Blueberries are popular, easy-to-grow flowering plants that feature fresh produce throughout the garden season. Home gardeners can grow their own blueberries without the use of synthetic pesticides or fertilizers. However, alternative products must be used to keep insects away from this bountiful berry plant. Organic pesticides can be used on a blueberry plant that shows signs of infestation, such as yellow spots on leaves, holes along foliage or smaller than normal fruit.
Limonene, specifically called d-Limonene, is comprised of citrus oil extracted from citrus rind. According to the University of Maine (UM), limonene acts as an antifeedant to insects and pests attracted to blueberry plants. This could be related to the acidic nature of limonene. "After having fed on leaves coated with this non-toxic plant compound, they stop feeding," according to UM. However, this natural pesticide is not effective against thrips, strawberry rootworm, flea beetle or blueberry spanworm.
Sulfur is a mineral-based pesticide deemed safe for organic use. Colorado State University (CSU) states that sulfur is the oldest known pesticide that is still used today. The Greek poet Homer discussed the merits of "pest-averting sulfur" more than 3,000 years ago. This mineral is generally applied in a powder form by sprinkling the substance over the plant. Sulfur is primarily used to control powdery mildew, rust, leaf blight and fruit rot but is also effective against spider mites, psyllids and thrips. CSU states that sulfur can cause plant injury in dry, 90 degree-plus weather. In addition, sulfur is incompatible with other pesticides. "Don't use sulfur on plants within 20 to 30 days of applying spray oils," according to CSU.
Cayenne pepper is a great choice for a homemade organic pesticide. According to the University of Maine, this plant product has proven successful as an insect repellent. The pepper can be used in powder form or mixed with water to create a spray. After a heavy rain, the mixture should be applied again. However, UM states that this product is not effective against flea beetles, but cayenne does deter other insect pests as well as wildlife such as deer and rabbits.