Archive for the Pests Category

MEET THE FALL CANKERWORM

Posted in Insects, Moths, Pests on January 19, 2011 by Dr. Art Evans

By Arthur V. Evans

Adult male fall cankerworm, Alsophila pometaria. ©2011, A.V. Evans

During a recent warm spell on the heels of New Year’s Day, a small collection of somberly hued moths gathered at my front porch light. I posted a picture of one of these moths on my entomology page on Facebook, and it was immediately identified as the fall cankerworm, Alsophila pometaria (Harris), a moth in the family Geometridae. The caterpillars of geometrids are collectively called inchworms. Adult fall cankerworms present a striking example of sexual dimorphism. Males are fully-winged, while the females are wingless. Native to North America, fall cankerworms are found from Nova Scotia to South Carolina, west to western Alberta, Colorado, Kansas, and California.

Adult female fall cankerworm, Alsophila pometaria. ©2011, A.V. Evans

Adults are typically active in fall and early winter. Females lay batches of 50-200 carefully aligned and upright eggs on small twigs and branches. Before leaving, they cover their eggs with scales from their abdomen. Upon hatching in late spring, each caterpillar descends from its egg on a single silken strand and is dispersed by the wind.

The ravenous larvae consume leaves and young fruits of many kinds of deciduous tree and are especially fond of maple, oak, and elm. Young larvae “skeletonize” patches (cankers) on the undersides of leaves by eating only the leaf tissues between the small veins. Older larvae consume nearly all leaf tissues and leave only the major veins behind. After 4-5 weeks of feeding the caterpillars reach maturity and lower themselves on to the ground via silk strands to enter the soil to pupate.

Fall cankerworm. © 2012, A.V. Evans

Large numbers of fall cankerworm larvae can defoliate trees and seriously damage fruit trees. Most trees and shrubs can withstand the onslaught, but mortality is possible if the plants are already stressed from drought and other adverse conditions. Check with your local nursery or extension agent for information on effective controls for fall cankerworms.

References

Cranshaw, W. 2004. Garden insects of North America. The ultimate guide to backyard bugs. Princeton University Press, Princeton, NJ. 656 pp.

Johnson, W.T. and H.H. Lyon. 1994. Insects that feed on trees and shrubs. Second edition with corrections. Cornell University Press, Ithaca, NY. 560 pp.

Powell, J.A. and P.A. Opler. 2009. Moths of western North America. University of California Press, Berkeley, CA. 369 pp.

© 2011, A.V. Evans

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TIPPING THE SCALES

Posted in Pests, Scale insects, Virginia with tags , , , , on September 19, 2010 by Dr. Art Evans

By Arthur V. Evans

Wax scales that is. Indian wax scales to be precise.

While trimming our nandina hedge this afternoon, I noticed a couple of small, white, barnacle-looking lumps on a stem. They were female Indian wax scales, Ceroplastes ceriferus (Fabricius). Sexing Indian wax scales is easy since males are not known in any wild population in Virginia. Adults are covered with a thick, white waxy layer that not only protects them from predators, parasitoids, and pesticides, but also helps them to survive freezing temperatures during the winter.

Reproduction is by parthenogenesis. One generation is produced annually in Virginia, but two or more appear in warmer climates. The first instars, or crawlers, hatch in spring and early summer and feed on leaves. They are not covered with a protective wax layer and are very susceptible to dehydration, parasites, and pesticides.

Adult Indian wax scales are conspicuous in late summer and early fall and suck sap from at least 122 plant species in 46 families. Prolific breeders, they quickly cover ornamental plants. Burgeoning wax scale populations not only ruin the plant’s appearance, but also cover them with sooty mold that develops on the prodigious amount of sticky waste (honeydew) that they produce.

Carefully tipping or lifting the scale to one side to detach the it from the plant stem reveals the orange and segmented body underneath. In the adjacent photo, the anterior of the body is on the lower right, while posterior is on the upper left. The mouthparts are visible and appear as a dark central spot at about the anterior third of the body.

Resource: Kosztarab, M. 1996. Scale Insects of Northeastern North America. Identification, Biology, and Distribution. Virginia Museum of Natural History, Special Publication No. 3. Martinsville, VA. 650 pp.

© 2010, A.V. Evans

CARPENTER BEES ARE BORING!

Posted in Ants, bees, wasps, Insects, Parental care, Pests with tags , , , , on April 1, 2010 by Dr. Art Evans

By Arthur V. Evans

It's spring and the eastern carpenter bees, Xylocopa virginica, are back!

