- Author: Ben Faber
Biological control is the management of pests and their damage by the beneficial action of parasites (parasitoids), pathogens, and predators. These beneficial organisms, collectively, are named natural enemies.
Conserving (or protecting) and releasing natural enemies are important components of integrated pest management (IPM). In most situations, employing practices that conserve natural enemies is more effective, and less expensive and time consuming, than purchasing and releasing them.
Learn about the specific situations where purchasing and releasing parasites and predators can increase the effectiveness of biological control. Before purchasing natural enemies, consult the University of California (UC) IPM Pest Management Guidelines for that crop to learn whether UC research has shown that releasing them is effective. Some natural enemies on the market have never been demonstrated to effectively control any agricultural pest in California.
Obtaining Natural Enemies
Natural enemies can be purchased directly from various producers (companies that rear them) and suppliers (companies that purchase from producers and repackage and resell them). Some sources of parasites and predators are members of the Association of Natural Biocontrol Producers (ANBP). All ANBP members formally agree to a code of ethics and standardized methods.
Natural enemies purchased by users are commonly delivered via shipping services. Purchase parasites and predators only from in-state providers. It is illegal to obtain insects and other arthropods outside of California and carry or have them shipped across state lines without a permit from agricultural officials. Some pest control advisers and pest scouts will procure and release natural enemies as a service for growers.
Methods for Releasing Natural Enemies
Two methods for releasing natural enemies are inoculation and inundation:
- Inoculation—relatively few natural enemies are released. The offspring of these natural enemies provide biological control, not the individuals released.
- Inundation—large numbers of natural enemies are released, often several times over a growing season. The natural enemies released, and possibly their offspring, provide biological control.
The mealybug destroyer is an example of a natural enemy that is only released through inoculation—at relatively low numbers once per year early in the growing season. Aphytis melinus and Trichogramma parasites are released by inundation—at regular intervals over the growing season—to control California red scale and eggs of pest moths, respectively. Both inoculation and inundation can be used with predatory mites, depending on the situation.
Releasing Natural Enemies Effectively
Releasing natural enemies is most likely to be effective in situations where: 1) University of California researchers or other pest management experts have previously demonstrated success and 2) some level of pests and their damage can be tolerated in that crop. Desperate situations are not good opportunities for releasing natural enemies. Pests or their damage may already be too widespread for any release of parasites or predators to prevent economic loss of crop quality or quantity.
Increase the likelihood that natural enemy releases will be effective by
- Accurately identifying the pest and its natural enemies.
- Learning about the biology of the pest and its natural enemies.
- Releasing the appropriate natural enemy life stage and species.
- Releasing when the pests' vulnerable life stage(s) are present and at numbers that can be controlled by natural enemy releases.
Natural enemies are unlikely to be effective when released as if you were applying a pesticide. Instead, anticipate pest problems and begin making releases before pests are too abundant or economic damage is imminent.
- Remember that natural enemies are living organisms that require food, shelter, and water. Protect them from extreme conditions. For example, release them at night or early in the day during hot weather.
- Avoid applying broad-spectrum, residual (persistent) insecticides and miticides, and in some situations certain systemic or other pesticides, before or after releasing natural enemies. When needed, use pesticides selectively. For example, spot spray only where pests are abundant but localized.
Common reasons for the lack of satisfactory biological control after releases include the
- Application of broad-spectrum, residual insecticides, or in some situations systemic or other pesticides, prior to or after a release.
- Incorrect timing of release.
- Release of the wrong natural enemy for the pest situation.
- Release of a natural enemy species that is known to be ineffective.
For information on the use of biological control, see the UC IPM Pest Management Guidelines for your crop and specific pests. Most crops have a table called “Relative Toxicities of Insecticides and Miticides to Natural Enemies and Honey Bees” in the “General Information” section. Use these resources to guide pesticide selection to conserve natural enemies and improve biological pest control.
More Information
- Association of Natural Biocontrol Producers, Clovis, CA
- Grower Guide: Quality Assurance of Biocontrol Products (pdf), Vineland Research and Innovation Centre, Ontario
- Insectary Plants
- Natural Enemies Gallery
- Natural Enemies Handbook: The Illustrated Guide to Biological Pest Control
- Protecting Natural Enemies and Pollinators
- UC IPM Pest Management Guidelines
this is a repost from:
Photo: Adult Aphytis melinus parasite laying her egg in California red scale, Aonidiella aurantii. Releases are most effective when ants are controlled, dust is minimized, and broad spectrum pesticide applications are avoided. Credit: Jack Kelly Clark, UC IPM Program
/h2>/h2>/h2>/h2>- Author: Ben Faber
It seems the humble earwig that can cause so much damage in citrus orchards in some years on some small trees can be a great boon in biocontrol. Read on:
WSU scientists unmask the humble earwig as an apple-protecting predator
By Seth Truscott,
College of Agricultural, Human, and Natural Resource Sciences
https://news.wsu.edu/2019/06/05/wsu-scientists-unmask-humble-earwig-apple-protecting-predator/
Helping Northwest apple growers protect their crops, WSU scientists have found new proof that earwigs are actually valuable predators in apple orchards, rather than the creepy, crawly, apple‑damaging pests they're sometimes assumed to be.
