Insect and mite activities reported in the Ohio State University Extension's Buckeye Yard & Garden Line (BYGL) and Pest Evaluation and Supression Techniques (PEST) newsletter are summarized and compared to previous seasons. A cool and rainy spring caused significant changes in pest activity. Special discussions of caterpillars, sawflies, weevils, white grubs, lace bugs, scales, and mites are presented. Unusual insect and mite activity is also reported.
Several reports made in both the BYGL and the PEST emphasized the significant effects this season's weather had on insect and mite developmental rates, pest population levels, and pest/host relationships. Heavy spring rains and/or extended cool temperatures and a mid-summer mini drought were reported as having a meaningful impact on European earwigs (Forficula auricularia), yellow jackets (Vespula spp.), hairy chinch bugs (Blissus leucopterus hirtus), bluegrass billbugs (Sphenophorus parvulus), black turfgrass ataenius (Ataenius spretulus), sod webworm (Lepidoptera: Pyralidae: Crambinae), bagworms (Thyridopteryx ephemeraeformis), aphids (Homoptera: Aphididae), spruce spider mite (Oligonychus ununguis), two-spotted spider mites (Tetranychus urticae), and white grubs (Coleoptera: Scarabaeidae).
Spring Rains A record breaking wet spring throughout much of Ohio provided favorable conditions for some pests, but limited population development of others. For example, the following appeared in BYGL 96-11 (June 13): "The continual wet weather is producing a bumper crop of earwigs. Extension offices are being deluged by homeowner horror stories spawned by the frightful appearance of these nocturnal creatures and their repugnant habit of emitting a foul-smelling, yellowish-brown liquid from their scent glands when disturbed."
The wet weather proved less congenial for other insects and for some mites. In BYGL 96-5 (May 2), BYGLers theorized that the heavy April rainfall may have had a deleterious effect by drowning certain turfgrass insect pests such as white grubs, chinch bugs, billbugs, and sod webworms. However, Dave Shetlar noted that the ultimate impact of the heavy rainfall on insect populations could only be speculated, and that it probably would not be enough to limit population rebound.
The pernicious effects of the wet spring were not limited to turf insects. In BYGL 96-10 (June 6), Dave Shetlar reported that heavy spring rains have reduced populations in central Ohio of spruce spider mites, first instar bagworms, and several species of aphids.
Wet weather did indeed cause the population pendulum to swing back and forth for various species of aphids. As noted above, aphid populations appeared to be suppressed by heavy rains for the first part of the season - the aphids were simply washed from the plants. However, as conditions became drier during July and August, aphid populations recovered.
Yellow jacket populations appeared to remain relatively low throughout the season over most of Ohio. In BYGL 96-20 (August 15), BYGL participants speculated that heavy spring rainfall may have drowned yellow jacket queens as they attempted to construct nests below ground. In addition, unseasonably cool temperatures this summer may have slowed nest expansion and delayed development. Yellow jacket populations did tend to rise toward the end of the season. Of course, the highest seasonal population densities for yellow jackets are normally observed from mid-August into October.
Cool Temperatures Coupled with heavy rainfall, unseasonably cool temperatures also occurred throughout much of Ohio from April through late June. July and August also had below normal temperatures except for a few short days of temperatures in the 90 deg F range. As was already discussed relative to yellowjackets, the cool temperatures appeared to have a notable influence on delaying insect development.
For example, in BYGL 96-7 (May 16), Vanhoutte and bridal wreath spiraea, as well as horse-chestnut, were reported to be blooming in southwest Ohio. These phenological observations normally coincide with movement of black turfgrass ataenius adults from overwintering sites (e.g., under leaves in woods) to egg-laying sites such as turf on golf courses. However, PEST 5:5 (May 13) indicated that "This year, this activity [movement of ataenius to oviposition sites] has been greatly delayed."
Other insects, such as bluegrass billbug, were also slow in making an appearance. Normally, adults go on a walkabout searching for egg-laying sites from late-April to mid-May. However, ovipositing bluegrass billbugs were not observed in central Ohio until mid-June (BYGL 96-11, June 13).
Given that 1993 was tagged "the year of the sawflies" (1), 1996 could very well be called "the year of the sawflies, part two." These wasp-related insects were a significant part of the landscape this season. The usual suspects such as the early season European pine sawfly (Neodiprion sertifer), the introduced pine sawfly (Diprion similis), azalea sawfly (Amauronematus azaleae), dogwood sawfly (Macremphytus tarsatus), and the late-season white pine sawfly (Neodiprion pinetum) were joined this year by some unusual suspects. These included the maple petiole borer (Caulocampus acericaulis), the willow/poplar sawfly (Trichiocampus viminalis), and the dusky birch sawfly (Croesus latitarsus).
