Post by Ask Jan on Nov 28, 2011 11:19:58 GMT -8
Biocontrol uses living organisms to kill pests—it is a bug- eat- bug world. Biocontrol organisms have to be reintroduced into the unnatural (cannabis) environment. There are two types of release strategy: inoculative release and inundative release.
Inoculative release or permanent introduction happens when you release a number of insects eg. ladybeetles into your environment to kill the marauding pests eg. aphids. This method works best if there is a steady supply of pests available. This is suppose to be a long term solution to the problem. However, if the introduced insect is put into a less than ideal environment, it will not last. If the environment gets too cold in the winter, the insect cannot overwinter and dies out. Then it will have to be reintroduced each spring. This is called seasonal inoculation.
To achieve rapid pest control, a different strategy is used—inundative release. This tactic involves the repeated release of many biocontrol organisms. Inundative biocontrol uses beneficial organisms as “living pesticides.” This is an expensive tactic but appropriate for high income crops (medical marijuana). This method works best for controlling localized areas of heavy pest infestation, especially in enclosed spaces (grow rooms).
Inundative and inoculative biocontrol work best in a managed environment—uniform temperatures, and year round plant cultivation—greenhouses and grow rooms are ideal.
To work most effectively, biocontrols should be introduced before the appearance of pests, or early in the infestation. Most biocontrols reproduce faster than pests, and soon overtake the pest infestation. But if pests get a head start, crop damage occurs before the biocontrols catch up. That is why preventative biocontrols work best. Heavy populations of pests may need help (chemical control) before biocontrols can work effectively. To meet these emergencies, entomologists selected biocontrols with resistance to pesticides, so two controls can be combined.
There are several categories of biocontrols: predators, parasitoids, microbial pesticides, companion plants, trap crops and autocidal controls. Some of the catagories can be combined. Example, to control whiteflies you can combine a parasitoid wasp with a predatory beetle.
Biocontrols work as a ratio of biocontrol organisms to pest organisms. How heavy the infestation is of little consequence. Effective inundative biocontrol is at a ratio of 2:1 (adult parasitoids: adult pests). For predators, the optimal predator-to-pest ratio is 1:2 (reversed).
Some biocontrols come naturally, and others have to be purchased.
By definition, a predator must consume more than one pest before reaching its adult stage. Predators have either chewing mouthparts (ladybeetle) or piercing, sucking mouthparts (lacewing larvae, assassin bugs). Piercing, sucking predators suck the fluids out of pests rather than eating them whole. Dead pests remain attached to plants.
Many predators are natural in outdoor crops: centipedes, spiders, predatory mites, lady beetles, ground beetles, lacewings, bees, and wasps. Some predators are general consumers. Praying mantids are well-known generalists. Unfortunately, generalists may eat other biocontrols and beneficial honeybees. A lacewing larva, even if it is surrounded by millions of baby aphids, would rather eat a fat caterpillar. This is why selective predators are the best choice.
The most popular mail order predators are mites and ladybeetles.
Some predators go dormant (diapause) when the crops begin to flower in the fall. This is triggered by a short daylight (photoperiod) and affected by temperatures. Scientists have overcome this trait in some species by selective breeding. Nondiapausing breeds are available now.
Winged predators may fly away from crops. Hopefully they leave behind their eggs which will hatch into more biocontrols. You can entice them to stay and lay their eggs by providing water and artificial honeydew (excrement) or nectar.
Parasitoids kill their prey from within. Parasitoids only consume one individual host to reach their adult stage. Adult parasitoids usually insert individual eggs into multiple hosts. The eggs hatch into larvae which eat hosts alive. Parasitoid larvae usually pupate in pest cadavers and emerge as adults then off to lay more eggs. Examples of commercial parasitoids include: Encarsia formosa, Trichogramma wasps, and braconid flies. These wasps and flies do not bite or sting, or bother people or plants. Some biocontrols are parasitoids and predators—larvae consume one pest (host), then they moult into adults which feed on many pests.
