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>
It's a dog-eat-dog world out there.
It's also a 'cat-eat-'cat world, that is, when a caterpillar eats another caterpillar. Or in this case, when larva eats larva.
We recently spotted this lady beetle larva eating a syrphid fly larva on our yellow rose bush, "Sparkle and Shine." Both eat aphids, and that's exactly what they were doing until the lady beetle larva attacked--and began eating--the syrphid larva.
These insects are beneficial. The lady beetle, as an adult, continues to consume those pesky aphids. The syrphid fly adult, aka hover fly or flower fly, is a pollinator.
The hungry larva reminded us of Eric Carle's award-winning children's picture book, The Very Hungry Caterpillar, first published in 1969.
The synopsis (Wikipedia):
"One Sunday morning, a red-faced caterpillar hatches from an egg, and begins to look for some food. He eats through increasing quantities of fruit on the following five days, one apple on Monday, two pears on Tuesday, three plums on Wednesday, four strawberries on Thursday, and five oranges on Friday, and then, on Saturday, he has an enormous feast. By the end of Saturday, the inevitable happens and he is ill. After recovering from a stomach-ache, he returns to a more sensible diet by eating through a large green leaf before spinning a cocoon in which he remains for the following 2 weeks. Later, the 'big fat caterpillar' emerges as a beautiful butterfly with large, gorgeous, multi-coloured wings."
Well, in this case, the menu differed. Our lady beetle larva didn't eat an apple, pear, plum, strawberry or orange.
He/she ate its competitor.
Have you ever seen a monarch butterfly (Danaus plexippus) lay an egg on her host plant, the milkweed?
Have you ever seen a close-up of the egg? The larva or caterpillar? The chrysalis? The eclosure (when the adult emerges from the chrysalis)?
It's a fascinating sight.
Not all eggs will make it. Predators, such as lady beetles and their larvae, gobble up monarch eggs along with those tasty aphids. Birds, such as scrub jays, swoop down and make off with an occasional caterpillar. Then when the fifth instar finally starts to form a chrysalis, there's always the question of whether it will do so. Some are deformed and turn out to be half chrysalis and half caterpillar.
But once you've watched a complete metamorphosis, you'll never underappreciate monarchs again. In fact, you'll probably start rearing them every year. We just reared our first two this month.
It's easy to see why teachers and their students get so excited. We remember writing about Sal (Sally) Levinson's newly published book, Butterfly Papercrafts, which contains 21 indoor projects for outdoor learning. Levinson, who studied entomology at the graduate level at UC Riverside and UC Berkeley, wants to inspire youngsters to learn about our amazing world of butterflies through art and a little science.
It's intended for youngsters ages 5-12, but really, it's also a beginner's book for all ages and a teacher's treasure. And it's priced right--under $10 ($9.99). Readers can learn about the life cycle, from egg to caterpillar to chrysalis to adult; and craft a butterfly paper airplane, a caterpillar flip book, and a monarch finger puppet.
Meanwhile, North America's monarchs are heading for their overwintering sites in two main areas: the mountains of central Mexico, and choice spots along the California coast, including Pacific Grove and Santa Cruz.
"The annual migration of North America's monarch butterfly is a unique and amazing phenomenon," according to the U.S. Department of Agriculture's Forest Service website. "The monarch is the only butterfly known to make a two-way migration as birds do. Unlike other butterflies that can overwinter as larvae, pupae, or even as adults in some species, monarchs cannot survive the cold winters of northern climates. Using environmental cues, the monarchs know when it is time to travel south for the winter. Monarchs use a combination of air currents and thermals to travel long distances. Some fly as far as 3,000 miles to reach their winter home."
Not to worry. Put it all in perspective by thinking about the larvae of the honey bee.
Extension apiculturist Eric Mussen of the UC Davis Department of Entomology, likes to talk about the massive weight gain that occurs during the larval stage of the honey bee. He speaks at scores of beekeeping functions throughout the year and what he says about the larval weight gain always draws a "Wow!" or "Incredible!" or "Amazing!"
"A honey bee egg weighs about 0.1 mg," Mussen says. "The first stage larva weighs the same. Over the next six days of larval life the larva goes from 0.1 mg to around 120 mg. It defecates once, just before pupating, and the resulting adult bee weighs around 110 mg. Thus, the new bee weighs about 1,000 times the weight of the one-day-old larva."
Now get this:
"If a human baby, weighing eight pounds at birth, were to grow at the same rate, the baby would weigh 8,000 pounds, or 4 tons, at the end of six days."
Four tons in six days? Fortunately, what goes on with Apis mellifera does not apply to Homo sapiens.
Now go get that second helping of pumpkin pie.
As for Mussen, he quips: "I only feel that heavy some days!"
Our Artemisia, a silvery-leafed shrub bordering our bee friendly garden, looks quite orange and black these days.
It's not for lack of water or some exotic disease. It's the ladybug (aka lady beetle) population.
If you look closely, you'll see eggs, larvae and pupae and the adults. And if you look even more closely, you'll see aphids.
The predator and the prey.