Twolined Chestnut Borer Research Articles

Current and Future Insect Threats to Oaks of the Midwest, Great Lakes, and Northeastern United States and Canada

Increasing temperatures, prolonged drought, the increased severity and intensity of storms, and other effects of climate change are being felt globally, and long-lived forest tree species may struggle in their current ranges. Oaks (Quercus spp.) have evolved a range of adaptations to dry and hot conditions and are believed to be a “climate change winner” by increasing their suitable habitat. However, a mixture of life history traits and increasing susceptibility to herbivores and xylovores as well as secondary pathogen infections still put oaks at risk of decline. Oak species found in the Midwestern, Great Lakes, and Northeastern United States and Canada are important keystone species with high ecological and economical importance. They are also vulnerable to existing, new, and emerging threats that have the potential to cause mortality across entire stands quickly. Current examples of insect threats include the Lymantria dispar (spongy moth), Agrilus bilineatus (twolined chestnut borer), and Nitidulidae (sap beetles) as disease vectors. Examples of emerging insects of concern include Cynipidae (oak gall wasps) and Enaphalodes rufulus (red oak borer). This study describes these insects, explains their mechanisms of action and the effects on oaks, and explores mitigation strategies for each.

Agrilus bilineatus (two-lined chestnut borer)

Agrilus bilineatus (two-lined chestnut borer)

Improving trapping methods for buprestid beetles to enhance monitoring of native and invasive species

AbstractMost of the current understanding of the orientation and communication of jewel beetles arose from research on the Asian emerald ash borer (EAB), Agrilus planipennis, which has become one of the most destructive invasive forest insect pests in history following its introduction to North America and European Russia. From a European perspective, a number of jewel beetles have a high invasive risk similar to that of the emerald ash borer, including the potential threat of the bronze birch borer Agrilus anxius, the goldspotted oak borer Agrilus auroguttatus, and the twolined chestnut borer Agrilus bilineatus. Native jewel beetles expanding their geographic range include the cypress jewel beetle Ovalisia festiva and the black-banded oak borer Coraebus florentinus. Other native species are increasing in their importance, including the flathead oak borer Coraebus undatus, the two-spotted oak borer Agrilus biguttatus, the flatheaded beech borer Agrilus viridis and Agrilus cuprescens. Commonly used prism and multi-funnel trap designs and other promising experimental trap designs have been tested and compared in the US and in Europe. One factor considered has been colouration, typically purple and green. Another is olfactory attraction, both to plant volatiles and extracts such as (Z)-3-hexenol, Manuka oil, Phoebe oil and Cubeb oil, and also to pheromones such as (Z)-3-lactone, for emerald ash borer. Field observations have been made of mating and host-finding behaviours of oak buprestids based upon visual stimuli in North America and Europe. By using pinned dead EAB models, visual mating approaches have been observed by males of Agrilus biguttatus, Agrilus sulcicollis and Agrilus angustulus, which is a behaviour similar to that previously observed in EAB. Green plastic-covered branch-traps significantly out-performed other trap designs and caught more Agrilus jewel beetles if an artificial visual decoy that copies a beetle body was included. A higher fidelity decoy offered the same distinctive light-scattering pattern as real resting EAB females and elicited the full sequence of stereotypical male mating flight behaviour of EAB and A. biguttatus from up to 1 m away. An optimization of visual, olfactory and other possible stimuli has likely not yet been achieved. More sophisticated trap designs could lead to more sensitive detection capabilities with increased selectivity.

Mating Behavior and Reproductive Biology of Emerald Ash Borer (Coleoptera: Buprestidae) and Two of Its Native Congeners, the Twolined Chestnut Borer and the Bronze Birch Borer.

