Pest management is a challenge in south Florida. Rarely do we have a cold or dry period that greatly reduces pest populations. Luckily, the development of many new, safer pesticides helps us to be able to produce crops in spite of these pests. With very few exceptions (and those are quickly disappearing from the market), the pesticides used today are not the same as those that were used in the 1950's-80's. Most of the older pesticides killed living organisms by attacking them at several places in their metabolic and/or reproductive processes. This meant that they often killed or damaged different types of organisms, in addition to the target pests. These chemicals were easy and cheap to use because one pesticide could often kill all the insects in a crop, and had enough residual effects to keep killing them, sometimes for even several weeks.
Many of the newer classes of chemicals are synthetic forms of naturally occurring pesticides, which generally break down quickly in the environment and often attack only one site in the organism. So, they are usually specific for one or more closely related pest species and do not affect beneficial insects, unless they are closely related to the target pest. While this is an advantage as far as safety and environmental effects, it can also mean that the pests are more likely to develop resistance. So, it is important to rotate them with others which have different “modes of action”. These new pesticides are also much more expensive than the older ones, so all growers are careful not to use more than we need.
Container of beneficial insects
Several times, we have purchased beneficial insects, but we find that we usually do better by encouraging the natural, local populations of “beneficials”. For instance, aphids on our farm are often eaten by ladybugs or lacewings or parasitized by tiny wasps. However, sometimes we have to spray the aphids. That's because, on certain crops, if we allow the aphid populations to build up to the point where the beneficials are working well, we may lose the crop to viruses which are carried by the aphids.
During most of the growing season we spray twice a week. However, the chemicals used in the spray mix vary a lot. When possible, we use pesticides that would be allowed under organic rules, and we also use many of the newer synthetic ones. We scout the crops and try to spray only for the problems we see.
However, sometimes it is necessary to use preventative applications. For instance, especially in the late spring and fall growing season, high temperatures and humidity increase fungal and bacterial diseases. Since most fungicides prevent, rather than cure, diseases, we must anticipate the disease problem in order to effectively control it. So, when conditions are right for development of diseases that are usually a problem here, we spray with fungicides. On the other hand, during a cool, dry winter, we may not have to use fungicides for several weeks.
Caterpillar damage to squash plants
There are always one or more species of caterpillars (popularly called “worms”) trying to eat our crops. Their adult forms are moths or butterflies and include fall armyworms, beet armyworms, cabbage worms, corn earworms, and diamondback moths. So, our spray mix always contains an insecticide to control worms. Most of the time it is one of the forms of Bacillus thuringiensis (BT), a biological worm control. Periodically, especially around a full moon (when the mama moths like to lay a lot of eggs), we alternate with a Spinosad (another biological) or an insect growth regulator which kills the worms by preventing them from continuing their life cycle. Beginning in late 2016, diamondback moths have become the major caterpillar problem, often destroying all our collards, cabbage, broccoli, cauliflower and kale.
Periodically, spider mites or broadmites may build up on some crops. Since they are related to spiders, rather than being insects, they require use of a miticide.
Tomato plant infected with a virus
Some insect pests are more of a problem because of the diseases they carry than because of the actual damage they do. Whiteflies and thrips are the worst for us-they carry viruses which are often the limiting factors in the production of squashed and tomatoes. In addition to the use of a silver reflective plastic which confuses flying insects, at planting time, we also add a systemic insecticide with the starter fertilizer solution.
Since we never have much winter, some kinds of weeds are growing in our fields all year round. Plastic mulches help to control them, and when possible, we also use pre-emergent herbicides to prevent weed seeds from germinating. And, during the growing season we sometimes have to spray or wipe the alleys between the crops with non-persistent herbicides. The crew also does a lot of hand-weeding and hoeing.