As the summer heat sets in, gardeners are starting to notice more nuisances in the garden: insects. From chewing pests like caterpillars to piercing insects (covered in next month’s article) like leaf-footed bugs, they are all appearing, and each presents its own unique set of problems. In addition to physical damage to plants and fruit, these insects can spread diseases, some of which can reduce a healthy plant to a withered mess in a single day.
There are a number of caterpillars that you may find in your garden. Hornworms are among the most recognizable. All cause chewing damage, usually to leaves and stems, but some will burrow into the fruit such as tomato fruitworms. If possible, hand picking the worms is the best option rather than using an insecticide. However, if an insecticide is necessary, the good news is that identifying the type of caterpillar you have is not necessary for treatment. Bacillus thuringiensis (Bt) is an effective organic option for getting rid of caterpillars. If you have a high number of caterpillars, another organic option is spinosad. Spinosad will provide faster control than Bt. Spinosad is a contact herbicide while Bt must be consumed by the caterpillar. Other options include bifenthrin, carbaryl, and others. Always read and follow the directions on the label and pay special attention to the pre-harvest interval (PHI), which specifies the amount of time required between treatment and harvest.
Another commonly encountered garden insect is the cucumber beetle. There are three types of cucumber beetles: striped, spotted, and banded. Both the larvae and adult feed on plants, especially the foliage and fruit of cucurbits. The striped cucumber beetle can also spread bacterial wilt to plants that it feeds on. Bacterial wilt causes plants to wilt and die very fast. Often, plants are fine in the morning and dead by the evening of the same day. There is nothing that can be done for bacterial wilt. Products such as permethrin, bifenthrin, and carbaryl are broad spectrum insecticides that can be used against cucumber beetles. Neem can also be used.
For more information contact Randall Mallette, County Agent, at the local LSU AgCenter Extension Office 318-357-2224.