We studied the mating behavior and reproductive biology of three members of the genus Agrilus: the bronze birch borer, Agrilus anxius Gory; the twolined chestnut borer, Agrilus bilineatus (Weber); and the emerald ash borer, Agrilus planipennis Fairmaire. All three species share a highly stereotyped mating behavior. However, the copulation duration of A. planipennis was 90% longer than that of its two congeners. Female reproductive tracts of the three species were anatomically similar, as were the spermatophores. Within the spermatophores, sperm were single in A. anxius and A. bilineatus, while in A. planipennis, sperm were bundled in groups of approximately 20 in a hyaline sheath. We found that field-caught A. anxius and A. bilineatus had higher rates of female insemination than A. planipennis. In additional studies with A. planipennis and A. anxius, we found that mating duration was related to mating success, and fecundity for A. planipennis, but not for A. anxius. For both A. planipennis and A. anxius, the spermatophore was passed to the female toward the end of the copulatory period. Sperm were found in the spermatheca immediately after copulation ended in A. planipennis and 30 min after copulation ended in A. anxius. We present possible explanations for these differences.

The First Record of Two-Lined Chestnut Borer Agrilus bilineatus (Weber, 1801) (Coleoptera: Buprestidae) from Europe

The two-lined chestnut borer Agrilus bilineatus (Weber, 1801) is recorded for the first time from Europe. Two specimens were collected from Belgrad Forest (European part of Istanbul, Turkey). The new record extends the known distribution.

Near Absence ofAgrilus bilineatusfrom an Oak Decline Event in the Ozark Mountains of Arkansas

It was unknown whether twolined chestnut borer, Agrilus bilineatus (Coleoptera: Buprestidae), a common secondary agent of tree decline in eastern US oak forests, contributed to tree mortality during a recent (1999–2003) episode of oak decline in the Ozark Mountains. Adult beetle flight was monitored by trapping in 2001, 2003, and 2004 and oak branches and trunks were visually examined for exit holes and dissected to examine larval galleries. Very few A. bilineatus adults were found each year by trapping (< 10 as opposed to > 100 red oak borers [Enaphalodes rufulus; Coleoptera: Cerambycidae]), and no evidence of A. bilineatus was found in 70 dissected tree boles or in upper crown material, although other buprestids (Chrysobothris femorata) were noted.

Biology of the European oak borer in Michigan, United States of America, with comparisons to the native twolined chestnut borer

AbstractIn 2010–2011, we studied the European oak borer (EOB),Agrilus sulcicollisLacordaire (Coleoptera: Buprestidae), in Michigan, United States of America, and made comparisons with the native twolined chestnut borer (TLCB),Agrilus bilineatus(Weber). EOB adult flight began and peaked before TLCB. More EOB females were captured on purple and white compared with yellow and green sticky traps. More TLCB females were captured on purple, followed by yellow, green, and white, respectively. Male EOB and TLCB did not show a significant colour preference. EOB completed development primarily from areas of artificially girdled trees where the phloem had died soon after trees were girdled, while TLCB usually developed in areas of girdled trees that had some live phloem present. Both EOB and TLCB successfully attacked and emerged from girdledQuercus albaLinnaeus,Quercus roburLinnaeus, andQuercus rubraLinnaeus (Fagaceae) trees. No live EOB or TLCB were found in two ungirdled and apparently healthyQ. roburtrees that were dissected. EOB attacked and emerged fromQ. alba,Q. robur,Q. rubra, andQuercus velutinaLamarck trap logs. Differences in the pronotal groove and terminal processes can be used to distinguish EOB from TLCB larvae. Five species of parasitoids were reared from EOB and four from TLCB.

Dynamics of twolined chestnut borer Agrilus bilineatus as influenced by defoliation and selection thinning

Abstract1 The twolined chestnut borer, Agrilus bilineatus (Coleoptera: Buprestidae), is a major mortality agent of stressed oak trees. However, patterns of abundance and population change are not well understood.2 We studied the spatial and temporal variation in abundance of twolined chestnut borer adults during a gypsy moth, Lymantria dispar (Lepidoptera: Lymnatriidae), outbreak and examined the influence of both defoliation and thinning on twolined chestnut borer abundance.3 In stands that were defoliated by gypsy moth, extensive defoliation occurred in one year, and major overstory tree mortality followed in the next. Most mortality occurred in the year preceding the peak year of twolined chestnut borer abundance and abundance of twolined chestnut borer was positively associated with defoliation and mortality in the previous year.4 Twolined chestnut borers were more frequently associated with poor or fair crown condition trees than trees with good crown condition and were more abundant on members of the red oak group than the white oak group.

