The elm leaf beetles and their larvae don't want to hold your hand--unless perhaps you're holding a elm leaf that they can eat.
A recent walk down the 200 block of Buck Avenue, Vacaville, California, revealed the damage this pest does. The stately canopied elms don't look so stately, what with the dry skeletonized leaves, the browning and the dieback.
And if you look closer, you'll see the leaves--the feeding site--dropping prematurely, and beetles and their larvae falling with them.
Infestations of these beetles can defoliate large elm trees, according to the UC Integrated Statewide Management Program's Pest Note on this pest, Xanthogaleruca (=Pyrrhalta) luteola.
Have you ever seen them? They're about 1/4 inch long, yellow to olive-green with a black stripe on each side and four black spots near the head. They are an invasive species from southern Europe, introduced here in the 1800s, and considered the most serious elm defoliator in the United States.
"Females lay yellowish eggs in double rows of about 5 to 25 on the underside of leaves," according to UC IPM. "Eggs become grayish before hatching. Larvae resemble caterpillars and are black when newly hatched and shortly after molting (shedding the old skin). After feeding, larvae become yellowish to green with rows of tiny dark tubercles (projections). Third-instar larvae grow up to 1/3 inch long and have dense rows of dark tubercles down their sides that resemble two black stripes. Pupae are orange to bright yellow."
We observed some natural enemies on site: lady beetles, aka ladybugs, and their larvae munching on the larvae of the elm leaf beetles. Yes, beetle larvae eating beetle larvae. Lady beetles and their larvae target soft-bodied insects, and not just aphids.
UC IPM says:
"The elm leaf beetle develops through four life stages: egg, larva, pupa, and adult. Adults commonly overwinter in bark crevices and woodpiles or in buildings. In spring they fly to elm foliage and chew leaves, and females lay eggs. Eggs hatch into larvae that develop through three instars (growth stages) over a period of several weeks while chewing on foliage and then crawl down the tree trunk. Mature larvae become curled and inactive (a stage referred to as prepupae), then pupate, sometimes in large numbers, around the tree base. After about 10 days as pupae, adults emerge and fly to the canopy to feed and, during spring and summer, lay eggs. The elm leaf beetle has at least one generation a year in northern California and two to three generations in central and southern California."
Elm trees with massive defoliation can weaken the tree and pave the way for diseases and damage from other pests.
If you have elm trees, especially European elm species, and you have these little buggers all over them, you might want to access the UC IPM Pest Notes to see how to manage them.
These beetles mean business./span>
No, this is not a historical reference to that famed rock band from Liverpool.
These are real beetles. The insects.
Lynn Kimsey, director of the UC Davis Bohart Museum of Entomology and a UC Davis distinguished professor of entomology, is fielding scores of calls--some panicked calls--about a beetle invasion in Davis.
In response, Kimsey has just created a public service announcement (PSA) of what they are (they are red flour beetles) and what folks should do and not do (don't panic).
"We have had a lot of reports and panic about small beetles invading people's houses in Stonegate and other parts of Davis," she relates on YouTube, "and just thought we ought to just clear the air a little bit with this and tell you a little about these guys. So as you can see they are very tiny. These are grain beetles. They are called the red grain flour beetle." They are Tribolium castaneum.
"They feed on dried, starchy materials," she says. "They will even occasionally feed on things like raisins, but nothing else. They are a stored product pest. They are probably coming out of a field of grain--grain fields were harvested in the last month or so. So they are coming out of the fields and they are flying at night."
Kimsey points out that they "will come into homes because of the lights. Also, the north wind we had blowing for awhile that didn't help."
The fastest way to get rid of them? "Vacuum them up," Kimsey says. "Dispose of the bag. Don't spray because it won't do any good."
She also urges folks to store their flour and other grains in tight-fitting lidded plastic containers, which "will prevent beetles as well as meal moths and things like this from getting in and starting an infestation."
If you do find an infestation, Kimsey says, the "fastest way to take care of it is to either put the material that is infested in the freezer, throw it out, or put it in the sun. It is still edible. These beetles are not harmful. They don't contaminate materials, unless you don't like eating beetles."
