Joseph F. Boggs
David J. Shetlar
Jane C. Martin
Pamela J. Bennett
James A. Chatfield
Gary Y. Gao
Chris Carlson
High populations of several web-spinning caterpillars occurred this season in various areas of Ohio. Damaging population levels of the common bagworm (Thyridopteryx ephemeraeformis) were observed in the southern and central part of the state. Gypsy moth (Lymantria dispar) caterpillars appeared in both the northeast and northwest parts of the state; however, infection by the entomopathogenic fungus, Entomophaga maimaiga, suppressed populations in some areas of northeastern Ohio. Sawfly populations remained low throughout the state with the exception of the European pine sawfly (Neodiprion sertifier) and the elm leafminer (Fenusa ulmi). Although lace bugs and spruce spider mites (Oligonychus ununguis) appeared in the spring, damaging populations were not observed until late summer and early fall, respectively.
Several insects had atypical life cycles this season. Various scale insects had unusually long crawler stages or crawlers appeared at unusual times of the year. Japanese beetle (Popillia japonica) adults were present for an extended period of time, and most late fall larvae were second instars rather than third instars, the stage that normally overwinters.
Insect and mite activities reported in 1997 in Ohio State University Extension's Buckeye Yard and Garden Line (BYGL) and Pest Evaluation and Suppression Techniques (PEST) newsletters as well as other sources are summarized and compared to previous seasons. Unusual insect and mite activity are also reported.
Populations of the common bagworm (Thyridopteryx ephemeraeformis) have been increasing each year in Ohio since the severe winter of 1993-94 significantly reduced the occurrence of this insect (3). However, the distribution of bagworm remains highly variable between the northern and southern parts of the state. For example, it was noted in July that this insect was common in the southern part of the state, slightly less evident in the central part, and less common in the extreme northern parts of Ohio.
Bagworms were reported hatching in southern Ohio in late May. Upon hatching, first instar larvae produce single threads of silk to catch the wind and "balloon" to new sites where they immediately begin feeding and constructing silk-lined bags from host plant material. Small bags were observed in early June in the southern part of the state and in mid-June in central Ohio. Insecticide efficacy is maximized if these early instar larvae are targeted.
High populations and heavy defoliation of many conifers and certain deciduous trees, particularly honeylocust and boxelder, were observed in central and south-central Ohio in mid- to late-July. Bagworms pupated in southern Ohio in mid-September, and male moths were observed in central Ohio in late September.
Dave Shetlar designated 1997 as "The Year of Webbing Caterpillars." The abundant webbing produced in the spring by the Eastern tent caterpillar (Malacosoma americanum) on roadside cherries and landscape crabapples was soon followed by the bountiful nests of fall webworm (Hyphantria cunea) on cherry, walnut, and hickory. Mimosa webworm (Homadaula anisocentra) prominently displayed its unsightly nests on honeylocust, and baldcypress webworm (Coleotechnites apicitripunctella) added its handiwork to the tangled season.
Although fall webworm was evident in southern and central Ohio, populations were particularly heavy in northern Ohio. In early July, Dan Herms (Ohio State University, Entomology) was the first BYGLer this season to report that early instar larvae were spinning nests in Ohio. Dan noted in late July that nests throughout Ohio contained all larval instar stages, indicating a wide variation in developmental rates within the state. Heavy webbing and substantial larval feeding damage in north-central and northeastern Ohio were reported throughout August.
By mid-September, larvae were reported to be "bombarding" homes in northeastern Ohio as they searched for locations in which to pupate for the winter. Although larvae often pupate within the nests, under high population densities, the caterpillars may leave the trees and pupate in the ground or in other protected areas such as under decking.
Ohio State University Extension Fact Sheet HYG-2065-95, Fall Webworm Management, indicates that more than 80 species of parasites and predators have been identified as potential invaders of fall webworm domiciles, the large silk webs which enclose leaves at the tips of branches. On August 21, Dan Herms reported that a significant num-ber of parasites were emerging from field-collected fall webworm colonies that he was maintaining for research purposes. He noted that "these parasites, as well as numerous predators, are responsible for the cyclic na-ture of fall webworm populations. Although this happens to be a particularly good year for this insect (or bad year, depending upon your perspective!), populations should continue to follow a 'peak and valley' cycle historically observed and begin to decline either next year or the year following."
