Maintaining the health of plants can be a challenging task, particularly when combating diseases and pests. The proper use of chemicals can significantly enhance plant vitality and yield. However, it is crucial to use these chemicals judiciously to ensure safety and effectiveness.
Each pesticide has its own “mode of action” – MOA – to control the pest. Some strip off protective coatings leading to suffocation and/or desiccation, others interrupt digestion or reproduction, while still others interfere with nerve conduction, to name but a few. The classifications are established by the Insecticide Resistance Action Committee (IRAC), who’s intent is to prolong the effectiveness of pesticides by battling the development of resistant strains. You can read more about them in this Chemical Class Chart.
Understanding the types of treatments
Before treating anything, it is important to properly diagnose the problem and to select the type of product that will address it. There are a lot of misunderstanding in this area, so let’s take a look at the types of products available.
Insecticides
Insecticides are designed to control insect pests. They can be contact insecticides, which kill insects on contact, or systemic or translaminar insecticides, which are absorbed by the plant and target pests when they feed on it. Not all insecticides control all insects. Read the label carefully to make sure you have chosen properly. This Pesticide Selelction Guide can help.
Most insecticides only affect adults, leaving eggs and juveniles unaffected. That is why the “3@7” regimen is recommended. By thoroughly treating the plants three times at one-week itervals, it is likely that newly-maturing adults will be killed before they have the opportunity to reproduce.
Miticides
Mites are arachnids, not insects, so are not controlled by insecticides. In fact, treating mites with an insecticide can exacerbate the issue by killing predatory insects that would otherwise help control the mite population.
The most common mites seen infesting orchid collections are two-spotted spider mites and flat mites.
Fungicides
A fungus is an organism that survives by secreting digestive enzymes to attack host tissues and absorbing the nutrients realeased. They can spread through colony growth or through the dispersal of spores via wind or water, leading to the infection of several plants.
There are a wide variety of fungi that attack plants, such as powdery mildew, scabs, rusts, smuts, and downy mildew (which isn’t a true fungus, but has a similar lifestyle). Identifying the type of fungus affecting your plants goes hand-in-hand with treatment selection.
Bactericides
Bacteria – good and bad – are ubiquitous. Pathogenic bacteria can cause discoloration or dark spots on leaves, leaves that turn brown and watery, soft rot in fleshy plants, or create areas that look dark, black, and wet.
Bacteria are not effected by fungicides and fungi are not affected by bactericides.
Virucides
Viruses may be killed on surfaces to prevent transmission, but once a plant is infected, there is no cure.
Disinfectants
Disinfectants may kill molds, bacteria and viruses on surfaces, but cannot be used to cure and infected plant.