When reported in previous years' BYGL and PEST, the maple petiole borer was most noticeable in central and northeastern Ohio. Conspicuous damage this season was located in southwest Ohio (BYGL 96-9, May 30). The small larvae burrow inside the petiole, causing leaf bases to turn brownish-black, droop, and then drop from the tree. Larvae remain inside the petiole attached to the twig, so raking and destroying fallen leaves will not reduce the population.
Willow/poplar sawflies are black or greenish-black with conspicuous yellow spots on the sides. Larvae feed in colonies, eventually consuming entire leaves and more than one generation may occur in Ohio. Heavy damage was reported in BYGL 96-22 (August 29).
The dusky birch sawfly also feeds gregariously. Heavy infestations on gray birch in southwest Ohio were reported in BYGL 96-25 (September 19). Early instars have shiny black head capsules and yellowish-green bodies. Later instars have distinct rows of black spots. Larvae consume all but the large lateral veins and midvein.
Numerous species of caterpillars were reported in 1996; however, with the exception of gypsy moth (Lymantria dispar) and the mimosa webworm (Homadaula anisocentra), no major outbreaks were reported. Common spring caterpillars such as eastern tent caterpillar (Malacosoma americanum), spring cankerworm (Paleacrita vernata), and forest tent caterpillar (Malacosoma disstria) made widespread but moderate appearances. Eastern tent caterpillars hatched in early to mid-April (PEST, April 15), and spring cankerworms were observed at the end of the month.
Forest tent caterpillar feeds on oak as well as blackgum, sweetgum, water tupelo, and quaking aspen. The larvae may appear on trees at the same time as gypsy moth and eastern tent caterpillars. The overlapping time-frame caused identification confusion for some Extension clientele (BYGL 96-15, July 11).
Although the forest tent caterpillar is called a tent caterpillar, larvae construct only rudimentary mat-like nests near the ends of branches rather than tents in branch forks or crotches like the eastern tent caterpillar. Also, forest tent caterpillars have distinct "keyhole-shaped" markings running down their backs rather than the solid white line found on eastern tent caterpillars. Late instar gypsy moth larvae have colored spots - five pairs of blue spots followed by six pairs of red spots - running down their backs.
The high gypsy moth populations and defoliation projected for the northeastern and east-central counties did not generally materialize because the larvae were commonly infected with fungal diseases. Populations around Toledo continued to expand, and activity in this area will cause considerable public concern over the next few years.
Summer/fall caterpillars such as yellow-necked caterpillar (Datana ministra), hickory tussock moth (Lophocampa caryae), catalpa sphinx (Cera-tomia catalpae), and fall webworm (Hyphantria cunea) were also reported in localized areas across Ohio. Although called "fall" webworm, larvae of this moth were reported in early August (BYGL 96-19, August 8), not unusual for Ohio.
As with previous years, mimosa webworm was observed causing considerable damage to honeylocust in several areas of the state (1, 3). Since at least two generations occur per year and larvae continue to feed until first frost, early control of this insect is essential to avoiding heavy damage. Early instars are easier to control (later instars are shrouded in webbing); however, since adults lay eggs over an extended period of time, two applications, 10-14 days apart, are recommended. The second application will kill new larvae hatching from the pearly, bright-pink eggs.
Owing to its broad host range of more than 100 plants, black vine weevil (Otiorhynchus sulcatus) remained one of the most commonly reported insects in Ohio. However, other important weevils were observed and reported in 1996. These included the white pine weevil (Pissodes strobi), the yellow poplar weevil (Odontopus calceatus), and the Japanese weevil (Callirhopalus bifasciatus).
White pine weevils received little attention in previous BYGLs due primarily to its distribution in Ohio. It is seldom seen in the central or western parts of the state. However, in eastern Ohio woodlands the insect often achieves major pest status, particularly in Christmas tree plantations. Although white pine weevil is the common name generally used for this insect, the weevil also has two other recognized common names - the Engelmann and Sitka spruce weevils. These common names illustrate the point that this weevil will feed and breed on spruces as well as white pine. It will also do the same on other pines and Douglas fir. For example, in BYGL 96-13 (June 27), the characteristic "shepherd's crooks" produced by white pine weevil larvae tunneling down terminal shoots were reported to have been observed on Douglas fir in southwest Ohio.
