Biological Pest Control Examples With Sourced Numbers

Biological pest control means using living natural enemies, such as lady beetles, parasitic wasps and disease-causing microbes, to hold pests below damaging levels. Good examples include imported vedalia beetles against cottony cushion scale, Trichogramma wasps against moth eggs, and Bt sprays against caterpillars. Results vary a lot by crop, pest and weather, so this guide gives examples with field numbers from university and government sources, and a calculator to compare a release program with spraying.

The seven examples below start with predators, parasitoids and pathogens, then the three ways of using natural enemies (conservation, classical and augmentative), and finally competing microbes. Most have a “best for” line and a “watch out” line, because several popular claims online are too strong for what the research shows.

Biological pest control examples at a glance

The table sums up the seven examples. The “evidence” column gives what a named source says, not a general success rate. No single percentage fits all of them.

How we chose and checked these examples

We picked examples that a grower can actually buy or do, and that a university, government or journal source describes with numbers. Where a source gave only a lab result, a foreign figure or an undated total, we say so.

Natural enemies are not a drop-in replacement for a spray. Many work slowly and need pests to be present as food. Many chemicals also harm them, so check the product label and local rules before mixing the two, and get advice from your extension service or a licensed advisor.

1. Lady beetles and lacewings (predators)

Predators eat pests directly. Lady beetles, lacewings and hover fly larvae eat aphids, and the University of California’s pest guide lists these among the common natural enemies of aphids, along with parasitic wasps that leave round, discoloured “mummies”.

Often a fit for: gardens, greenhouses and small plantings where you can release often. Watch out: purchased convergent lady beetles are collected from overwintering sites and tend to leave. UC IPM says most fly away within 1 or 2 days of release even when aphids are plentiful, although each adult can eat about 100 aphids a day before it goes. It gives about 1,500 beetles per rose shrub, repeated every 1 to 2 weeks, as the rate for aphids on roses. UC IPM also calls resident lady beetles important predators.

Iowa State University extension says that in soybean, natural enemies can be very effective in Iowa, and it advises spraying only when counts reach its threshold of 250 aphids per plant on average, with at least 80% of plants infested and numbers rising. Counting before you spray gives predators time to work.

▶ Farmonaut video on soybean aphid scouting and control strategies. · 22:28

2. Trichogramma and Aphidius wasps (parasitoids)

Parasitoids lay eggs in or on a pest, and their young kill it. Trichogramma wasps are tiny and attack moth eggs, so the caterpillar never hatches. Aphidius wasps lay eggs inside aphids.

Often a fit for: crops with a known moth pest and a program that releases on a schedule. The largest sourced area figure we found is from Brazil. A 2019 review in the Journal of Insect Science by Parra and Coelho reports about 2 million hectares of sugarcane treated with Trichogramma galloi in the 2018 growing season, and about 3.5 million hectares with the parasitoid Cotesia flavipes (no year given). The chart further down compares these.

Watch out: results depend on the crop. UC IPM says that for codling moth in apples, releases of Trichogramma platneri showed limited effectiveness and are too expensive for practical use in California. A parasitoid that works on sugarcane borers does not automatically work in an orchard.

3. Bt, fungi and nematodes (pathogens)

Bacillus thuringiensis (Bt) is a bacterium. Different strains target different groups: the kurstaki and aizawai strains target moth and butterfly caterpillars, israelensis targets mosquito and fly larvae, and tenebrionis targets some beetle larvae. The National Pesticide Information Center at Oregon State University notes the US EPA has registered Bt as a pesticide since 1961, and that some Bt products are approved for organic farming.

Often a fit for: caterpillar outbreaks where you want to spare beneficial insects. NPIC reports that studies found little to no direct toxicity to lacewings, predatory beetles or parasitic wasps, though a few studies found harm to non-target moths. Watch out: Bt does not last. On leaves its typical half-life is 1 to 4 days, so timing matters, and a spray must be eaten by young larvae to work. Bt products are still pesticides: follow the label, because some have caused eye and skin irritation.

