Predators kill and feed on several to many individual prey during their lifetimes. Many species of amphibians, birds, mammals, and reptiles prey extensively on insects.
Predatory beetles, flies, lacewings, true bugs (Order Hemiptera), and wasps feed on various pest insects or mites. Most spiders feed entirely on insects.
Predatory mites that feed primarily on pest spider mites include Amblyseius spp., Neoseiulus spp., and the western predatory mite, Galendromus occidentalis.
Natural enemy pathogens are microorganisms including certain bacteria, fungi, nematodes, protozoa, and viruses that can infect and kill the host.
Populations of some aphids, caterpillars, mites, and other invertebrates are sometimes drastically reduced by naturally occurring pathogens, usually under conditions such as prolonged high humidity or dense pest populations.
In addition to a naturally occurring disease outbreak (epizootic), some beneficial pathogens are commercially available as biological or microbial pesticides.
These include Bacillus thuringiensis or Bt, entomopathogenic nematodes, and granulosis viruses.
A parasite is an organism that lives and feeds in or on a host. Insect parasites can develop on the inside or outside of the host’s body. Often only the immature stage of the parasite feeds on the host. However, adult females of certain parasites (such as many wasps that attack scales and whiteflies) feed on and kill their hosts, providing an easily overlooked but important source of biological control in addition to the host mortality caused by parasitism.
Although the term “parasite” is used here, true parasites (e.g., fleas and ticks) do not typically kill their hosts. Species useful in biological control, and discussed here, kill their hosts; they are more precisely called “parasitoids.”
Most parasitic insects are either flies (Order Diptera) or wasps (Order Hymenoptera). Parasitic wasps occur in over three dozen Hymenoptera families. For example, Aphidiinae (a subfamily of Braconidae) attack aphids. Trichogrammatidae parasitize insect eggs. Aphelinidae, Encyrtidae, Eulophidae, and Ichneumonidae are other groups that parasitize insect pests. It’s important to note that these tiny to medium-sized wasps are incapable of stinging people. The most common parasitic flies are the typically hairy Tachinidae. Adult tachinids often resemble house flies. Their larvae are maggots that feed inside the host.
Biological control is the beneficial action of parasites, pathogens, and predators in managing pests and their damage.
Biocontrol provided by these living organisms, collectively called “natural enemies,” is especially important for reducing the numbers of pest insects and mites.
Use of natural enemies for biological control of rangeland and wildland weeds (e.g., Klamath weed, St. Johnswort) is also effective.
Plant pathogens, nematodes, and vertebrates also have many natural enemies, but this biological control is often harder to recognize, less well understood, and/or more difficult to manage. Conservation, augmentation, and classical biological control are tactics for harnessing natural enemies’ benefits.
Spinosad is a natural substance made by a soil bacterium that can be toxic to insects.
It is used to control a wide variety of pests. These include thrips, leafminers, spider mites, mosquitoes, ants, fruit flies and others.
Many products containing spinosad are used on crops and ornamental plants.
| Test | Applications | 1day Average control（%） | 3days Average control（%） | 7days Average control （%） | 14days Average control （%） |
| 1 | 2billion PIB/ml Mamestra Brassicae NPV SC —450ml/Ha | 72.3 | 90.7 | 98.6 | 97.9 |
| 2 | 2billion PIB/ml Mamestra Brassicae NPV SC —600ml/Ha | 74.5 | 95.9 | 100 | 100 |
| 3 | 2billion PIB/ml Mamestra Brassicae NPV SC —750ml/Ha | 75.8 | 98.4 | 100 | 100 |
| 4 | 20% Chlorantraniliprole —150ml/Ha | 33.6 | 85 | 97.6 | 96.2 |
| Test | Applications | 3days after application Average control（%） | 7days after application Average control（%） | 14days after application Average control （%） |
| 1 | 8billion spore/ml Metarhizium anisopliae OD | 37.55（±0.73）h | 51.75（±0.99)e | 77.27（±0.17)c |
| 2 | 3billion PIB/ml Mamestra Brassicae NPV SC | 84.42（±0.66）c | 82.91（±0.32)c | 76.97（±0.27)c |
| 3 | Compare (60% spinetoram SC) | 74.45（±0.93）f | 88.82（±0.58)b | 69.49（±0.62)e |
Insect viruses are unable to infect mammals, including humans, which makes them very safe to handle.
Most insect viruses are relatively specific, so the risk of non-target effects on beneficial insects is very low.
Many viruses occur naturally and may already be present in the environment.
Even in cases where they are applied, successful infections can perpetuate the disease outbreak making repeat applications within a season unnecessary.
To know insect virus of Lin chemical:
Mamestra brassicae nucleopolyhedrovirus (MabrNPV) has a wide host range, including 32 species spanning five Lepidoptera families.
Some of its targets are important pests, such as Plutella xylostella, H. armigera, S. exigua, and Xestia c-nigrum. A Mamestra brassicae nucleopolyhedrovirus (MabrNPV), originally isolated from M. brassicae larval cadavers on oilseed rape in 1979, was successfully developed as an insecticide produced in either H. armigera or S. exigua reared on an artificial diet.
For insect virus from Lin chemical:
Virus infection begins in the insect’s digestive system but spreads throughout the whole body of the host in fatal infections. The body tissues of virus-killed insects are almost completely converted into virus particles. The digestive system is among the last internal organ system to be destroyed, so the insects usually continue to feed until they die. Infected insects look normal until just prior to death, when they tend to darken in color and behave sluggishly. They often develop more slowly than uninfected individuals.
Most virus-infected insects die attached to the plant on which they feed. Virus-killed insects break open and spill virus particles into the environment. These particles can infect new insect hosts. Because of the destruction of the internal tissues, dead insects often have a “melted” appearance. The contents of a dead insect can range from milky-white to dark brown or black.
While natural virus outbreaks tend to be localized, virus particles can be spread by the movement of infected insects, the movement of predators such as other insects or birds that come into contact with infected insects, or non-biological factors like water run-off, rain-splash or air-borne soil particles. Many virus-infected insects also climb to higher positions on their host plant before they die, which maximizes the spread of virus particles after the insect dies and disintegrates.
The number of virus infection cycles within a growing season depends heavily on the insect’s life cycle. Insect pests with multiple generations per season or longer life cycles can be more heavily impacted by virus outbreaks since there is a greater opportunity for multiple virus infection cycles within a growing season.
Insect virus from Lin chemical:
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