Mimosa webworm on honeylocust has been reported in Ohio in past years; however, populations were unusually abundant during the 1997 season (3, 4). Larvae of this moth skeletonize the lower leaf surface as they feed within "nests" consisting of webs spun over the foliage. Small nests constructed by early instar larvae were first observed this season in early July in southern Ohio. Nests expanded rapidly, and heavy damage was reported in southern and central Ohio in late July. Some damage was also observed in northern Ohio. Spray programs to control this insect appeared to be most effective on early instar larvae since dense webbing produced by later instars is not easily infiltrated by insecticide materials.
Three generations of mimosa webworm occurred in Ohio this season. The first two generations overlapped, and the nearly continuous larval feeding activity caused extensive damage. However, the third generation did not appear until after a two- to three-week pause in feeding activity which lasted from mid-August to early September. This brief respite allowed some heavily defoliated honeylocusts to produce a flush of new growth which became fodder for the final generation. The third generation appeared in September and pupated in early to mid-October.
Two reports this season illustrated the importance of bio-allies in reducing mimosa webworm populations. The August 7 BYGL noted that nests on several trees in northern Ohio were found to be free of webworm larvae but were heavily populated by predaceous Hemipteran bugs. In the October 16 BYGL, third-generation pupae found in central Ohio were reported to be heavily parasitized. These observations are significant since the wide distribution and profusion of this insect during the 1997 season may cause some to conclude that mimosa webworm could be a serious problem next year.
In early July, Dan Balser (Ohio Department of Natural Resources, Division of Forestry) reported baldcypress webworm on bald-cypress in several western Ohio counties. The tannish-green larvae of this small Gelechiid moth first mine the leaves of baldcypress or hemlock, then they web the mined leaves together, forming broad, flat nests. The insect seldom causes significant damage; however, Dave Shetlar observed a baldcypress on the Ohio State University campus that was completely defoliated by this insect earlier this year. Thus, high populations do sometimes occur and could warrant control measures.
Gypsy moth (Lymantria dispar) eggs hatched this season in northeastern and northwestern Ohio in early to mid-May. Second and third instar larvae were observed in both areas of the state in late May to early June. By mid- to late-June, larvae in those parts of Ohio had reached the third and fourth instar stages, and some fifth instar larvae were found by the end of the month. Populations were high, and damage was heavy this season in some areas of northwestern Ohio; however, in northeastern Ohio, Dave Shetlar observed substantial larval infection by the entomopathogenic fungus, Entomophaga maimaiga, in early July. Dave Shetlar also reported that some populations in northeastern Ohio were seriously depleted by fungal infection.
In past years, gregarious feeding caterpillars such as the yellownecked caterpillar (Datana ministra), walnut caterpillar (D. integerrima), and the hickory tussock moth (Lophocampa caryae) were common, and some sporadic outbreaks were observed (3, 4). However, of the three, only the yellownecked caterpillar was observed causing significant injury this season in Ohio.
Also reported in BYGL in mid-September was the occurrence on maples in southwestern Ohio of another gregarious feeding caterpillar, the orangehumped mapleworm (Symmerista leucitys). The orangehumped mapleworm looks similar to another "Quasimodo" moth larva, the redhumped oakworm (S. canicosta); however, the mapleworm has an orange head capsule and hump (on the eighth abdominal segment) and three fine, black dorsal stripes. The redhumped oakworm has a reddish-orange head capsule and hump, and five fine, black dorsal lines. Early instar larvae of both insects feed in groups and skeletonize leaves. Later instars feed singly and devour the entire leaf, leaving only the midvein. There is one generation per year for both insects.
Large solitary-feeding caterpillars, such as the 4- to 6-inch-long hickory horned devil (regal or royal walnut moth, Citheronia regalis), the catalpa hornworm (catalpa Sphinx moth, Ceratomia catalpae), the tomato hornworm (five spotted hawk moth, Manduca quinquemaculata), and the parsleyworm (black swallowtail butterfly, Popilio polyxenes), were also common this season. However, heavy parasitism and predation were reported relative to these "giant caterpillars" in late August.
The abundance of sawflies in 1993 and 1996 caused those years to be tagged "the years of the sawflies" (1, 4). Conversely, the relative scarcity of these insects this season could justify calling 1997 "the year (nearly) without sawflies." The following sawflies were observed in Ohio landscapes - the introduced pine sawfly (Diprion similis), maple petiole borer (Caulocampus acericaulis), azalea sawfly (Amauronematus azaleae), dogwood sawfly (Macremphytus tarsatus), dusky birch sawfly (Croesus latitarsus), and the late-season white pine sawfly (Neodiprion pinetum). However, with few exceptions, little widespread damage from these sawflies was noted.