In the May 2019 edition of the journal Biological Control, Robert Orpet, recent doctoral graduate at Washington State University's Tree Fruit Research and Extension Center, details findings from his multi‑year effort to shed light on the European earwig and its role in combating a costly orchard pest.
“Earwigs will eat just about anything, but we've found that aphid pests are high on their menu,” Orpet said. “By dining on pests and reducing growers' need to spray insecticides, earwigs are unappreciated predators that have important benefits for agriculture.”
Shy, invasive omnivore
An invader in U.S. orchards and gardens, the European earwig was first found in Seattle in 1907, spreading across the continent soon after. With their wriggly bodies and scary‑looking tail pincers, earwigs have always suffered from a bad reputation.
“Apple pickers don't like them, because they have a tendency to hide in apple clusters,” Orpet said. “Farmers often find them inside damaged fruit, and since earwigs feed mostly at night, it's hard to see what they feed on. “Some growers wonder if they cause damage themselves.”
Scientists like Orpet, however, have long suspected that earwigs are an important predator of aphid pests.
Apple trees covered in “snow”
Orpet came to the earwig through his research into the woolly apple aphid, a costly pest of Washington's $2.4 billion apple industry.
Gaining its name from their coat of cottony fibers, woolly apple aphids feed on the roots and branches of apple trees, stealing nutrients and water and causing galls, or abnormal growths. Infestations can decrease tree growth and keep fruit from developing, while the aphid's sticky honeydew secretions can bring on fungal infections.
About the size of a sesame seed, woolly apple aphids can amass in fluffy, meter‑long colonies.
“In bad years, infestations make apple trees look like they're covered in snow,” Orpet said. “That's when growers really take notice.”
Growers have difficulty managing woolly aphids with insecticides, because there are few effective insecticides, and no organic ones, currently available. Well‑known predators like ladybugs and lacewings could take a bite out of the woolly aphid population, but Orpet wanted to know if the earwig makes a difference.
Working with Jessica Goldberger, an agricultural sociologist at WSU's Department of Crop and Soil Sciences, Orpet interviewed 15 orchardists and managers in Washington state, gauging their opinions on the insect's role.
Most growers weren't sure whether earwigs make a real difference for their crops, and some thought of them as minor pests.
At the same time, Orpet was learning what earwigs are really up to in Washington orchards. Working with managers at four different commercial orchards, Orpet set about catching earwigs with cardboard traps.
Aphids: Earwigs' favorite food
Active at night, earwigs hide by day in tight spaces. Corrugated cardboard sheets are a perfect shelter, so he could easily shake them out and count them.
Sectioning off orchards, Orpet removed earwigs in some places, adding them at others. In every site, he counted woolly aphid colonies and checked for fruit damage.
“There was an obvious difference,” Orpet said. “There were fewer aphid colonies in places where I released earwigs.” He found no evidence that earwigs were causing damage themselves, but captured video footage of earwigs eating aphids and destroying their colonies.
Orpet also inspected the contents of trapped earwigs' digestive systems to see what they actually eat. He found that earwigs regularly dine on aphids, even when local aphid populations are small.
“Our results show that earwigs aren't pests, and actually improve biological control,” Orpet said. “Some farmers spray chemicals to knock down their populations, but this research shows they don't have to, and probably shouldn't.
“Growers can reduce pesticide use, save on chemicals and labor, and leave this misunderstood predator to do its beneficial work, protecting their apples from aphids,” he added.
Along with Orpet and Goldberger, co‑authors include WSU entomology professors David Crowder and Vince Jones.
Their research was funded by the Washington Tree Fruit Research Commission, USDA's National Institute of Food and Agriculture, and the Western Sustainable Agriculture Research and Education Program.
Media contact:
- Robert Orpet, doctoral graduate, Department of Entomology, 847‑337‑4480, robert.orpet@wsu.edu
- Author: Ben Faber
If you hang around an orchard long enough something unusual will show up, especially when seasons change and there's more rain than usual and it's cold, but not so cold that it freezes and it's prolonged. So out of San Diego comes a request for an identification of a brown bump on avocado stems. It's a brown aphid. Is it something of concern? Likely not. Over the years there have been reports of several aphids on avocado. Check out Walter Ebeling's "Subtropical Fruit Pests" at Avocadosource.com:
http://www.avocadosource.com/papers/research_articles/ebelingwalter1959b.pdf
These things come and go, and they don't do any damage because once the biocontrol bugs get going, they are fresh meat for them.