The usual suspects of spring are all around me once again, including large, buzzing, blue-black eastern carpenter bees, Xylocopa virginica. They are noisily patrolling dead limbs and wooden structures in our neighborhood as they search for mates and nesting sites. Unlike the social honey bee imported from Europe, carpenter bees are solitary creatures native to North America. The bees buzzing around now reached maturity last summer. Back then they stretched their wings for a bit before tucking themselves away for the winter deep within the recesses in the very nest chamber where they had grown up.

Unlike the dark-faced female, the male Xylocopa virginica has a white "face."

White-faced and stingless, males are very territorial and spend much of their time claiming prominent flowering plants and bare patches of ground as their own. They aggressively drive off other bees and insects and often face-off with unsuspecting humans that unwittingly venture into their territory. The territorial borders of male carpenter bees are quite fluid and change from day-to-day. Amorous males regularly patrol flowers in search of females. Courtship involves lots of loud buzzing and aerial acrobatics, with the pair flying apart and coming together several times.

Dark-faced females are capable of delivering a painful sting, but are relatively docile. They chew their nest tunnels in dead trees, logs, or unfinished wooden structures, especially those with southern or eastern exposures. Females will consider exposed rafters, old house frames, picnic tables, rail fences, posts, trellises, and other exposed wood surfaces as potential nest sites.

With their powerful jaws working non-stop day and night, female carpenter bees will chew a perfectly round entrance hole that is about one half-inch in diameter. After tunneling in about one body-length, the tunnel turns sharply to the left or right at a 90º angle to follow the timber’s grain. They may construct two or more parallel tunnels from the main entrance that measure up to 14 inches long, each slightly wider than the entrance in diameter.

Sometime in May or June, the first egg is laid on a doughy pill of pollen about the thickness of a kidney bean at the end of a blind tunnel. The provision of pollen serves as the sole food source for the developing bee grub. The surrounding wood in the tunnel is then chewed into a fine pulp for form a disk-shaped partition that seals the egg off in its own cell. Each tunnel may have up to 6-8 cells.

Carpenter bees do not eat wood, but rely instead on flowers for nourishment. As the adults forage for pollen and nectar, they will mark each flower that they visit with a repellant chemical, or pheromone, that lasts up to 10 minutes. By skipping marked flowers carpenter bees can save time and effort by avoiding flowers recently depleted of their resources by other carpenter bees.

Tolerance is the key to appreciating carpenter bees. In spite of all the sawdust created by their nesting activities, they seldom cause severe damage. What damage they do cause is easily offset by their pollination services. Our gardens, fields, orchards, and forests would not be nearly as productive if it were not for their efforts and those of other pollinators. Besides, whether they are energetically visiting flowers, zooming through the air in conjugal bliss, or tirelessly engaged in nest-building, carpenter bees are just darned fascinating animals to watch!

© 2010, A.V. Evans

A BOUNTY OF BOXELDER BUGS

Posted in Insects, Pests, True bugs with tags , , , on March 24, 2010 by Dr. Art Evans

By Arthur V. Evans

A neighbor recently sought my advice about tiny, scarlet insects scurrying across his deck and up his walls, some of which were no larger than bits of coarsely ground pepper. Some had apparently found their way into his home and congregated in the well-lit windows on the south side of the house. A quick inspection of his home and property confirmed my suspicions; the tiny invaders were boxelder bugs.

For the past few weeks, I had noticed congregations of both adults and nymphs sunning themselves along back fences alleys and in trees growing along roadsides. I assured my neighbor that they posed no threat to property or pets, and that only in large numbers might they cause some damage to some plants.

The eastern boxelder bug, Boisea trivittata, is widespread throughout eastern United States. The wester boxelder bug, B. rubrolineata, is similar in appearance, but its found mainly west of the Rockies.

Adult boxelder bugs are flat, dark-gray insects with three red lines behind the head and may reach ½ inch in length. The thickened portions of their wings are bordered with red, while the membranous tips are blackish. They are strong fliers, flashing their bright red abdomens as they spread their wings and take to the air. Young nymphs are mostly red, but later stages appear darker as their wing pads grow larger. Both adults and nymphs have long, thin antennae.

Hibernating adults leave their winter hideaway with the advent of warm weather in late March or early April. Soon the females begin laying their dark reddish eggs in the crevices of bark on box elder trees and other nearby objects. The eggs hatch in two or three weeks, just as succulent new box elder leaves are beginning to appear. The nymphs eat and grow, shedding their external skeleton five times before becoming a fully winged adult. Up to two generations of boxelder bugs are produced annually.