The two sawflies that proved to be exceptions to the general observation that sawflies were scarce this season were the early season European pine sawfly (N. sertifier) and the elm leafminer (Fenusa ulmi). High populations of European pine sawfly and heavy damage to pines in Christmas tree plantations and landscapes in southwest Ohio was reported in mid-May. The elm leafminer also appeared in impressive numbers in southwest Ohio (see "Leaf-miners" which follows).
LeafminersThe annual ravaging of black locust leaves by locust leafminer (Odontota dorsalis) occurred this season throughout much of Ohio (3). The digitate blotch mines produced by the larvae coupled with the skeletonized leaves produced by the adults caused many trees to become completely brown. Mimosa webworm damage on native honeylocust and locust leafminer damage on black locust caused Gleditsia and Robinia to both appear "flamed" and almost indistinguishable to the casual observer traveling on Ohio's interstate highway system this season.
Heavy elm leafminer infestations were observed on elms in several landscapes in southwestern Ohio by early June. This sawfly overwinters as prepupae in the topsoil. Pupation occurs in the spring, and adults emerge and lay eggs in the upper leaf surface in early to mid-May. The larvae tunnel between the upper and lower leaf surfaces, producing blotch or blister-like mines. Although there is only one larva per mine, multiple mines may occur on a single leaf. As the mines coalesce, entire leaves may become hollowed out and drop from the tree. By early June, larvae drop from mines in attached leaves or crawl from fallen, heavily damaged leaves, move into the soil, and form a cocoon. There is only one generation per year.
Several clearwinged moths (Family: Sesiidae) such as peach tree borer (Synanthedon exitiosa), lilac borer (Podosesia syringae), and dogwood borer (S. scitula) emerged unusually late this season, and adult flights lasted several weeks longer than "normal." Usually, adults of these borers fly during a rather narrow seasonal "window," which is open for only a few weeks sometime in late spring or early summer. For example, in 1996, these clearwing moths were first caught in pheromone traps in northeastern Ohio in early June. However, adults were first caught in traps this season in late June and were still being caught in high numbers in central Ohio in late July. This was significant since the adult stage is the most sensitive to control applications. Applications made when pheromone traps first indicated adult emergence had begun may have lost their efficacy while adults were still flying, mating, and laying eggs.
Other borers such as the Agrilus beetles were also sporadic in their activity this summer. Bronze birch borers (Agrilus anxius) were early in some locations and late in others, and twolined chestnut borers (A. bilineatus) appeared to have an extended period of activity.
Hawthorn lace bug (Corythuca cydoniae) egg hatch was reported in southwestern Ohio early in May; however, the characteristic small yellow spots, or stippling, produced by lace bug feeding activity did not become noticeable on hawthorn in that part of the state until late June. Heavy feeding damage by hawthorn lace bug on cotoneaster was observed in northeast Ohio in early July.
Damaging populations of various other lace bugs were also observed in several areas of Ohio. These lace bugs included sycamore lace bug (C. ciliata), oak lace bug (C. arcuata), walnut lace bug (C. juglandis), azalea lace bug (Stephanitis pyriodes), and rhododendron lace bug (S. rhododendri). Although azalea lace bugs were particularly plentiful throughout the season, all of the aforementioned lace bugs seemed to benefit from dry periods in July and August, and high late-season populations occurred.
Unusual life cycles this season for certain "hard" and "soft" scale insects presented serious control challenges. The hard scales, pine needle scale (Chionaspsis pinifoliae) and euonymus scale (Unaspis euonymi), both had unusually long crawler stages. This mobile form of the hard scale insects is devoid of the hard, waxy covering that generally protects these insects from the effects of most insecticides. Thus, multiple insecticide applications were required this season to effectively suppress populations of these insects. It was speculated that the life cycles of these insects were greatly altered because of the cool, wet spring weather.
Crawlers of the magnolia scale (Neolecanium cornuparvum), a soft scale, are generally first apparent in Ohio in late July; however, this season they were most evident in mid- to late-August. As with the hard scales, proper timing of insecticide applications targeting the vulnerable crawler stage of this insect required close inspection of plant materials rather than reliance upon "calendar dates."
As with 1995 and 1996, large numbers of spruce spider mites (Oligonychus ununguis) appeared to have been washed from their hosts by heavy spring rains (3, 4). Although eggs of this cool season mite hatched in late April and early May, damaging populations generally failed to appear in the spring. However, after their usual hiatus during the warm summer months, high populations of this mite were observed in late September and October.