Fungi and nematodes work on the same idea. In Brazil, the fungus Metarhizium anisopliae is reported on about 2 million hectares of sugarcane against froghoppers (Parra and Coelho, 2019, no year given for the area). We found no comparable area figures for beneficial nematodes in the sources we opened.

4. Flowering strips and hedgerows (conservation)

Conservation control changes the farm so that the natural enemies already there survive and breed. The practical steps are to keep nectar plants near fields, avoid broad-spectrum sprays when you can, and leave some refuge. UC IPM advises growers to plant flowering plants that provide nectar and pollen and avoid insecticides that are toxic to natural enemies.

Often a fit for: any farm, as a slow investment. Watch out: it takes seasons, not days, and gives no guarantee against a heavy outbreak. The cost of a strip is mostly land taken out of crop, which you can enter in the calculator below as part of the program cost.

Resident enemies can do real work without any purchase. In coastal California avocado, UC IPM reports that the egg parasitoid Megaphragma mymaripenne often kills about 25 to 50% of greenhouse thrips eggs, and that broad-spectrum pesticides often lead to outbreaks of caterpillars and mites. So the first conservation step is simple: do not spray what you do not need to spray, and see which enemies you already have. Walk the field, turn leaves over, and look for eggs with a round exit hole, mummies and larvae of lady beetles. Photograph what you find and send it to your extension office if you cannot identify it.

▶ Farmonaut video on organic vineyard protection against leafhoppers with integrated pest management. · 6:35

5. Imported natural enemies (classical control)

Classical control brings a pest’s natural enemy from its home region to a place where the pest arrived without enemies. The textbook case is the vedalia beetle. UC IPM records that it was introduced from Australia in the early 1890s and, with a parasitic fly, now controls cottony cushion scale on citrus.

Watch out: success can be undone. The same page says infestations return in the San Joaquin Valley when pyrethroids, neonicotinoids and insect growth regulators temporarily destroy the natural enemies.

A newer case is the emerald ash borer, an invasive beetle that kills ash trees in North America. A 2016 EPPO report lists four parasitoid wasps approved for release in the US and says that, as of February 2016, more than 3 million had been reared and released in 22 US states and two Canadian provinces. The percentages it gives are parasitism found in the wasps’ native range (China and Russia), not results on North American trees. EPPO also says Spathius agrili has not been able to establish in northern US states, so a high native-range figure does not mean success in North America. Treat the chart below as a sign of promise, not a prediction.

6. Timed releases of reared insects (augmentative)

Augmentative control means releasing mass-reared natural enemies when pests rise. In a 2012 review in BioControl, J.C. van Lenteren reports that 230 species of natural enemies are commercially available, yet the method is applied on a frustratingly small area.

Often a fit for: greenhouses, high-value crops and pests that you can see early. A real example of a release rate: UC IPM recommends about 500 mealybug destroyer beetles per acre in California citrus in spring where mealybugs have been a problem. It also says the species is tropical, overwinters poorly in California, and that supply can be limited. Order early, and ask the supplier for the species, number and release dates.

7. Competing microbes in the soil

The idea is that helpful fungi or bacteria use up space and food that a pest or pathogen needs. We found no area or yield figures for it in the university and government sources we opened, so we do not give a success rate. If a product claims one, ask for trial data from your crop and region.

Where biological control is used at scale

The 2019 review gives area figures for several agents in Brazil, taken from the industry association ABCBio (personal communication). The chart shows those figures. They come from different years and some have no year, so compare them as rough sizes, not as a ranking of effectiveness.

Chart

Area treated with natural enemies in Brazil

Million hectares, selected agents, as reported in a 2019 review (years differ)

Parasitoid wasps against emerald ash borer

The chart shows the highest parasitism reported in each wasp’s native range. These are results from studies in China and Russia as summarised by EPPO in 2016. The US program was still establishing the wasps at that time.

Chart

Highest parasitism reported in the native range

Percent of eggs or larvae parasitised, China or Russia, as summarised in 2016

How long do Bt sprays last?