Interactive effects of acidic deposition, drought, and insect attack on oak populations in the midwestern United States

The objective of this study was to determine if acidic deposition predisposes oaks to decline after drought. Associations were evaluated between oak decline and mortality after drought and (1)pre-drought growth; (2)tree size, age, and competitive status; (3)attack by twolined chestnut borer (TLCB); (4)acidic deposition; and (5)soil acidity. This study was conducted in the Ohio River region of the United States. White oak (Quercus albaL.), black oak (Quercus velutina Lam.), and the locally dominant oak (chestnut oak (Quercus prinusL.) or post oak (Quercus stellata Wangenh.)) were studied at six similar sites along an acidic deposition gradient during the period 1988-1992. Prevalence of severe branch dieback and mortality was low ( &lt; 10%) at all sites, but fewer oaks in Illinois were in the 0-10% dieback class than in other states. Also, fewer oaks in Illinois than Ohio exhibited immediate recovery after the 1988 drought. Prevalence of TLCB attack was similar across all sites; &gt;85% of dead trees had been attacked, but &lt;10% of living trees were damaged. Most dead oaks had lower pre-drought radial growth than survivors of the same species. Branch dieback, growth decline, and mortality were more prevalent in the black oak population than the other oak species. There was no evidence that acidic deposition predisposed oaks to post-drought decline.

Interactive effects of acidic deposition, drought, and insect attack on oak populations in the midwestern United States

The objective of this study was to determine if acidic deposition predisposes oaks to decline after drought. Associations were evaluated between oak decline and mortality after drought and (1) pre-drought growth; (2) tree size, age, and competitive status; (3) attack by twolined chestnut borer (TLCB); (4) acidic deposition; and (5) soil acidity. This study was conducted in the Ohio River region of the United States. White oak (Quercus alba L.), black oak (Quercus velutina Lam.), and the locally dominant oak (chestnut oak (Quercus prinus L.) or post oak (Quercus stellata Wangenh.)) were studied at six similar sites along an acidic deposition gradient during the period 1988-1992. Prevalence of severe branch dieback and mortality was low ( 85% of dead trees had been attacked, but <10% of living trees were damaged. Most dead oaks had lower pre-drought radial growth than survivors of the same species. Branch dieback, growth decline, and mortality were more prevalent in the black oak population than the other oak species. There was no evidence that acidic deposition predisposed oaks to post-drought decline.

Can Tree Susceptibility to Borers be Predicted from Root Starch Measurements?

The twolined chestnut borer (TLCB) attacks and kills stressed oak trees, especially those that have been weakened by severe drought. We tested the hypothesis that winter root starch reserves of white oak are an indicator of tree vigor, and that trees low in stored starch are especially vulnerable to borer attack during the following summer. Only those trees that were very low in stored root starch were heavily attacked by the TLCB and showed signs of decline or died. A few oaks with high starch reserves were also successfully colonized, but those trees did not show signs of decline and did not die. Thus, winter starch reserves were generally a good predictor of TLCB attacks. Further research is needed to determine if this relationship holds for other hardwood trees and their respective wood borers. Use of root starch ratings to assess tree susceptibility to borers needs further testing in urban settings to determine its practicality for pest management.

Carbohydrate reserves, radial growth, and mechanisms of resistance of oak trees to phloem-boring insects.

The twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae), attacks oaks (Quercus spp.) that have been weakened by prior environmental or biotic stress. Our earlier work showed that trees with relatively low winter starch reserves are more likely to be attacked by A. bilineatus the following summer. We hypothesized that such trees may have less energy available for defense (Callus formation and allelo-chemical synthesis) in tissues wounded by borer larvae. However, wounding experiments showed little or no relationship between winter or summer carbohydrate reserves, callus formation, radial growth, or concentrations of tannins and phenolics in wounded or nonwounded phloem tissues. Trees with relatively low winter carbohydrate reserves were again found to be attractive to adult A. bilineatus, although not all low starch trees were attacked or successfully colonized by borers. There was a trend for carpenterworm larvae, Prinoxystus robiniae (Lepidoptera: Cossidae), a generalist bark and wood borer, to be more successful in establishing galleries on low starch trees. Carpenterworms gained significantly more weight when fed phloem from trees attractive to A. bilineatus. Oaks that attracted large numbers of A. bilineatus or that were successfully colonized by the borer produced significantly less callus than did non-attacked trees when experimentally wounded at about the time of Agrilus egg hatch. Callus formation may limit the establishment of small larvae that feed slowly in the cambial region. These results indicate that current theory regarding relationships between increased tree stress and decreased allocation of energy reserves to radial growth and defense against phloem borers may be an oversimplification. We suggest that tree growth and the defensive response of phloem tissues may be limited more by the rate of carbohydrate utilization or by changes in source-sink relationships than by storage levels. Callus formation and synthesis of allelochemicals in wounded phloem may be under the same control as cambial activation, which is mediated by plant growth regulators and can be influenced by environmental conditions.

Attraction of the Twolined Chestnut Borer (Coleoptera: Buprestidae) to Scarlet Oaks Infected with Chestnut Blight Fungus

Chestnut blight fungus, Cryphonectria (Endothia) parasitica , causes bark and wood deformity to the lower bole of scarlet oak, Quercus coccinea L., but does not kill the tree. We tested the hypothesis that C. parasitica infection stresses the tree and predisposes it to attack by the twolined chestnut borer, Agrilus bilineatus (Weber). Scarlet oaks with obvious disease symptoms attracted significantly more A. bilineatus , cerambycids, and scolytids than did apparently healthy trees. However, only 9 of 21 diseased trees were successfully colonized. Total nitrogen and tannin concentrations of the phloem did not differ significantly between diseased and control trees; however, phenolic concentrations were significantly higher in the phloem of diseased trees that were colonized by borers. Total carbohydrate concentrations of xylem and phloem in July did not differ significantly between diseased and control trees, even in those diseased trees that were colonized. However, starch concentrations of the outer sapwood were slightly lower in all diseased trees. This tree decline complex is unusual in that the apparent predisposing stress, C. parasitica , did not reduce radial growth or total carbohydrates, which are generally regarded as indicators of tree vigor.

EVIDENCE FOR SEXUAL ATTRACTION BY THE TWOLINED CHESTNUT BORER, AGRILUS BILINEATUS (WEBER) (COLEOPTERA: BUPRESTIDAE)

In the eastern deciduous forests of North America, oaks (Quercus spp.) that have been weakened by stress are often attacked and killed by the twolined chestnut borer, Agrilus bilineatus (Weber) (Dunn et al. 1986a). This borer attacks stressed and dying trees but does not attack healthy or dead trees (Haack and Benjamin 1982; Dunn et al. 1986a, 1987).

Winter starch reserves of white oak as a predictor of attack by the twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae)

The twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae), attacks oaks (Quercus spp.) and is associated with extensive mortality of trees in the eastern deciduous forests of North America. We tested the hypothesis that winter starch reserves of oak roots are an indicator of tree vigor and that only trees low in stored starch would be attacked by A. bilineatus. We measured the levels of stored starch in the roots of 200 non-infested healthy white oaks during the dormant season and determined their correlation with A. bilineatus attacks the following spring. There was a significant increase in A. bilineatus captures on sticky traps with a decrease in winter starch reserves. Trees low in stored starch that were also stressed by phloem-girdling attracted 3.7 times as many beetles as did non-girdled trees that were low in starch. However, non-girdled trees that had low winter starch reserves were also attacked. Only oaks that had had extremely low winter root starch reserves (<5mg/g dry weight of root sapwood tissue) were heavily attacked by A. bilineatus and subsequently died. One third of non-girdled low starch trees and 67% of phloem-girdled low starch trees died, whereas none of the trees with root starch >5 mg/g dry wt died. These results indicate that winter starch reserves are a good predictor of A. bilineatus attack.

