Increasing Predator Insects

Insects damage over 30% of all crops worldwide amounting to at least 220 billion dollars lost annually. Insect damaged plants allows many plant diseases a way to enter wounds, further complicating crop damage. Insects can sense when a plant is unhealthy. These plants become a preferred food source, since they feast on plants high in nitrates due to incomplete photosynthesis. Healthy plants produce full proteins which the insects cannot digest, so they avoid healthy plants. Good plant nutrition decreases insect and disease crop damage.

Another way to reduce crop damage is through predators that consume both insects and disease organisms. Most predators need food, shelter, and habitat to help these beneficial predators thrive. Small fields surrounded by natural vegetation offer refuge and extra food. Diverse crops and multispecies cover crops with small open flowers promote predators. Soils high in crop residue (mulch) and biological activity offer winter refuge and food for predators. Undisturbed soil and large chunks of residue insulate predators from cold weather. Other natural tactics might include mowing every other cover crop row or raising the mowing height to create a diversity of plant height and food sources. Minimizing the use of broad-spectrum insecticides on soybeans like neonicotinoids (Cruiser, Poncho, Gaucho) especially may help increase beneficial insect populations.

Many beneficials have several different life stages. During at least one life stage, often a source of pollen is needed to help them grow and transform into the next life stage. Pollinators or cover crops that supply nectar help increase beneficial predator populations. Promoting nectar in early spring, mid-summer, and late fall provides a constant source of pollen for beneficials to complete their life cycle. In early spring, dandelions and henbit are natural sources of pollen. In mid- summer: buckwheat, sunflower, and flowering legumes: crimson or Balansa clover, sweet clover, hairy vetch, red clover, and alfalfa are good pollen sources. In late fall: wild carrot (Queen Ann’s Lace), and goldenrod are natural sources of pollen. Marigolds and Zinnas confuse many damaging insects and are also a source of pollen.

Pollinators can also increase crop yields. Soybeans are self-pollinating but beneficial insect pollinators increased soybean pod set, resulting in higher yields. Preliminary ongoing research in Ohio shows a 10% increase in soybean yields the first year but it may take 3-5 five years to fully recover beneficial insect populations. Planting pollinator plant species in 15 to 30- foot permanent strips may be necessary, due to the problem with chemical drift. Australia has documented 10-40% soybean yield increases and up to 50% in Brazil. Keeping soils undisturbed, having adequate above ground crop residue, promoting pollinating plants, and creating crop diversity are all sound soil health principles that promote many beneficial insect species.

Dr. Dwayne Beck in South Dakota proved that using long-term no-till (stable environment) with pollinating cover crops (critical food source) to help increase natural predators. For ten years, no insecticides were applied to corn in an area infested by corn root worm. When South Dakota entomologist investigated, they found that Dr. Becks fields had almost zero corn rootworm damage because these corn fields had an estimated 1 billion insect predators per acre. Corn root worms are not a preferred food source (they taste yukky), but apparently, when beneficial insect predators get hungry, they will eat anything! High populations of natural predators can greatly reduce damaging insects and crop diseases.

There are numerous beneficials that can help reduce crop damage. Some are extremely tiny and almost unseen, attacking soft bodied insect larva. These include 5,500 species of flies (Diptera) and Hymenoptera species including 4,000 species of wasps, 4,000 tiny bees, 3,800 true bugs (Lady bugs) and almost 1,000 ants. Assassin bugs are great predators in this last group. Some larger predators include 3,000 spiders (Arachnids), 91,000 species beetles(Order:Coleoptera), and earwigs (Dermaptera). Beneficials predators include soldier beetles, lightning bugs, and ground beetles. Soldier beetles are good pollinators and eat many aphids. Lightning bugs live over 18 months in the soil, consuming many soft bodied larva and grubs. Ground beetles (Carabidae) only lay 10-20 eggs per year but consume many damaging insects and weed seed, so when their population declines, it can take several years to recover.

Many beneficial predators are killed off when broad-spectrum insecticides are over used. It may take 3-5 years for beneficial predator insect populations to recover once their habitat and population have been destroyed. Insect resistance becomes a problem as harmful insects adapt to the chemicals and insecticides. Insecticides may also be harmful to human health. Beneficial insects also pollinate USA agricultural crops worth an estimated $5 billion dollars per year. Healthy predator insect populations are beneficial to healthy crops.