Timing is the main limit for pathogens. The chart shows the ranges NPIC reports, so you can see why repeat applications and good scouting matter.

Chart

How long Bt lasts

Half-life in days; foliage is the typical range; soil is toxins, low end stated as under 1 day (shown as 1), and some toxin can stay up to six months

Is a release program cheaper than spraying?

Costs differ more between farms than the effect of any one agent. Use this calculator with your own numbers: a quote for the natural enemies, your product price and your cost to apply. It compares program cost only. It does not value crop loss, which is the real test, so keep records of pest counts and yield for both options.

Try the numbers for your own farm below.

How to read claims about biological control

Three questions help you judge any claim you read, including ours. First, what is the basis? A figure may be area treated, share of pests killed in a lab dish, or share of eggs parasitised in one orchard, and these are not the same. Second, what is the year and place? The Brazil figures above come from a 2019 review and some have no year, while the ash borer figures are from 2016 and from the wasps’ home range. Third, who gains from the claim? Treat any success rate with no named study as a sales line. A range such as “50-95% control” is too broad to trust, because the result changes with pest density, weather, crop stage and the sprays used before and after the release.

A fair on-farm test is easy to run. Leave one strip untreated or treated the usual way, release or spray the rest, and count pests on the same plants every week. If you do it for two seasons you will know more about your own fields than any average can tell you.

How to choose the right option

1. Identify the pest. A wrong ID means the wrong agent. Send a sample to your extension service if unsure.
2. Count it. Use a published threshold, such as Iowa State’s soybean aphid threshold above, before you spray or release.
3. Check what is already there. Look for lady beetles, lacewings, mummies and fungus-killed aphids.
4. Match the agent to the crop and climate. The mealybug destroyer does poorly in cold, and the codling moth case shows a wasp can fail on one crop.
5. Protect what you release. Ask the supplier which sprays are safe, and read the label of any pesticide.
6. Keep a record and compare with an untreated or sprayed strip.

Pesticide labels carry legal limits: follow the product label and local rules, and get advice from a licensed advisor before combining products.

Using satellite images to time scouting

Satellites do not see an aphid or a wasp. They show changes in plant greenness over a field, which can tell you where to walk first. Farmonaut Satellite + AI Farm Monitoring System offers this through its web app, its Android app and an API for developers; see also the app download page. Use the images to choose scouting spots, then confirm the pest on the leaf before you release or spray.

▶ Farmonaut video asking whether AI pest detection can work in smart farming. · 6:32

Limits and risks

• Slow action: parasitoids and predators need days or weeks, so a fast-rising pest may still need a spray.
• Cost: the codling moth example shows a release can be too expensive for practical use.
• Non-target effects: introduced species must be reviewed by regulators. Never release a species not approved in your region.
• Pesticide conflicts: broad-spectrum sprays can wipe out the enemies you paid for, as the cottony cushion scale example shows.
• Evidence gaps: area totals from the sources above differ by year and basis, and several are undated.

FAQ

What are the main examples of biological pest control?

Predators such as lady beetles, parasitoid wasps such as Trichogramma, microbes such as Bt, protecting resident enemies with flowering strips, importing enemies of invasive pests, and releasing reared insects at the right time.

Does biological control work as well as pesticides?

It depends on the pest, crop and timing. Some programs work well, such as vedalia beetles on cottony cushion scale, and others do not, such as Trichogramma releases against codling moth in California apples (UC IPM).

Are bought lady beetles worth it?

Often not, if you hope they will stay. UC IPM says most bought convergent lady beetles fly away within 1 or 2 days of release, and calls resident lady beetles important predators.

Is Bt safe for organic farms?

Some Bt products are approved for organic farming, according to NPIC. Approval depends on the product and your certifier, so check the label and the certifier’s list first.

Can I use satellite data for pest control?

Satellites show where a crop looks different. They cannot name the pest. Use them to decide where to scout, then confirm by looking at the plants.

Related pages on our site: alternative pest control methods, Farmonaut crop loan and insurance page, Farmonaut product traceability page, Farmonaut carbon footprinting page and Farmonaut weather API documentation.