Raspberry & Blackberry Pest and Disease Alerts

Our friends at Cornell Cooperative Extension share these tips for managing pests and diseases in raspberry and blackberry during this unusually wet summer.

Tarnished plant (lygus) bug levels are high in caneberries. We’re also seeing some damage to cut flowers following feeding on buds.  Insect feeding through buds, in open blooms, or on developing fruits stunts berries. Cornell Guidelines suggest a threshold of 10-20% infested canes. In caneberries Assail, Befenture 10DF, carbaryl/Sevin, Danitol, are labeled; Brigade DF can be used in caneberries but isn’t labeled for TPB but will provide incidental control used for other labeled pests (Brigade also has a supplemental label in NY for spotted-wing drosophila). In organic production Mycotrol, Grandevo, PFR-97 and PyGanic are labeled, but emphasize good weed management. (This information is from Dan Gilrein, CCE Suffolk.)

Spur blight (Didymella applanata) has unsurprisingly reappeared in many cane berry plantings. This fungal disease loves the wet humid weather we are having. Dense plantings usually have problems even in dry years, but this year even well-pruned plantings may see this disease. Chocolate brown to purple blotches appear at the buds of canes. This results in weak or no growth from those buds and an overall lack of vigor. 

Prune and destroy diseased canes before next spring. There are plenty of fungicides labeled for this disease but take care when applying at this time of year, especially in hot weather. You can get foliar burn from some of the pesticides. The best time for control is delayed dormant in the spring. 

Cane blight (Leptosphaeria coniothyrium) are similar in appearance to spur blight, but the lesions can be found all along the cane. Often the two diseases appear together. Cane blight is more common in black and purple raspberries, but can also infect red raspberries. Prune and destroy infected canes asap. Best control comes from delayed dormant sprays of lime sulfur. 

What You Need to Do for a Successful Blueberry Harvest This Summer

Our friends at Cornell Cooperative Extension have shared these important tips for ensuring the success of this season’s blueberry crop.

Blueberry harvest is underway and looks surprisingly good in most places – despite the May freeze, early drought, and occasional hail events around the region. Fruit is sizing very well and plant growth is great – these plants LOVE all this rain! But unexpected weather is when you will discover how effective your disease management program was.

Anthracnose fruit rot (Colletotrichum acutatum) is widely apparent in plantings. This disease should be prophylactically sprayed before and during bloom. You can spray now in hopes that you can thwart the spread of the disease, but look carefully at the REI and days to harvest all chemicals.   

This disease will present as a sunken spot on the fruit. In this humid weather, you will undoubtedly see the pink-orange fruiting spores that will grow on the sunken areas. Make a note to focus on next season to control this disease.

Mummyberry (Monilinia vacinii-corymbosi) is less widely apparent, but definitely out there. Mummyberry spores can be moved by pollinators, so even if you’ve never dealt with this disease before, there is always a chance. That is why we encourage growers to manage for it, despite the history in your own patch. This disease is controlled at the vegetative green tip – so pretty early in the spring. 

Blueberry tip borer moth (Hendecaneura shawiana) is a pest that we are seeing much more frequently than in the past. The pest doesn’t damage the fruit from this season. But the overall impact is more significant. The moth lays eggs in the tip of the newest canes, causing the cane to abort vertical growth and branch much lower than it normally would. This means that there is less opportunity for overall growth, the fruiting wood is too low, and over time the plant becomes less productive due to the architectural change. 

The small brown moth lays eggs in June, which hatch in July. The larvae drill down several inches, causing distortion and then death of the shoot tip. This flagging can look something like canker, but it’s more localized to the top 6” of the shoot. There are no labeled conventional insecticides. Use azadirachtin and pyrethrin products at petal fall for control.  

Japanese beetle (Popillia japonica) have started feeding on blueberry foliage. I’ve yet to get a report of fruit feeding, but that is when they become a problem worthy of spraying. Despite the foliar damage, they usually don’t do lasting damage to the plant. There are many pesticides that can be used on this insect, but don’t pull the trigger unless you really need to and make sure to read the label for Days to harvest. 

Canker diseases (Fusicoccum putrefaciens and Phomopsis vacinii) are exhibiting the tell-tale cane flagging. New shoots will wilt rapidly and die back from the tip towards the crown. Healthy vigorous canes will wilt and collapse. When you see this happen in an otherwise perfectly healthy plant, the likelihood is high that it’s canker. Fusicoccum canker forms bulls-eye type lesions on the stem, which is another diagnostic help. Prune the dead out as it appears and make a note to use a delayed dormant spray next spring.  