Parasitoids are more efficient at finding their prey than predators. Parasitoids aggressively hunt prey until they are gone. Many predators like to be surrounded by many prey. When their prey populations are down some, they move to another area, leaving many prey behind. Parasitoids stick around. They are very well suited for preventative control. They tend to work too slowly for large infestations.
Parasitoids are more pest specific than most predators. Some are even pest-crop specific. When they are born, they imprint the crops odor. Imprinted adults remain in that crop to search for prey and will not fly away.
In the future, “customized biocontrols” (raised on cannabis), will be available for purchase.
Containers (biocontrol in a can) of microbial pesticides (MPs) contain millions to trillions of freeze dried bacteria, viruses, protozoans, or nematodes. You mix them with water and spray onto the foliage or pour it into the soil. Some MP’s are genetically engineered organisms
MP’s rarely harm beneficials. Most MP’s must be ingested (swallowed) to kill pests. Examples are: Bacillus thuringiensis (Bt, a bacterium), and NPV (a virus). They do poorly against piercing, sucking insect pests (aphids, whiteflies, leafhoppers). Fungal MP’s are the exception. Fungi like Verticillium lecanii do not have to be ingested. They work on contact, infecting insects right through their skin. Unfortunately, most fungi need high humidity to live and that is not good for cannabis plants. Also some are infected with RNA viruses that decrease their effectiveness.
The use of MPs against other microorganisms is called antibiosis. They produce antibiotics that suppress the growth of other bacteria and fungi, and they ooze enzymes which puncture the cell walls of pathogens. Some examples: Bacillus subtilis, Pseudomonas fluorescens, and Agrobacterium radiobacter. All are commercially available.
MPs for soil application survive best if applied during a heavy rainfall or through an irrigation system. MPs can be applied to soil five different ways. MPs for foliage application often require high humidity for germination and survival. This is bad for cannabis because high humidity encourages plant pathogens like the grey mold fungus.
To spray MPs on foliage, you have to use spray carriers and/or spray adjuvants. Safe carriers include non-chlorinated water and spray oils. Spray adjuvants include spreaders (wetting agents), stickers (adhesives), extenders (UV protectants), buffers, and feeding attractants.
MPs have been added to moth pheromone traps. The moths get coated with MP spores in the traps, then they fly to the environment where they deliver the MPs to larval populations.
Epiphyte organisms are microscopic. They colonize the surface of plants, eating cell leakage. They do no harm to plants. They are used to suppress pathogens. Epiphytes do not infect pathogens or produce toxins, they just outgrow pathogens. Many pathogens depend on cell leakage for spore germination. Epiphytes consume cell leakage, so pathogens are starved of nutrients and squeezed for space. Epiphytes do not produce toxins, so they are safer than microbial pesticides.
The use of epiphyte antagonists is exacting. Cannabis may not support a rich diversity of epiphytes since it produces antifungal and antibacterial compounds (CBD and THC). Trichomes also restrict microbial growth.
Plants cannot run away from their enemies. They have evolved defence mechanisms (repellent chemicals). The chemicals produced by companion plants are powerful. Two popular companion plants are marigolds (Tagetes species) and tansy (Tanacetum vulgare). Intercrop companion plants with your regular crop to repel pests. However, some feel that the allelopathic effects of marigolds on cannabis outweigh the beneficial effects of repelling pests.
Trap plants- draw pests from neighboring crops. Some plants work by their attractiveness to pests. Example: Japanese beetle is especially attracted to Zinnia elegans (flower). An effective trap plant will attract 70-85 % of a pest population.
Decoy crops-are nonhost crops planted to control nematodes. They cause nematode eggs to germinate, but the nematodes cannot complete their life cycle on the decoy plants, so they die. Examples: marigold, sesame, castor bean, and Chrysanthemum species.
Male insects raised in captivity are sterilized with gamma radiation, then released to mate with normal females, producing infertile eggs. The biggest disadvantage of autocidal control is the lack of babies; sterile insects must be recreated each pest generation.
Biotic, Abiotic and Procedural Factors Biocontrol Center (Europe) one insect parasitizing a pest insect
1) Hemp Diseases and Pests, Management and Biological Control. J. M. McPartland, R. C. Clark, D. P. Watson