Yellow poplar weevil damage to leaves of magnolia, tuliptree, and sassafras was reported to be severe in 1993 (1). Since that time, BYGLers have closely monitored these trees for the bean-shaped holes cut in leaves by the adults and for the blotch mines produced by the larvae. However, populations remained low this season as they did in 1994 (2).
Black vine weevil adult emergence was delayed this year, presumably because of the unseasonably cool spring and early summer temperatures experienced throughout much of Ohio. The June 10 PEST noted: "In the landscape, we normally find a few adult weevils by the last week of May. We haven't seen any sign of notching and no weevils have fallen into my pitfall traps - yet." Black vine weevil notching did appear later in the season.
However, observers in northeast Ohio found that not all notching is produced by the black vine weevil. The relatively small (about 1/4 inch) Japanese weevil - a newcomer to BYGL participants (and possibly a new state record) - produces leaf notches which appear very similar to black vine weevil.
White grub reports this season varied somewhat from observations made in previous years (1, 2, 3). First, imidacloprid became available for use by home owners (e.g., GrubEx ), and its early application timing for grub control caused some confusion in the retail market. Second, owing to this season's unusual weather, overall grub activity was difficult to predict.
Five reports on imidacloprid aimed at explaining the compound's application timing were made in the BYGL and two in the PEST. A report made in BYGL 96-19 (August 8) regarding white grub control was typical: "In previous BYGLs, we reported that this product [imidacloprid] should be applied 30 days prior to grub emergence for best results. Dave [Shetlar] noted that there is still time to apply this product for grub control; however, the window closes around August 15th."
"At this time, 80% of grubs are either in the egg or first instar stage. Imidacloprid applied before August 15th and watered in thoroughly will provide control. If it is applied during the third or fourth week of August, Dave suspects the results will drop from 90-95% efficacy to 70-90%. By the time the grubs reach the third instar, the efficacy drops to 50-70%."
Cool and wet spring weather and summer mini droughts caused white grub population predictions to fluctuate widely in 1996. Some predicted that the heavy spring rains could suppress beetle populations by reducing grub numbers. However, observations of spring grub numbers, which remained relatively stable, did not seem to support the "death by drowning" conjecture.
When Japanese beetle (Popillia japonica) adults appeared in late-June to early-July, overall adult activity appeared to be unusually low for that time of year (PEST, July 8). Since grub numbers had not appeared to be suppressed, it was speculated that unusual spring and summer weather in 1995 coupled with 1996 heavy spring rains produced an extended adult emergence (3). Thus, it was predicted that rather than a having a large surge of adults, there would be a slow trickle, and feeding as well as oviposition would extend over an unusually prolonged period of time. This prediction was supported by observations of adult Japanese beetles feeding well into August in some parts of the state.
Based on those observations and follow-up reports of grubs appearing to be developing normally in late-August to early-September, predictions were made that Ohio would experience a "banner" grub year. However, as of late-September, reports of significant grub damage had still not yet materialized. Grub sampling in early October indicated that Japanese beetle grubs were, indeed, slow to develop with many second and early third instar grubs present. On the other hand the masked chafers (Cyclocephala spp.) had developed normally, but their populations were greatly reduced, possibly because of the mini drought in late June and early July.
In 1995, heavy spring rains caused lace bug populations to develop slowly; however, once rains subsided, lace bug numbers climbed quickly to damaging levels (3). In 1996, early heavy rains seemed to have little effect on lace bug populations, especially in the southern half of Ohio.
By late May, azalea lace bugs (Stephanitis pyriodes), hawthorn lace bugs (Corythucha cydoniae), and a buckeye lace bug (C. aesculi) were reported to be causing their characteristic yellow stippling to the upper surface of their host's leaves. In early June, damaging population levels of oak lace bugs (C. arcuata) were observed on burr oak in southwest Ohio and other white oaks in northern Ohio through the rest of the summer. Damage reports from these lace bugs continued throughout the season.
In late September, heavy infestations of lace bugs caused severe damage to black cherry in Harrison County, Ohio. Although a positive identification was not obtained, there are two lace bug species that feed on black cherry - the cherry lace bug, C. pruni, and C. associata.
The most commonly reported armored scales in the BYGL and the PEST included pine needle scale (Chionaspis pinifoliae), euonymus scale (Unaspis euonymi), and oystershell scale (Lepidosaphes ulmi). Common soft scales included cottony maple scale (Pulvinaria innu-merabilis), European fruit lecanium (Lecanium corni), terrapin scale (L. nigrofasciatum), tuliptree scale (Toumeyella liriodendri), and magnolia scale (Neolecanium cornuparvum).