Berry Disease Snapshot: Mycosphaerella Leaf Spot of Strawberry

By David Strickland and Kerik Cox

Cornell AgriTech

Disease Snapshot: Mycosphaerella Leaf Spot of Strawberry (Bird’s Eye Spot, White Spot)

Causal Pathogen: Mycosphaerella fragariae

When to watch for it: Year round

First line of defense: Plant disease-free nursery stock

Summary:

Infections can occur on fruit (black seed), petioles, stolons, and leaves. Foliar lesions first appear as irregular purple spots on both the upper and lower surfaces of the leaf. Lesions develop a brown to white center as they mature, with a rusty brown border surrounding the necrotic area of the lesion. Severe infection on a susceptible cultivar will kill the leaf as lesions coalesce over the entire surface. Symptom expression varies by cultivar, temperature, and strain of M. fragariae. M. fragariae can overwinter as lesions on living leaves under snow cover, as conidia from overwintering dense masses of mycelia (sclerotia), and as sexually recombinant ascospores. Conidia from sclerotia are rain-dispersed from dead leaves in the field in the early spring, and ascospores are disseminated by wind. Virtually all parts of the plant are susceptible regardless of age, but lesions are most severe on middle-aged leaves. Severely infected plants are less likely to survive the winter, and those that do will have a reduced number of flowers in the spring.

Resistance reports have varied by state, and resistant cultivars may or may not be an effective means of disease control. Removing dead plant matter before winter will reduce inoculum carry over between seasons.  Fungicide applications are recommended for plantings with susceptible varieties in the early season to eliminate overwintering inoculum.

Berry Disease Snapshot: Blueberry Powdery Mildew

By David Strickland and Kerik Cox
Cornell AgriTech

Disease Snapshot: Blueberry Powdery Mildew

Causal pathogen: Microsphaera vaccinii

When to watch for it: July through season’s end

First line of defense: Use of resistant cultivars

Summary:

The signs of M. vaccinii infection do not typically appear until midsummer, when white fungal growth appears on the upper leaf surface. Leaf reddening may occur as chlorotic spots with reddish borders, and the leaf surface may become puckered. This reddening may be mistaken for symptoms of red ringspot virus (RRSV) infection but can be distinguished by the presence of water-soaked areas on the leaf’s lower surface opposite the chlorotic areas. If left uncontrolled, blueberry powdery mildew may lead to premature defoliation and a long-term reduction in bush productivity.

The planting of resistant cultivars is the best option for management of powdery mildew. Fungicide applications should begin just after petal fall, which targets primary inoculum. If these infections are managed early, an epidemic can be avoided. Suggested products are oils (e.g. stylet oils) or sterol biosynthesis inhibiting fungicides such as propiconazole (on 14-day intervals). Remember that fungicide products containing sulfur should not be applied within a 2-week period of an oil product application due to the potential for phytotoxic effects. Postharvest burning of infected leaf matter has not been shown to decrease the incidence of disease in subsequent years.

Berry Disease Snapshot: Rhizopus Rot of Strawberry (Leak)

Soft, collapsed strawberries that begin to mold can be a sign of rhizopus rot.

By David Strickland and Kerik Cox
Cornell AgriTech

Berry Disease Snapshot: Rhizopus Rot of Strawberry (Leak)

Causal pathogen: Rhizopus stolonifer, R. sexualis

When to watch for it: During the fruit-ripening period

First line of defense: At harvest, rapidly cool harvested fruit below 45°F

Summary:

Primarily a postharvest rot, Rhizopus rot may also occur in the field on ripe fruit. Modern storage and shipping have reduced this disease’s incidence worldwide, but it may readily appear if fruit are not cared for properly. Fruits infected with Rhizopus spp. appear slightly discolored, gradually turning light brown. The fruits rapidly soften and collapse, allowing their juices to leak out. Under humid conditions, white fluffy mycelium with large black sporangia appear. Rhizopus spp. can successfully overwinter on leftover plant material and in soil.

Protective broad-spectrum fungicides can be used to control Rhizopus rot in the field. Rhizopus spp. can only infect wounded fruit, so a vigilant insecticide program to manage fruit-feeding insects is encouraged. At harvest, Rhizopus rot is best controlled by rapidly cooling berries and maintaining storage temperatures below 45°F.

