dry out too much.
Raspberry brambles can quickly become challenging to manage without consistent pruning. Floricanes, or summer-bearing raspberries, produce fruit on second year canes. In contrast, everbearing raspberries, or primocanes, develop fruit on their new growth in the late summer. As such, you must prune primocane raspberries to ground level every year. For floricane raspberry varieties, only prune the old canes that have already fruited in late fall or early spring while they’re dormant.
One of the first symptoms of plant distress is seeing your raspberry leaves turn brown or yellow. Raspberry leaf discoloration can indicate several different problems, so it’s critical to pay attention to other symptoms as well.
Also, it’s essential to keep in mind that insecticides also affect beneficial insects. In addition to helping out in your garden, they’re crucial to the overall environmental health of their natural habitat. For this reason, it’s vital to be mindful about spraying raspberry plants and target only severe infestations, especially when the plants are flowering.
Bacterial Raspberry Disease
Raspberry canes are sometimes attacked by harmful bacteria, causing previously healthy canes to stop producing fruit and turn brown. The most frequent bacterial raspberry cane diseases are bacterial blight (Pseudomonas syringae) and fire blight (Erwinia amylovora).
Both conditions produce dark, burned patches on raspberry leaves and canes. The bacteria thrive best in damp conditions and can overwinter in old wood. The bacteria enter through the flowers or via open wounds, cankers, or frost damage in raspberry canes.
However, once the plants become infected, there’s unfortunately no cure for these bacterial raspberry diseases. As such, proactive steps toward prevention are crucial. Remove all dead or infected canes by pruning them down to ground level. Then, burn or dispose of them in a sealed garbage container. Never put infected plant material in your compost pile.
If you’ve had blight issues in the past, treating raspberry plants with a copper fungicide in early summer may help prevent infection. To learn more about causes and cures for raspberry disease problems, this article from the Alberta Ministry of Agriculture has helpful information.
Raspberry Problems From Fungal Diseases
Fungal diseases frequently spread between plants through splashing water droplets. Ensure sufficient air circulation between plants and use a soaker hose or drip irrigation to keep raspberry leaves dry when watering.
Prevalent fungal diseases for raspberries include cane blight, spur blight, anthracnose, and powdery mildew. Remove all affected canes and dispose of them as described above. Fungal spores can easily overwinter in dead or dormant plant material and return in full force come spring. Additionally, treat the affected plants using organic fungicides containing copper or sulfur. However, fungicides only partially control raspberry diseases. As such, preventative measures and cultural controls are essential. If you’d like to find out more about these types of raspberry disease, this article from the University of Minnesota Extension has plenty of helpful information.
Anthracnose (Elsinoe veneta) infects raspberry plants’ bark and wood. This fungal disease leads to white or beige cankers on the cane sections between leaf nodes. Eventually, the edges of the cankers may turn purple. They’re usually less than a quarter-inch wide and have raised edges. In extreme cases, the raspberry leaves also develop purple spots with light-colored centers.
Cane blight (Leptosphaeria coniothyrium) results from wounds on raspberry canes that become infected. The most common infection site is where canes rub against a trellis, fence, or other canes. Reddish-brown streaks expand outwards, eventually forming cankers and making the whole cane die back. Raspberry cane blight also makes the leaves of the infected stem wilt and die.
Powdery mildew (Sphaerotheca macularis) appears as a fuzzy white coating on raspberry leaves, canes, and fruit. In most cases, the spores first develop on the undersides of the leaves, resulting in light green or yellow patches on the leaf surface. The fungus also causes young canes to grow spindly or stunted and die back. Furthermore, the newly formed berries won’t fully develop, withering and eventually falling off the plant.
Spur blight (Didymella applanta) initially develops at the leaf nodes on raspberry canes. You’ll first notice raspberry bush leaves turning yellow, starting with the lower sections. Then, they progress to brown or black before eventually dropping off. Eventually, the infection moves into the stem, forming purple or brown lesions. In later stages, the bark may begin to dry out, crack, and peel away from the stem.
Verticillium wilt (Verticillium albo-atrum) and phytophthora root rot result from soil-borne fungi. Unfortunately, there’s no known cure for verticillium wilt other than completely removing the infected plants. The fungal spores can persist in garden soil for many years, so it’s best to avoid growing susceptible crops in that area.