ATTRACTION OF THE TWOLINED CHESTNUT BORER,AGRILUS BILINEATUS(WEBER) (COLEOPTERA: BUPRESTIDAE), AND ASSOCIATED BORERS TO VOLATILES OF STRESSED WHITE OAK

AbstractThe twolined chestnut borer,Agrilus bilineatus(Weber) (Coleoptera: Buprestidae), is associated with mortality of stressed oaks in the eastern deciduous forests of North America. Beetles were attracted to stressed trees within hours of the onset of stress. We hypothesized that adult beetles rapidly locate suitable hosts by olfactory detection of tree-released volatiles. Trees with sticky-band traps and vane traps baited with crude steam distillates from inner bark of stressed white oaks, or with combinations of ethanol and oak volatiles, captured significantly more beetles than did water controls. Ethanol alone did not attract significant numbers ofA.bilineatus. Eighty-two percent of beetles captured were females. Ethanol-baited traps captured large numbers of Cerambycidae, Scolytidae, and a few Cleridae, and these insects were not attracted to oak volatiles. Sticky-band traps were more effective than vane traps in capturingA.bilineatusand other Buprestidae, but Cerambycidae and Scolytidae were more effectively captured in vane traps. Our results show thatA.bilineatusis attracted to oak volatiles but later successional beetles are attracted to ethanol.

The role of host tree condition in attack of white oaks by the twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae)

The twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae), attacks stressed oaks (Quercus spp.) and is associated with extensive mortality of trees in the eastern deciduous forests of North America. We examined host location by the insect and subsequent host mortality in experimentally stressed trees. A. bilineatus adults were able to rapidly and specifically locate stressed oak trees. Up to 160 beetles per week were captured on sticky band traps on the trunks of stressed trees, while beetles rarely landed on unstressed control trees. This suggests that adult borers have an acute perception of host tree "quality", and that this perception is from a distance. One mechanism of host location may be detection of volatile compounds produced by stressed trees.The condition of the host tree appears to regulate both beetle attraction and successful colonization. Mortally wounded (xylem-girdled) trees attracted beetles only until the cambium died. Xylem-girdled trees were attacked early in the beetle flight season, but larvae did not survive to emerge as adults from these trees. In contrast, phloemgirdled trees continued to attract beetles throughout the flight period. Phloem-girdled trees which were heavily attacked by A. bilineatus died late in the season in which they were attacked. Lightly attacked trees survived until the following growing season, and were then heavily attacked and killed. In one stand, phloem-girdled trees were not attacked, healed over the girdling wounds and were still alive three years after girdling. These results indicate that oak trees are only attractive to A. bilineatus within a narrow range of physiological conditions following stress but prior to mortality. A. bilineatus appears to be a proximate agent of mortality in stressed oaks in eastern North America.

