Growing blackberries yields delicious fruit and attractive foliage. However, these plants often face insect pests that impact health and fruit production. Understanding common pests and effective management strategies is important for a thriving patch.
Common Blackberry Insect Pests
Spotted Wing Drosophila (SWD) is a small fruit fly that threatens ripening blackberries. Males have a distinct black spot on wing tips; females pierce ripening fruit with a saw-like organ. Infested fruit becomes soft, mushy, and prone to fungal infections.
Cane borers are beetle larvae that tunnel into blackberry canes, causing wilting and dieback. These legless, white grubs feed inside the pith, disrupting nutrient and water flow. Signs include entry holes, sawdust-like frass, or galls on affected canes.
Japanese beetles are recognizable by metallic green heads and coppery-brown wing covers, about half an inch long. These beetles feed voraciously on blackberry leaves, skeletonizing them by consuming tissue between veins. Large populations can severely defoliate plants, reducing photosynthesis and fruit quality.
Aphids are small, soft-bodied insects varying in color, clustering on new growth, leaf undersides, and stems. They feed by sucking plant sap, causing leaves to curl, distort, yellow, and stunt growth. They also excrete honeydew, leading to black sooty mold.
Spider mites are tiny arachnids, often reddish-brown or green, barely visible, thriving in hot, dry conditions. They feed on plant cells, causing tiny yellow or white speckles (stippling) on upper leaf surfaces. Severe infestations cause leaves to bronze, yellow, and drop prematurely, often with fine webbing on leaf undersides.
Preventative Measures for Pest Control
Providing ample space between blackberry plants, typically 3-5 feet apart, improves foliage air circulation. Airflow reduces humidity, discouraging fungal issues and pest susceptibility. It also allows better light penetration, promoting plant vigor.
Regularly removing fallen leaves, overripe fruit, and old, dead canes from plant bases eliminates overwintering sites for many pests and their eggs. This disrupts pest life cycles and reduces the initial pest population. Promptly disposing of infested plant material away from the garden prevents reinfestation.
Research varieties with natural resistance or tolerance to regional pests. While no variety is completely immune, choosing robust cultivars reduces pest problem likelihood and severity. Local agricultural extension services can advise on suitable resistant options.
Planting flowering herbs and annuals (e.g., dill, cilantro, sweet alyssum, marigolds) attracts natural predators. Ladybugs, lacewings, hoverflies, and parasitic wasps feed on or parasitize common pests like aphids and spider mites. Consistent nectar and pollen sources encourage these insects to remain.
Consistent soil moisture with proper watering helps blackberry plants develop strong root systems and healthy foliage, increasing pest resilience. Over-fertilization, especially with excessive nitrogen, can promote lush, tender new growth attractive to sap-sucking insects like aphids. A balanced fertilization program supports robust plant development.
Pruning old fruiting canes after harvest and thinning crowded new canes improves air circulation. This reduces pest hiding places and allows better spray coverage if treatments are necessary. Promptly removing any canes showing pest damage or disease also limits pest spread.
Treatment Options for Blackberry Pests
Hand-picking visible pests like Japanese beetles into soapy water is an effective direct control. Small infestations of aphids or spider mites can be dislodged from leaves with a strong hose stream, especially from undersides. Do this in the morning to allow foliage to dry.
Insecticidal soaps dissolve the protective outer layer of soft-bodied insects, causing dehydration. They are effective against aphids, spider mites, and whiteflies, with low impact on beneficial insects once dry. Neem oil acts as an anti-feedant and growth regulator for more pests. Apply both thoroughly, covering all leaf surfaces and reapplying as directed.
Traps, such as pheromone traps for Japanese beetles, require careful placement; too close to plants, they may attract more beetles than they capture. Position them a significant distance from plants to draw pests elsewhere. Monitoring traps for Spotted Wing Drosophila, baited with apple cider vinegar, can gauge pest pressure and inform other interventions.
If pest pressure is severe and non-chemical methods fail, targeted chemical pesticides may be a last resort. Before applying, accurately identify the pest to ensure the correct product is chosen. Always read and follow all label instructions regarding application rates, timing, safety precautions, pre-harvest intervals, and protecting pollinators by spraying during non-foraging hours.