Warm season mites generally flourished during the hot, dry weather experienced this season in July and August. In mid-August, damaging populations of two-spotted spider mite (Tetranychus urticae) were observed on roses and marigolds in central Ohio. Also in the same landscaping, high numbers of the mite were found on various weeds such as nightshade, oxalis, and crabgrass. This observation illustrates the point that since this mite has multiple hosts, it may develop on weeds in the landscaping and then move to more preferred plants. Thus, an effective weed control program may also function as an effective mite management program.
The oak spider mite (Oligonychus bicolor), another warm season mite, was also common in Ohio this season. In the July 14 BYGL, Dave Shetlar reported that hot temperatures had been conducive to the rapid build-up of this mite in central Ohio, and heavy damage was observed.
Had Dave Shetlar not christened 1997 "The Year of the Webbing Caterpillars," it could very well have been dubbed "The Year of the Eriophyid Mites." Beginning with a report in early May of the leaf-epidermis-rupturing pearleaf blister mite (Phytoptus pyri) on callery pear and ending with a report in mid-October of the bronzing effects of baldcypress rust mite (Epitrimerus taxodii), more than 11 eriophyid mite species found their way into BYGL reports this season. Most lack common names and are usually identified by their host and by the type of damage they produce.
Eriophyid mite species reported in BYGL included Eriophytes tiliae which produces light green, felt-like erineum galls on little leaf linden and Acalitus fagerinea which creates green to yellowish-brown erineum galls on American beech. Eriophyes caulis causes pubescent, reddish-brown leaf petiole galls to form on walnut, and Phytoptus tiliae produces "nail galls," or elongated growths with pointed tips, on the upper leaf surface of linden. These galls look similar to the finger-like "spindle galls" generated by Vasates aceriscrumena on the upper leaf surface of sugar maple as opposed to the globose, pouch-like "bladder galls" on the upper leaf surfaces of red and silver maples, caused by V. quadripedes.
BYGLers learned this season that trees aren't the only plants affected by eriophyid mites. Aculops toxicophagus produced puckered, irregular, wart-like galls on the lower and upper leaf surfaces of poison ivy. These galls turn from yellowish-green to brilliant red and make the usually dark-green ivy leaves very colorful.
Of course, as mentioned, rust mites were also observed this season, including the hemlock rust mite (Nalepella tsugifolia), which causes hemlock foliage to turn blue-green then reddish-brown, and Nalepella halourga (no common name), which causes bronzing of the inner needles of Colorado blue spruce. These eriophyid rust mites, as well as the aforementioned baldcypress rust mite, behave as "cool season" mites. High populations are generally observed during cool months, especially in the fall.
The 1997 season presented some serious grub management challenges. Although some of the grub-producing beetles behaved in a relatively predictable fashion, several behaved very unpredictably. May/June beetle (Phyllophaga spp.) adults appeared on schedule, bouncing off windows and window screens and shattering the evening calm in mid-May. Despite their common name, green June beetles (Cotinis nitida) also arrived within their "normal" calendar-date window. The big metallic-green beetles emerged en masse and began cruising lawns in southern Ohio, terrorizing backyard gardeners, sunbathers, small pets, and others in early August.
Now for the "unusual." Japanese beetle (Popillia japonica) adults first appeared in southern and central Ohio landscapes in early July. This is not an unusual date for adult emergence; however, beetles continued to remain on the scene through July, August, and September. This extended tour prompted BYGLers to give the beetles a new moniker - Energizer beetles - because they just kept going, and going, and....
This unusually long period of adult activity also had an impact on grub production. As Dave Shetlar reported in PEST: "Japanese beetle grubs are still mainly second instars, and it appears that these will have to overwinter before reaching the third instar, their normal overwintering stage. This may set us up for spring damage that we haven't seen for many years."
Dave Shetlar also summarized the late-season status of other white grubs in the October 20 PEST. He noted: "Masked chafer (Cyclocephala spp.) populations have certainly caused their damage, and large grubs are beginning to dig down - where the soil is moist enough to allow for such movement! Much of central and southern Ohio is so dry, the turf has again entered drought dormancy. This has masked much of the damage. Even the moles, skunks, and racoons have slowed their digging because of the dry soil conditions.
"In the counties bordering Lake Erie, the European chafers (Rhizotrogus majalis) have been hanging low in the soil profile. These pests are very resilient and capable of moving deep into the soil profile in periods of drought. They will return with the rains, and they will feed well into November and December before going down. Watch out for late appearing patches of dead turf."
