Diagnosing and treating problems in a garden is a continuous learning process. Next year I will know that a black spot on a tomato indicates that the invasion has begun. Next year when holes start to appear on the tomato leaves, I will know where to look and what to look for. I finally found the cause of the problems, a caterpillar hanging on the underside of a branch, a southern armyworm. The nasty caterpillar in the photo and his friends that have appeared since then are large enough to pull off, but I have also treated cherry tomato plant with BT (Bacillus thuringiensis). BT is a microbial insecticide.
- The organisms used in microbial insecticides are essentially nontoxic and nonpathogenic to wildlife, humans, and other organisms not closely related to the target pest. The safety offered by microbial insecticides is their greatest strength.
- The toxic action of microbial insecticides is often specific to a single group or species of insects, and this specificity means that most microbial insecticides do not directly affect beneficial insects (including predators or parasites of pests) in treated areas.
- Because their residues present no hazards to humans or other animals, microbial insecticides can be applied even when a crop is almost ready for harvest.
- Because a single microbial insecticide is toxic to only a specific species or group of insects, each application may control only a portion of the pests present in a field, garden, or lawn. If other types of pests are present in the treated area, they will survive and may continue to cause damage. Conventional insecticides are subject to similar limitations because they too are not equally effective against all pests. Nonetheless, the negative aspect of selectivity is often more noticeable for microbials.
- Heat, desiccation (drying out), or exposure to ultraviolet radiation reduces the effectiveness of several types of microbial insecticides. Consequently, proper timing and application procedures are especially important for some products.
- Special formulation and storage procedures are necessary for some microbial pesticides. Although these procedures may complicate the production and distribution of certain products, storage requirements do not seriously limit the handling of microbial insecticides that are widely available. (Store all pesticides, including microbial insecticides, according to label directions.)
I’m trying to use organic methods, but the reality is that sometimes I have to do something or give up the plant to the pests. BT does not instantly kill the caterpillars, but there is less activity until the caterpillars die in 2-3 days.
I continue to research solutions to problems, but more importantly what I am doing is learning to recognize problems so that next year I will anticipate the problems and will be ready with solutions faster. Luckily I started with a small vegetable garden this first year in Florida. I would be more frustrated than philosophical about the loss of vegetables to the pests if I were managing a larger garden. The smaller size allows me to regard this as a year of learning, not a year of “farming”. In the meantime, we enjoy the tomatoes, ochra and radishes plus the herbs that we have harvested, and we are happy that everything we have eaten so far was organically grown without application of pesticides.