Both adults and nymphs prefer to feed on the seed-bearing female box elder trees, sucking sap from the new leaves, tender twigs, and developing seeds. They will also attack ash, maple, plum, cherry, apple, and peach trees, as well as grapevines and strawberries. Damage from their feeding activities may cause blotchy yellow patches or brown spots on fruit and leaves. Severe infestations of boxelder bugs can result in misshapen leaves and fruit, but mature and healthy plants seldom suffer any serious harm.

In the late spring and early fall, flying or crawling boxelder bugs converge on stone piles, tree holes, and other protected places, sometimes by the hundreds. They may invade buildings, crowding into cracks and crevices in walls, door and window casings, and around foundations. They do not bite, nor do they damage buildings, furnishings, clothing, or food. However, they will soil curtains and walls with their waste and will definitely leave a stain if crushed.

The best way to keep unwanted boxelder bugs, as well as other insects and spiders, out of your home is by improving security. Replace screens and door sweeps. Repair thresholds and secure pet doors. Apply screens to vents and other openings. Caulk and seal all possible entry sites near doors, windows, crawl spaces, light fixtures, utility pipes or wires, weather boarding, and in areas along the foundation.

For boxelder bugs already in the house, vacuuming, sweeping, or picking them up are the most effective methods for dispatching them. They do not feed on household structures or reproduce indoors, so there is no need to use chemical controls inside the home. Aerosol sprays designed to kill ants and cockroaches are generally ineffective against boxelder bugs.

Removing leaf litter and other debris that serve as egg-laying sites near the base of female (seed-producing) box elder trees will reduce large populations of boxelder bugs outdoors. Eliminate other hiding places, such as piles of boards, rocks, leaves, grass, and other debris close to the house. Clear leaves and grass away from the house, especially on the south and west sides of the structure. Since boxelder bugs prefer to feed and lay their eggs on female box elder trees, plant male box elder trees instead. Male trees, propagated from cuttings taken from other male trees, are purchased from the nursery. These measures will significantly reduce the numbers of boxelder bugs looking to get inside your warm and cozy home.

As with many other insects labeled as “pests,” a little knowledge of their habits can help to reduce costly and sometimes unnecessary reliance upon pesticides, while at the same time raising our levels of tolerance and wonder. To me, this year’s appearance of boxelder bugs is just another marvelous pulse in the seasonal cycle of life. I am not the only one who feels this way. Just ask the folks in Minneota, Minnesota. They celebrate these little creatures each year with Boxelder Bug Days, a fall festival featuring bug races, bug poetry, plays, and other activities. If you can’t beat ‘em, join ‘em!

© 2010, A.V. Evans

WHAT’S IN YOUR ATTIC? BROWN MARMORATED STINK BUGS, PERHAPS

Posted in Environment, Insects, Pests, True bugs, Winter with tags , , , , , on March 15, 2010 by Dr. Art Evans

By Arthur V. Evans

Last month, while attending a meeting of the Bull Run Mountains Conservancy held in The Plains, Virginia, I was approached by several members who wanted to know about a stink bug that had invaded their homes by the dozens or hundreds in the fall. At first I thought they were referring to a species of bark stink bug, Brochymena, which sometimes enters homes by hiding under the bark of firewood hauled inside for the fireplace. Just as I was going into my spiel about sending me a photograph or a specimen for identification, someone said, “Look! There’s one!”

 

The brown marmorated stink bug, Halymorpha halys Stål, is steadily expanding its range across North America.

 

Sure enough, a robust gray stink bug was slowly making its way up the wall toward a window through which the day’s last rays of sunlight were shining. Judging from its distinctive markings, I knew that it was not a species of Brochymena and wondered if it might be the brown marmorated stink bug (BMSB), Halymorpha halys Stål. My suspicions were soon confirmed.

This uninvited insect from Asia has proven to be quite a nuisance to many homeowners in northeastern United States for the past several winters. They are much more likely to take up residence inside buildings than either of their native look-alikes, Brochymena and Euschistus.

BMSB was first reported from Allentown, Pennsylvania in 2001, but it turns out that the species has been in that area since at least 1996. The very first individuals probably arrived in America as stowaways, possibly as eggs, on packing crates most likely shipped from China or Japan. Since then, they have spread throughout Connecticut, Maryland, New Jersey, New York, Pennsylvania, Virginia, and West Virginia. As of 2004, an isolated population has become established in Oregon.