However, phytophthora root rot can be treated using a hydrogen peroxide soil drench. Here’s an easy DIY recipe to treat raspberry root rot.
Hydrogen Peroxide Root Drench
- 6 cups of distilled water
- 2 cups of 3% hydrogen peroxide
- Sterilized bucket or watering can
In a clean watering can or bucket, combine one part hydrogen peroxide with three parts distilled water. Mix thoroughly, then pour the solution around the base of your raspberry plants. Wait until the top two or three inches of soil are completely dry before rewatering. That way, the root system can fully absorb the treatment. Repeat this process two or three times over the course of two weeks.
Disease Resistant Raspberry Varieties
Planting disease-resistant cultivars significantly reduces the risk of your raspberry plants developing problems later on. Here are some of the best disease resistant raspberry varieties.
- Autumn Bliss – primocane, red fruit, sweet flavor, self-supporting canes, fall harvest, USDA zones 4-8
- Boyne – floricane, red fruit, moderately sweet flavor, remarkably cold-hardy, fall harvest, USDA zones 3-8
- Bristol – floricane, black fruit, rich flavor, self-supporting canes, mid-summer harvest, USDA zones 4-8
- Caroline – primocane, red fruit, bold flavor, doesn’t tolerate heat and drought well, fall harvest, USDA zones 4-8
- Double Gold – double-bearing (floricanes that also produce a fall crop in the first year), champagne pink fruit, sweet flavor, fall and mid-summer harvests, USDA zones 5-7
- Heritage – primocane, red fruit, moderately sweet flavor, self-supporting canes, fall harvest, USDA zones 4-8
- Jewel – floricane, black fruit, rich floral flavor, low seed content, mid-summer harvest, USDA zones 5-8
- Nova Red – floricane, red fruit, sweetly tart flavor, great for container gardens, mid-summer harvest, USDA zones 3-8
Flying Raspberry Bugs
Unfortunately, we’re not the only ones who think raspberries are delicious. Aphids and raspberry cane borers are some of the most widespread raspberry pests.
Aphids feed on sap from raspberry leaves, leading to problems like leaf curl and yellowing. Spray the affected canes with an organic pesticide like insecticidal soap, neem oil, or horticultural oil.
Raspberry cane borers cause severe damage to the plants. The adult beetles feed on the tender cane tips, resulting in brown scarring on the bark. In early June, females bore into the canes about six inches below the tip to lay their eggs. You’ll see wilting, blackened cane tips, and diminished fruit production on affected canes. Once the eggs hatch, the larvae burrow down through the cane to overwinter in the plant’s crown. This often causes the cane to grow stunted or die off completely the following spring.
To eliminate cane borers, remove all infested canes, where the larvae spend most of their first year. When the females lay eggs, they chew two rings or girdles on the canes and lay an egg in between them. Cut the cane several inches below the lowest girdle to prevent the larva from reaching the crown. To learn more about controlling raspberry cane borers, check out this article from the Michigan State University extension.
Soil-Borne Raspberry Pests
Nematodes are microscopic soil-dwelling worms. Although most nematodes are harmless, and some types are even beneficial, there are several nematode species that damage raspberry plants.
Lesion nematodes are the most common. Their feeding creates lesions on the roots, which leads to stunted growth, wilted and yellowing leaves, and poor fruit production. The root damage hinders water and nutrient uptake and provides potential entry points for pathogens.
The effectiveness of insecticides against nematodes is limited. Therefore, the most effective nematode control is keeping your plants healthy and encouraging their natural predators, which include fungi and other soil-dwelling insects. Adding organic compost to your garden soil each year helps maintain a balanced soil environment and supports beneficial microbes.
No matter which raspberry varieties you’re growing, it’s essential to familiarize yourself with the plants’ most frequent pest and disease problems. Monitor your raspberry plants carefully for signs of distress throughout the growing season. If you notice the raspberry leaves turning brown or yellow, wilting, or curling, look closer to learn whether you’re dealing with raspberry bugs or a plant disease. Catching the problem as early as possible gives you the best chance for successful treatment.
Do you have any questions or suggestions about treating raspberry pests and diseases? Please share them in the comments! If you found these gardening tips useful, don’t hesitate to share this article with your fellow gardeners.