Observations on Shade Tree Insects

The elm leaf beetle, Galerucella xanthomelaena, the Japanese beetle, Popillia japonica, the willow leaf beetle, Plagiodera versicolora, and the larch case bearer, ColeoPhoralaricella, were all abundant and possibly as destructive as in 1931. The occurrence of many parasites, Scolia dubia, on a lawn badly injured by the Japanese beetle and the green June beetle, Allorhina nitida, is recorded. Notes are given on the cypress leaf miner, Recurvaria apicitripunctella, a leaf beetle, Calligrapha philadelPhica, a privet thrips, Dendrothrips ornatus, and the black vine weevil, Brachyrhinus sulcatus. The two-lined chestnut borer, Agrilus bilineatus, and the bronze birch borer, Agrilus anxius, were killing trees locally. They were probably favored by the series of droughts in recent years. A bad infestation of rhododendron stems by the pitted ambrosia beetle, Corthylus punctatissimus, is recorded from Long Island, and the local prevalence of the leopard moth, Zeuzera pyrina, on Nantucket Island is reported. The oak pruner, Hypermallus villosus, has been extraordinarily abundant in. the northeastern United States. The fruit tree bark beetle, Scolytus rugulosus, and the European elm bark beetle, Scolytus multistriatus, have developed in great numbers on weak trees. The European pine shoot moth, Rhyacionia buoliana, continues as a destructive pest, and the Nantucket pine moth, Rhyacionia frustrana, has been extremely abundant on Nantucket Island. The recently discovered white pine tip moth, Eucosma gloriola, is becoming somewhat widely distributed, though not seriously injurious. The unusual local abundance of the pitch mass borer, Parharmonia pini, was observed at Bedford Hills, N. Y. The elm lace bug, Corythucha ulmi, and the sycamore lace bug, Corythucha ciliata, have been unusually prevalent, and the work of the linden lace bug, GargaPhia tiliae, came to notice on account of its abundance at Stockbridge, Mass. An elm pouch gall, ErioPhyes sp., was very numerous on elms at Wakefield and Lynnfield, Mass., and the maple bladder gall, Phyllocoptes lJ.uadripes, was extremely abundant on a soft maple at Newburgh, N. Y. The tulip tree scale, Toumeyella liriodendri, was quite prevalent, though it was preyed upon locally by the caterpillars of Laetillia coccidivora. The Euonymus scale, ChionasPis euonymi, has been extremely numerous in various plantings. A new hemlock leaf scale, Fiorinia, near F. fioriniae Kuwana, is becoming established and injurious at several Long Island and southwestern New England localities. The Chinese mantid, Paratenodera sinensis, has been unusually abundant in southwestern New England and southeastern New York.

Observations on Three Important Forest Insects1

The pine spittle bug ( Aphrophora parallela Say) has caused severe damage to Scotch pine plantings in Pennsylvania. The extensive feeding of the adults and nymphs causes retardation in growth to such an extent that the trees die. The fruit-tree leaf-roller( Cacoecia argyrospila Walker) and the elm spanworm ( Ennomos subsignarius Hubner) have caused the death of many hardwoods, especially oaks, in various parts of the State. The larvae defoliate the trees and make them susceptible to the attack of secondary insects, chief of which is the two-lined chestnut borer ( Agrilus bilineatus Weber).

Observations on Shade Tree Insects

There has been widespread insect injury to shade trees the past season in the northeastern United States. Three introduced pests—the elm leaf beetle, (Galerucella xanthomelaena), the Japanese beetle (Popillia japonica) and the Europead willow leaf beetle (Plagiodera versicolora)—have defoliated an estimated one ann three quarter million trees. The larch case bearer (Coleophora laricella), seriously injured a quarter of a million larches growing as ornamentals; while the native fall webworm (Hyphantria textor) and the bagworm (Thyridopteryx ephemeraeformis) have seriously damaged an estimated quarter of a million trees each. In addition, the native walnut caterpillar (Datana integerrima) has been very injurious. The total seriously affected is estimated at two and a half million trees, many being well grown, handsome additions to lawns, streets or parkways. Not a few are highly prized for sentimental reasons. These trees may easily be worth an average of $100 each, the total value therefore being $250,000,000. Repeated annual defoliations mean serious lowering of vitality, and if continued for several years a condition obtaining in many sections, the beauty and utility of the trees are destroyed. The probabilities indicate more sweeping damage in 1932. Sickly, dying trees may be a liability rather than an asset. The time is approaching and has come in certain localities, when it will be necessary to provide systematic protection for shade trees, if we would avoid extensive and irreparable losses. The weakening of trees by several abnormally dry seasons and the general loss of foliage described above has produced ideal conditions for serious damage by borers, especially the hickory bark beetle (Scolytus quadrispinosus), the two-lined chestnut borer (Agrilus bilineatus) and the bronze birch borer (Agritus anxius). This has already commenced and more severe damage may be expected in the next season or two. It is by all means advisable to make comprehensive plans for spraying in areas where these various insects were numerous last year. This alone is not sufficient, since the weakened trees need feeding. Otherwise they may succumb to attack by various borers.