Blueberry bushes yield sweet, antioxidant-rich fruit but are susceptible to threats ranging from wildlife and pathogens to unpredictable weather and unsuitable soil conditions. A successful harvest relies on a proactive defense plan addressing these vulnerabilities throughout the growing season. Cultivators must employ a combination of physical barriers, cultural practices, and environmental management to ensure the long-term health and productivity of the bushes.
Physical Barriers Against Wildlife
Protecting developing fruit from animal consumption is often the most immediate concern for blueberry growers. Birds, in particular, can rapidly consume an entire crop, making physical exclusion highly effective. Bird netting is the standard defense and must be installed as soon as the berries begin changing color. Netting should feature a mesh size of 3/4-inch or smaller to exclude birds while still allowing beneficial insects access.
It is more effective to create a permanent or temporary cage structure over the bushes rather than draping the netting directly onto the plants. Draping can lead to birds pressing against the mesh to reach the fruit, and the netting can become tangled in the canes, causing damage during removal.
Larger mammals, such as deer and rabbits, pose a threat by browsing on foliage and tender new growth. Deer require a fence height of at least 7.5 feet to prevent jumping the barrier. For rabbits and other small ground-level pests, the base of perimeter fencing must be secured to the ground or buried a few inches deep to prevent burrowing.
Biological Management of Pests and Diseases
Managing biological threats requires a focus on sanitation and cultural practices to minimize insects and pathogens. One damaging insect pest is the Spotted Wing Drosophila (Drosophila suzukii), a vinegar fly that lays eggs in ripening fruit, leading to maggot infestation. Effective control hinges on rigorous sanitation, including removing all dropped and overripe fruit from the ground and quickly harvesting ripe berries.
Another destructive threat is Mummy Berry disease (Monilinia vaccinii-corymbosi), a fungus that causes berries to shrivel and harden into non-viable, mummified fruit. This fungus overwinters in the mummified berries on the ground, so removing this infected debris before spring growth is a necessary preventative measure. Pruning the bushes to open up the canopy improves air circulation, which helps foliage dry faster and reduces conditions favorable for many fungal issues, including stem blights.
Integrated Pest Management (IPM) strategies emphasize the use of monitoring traps to determine when treatment is necessary. If pest pressure is high, organic growers often rely on targeted sprays containing spinosad, an insecticide derived from soil bacteria, as it is effective against the Spotted Wing Drosophila. For fungal problems like root rot caused by Phytophthora, improving soil drainage and avoiding over-irrigation is the primary defense.
Protecting Bushes from Weather and Soil Stress
The long-term health of a blueberry bush is tied to its environment, making protection from extreme weather and inappropriate soil chemistry important. Blueberry bushes require acidic soils, needing a pH range of 4.5 to 5.5 to absorb nutrients efficiently, particularly iron and manganese. If the soil pH rises above this range, the plant struggles to take in these elements, resulting in nutrient deficiencies and plant stress.
Regular soil testing and the application of elemental sulfur or acidic amendments like peat moss are necessary to maintain the required acidity. Mulching with acidic materials, such as pine needles or pine bark, helps stabilize soil temperature, retain moisture, and suppress weeds, all while gradually contributing to soil acidity. For winter protection in cold climates, this acidic mulch should be applied in a layer up to three inches deep around the root zone, keeping it away from the crown of the bush.
Protecting delicate blooms from late spring frost is accomplished by covering the bushes with frost cloth or row covers, which can provide a temperature increase of a few degrees. When a hard freeze is predicted, overhead sprinkler irrigation can be employed; the continuous application of water releases heat as it freezes, insulating the buds and flowers. During the summer, deep, consistent watering is essential to mitigate drought stress. In regions with extreme heat, the temporary use of shade cloth can prevent sunscald on the berries and foliage.