Kimsey also acknowledges it is "quite possible to get these beetles from a product you bring in from the store."
"And that happens," she says. "It is just one of those things. So what I would say is take a deep breath. This too shall pass."
The red flour beetles are a worldwide pest of stored products. The adults are reddish brown, about 1/8th of an inch long, and oval and flattened in shape. They attack flour, cereals, pasta, biscuits, beans, and nuts, among other items, according to Wikipedia. "The United Nations, in a recent post-harvest compendium, estimated that Tribolium castaneum and Tribolium confusum, the confused flour beetle, are "the two most common secondary pests of all plant commodities in store throughout the world."
The females of both species are polyandrous, that is, they will mate with multiple different males.
The UC Statewide Integrated Pest Management Program (UC IPM) describes the red flour beetle (see photo of the red flour beetle) as a common pantry pest.
"Pantry pests usually enter your home in an infested package of food," UC IPM says. "You might not notice these small insects until you see moths flying around your kitchen or beetles crawling in your food. Get rid of these pests by removing infested food, tightly sealing stored dry food, and thoroughly cleaning the area."
UC IPM offers these tips on its website for preventing a pantry pest infestation:
- Store food in containers with tight-fitting lids, not plastic bags.
- Store bulk goods like pet food in airtight containers.
- Keep certain infrequently used food like flours, spices, and grains in a freezer if possible.
- Wash old containers before filling them with new food.
- Don't mix old and new food together.
- Clean shelves, bins, and other food storage areas regularly.
Meanwhile, listen to Professor Kimsey's PSA on YouTube and check out the images.
The beetles. They're not just coming. They are here.
At a recent visit to the UC Davis Ecological Garden at the Student Farm, we watched a honey bee, Apis mellifera, and a lygus bug nymph, Lygus hesperus, foraging on a batchelor button, Centaurea cyanus.
The bee: the beneficial insect.
The lygus bug or Western tarnished plant bug: a pest.
The lygus bug, which punctures plant tissues with its piercing mouthparts, was there first, but no matter. The bee joined in, edging closer and closer until they touched.
In photography insect circles, that's a "two-for"--two insects in one image.
The bee finally buzzed off, leaving the lygus bug to "dine" alone.
The lygus bug, distinguished by a conspicuous triangle on its back, is a very serious pest of cotton, strawberries and seed crops, including alfalfa. Scientists estimate that in California alone, the pest causes $30 million in damage to cotton plants each year, and at least $40 million in losses to the state's strawberry industry. The insect is also a pest of numerous fruits and vegetables, including apples, pears, peaches, eggplant, tomato, potato, artichoke, lettuce, sugarbeet, and beans. See what the UC Statewide Integrated Pest Management Program (UC IPM), says about the pest.
What do they look like? "Adult lygus bugs are green, straw yellow, or brown with a conspicuous yellow or pale green triangle on their backs," UC IPM says. "Nymphs are light green...Lygus can move into gardens or orchards from weeds, especially when they dry up. They are a particular problem in beans, strawberries, and orchard crops, feeding on developing flower buds and fruit. Fruit may become blemished and discolored, deformed, or twisted and may develop depressions or pustules."
Cotton? "Lygus bugs," says UC IPM, "migrate to cotton from other hosts, so management of this pest begins with assessing its populations outside the field. Check for them on weeds, in nearby alfalfa, and in other crops, and keep in touch with your pest control adviser, Extension agent or Farm Advisor for area-wide information on lygus bug populations. Proper management of alfalfa harvest can reduce damaging migrations to cotton."
Cooperative Extension specialist Ian Grettenberger, UC Davis Department of Entomology and Nematology, works closely with farmers in their lygus bug battles.
If you engage in social media, you've probably seen a "what-is-this" query about a spider that some unsuspecting person discovered quite unexpectedly in a garden, bedroom, bathroom or garage. Triple exclamation points usually accompany "Yecch!!!" (Expletives usually require quadruple exclamation points.)
For a good general view of spiders, check out the UC Statewide Integrated Pest Management Program's newly revised "Spiders" Pest Note.
