- What Are Biopesticides?
- Examples of Biopesticides
- Basics of Insect Resistance
- Systemic Acquired Resistance (SAR)
Conventional pest management has relied on using synthetic chemical pesticides in many industrial cannabis cultivation operations in the past. Increased pest resistance and evolving legislation has strained this method of pest management in horticulture and has called into place an alternative solution to crop protection or pest management. The social costs of using conventional pesticides is increasing and is worrisome for applicators and consumers alike. Social costs can include environmental factors and human health factors. Switching to biopesticides can possibly improve worker safety through shorter restricted entry intervals (REIs) and shorter half-lives leading to shorter field persistence. It is even possible to apply certain biopesticides all while preserving natural enemies because of their narrow range of target pests. This is why biopesticides are generally considered safer for humans and the environment when compared to conventional pesticides.
What Are Biopesticides?
Biopesticides are pesticides with main ingredients that are naturally derived from animals, fungi, bacteria, plants, or minerals. These sorts of pesticides usually control pests through non-toxic mechanisms and can potentially replicate in their hosts and persist in the environment due to horizontal and vertical transmission. This can help increase long-term suppression of pests and reduce the number of applications. A majority of biopesticides are insecticides and have specific modes of action as do conventional pesticides. Unlike conventional pesticides, biopesticides tend to suppress instead of entirely eliminate pest populations and only target a small number of pests and related organisms. In contrast with biopesticides, conventional pesticides may affect other non-target organisms including beneficial wildlife. A majority of biopesticides rapidly decompose which means there is a reduction in exposure to workers and the environment, but despite the fact that biopesticides may be relatively safer than conventional pesticides it is important for applicators and workers to follow safety procedures and utilizer personal protective equipment as the pesticide label states. There are over 300 registered biopesticide active ingredients today.
Examples of Biopesticides
Some examples of biopesticides include diatomaceous earth (a mineral), pyrethrum (a plant extract), azadirachtin (another plant extract), and beauveria bassiana (a fungi) to name a few. The use of azadirachtin in an IPM program can increase the efficacy of other biopesticides used by reducing the detoxification enzyme production in pests. Unfortunately spinosad products, which contain a mixture of bacterium, are registered as chemical pesticides and not as biopesticides. Another bacterium, bacillus thuringiensis (Bt), contains a toxin that is activated upon ingestion by an insect host and eventually causes insect death. Since the mode of action is a toxin, there is an increased likelihood for pests to develop a resistance to Bt pesticides.
Basics of Insect Resistance
The use of biopesticides can reduce the risk of insecticide resistance to toxic compounds which is another reason to implement them into any integrated pest management program. Insects and mites can develop a resistance to chemical pesticides through genetic, metabolic, or behavioral changes to reduce the efficacy of the pesticide. This means that insects and mites can excrete, isolate, shed, or change their target site on crops to prevent toxins from working efficiently. If the active ingredient of a pesticide is toxic, then it is likely that pests can develop resistance to the toxins. When the active ingredient of a pesticide is a microorganism that can cause infection, then pests are less likely to develop a resistance. How a pesticide affects a pest is known as the mode of action. Naturally, plants and insects continually evolve and adapt to their changing environment and when chemical pesticides are sprayed indiscriminately and excessively, then an increased rate of mutagenesis can occur which will lead to an increased resistance in pests. The different modes of action for biopesticides and how they can differ from conventional pesticides demonstrates how insects can develop a resistance to biopesticides like any other pesticide, but at a significantly lesser rate depending on circumstances.
Systemic Acquired Resistance (SAR)
Compounds that initiate a whole-plant resistance response and enhance the plant’s resistance to pests after use without direct interaction with pathogens or pests. In the SAR state, plants become primed or sensitive to pathogens which results in a faster and more aggressive defense response from plants. Some examples of compounds that activate SAR are Harpin αβ proteins and reynoutria sachalinensis or giant knotweed. Both active an internal defense response that helps prevent the growth of certain pathogens such as powdery mildew and gray mold. Since SAR-activating compounds do not directly interact with pathogens or pests, they cannot build up a resistance to these compounds as a result.
Having a solid understanding of pests that target your crops, and the basics of insect resistance can help minimize potential risks and maintain the efficiency of biopesticides as an effective part of an IPM system. As usual, biopesticides should be used sparingly and growers should rely on other aspects of their IPM system such as utilizing sticky traps, maintaining the cleanliness of their grow, and maintaining the cleanliness of individuals who may enter the cultivation center. Keep in mind that it is ideal for your cannabis plants to begin flowering in a healthy condition to minimize any foliar applications during the early flower period.