Autumn Pest Prevention Science: What Beneficial Insects Live in the Field? Not All Insects Are Pests

In pristine forests, the vegetation is lush and the variety of insects is great, yet it is rare to see any single pest species in large numbers, let alone running rampant and causing disaster. The reason is that in such an environment, although there are many kinds of insects, they are also divided into camps, struggling against one another while depending on and restraining one another, forming a relatively balanced state. Today, the editor will introduce a few natural enemies of pests, so that when you see them in daily life you will not mistakenly harm the “friendly forces.”

I. About Natural Enemy Insects

Pest damage is a major hidden danger to the healthy growth of crops, mainly manifesting as gnawing on plant organs, spreading viruses, creating favorable conditions for the invasion of diseases, and so on.

But among crop pests, the insects that are truly extremely harmful, cause economic losses year after year, and require frequent control are actually not many, accounting for only 1% of the total number of insect species. In fact, every pest has several, even dozens or hundreds, of natural enemies keeping it in check. For example, the rice planthopper and leafhopper have more than 200 kinds of natural enemies, which fully demonstrates the abundance of natural enemy insect resources in nature.

II. Main Types of Natural Enemy Insects

The types of natural enemy insects are mainly classified according to their pest-killing methods, and can be divided into predatory natural enemies and parasitic natural enemies.

1. Predatory natural enemies

There are many kinds of predatory natural enemies. The most common include dragonflies, mantises, assassin bugs, spiny assassin bugs, flower bugs, green lacewings, ladybugs, ground beetles, robber flies, hoverflies, hornets, mud daubers, spiders, and predatory mites.

These natural enemies generally have a very large prey intake. During their growth and development, they may need to feed on several, dozens, or even thousands of insect bodies before completing their growth and development. According to their feeding method, they can also be divided into chewing and piercing-sucking types. A few are briefly introduced below:

01. Mantis: can prey on more than 40 kinds of pests, such as flies, mosquitoes, locusts, moths and butterflies and their larvae and exposed pupae, crickets and other small insects, as well as cicadas, migratory locusts, katydids and other large insects.

02. Predatory ladybugs: prey on aphids, scale insects, whiteflies, spider mites, and so on on plants.

03. Predatory mites: their range is very broad, including the families Tetranychidae, Anystidae, Trombidiidae, Stigmaeidae, and the superfamily Phytoseioidea. They are omnivorous beneficial mites that mainly feed on plant leaf mites such as red spiders and rust mites.

04. Green lacewings: can prey on many kinds of pests. Such as whiteflies, red spiders, and various aphids. In addition, they also like to eat the eggs of many kinds of pests, such as those of cotton bollworm, cutworm, silver Y moth, angoumois grain moth, and cotton semi-looper, all within their food range.

05. True bugs: bugs of the families Anthocoridae, Miridae, and Nabidae can prey on leafhoppers, planthoppers, aphids, thrips, cotton spider mites, cotton bollworm eggs, and other pests.

06. Hoverflies: the larvae mainly prey on aphids and are effective natural enemies of aphids, scale insects, whiteflies, leafhoppers, thrips, small lepidopteran larvae, and other pests.

2. Parasitic natural enemies

Parasitic natural enemies are insects that parasitize the bodies of pests, feeding on the pest's body fluids or internal organs. They are mainly represented by parasitic wasps and parasitic flies.

01. Trichogramma wasps: egg parasitoid wasps that can parasitize the eggs of many lepidopteran pests such as the Asian corn borer, armyworm, sugarcane borer, cotton bollworm, tobacco cutworm, and cutworm.

02. Braconid wasps: parasitize the larvae of many kinds of moths and butterflies, playing a certain role in controlling their population numbers.

03. Parasitic flies: the larvae of most lepidopteran and sawfly insects can be parasitized; in addition, longhorn beetles and carpenter moth larvae living inside plant stems, scarab larvae living in the soil, and adult beetles and stink bugs can all be parasitized within their bodies.

III. Utilization of Natural Enemy Insects

1. Recognition

To use natural enemy insects for biological control, excellent natural enemies must be selected, that is, dominant species that play a relatively large role in a region or community should be chosen.

The conditions that excellent natural enemies must possess are: strong ability to find hosts; matching or closely coordinating with the host's life history, number of generations, and host population; strong dispersal ability; strong adaptability to the environment; strong selectivity toward hosts; and ease of mass rearing, and so on.

2. Protection

After pests have lived in a region for a long time, certain kinds and numbers of natural enemies are bound to accompany them. However, due to the limitations of various living conditions, the number of natural enemies is often insufficient to reach the level of controlling pest damage. At this time, appropriate measures can be taken, such as protecting natural enemies to overwinter safely; rationally using chemical pesticides; avoiding harming natural enemies; and promoting the reproduction of natural enemies to control the occurrence and damage of pests.

3. Release

Natural enemy insects in nature and their hosts or the host insects they prey on often occur one after the other. Not only is their occurrence time lagging behind, but their numbers are also far lower than those of the pests. At this time, one can consider artificial rearing or directly purchasing the corresponding products, and releasing them into the field when pests first appear to control the pests.

The field contains not only pests but also beneficial insects. When preventing pest damage, remember to distinguish the good from the bad.