"Many people fear or dislike spiders," according to the site, but "for the most part, spiders are beneficial because of their role as predators of insects and other arthropods, and most cannot harm people. Spiders that might injure people—for example, black widows—generally spend most of their time hidden outside homes in woodpiles or in clutter in the garage. The spiders commonly seen out in the open during the day are unlikely to bite people."
Spiders, which are arachnids, differ from insects in that they have eight legs (not six) and have no wings or antennae.
UC IPM offers information on black widow spiders, yellow sac spiders and recluse spiders (which, contrary to popular opinion, are NOT found in California). The website also touches on jumping spiders, hobo spiders, common house spiders, and tarantulas. A table, illustrated with photos, lists the common spider families in North America, including:
- Agelenidae, funnel weavers or grass spiders
- Araneidae, orb weavers or garden spiders
- Clubionidae (including Corinnidae), sac spiders or twoclawed hunting spiders
- Linyphiidae (=Microphantidae), dwarf spiders
- Lycosidae, wolf spiders
- Oxyopidae, lynx spiders
- Salticidae, jumping spiders
- Theridiidae, cobweb, cobweb weaver, or combfooted spiders
- Thomisidae, crab spiders or flower spiders
What about spider bites? "Unlike mosquitoes, spiders do not seek people in order to bite them," UC IPM says, tongue in cheek. "Generally, a spider doesn't try to bite a person unless it has been squeezed, lain on, or similarly provoked to defend itself. Moreover, the jaws of most spiders are so small that the fangs cannot penetrate the skin of an adult person. Sometimes when a spider is disturbed in its web, it may bite instinctively because it mistakenly senses that an insect has been caught."
If you've got a hankering to see a live tarantula (who doesn't?), you can do so when the Bohart Museum of Entomology at UC Davis opens its doors again to the public. The Bohart Museum, home of nearly eight million insect specimens, a gift shop (now online), and a live "petting zoo" (think Madagascar hissing cockroaches, walking sticks and taranatulas) is located in Room 1124 of the Academic Surge Building on Crocker Lane. UC Davis spider expert Professor Jason Bond and his lab usually present a program there at least once a year or engage with folks at the open houses. Bond serves as the Evert and Marion Schlinger Endowed Chair in Insect Systematics, UC Davis Department of Entomology and Nematology. (See his lab website)
As an aside, Professor Bond "bonds" with spiders. Yes, he does. And he's never met a spider he didn't like.
For the first butterfly, it was the right place at the right time.
An alfalfa or sulfur butterfly (Colias eurytheme) fluttered into our pollinator garden in Vacaville to sip some nectar from a Mexican sunflower (Tithonia rotundifolia). It lingered for several minutes.
But on another day, several miles away, an alfalfa butterfly wandered into a rural nursery, and splat! Nailed by a yellow sticky trap, which is used to lure, trap, monitor and detect insect pests.
Second butterfly: wrong place at the wrong time.
"There are four to seven generations per year of alfalfa caterpillar, and each generation is closely synchronized with the hay-cutting cycle so that the caterpillar pupates before cutting occurs," according to the UC Statewide Integrated Pest Management Program (UC IPM) website. "Caterpillar populations usually result from a flight of butterflies into the field when the alfalfa is less than 6 inches tall. Extremely large numbers of adults migrating between fields are often present from June to September in the Central Valley and from May to October in the southern desert."
UC IPM points out that factors contributing to economically significant caterpillar numbers are:
- Slow and uneven growth of the crop
- Lack of natural enemies
- Hyperparasites (other parasitoid wasps attacking the natural enemy wasps reducing their numbers)
- Hot, dry weather.
Butterfly guru Art Shapiro, UC Davis distinguished professor of evolution and ecology, says 2020 proved to be a major outbreak year for the alfalfa butterfly in the Sacramento, Yolo and Solano counties. (See butterfly invasion in the Aug. 28, 2020 Bug Squad blog).
Ever seen one in a sticky trap? Often you'll see assorted--and tiny--flies, gnats, beetles, leafminers, psylids and the like. So a yellow butterfly in a yellow sticky trap really stands out.