Although numerous reports were made this year in the BYGL and PEST newsletters regarding aphids on landscape and nursery plants, most involved relatively common species. One exception was the four-spotted hawthorn aphid (Macrosiphum crataegi). In mid-October, immense aggregations of this aphid were reported on and around a hawthorn tree in a southwestern Ohio home landscape. Aphids covered the underside surfaces of almost every leaf on the tree, and large numbers could be found marching up and down the twigs, branches, and main trunk. Also, massive aphid gatherings could be found at the base of the trunk and under hostas planted beneath the tree. However, despite the heavy infestation, no apparent damage could be found on the tree. No curled leaves, honeydew, or black sooty mold were observed.
The four-spotted hawthorn aphid is yellow-green, slightly ovoid in shape, and has four rectangular dark green spots on its back. The spots are arranged like the points of a rectangle. This aphid will execute mass migrations in the fall as the hawthorn leaves turn color; however, they generally abandon trees that have been severely damaged. Given the large population, the lack of apparent damage could not be explained.
In mid-August, Pete Lane (Ohio State University Extension, Montgomery County) reported observing evidence of an unusual turf-infesting webworm - the burrowing sod webworm (Acrolophus popeanuellus). Unlike sod webworm larvae, which live in silk-lined burrows oriented in a horizontal plane, burrowing sod webworm larvae live in two- to four-inch-long vertical burrows that extend into the soil. Larvae line their burrows with a paper-like white sac made of silk. These sacs may appear resting on the surface of the grass as the result of bird predation. Birds pull out the burrow lining, extract the larvae, and leave behind the silk sac to be discovered by startled homeowners or enquiring Extension agents. Pete described the sacs as looking like "partially smoked, hand-rolled...ciga-rettes." The larvae feed at night, and damage may appear similar to that caused by cutworms; however, this insect is seldom a significant pest of Ohio turfgrass, and control is usually not needed.
A significant infestation of brown recluse spiders (Loxosceles reclusa) in a home in southwestern Ohio was reported in September. Although not generally considered common to Ohio, more than a dozen adults and a few immatures were discovered, mainly in the garage and basement - "prime hangouts" for this spider. Brown recluse spiders are tan to dark brown, a quarter to one-half inch long, and they have long, delicate, grayish to dark-brown legs with a span-width about equal to the size of a half dollar. The most distinguishing identifying feature of this spider is a dark brown marking on the upper surface of the flattened cephalothorax. The marking is shaped like a fiddle or violin and gives the brown recluse another common name - the "fiddle-back spider." The "neck" of the fiddle marking points towards the bulbous abdomen. As their name implies, these spiders are reclusive and tend to hide in dark, secluded areas (e.g., basements, closets, etc.). Brown recluse spiders are not aggressive, but if harassed, they can inject very serious toxins into a bite victim. Children, the elderly, and individuals in poor physical condition are particularly at risk to the venom.
1. Chatfield, J. A., J. F. Boggs, P. Kauffman, D. J. Shetlar, N. Taylor, and R. H. Zondag. 1993-1994. Ornamental Plant Problems in Ohio: 1993. The Ohio State University, Ohio Agricultural Research and Development Center. Special Circular 142. Ornamental Plants: A Summary of Research, 1993-1994. pp. 28-31.
2. Chatfield, J. A., D. J. Shetlar, N. Taylor, J. F. Boggs, P. J. Bennett, R. H. Zondag, M. A. Ellis, and A. Baumgard. 1993-1994. Ornamental Plant Problems in Ohio: 1994. The Ohio State University, Ohio Agricultural Research and Development Center. Special Circular 142. Ornamental Plants: A Summary of Research, 1993-1994. pp. 24-27.
3. Boggs, J. F., D. J. Shetlar, G. Y. Gao, D. Balser, D. C. Caldwell, R. H. Zondag, and J. A. Chatfield. 1995. Plant Insect Pest Problems in Ohio: 1995. The Ohio State University, Ohio Agricultural Research and Development Center, Special Circular 152. Ornamental Plants: Annual Reports and Research Summaries. In partnership with Ohio State University Extension. pp. 38-41.
4. Boggs, J. F., D. J. Shetlar, J. C. Martin, P. J. Bennett, J. A. Chatfield, D. R. Balser, and G. Y. Gao. 1996. Insect and Mite Activity Noted in Ohio: 1996. The Ohio State University, Ohio Agricultural Research and Development Center, Special Circular 154. Ornamental Plants: Annual Reports and Research Reviews. In partnership with Ohio State University Extension. pp. 17-22.