Like other stink bugs in the family Pentatomidae, BMSB are “shield-shaped” in outline. They are about 17 mm in length and are nearly as wide as they are long. Unlike similar species of native stink bugs, BMSB has white bands on the antennae and dark bands along the edges of the abdomen surrounding the wings. The head and pronotum (upper surface of the mid section, or first thoracic segment) have patches of small, round coppery or metallic bluish pits. The glands that put the stink in these and other pentatomids are located on the underside of the thorax and upper surface of the abdomen.

 

A nymph of the brown marmorated stink bug, Halyomorpha halys.

 

Brown marmorated stink bugs probably produce a single generation per year in America, but records from the sub-tropical regions of China indicate that there are 4-6 generations annually. Local populations of adults emerge from their winter hideaways in early June and begin mating and laying eggs almost immediately. The small black and red larvae (nymphs) soon hatch and molt five times during the months of July and August. Adults appear in mid August and begin seeking overwintering sites by mid September as the evenings start to become cooler.

To escape the cold, BMSB enter homes, out buildings, office buildings, and other structures by crawling under siding and shingles, around door and window frames, and into crawl spaces and attics. Once inside, they will settle in and become inactive for short periods. However, reinvigorated by the warmth of home heating systems, they are driven to crawl over walls and furniture, or fly clumsily to lights and windows.

As they bumble about, BMSB leave their odor on everything they land and crawl on. The accumulation of this odor at a good hibernation site serves as a powerful chemical beacon that attracts their brethren to the same location year after year.

The best way to keep BMSB out of homes and other structures requires preventative measures to be taken during the summer, after the bugs have already left, to prevent a re-infestation in the fall. Seal cracks and spaces around doors, windows, vents, utility access points, siding, trim, fascia boards, and chimneys. Caulk is handy for small cracks, but wire mesh and screens may be required when dealing with larger spaces associated with attics and foundation vents.

The good news is that once inside your home, BMSB will not bite you or your pets, spread disease, nor lay their eggs. Their piercing-sucking mouthparts are adapted for drawing sap from plants, not damaging furniture, clothing, or other household items.

Using insecticides on BMSB indoors is not particularly effective. Crushing them or sucking them up with a vacuum cleaner causes them to release their noxious odors that may persist in a room or on cleaning implements for sometime. Any disturbance perceived by the bugs as a threat will cause them to stink as a defensive measure. The best thing to do is to simply let them walk on a piece of paper and take them directly outside.

What is being done about BMSB nuisance in America? Since they have yet to become serious agricultural pests here in the States, there is little incentive for chemical companies to develop pesticides to combat them. Pesticides of any kind are incredibly expensive to bring to market and the number of homeowners plagued by home invasions of these bugs will never support the company’s efforts to recoup their investment, much less generate a profit.

But all is not lost. Researchers are learning everything they can about BMSB so that they can identify the weak links in their life cycle and exploit them to affect some level of control. Select BMSB genes and proteins are being sought for the possible development of genetically modified crops that will help suppress their numbers. There is also the possibility of using parasitic insects that will attack stink bugs during egg stage, not only to lessen their potentially harmful impact on crops such as soybeans, cotton, and corn, but also to reduce the numbers of individuals seeking shelter for the winter.

One of the more promising avenues of research involves the synthesis of attractant chemicals, or pheromones, to use in stink bug traps. Although BMSB attractant pheromone is currently unknown, scientists have discovered that they are attracted to the pheromones produced by the male of another species of stink bug native to Japan, Plautia stali Scott. Traps in America baited with this pheromone not only attract BMSB, but also some native species of stink bugs and a tachinid fly, Trichopodes pennipes,  that parasitizes native stink bugs.

Why would these stink bugs and one of their natural enemies be attracted to the pheromone of another species of stink bug? Research on other stink bugs species suggests that some use the pheromones of stink bug species other than their own in an effort to locate better feeding sites. Further, this chemically induced aggregation of different species of stink bugs may serve as a defensive strategy known as the “selfish-herd effect.” As the herd, or aggregation, grows individual stink bugs are increasingly less likely to be selected by a parasitic fly that, not so coincidentally, uses the very same pheromone to locate its victims. The discovery of the attractiveness of this pheromone offers up a potentially useful tool for monitoring and managing BMSB in America.

BMSB is steadily expanding its range across North America. Although clearly annoying to homeowners, the degree to which this species will become an agricultural pest in America remains unclear, especially as it moves south into warmer climates. Within their native range of China, Japan, Korea and Taiwan BMSB is most certainly an agricultural pest, attacking soybeans, apples, peaches, figs, mulberries, citrus, persimmons, and a variety of ornamental plants.

For now, all we can do is batten down the hatches and hope that science will come to the rescue.

© 2010, A.V. Evans

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