Crawler stages for these scales appeared on schedule this season with two exceptions. By late May, the rusty-red colored pine needle scale crawlers and the yellowish-cream colored euonymus scale crawlers had been observed in southwest Ohio and in West Lafayette, Indiana. However, in Columbus, the euonymus scales had not laid eggs, and the pine needle scale crawlers had not yet appeared. Although the exact explanation for the variation is not known, speculation was that small differences in locations and hosts, not major differences in weather, accounted for the observed disparity in developmental rates (PEST, May 28).
As in 1995, large numbers of spruce spider mites (Oligonychus ununguis) were washed from their hosts by the heavy spring rains in 1996 (3). Populations rebounded quickly in late June to early July due to the relatively cool summer temperatures. Normally, this cool-season mite shuts down in early July, once temperatures rise into the mid-to-upper 80s, and doesn't reappear until mid-September. However, in early August, abundant adults and nymphs on spruces and junipers indicated that the mites never went dormant during the 1996 summer.
Two-spotted spider mite (Tetranychus urticae), a warm-season mite, was very common in mid June through August on several landscape plants. Because this mite resides on the underside of leaves, it was unaffected by early rains. Two-spotted spider mite was also reported on geraniums in an interior plantscape. This is unusual since geraniol oil, which gives geraniums their characteristic scent, has miticidal activity. However, the infested geraniums were "unscented." As Shetlar stated in PEST (August 5), "no odor, no geraniol, no spider mite protection!"
The oak spider mite (Oligonychus bicolor) was also common across Ohio, causing a general bronzing of oak foliage. In the past this pest has appeared to be most common on white oaks but damage was noticed on red oaks in 1996.
The most unusual mite "event" this year was a species of Tetranychus that resulted in ash trees "wrapped in cellophane" in late August and early September. Specimens sent to Rayanne Lehman (Pennsylvania Department of Agriculture) were tentatively identified as T. schoeni. However, as Lehman stated, out of the 1,000 some specimens sent, there were no males present. The males are necessary for accurate species identification. Since the first report of this mite, similar reports have been received from Indiana, Illinois, Iowa, and Wisconsin.
Several insects were reported in the BYGL and PEST which could be categorized as unusual. Either they have not been commonly seen before or they are not widely distributed throughout Ohio. These include the yucca plant bug (Halticotoma valida), cypress gall midge (Itonidae taxodii), and the apple-and-thorn skeletonizer (Anthophila pariana).
A heavy infestation of yucca plant bug was observed on Adam's needle yucca in southwest Ohio. This insect is common throughout the native range of yucca and is following its host plant into other areas of the country. The small (3/16 inch long) oval plant bugs have black wings or wing pads (immatures) and orange-red legs, head, thorax, and abdomen. Feeding produces small white spots (stippling) which coalesce, causing the foliage to appear light green to yellow.
Cypress leaf gall midge made its yearly appearance on bald cypress in southwest Ohio. This insect has been reported in the BYGL in previous years; however, all reports have centered on the southern part of the state. Sizes of the galls vary, ranging from 1/8 to 1.0-inches in length. Although produced by a midge, the cone-like white to bluish-green galls look like a miniature version of the growths produced by the Cooley spruce gall adelgid on Colorado blue spruce.
Like the Cooley galls, the midge galls are covered with a whitish powdery material and occur at or near the tips of the new growth. However, unlike the Cooley galls, the cypress galls are spongy, not woody, and sparsely covered with flexible needles. Also, the midge galls fall apart and disappear in the fall. The life cycle of the midge is poorly documented so no controls are currently available. Although not considered significant relative to plant health, the galls may diminish the plants' aesthetics.
The apple-and-thorn skeletonizer was reported in northeast Ohio as causing significant injury to certain crabapple cultivars in the crabapple plots at the Ohio State University/Ohio Agricultural Research and Development Center in Wooster, Ohio. Larvae of this relatively small moth (adults have a half-inch wingspan) feed mostly on the leaves of apples, pear, and hawthorn. They also attack mountain ash, birch, willow, plum, and sour cherry.
Early instar larvae skeletonize the undersurface of leaves under loose webs. Later instars move to the upper surfaces and draw the opposite sides of leaves together with silk. These structures look like "canoes." Larvae feed inside the fold, consuming everything except the lower epidermis and larger veins. Leaves curl, turn brown, and eventually drop. From a distance, damage appears similar to that produced by Japanese beetles, particularly when old webbing degrades, releasing the folded leaves. There are three and possibly four generations per year, so trees should be monitored closely. Although reported on apples in orchards, the insect seldom achieves damaging levels owing to multiple pesticide applications usually included in orchard management programs.