Berry Disease Snapshot: Black Root Rot of Strawberry

By David Strickland, Kerik Cox
Cornell AgriTech, Geneva, NY

Black Root Rot of Strawberry

Causal agent: many soil-borne fungal species, abiotic factors

When to watch for it: During the growing season

First line of defense: Good soil health maintenance practices

Summary:
A disease complex, black root rot does not have one specific cause. It may be caused by injurious environmental conditions such as freezing or waterlogged soils, root-lesion nematodes, and/or various soil-borne fungal pathogens alone or in combination. The disease has been observed on plants grown in soils with a high clay content. The most prevalent symptoms of black root rot are death of feeder rootlets, deterioration of structural roots, and declining plant vigor.

Maintenance of soil health is the best control against black root rot. Soil compaction reduces soil aeration, promoting conditions conducive to disease development. Poor irrigation practices and waterlogged soil does the same. Chemical fumigation of the soil is not recommended as the causal agent may not be fungal.

Western New York Berry Update

Western New York Berry Update

April 3, 2020

By Esther Kibbe

Western New York Berry Specialist, Cornell Cooperative Extension

April 3, 2020

Strawberries

New leaves are starting to push under the straw. With no extended cold in the forecast, research has shown that it is better to remove straw early, if leaves are emerging, rather than basing it on the calendar. Consider getting out there to rake it off soon.

This is also the time to apply preemergent herbicides against annual weeds. Chateau or Devrinol can be used. Aim, Axxe and Gramoxone are options as more weeds emerge, or against winter annuals, but should be applied with a shielded sprayer.

Strawberry leaves emerging from the crown.

Blueberries

Depending on microclimate, buds are just swelling to early green-tip. If you haven’t already, this is the time to go after cane diseases (Phomopsis, Botrytis, Fusicoccum) with a delayed dormant spray of lime sulfur or copper. Several fungicides are also labeled for these, but I would save them unless you are dealing with a severe, recurring level of infection.

As you finish pruning, be sure to cut out any diseased canes and gall wasp galls. Start planning your spring herbicide applications. Blueberries have many herbicide options—the best choice depends on what your weed issues are.

Blueberry buds are between bud-swell and early green tip.

Raspberries

Still looking pretty dormant. Copper, dormant oil or lime sulfur sprays can be applied for cane blights. This is the time to get started on weed control: Devrinol, Surflan, Sinbar for preemergent weeds (annuals), Axxe for post-emergent broadleaves, and Poast or Fusilade for perennial grasses.

Berry Disease Snapshot: Angular Leaf Spot of Strawberry

By David Strickland and Kerik Cox

Cornell AgriTech, Geneva, NY

Disease: Angular Leaf Spot of Strawberry

Causal pathogen: Xanthomonas fragariae

When to watch for it: Year round

First line of defense: Purchase disease-free stock

Summary:

Angular leaf spot of strawberry has been introduced to major production areas by the importing of infected plant material. The bacterial pathogen, X. fragariae, is very resistant to desiccation and can survive adverse conditions for extended periods in or on dead plant matter both in transit and in the field. The pathogen cannot overwinter freely in soil, which implies that one key cultural control is the removal of old strawberry plant matter before new fields are planted.

Young, vigorous plants are more likely to be infected during the spring when temperatures remain around 68°F during the day and when the leaf wetness is prolonged by rain or sprinkler irrigation. Symptoms begin as water-soaked lesions that enlarge but are delimited by veins, creating characteristic angular spots. During moist periods, viscous bacterial ooze may be visible on the undersides of infected leaves, which dries to a white film. Severe infections will result in the death of the leaf.

Preventing the introduction of X. fragariae on transplants has proven to be more effective than chemical control measures. If absolutely necessary, applications of streptomycin sulfate and oxytetracycline have been shown to be effective protectants in the early season. Applications of copper ammonium carbonate and cupric hydroxide have also been effective protectants in 6 day intervals. However, greater than 7 applications risks the development of severe phytotoxic symptoms. For organic production, the use of hydrogen peroxide at its highest labeled rate is suggested if disease pressure is severe.

A: Bacterial lesions observed on the underside of an infected strawberry leaf. In direct (transmitting) light, the lesions are transparent. Unlike in B: where the lesions are a different shade of green in reflected light, which is a characteristic feature for identification. C: the underside of a severely infected strawberry leaf.