Biopesticide course notes sharing, key content summary
Introduction: I have been in contact with organic agricultural products for more than ten years, but it was only in recent years that I began producing pesticide-free products. I have always wanted to move toward organic farming, so I signed up for the Farmer Academy's "Advanced Class on Biological Pesticides and Biofertilizers." Here I would like to first share my notes on biological pesticides with all of you seniors. The content may not be much, but I hope it will be helpful to everyone; afterward I will organize my "Notes on Microbial Fertilizers and Composting." Thank you, and I welcome more exchanges.
Biological pesticides start from the concept of natural enemies and have little impact on the environment
We know that chemical pesticides such as DDT, herbicides, DBCP, PCP, mercury-based agents, chlorobenzene, parathion 55%, mevinphos 25.3%, and 90% methomyl have already caused enormous or serious impacts on our environment and our bodies, but we do not know whether other chemical pesticides have the same problems. More researchers still need to be devoted to collecting data before this can be achieved.
Even if chemical pesticides pose no immediate danger, foreign research reports show that the environmental hormones produced by chemical pesticides accumulate layer by layer through the food chain. Humans are at the top of the food chain, so infants are often exposed to the harms of environmental hormones from birth. As a new generation of farmers, we must see ourselves in the role of caretakers of the land and must recognize the following three points:
(1) Agriculture is a way of life. (2) Agriculture must rely on farmers' experience and knowledge to care for the land. (3) Do not go against nature; the resources of nature are limited.
Why promote biological pesticides? Because biological pesticides start from the concept of natural enemies, they are close to the concept of nature's natural cycles. For this reason, biological pesticides are often targeted, meaning their control targets are relatively limited, but they have three major advantages that chemical pesticides do not have:
(1) No need to consider the pre-harvest interval. (2) Minimal impact on the environment. (3) Users do not need to worry about poisoning.
Biological pesticides use natural substances, without chemical refining or further synthesis, including pesticides made from natural materials, microbial pesticides, and biochemical agents. Microbial pesticides include bacteria, fungi, algae, viruses, and protozoa. Biochemical agents include pheromones, hormones, natural plant regulators, enzymes, and so on. Currently commercialized microbial pesticide products include Bacillus thuringiensis, Bacillus subtilis, entomopathogenic fungi, Trichoderma, nuclear polyhedrosis virus, and others. They are introduced separately below:
Introductions to various microbial pesticides --
1. Bacillus thuringiensis
Under nutrient-deficient conditions, Bacillus thuringiensis differentiates into spores and protein crystals. Both must be present at the same time to be useful in application. The presence of spores can increase the activity of the crystal protein, and the protein crystal only becomes activated under alkaline conditions with a pH > 9. Therefore, Bacillus thuringiensis can only act in the highly alkaline gut of insect larvae to produce toxins, causing the gut to break down and leading to death. The human gut generally has a pH of 1-3, so there is no possibility of it acting, and it can be used with peace of mind.
Like most microbial pesticides, Bacillus thuringiensis is sensitive to sunlight, so the earliest application time should not be before 3 p.m. Cloudy days, evenings, and before typhoons are all good times to use microbial pesticides. After application, insects will feed at night and the control effect will be achieved.
Bacillus thuringiensis has no effect on adults, so when more insects are found, it must be applied again after three days. When using it, note that Bacillus thuringiensis easily suspends on the water surface, so soapnut oil emulsion or spreading oil must be added as a spreader to make the Bacillus thuringiensis distribution more dispersed. If it can be shaken while spraying, the effect is even better, so powered spraying is best, and watering application is the worst. Another characteristic of Bacillus thuringiensis is that it remains effective even after the bacteria die, because it mainly relies on activation of the protein crystal, so there is also no need to prepare a nutrient solution to culture the bacteria.
Bacillus thuringiensis must be sprayed directly on the affected area to be effective, and it must be ensured that the insects will eat it. Bacillus thuringiensis can also be mixed with roasted rice bran into granules and placed in the field to lure insects to feed. Try to spray it before the third instar larval stage. Before and during the third instar, the larvae gather together. After the third instar, the application frequency and concentration may need to be increased. Bacillus thuringiensis can be mixed with any pesticide.
Currently, Bacillus thuringiensis products mainly have two strain types:
(1) Btk E-911, Chinese name Kursaki Bacillus thuringiensis, the English or Chinese type can be found by carefully checking the packaging. It is broad-spectrum and mainly controls the small white butterfly, stem borers, diamondback moth, tussock moths, and so on. The back of the product also lists the dilution ratio for each control target. During the corn flowering period, granular formulations can be used with a pepper shaker to sprinkle directly on the male or female flowers to control the Asian corn borer.
(2) Bta ABTS-1857, Chinese name Aizawa Bacillus thuringiensis, mainly controls tobacco cutworm and other noctuid moths.
Sex pheromones come in many forms; some are hung up and some are sprayed on yellow sticky boards (image source http://flora.coa.gov.tw/view.php?id=196)