- 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.
- Author: Ben Faber
It's been quiet for awhile, just odd winter weather and fire and ash and hot hot heat andsuddenly we see a beautiful insect we haven't seen in a while. Jarrell Larmon is a PCA who was nosing around in a Satsuma orchard and he turned up a Barnacle Scale, the likes we havent seen in about 4 years. Pretty little thing. Last time it came under pretty good biological control in no time.
This is the image from USDA
Jane Delahoyde,
a PCA here in Ventura, recently found an unusual scale in lemon here. It is barnacle scale with a typically long Latin name - Ceroplastes cirripediformis. It is unlikely to be any worse than other scales, but it's something to keep our eyes on. This is one of the soft scales, often called wax scales because of the wax they produce. It turns out that this has been described as being in Southern California for years, but some years they are just more present. For more on "Wax" scales see the University of Florida site:
http://entnemdept.ufl.edu/creatures/orn/scales/florida_wax_scale.htm
or our UC IPM website
http://ucipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html
And this is the scale that Jane found.
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