- Author: Ben Faber
A local Ojai grower asks why there seems to be more citrus thrips damage to 'Pixie' mandarins this year. Was it because of the extended bloom due to warmer spring last year? The hotter summer up there that was more similar to climate in the Central Valley? Was it due to the Area-Wide Spraying for Asian Citrus Psyllid - ACP? Or is this a remnant of the Thomas Fire that dumped ash all over the county, disrupting biocontrol agents like lady bird beetles?
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26095
And what else does fire do to citrus?
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=28315
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26510
This is classic thrips damage. In this area, it is not usually a problem. This year it seems to be more common. It's not always clear what is the main cause of and what all the interactions are that lead up to an outbreak like this. Just that there is damage now that occurred 10 months ago.
- Author: Ben Faber
When a biocontrol agent turns on you, it can be painful. Recently a grower called in asking about an insect that had bit him when he picked it up. It caused a fearsome pain and some swelling. This insect is an assassin bug, one of the numerous predators out there that help keep pest insects in control.
Assassin bugs (family Reduviidae) belong to the order Hemiptera and the suborder Heteroptera, the so called “true bugs.” Altogether, nearly 7,000 species of assassin bugs have been described worldwide, of which about 50 are native to California. All Hemiptera have tubular mouthparts with stylets that help them pierce tissues of plants and other creatures. The stylets may also help them suck blood. Indeed, 140 species of assassin bugs are specialized to feed on blood. Spreaders of Chagas disease, these are the kissing bugs, so named because they frequently bite people on the face around the mouth.
Within insects, they are one of the third biggest groups of predators that mostly feed on other insects. This determines where they are found: many species sit on flowers or leafs, where they stalk or ambush their prey. Others like to hide in special microhabitats, for example, underneath the bark of trees, and feed on insects – such as certain beetle and fly larvae – that live under the bark.
In general, the greatest numbers of assassin bugs are found in wet tropical places around the world, but some also live in subtropical, arid and even temperate places. About 50 species are native to California and the majority of them also occur in Southern California. In California, you can find different species of these bugs from the low deserts to fairly high elevations in the Sierras. Altogether, we have fewer than 190 species recorded from the United States and Canada, but as you get into Central and South America, diversity increases and the species numbers go up.
A common species in California is the leafhopper assassin bug that is frequently found even in backyards around Riverside. It is widely distributed from Canada to Central America. Although it is native to this region, it has been introduced and become established in Chile, Greece and Spain. Leafhopper assassin bugs hang out on various plants and are beneficial – as are many other assassin bugs – because they eat pests that can be a nuisance to crops and ornamental plants.
The smallest are about 3 millimeters long. The largest can be about 1.5 inches in length. As other true bugs, assassin bugs have “divided” wings, meaning that the forewings have a thick leathery texture close to the head and a more membranous structure further back. Assassin bugs can be recognized by the shape of the beak that is typically curved and pretty thick and has three segments. The bug uses this beak to grab and hold on to its prey. There is no need to panic when you see an assassin bug, but since they can inflict rather painful bites it is best not to touch them. Kissing bugs are somewhat unusual amongst assassin bugs in having a fairly slender and straight beak. Although their bite is painless in contrast to the bite of other assassin bugs, they are much more dangerous: their saliva can cause allergic reactions, and they can also spread Chagas disease.
The protozoan that causes Chagas disease, Trypanosoma cruzi, is not transmitted when the kissing bug bites you and sucks your blood. Instead, it is transmitted soon after the kissing bug has stopped feeding blood. When a kissing bug bites you, you don't feel anything at first because the bug injects an anesthetic and the bite will only get itchy shortly thereafter. Now, after its blood meal, the kissing bug defecates. The feces contain the Chagas-disease-causing protozoans. When you scratch, you get the feces into the wound and your blood stream. We have three species of endemic kissing bugs in California. Many of the specimens of our commonest species are to be found in Southern California; about 20-35 percent according to one of our studies, are infected with the protozoan and could serve as carriers. Typically, our native kissing bugs blood-feed on woodrats, but will also try to feed on other vertebrates, given the opportunity. In addition, dogs that sleep outdoors could also get infected with Chagas disease by eating the kissing bugs.
Persons who are bitten should wash and apply antiseptic to the site of the bite. Oral analgesics, such as aspirin or ibuprofen, may be useful to reduce the pain. Treatment by a physician is not usually needed, though Caladryl® or topical corticosteroids may help reduce swelling or itching at the site of the bite. As with any insect sting or bite, the victim should seek medical attention immediately if there is any sign of anaphylactic reaction, such as generalized swelling, itching, hives or difficulty breathing.