Robert A. Haack

Defensive Strategies of Woody Plants Against Different Insect-Feeding Guilds in Relation to Plant Ecological Strategies and Intimacy of Association with Insects

A major question confronting scientists who want to exploit plant resistance in the management of a particular insect or pathogen pest is whether the plant in question has any exploitable resistance, and if so, what are the likely resistance mechanisms (Harris 1980, 1982). This question is not trivial because its answer affects the entire research approach--how to search for resistance. To this end, we offer here, a framework for classifying defensive strategies by certain classes of plants against various feeding guilds of herbivores.

Evolving management strategies for a recently discovered exotic forest pest: the pine shoot beetle, Tomicus piniperda (Coleoptera)

Established populations of the Eurasian pine shoot beetle (Tomicus piniperda (L.); Coleoptera: Scolytidae) were first discovered in North America in Ohio in 1992. As of 31 December 2000, T. piniperda was found in 303 counties in 12 US states (Illinois, Indiana, Maine, Maryland, Michigan, New Hampshire, New York, Ohio, Pennsylvania, Vermont, West Virginia, and Wisconsin) and in 43 counties in 2 Canadian provinces (Ontario and Quebec). A federal quarantine imposed in November 1992 regulates movement of pine (Pinus) trees, logs, and certain pine products from infested to uninfested areas within US. The forest products, Christmas tree, and nursery industries are affected by the quarantine. This paper summarizes information on the discovery and spread of T. piniperda in North America, survey efforts, recent interception history, development and changes in the federal quarantine, development of a national compliance management program, and extension and research efforts.

Effects of Cutting Date, Outdoor Storage Conditions, and Splitting on Survival of Agrilus planipennis (Coleoptera: Buprestidae) in Firewood Logs

The emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an exotic pest of ash (Fraxinus spp.) in North America. We conducted studies in Michigan to evaluate how different tree cutting dates, outdoor storage conditions, and splitting affected A. planipennis survival in firewood logs. In 2002-2003, we cut logs from A. planipennis-infested ash trees each month, from July to October, and stored half of the logs in shade and half in full sun. In 2003-2004, we tested logs cut July-December; stored in sun versus shade; tarped versus untarped; and whole logs versus split logs. For both years, A. planipennis successfully emerged the summer after cutting from logs that represented all treatments and all cutting dates tested. Adult emergence density was significantly lower in logs cut in July and August. In 2003-2004, A. planipennis adult length was significantly shorter, and percentage of mortality was significantly higher for logs cut in August compared with later months. Emergence density was significantly lower for split logs compared with whole logs for all cutting months except for December. There was no significant difference in adult emergence density between logs stored in full sun versus shade in 2002-2003. In 2003-2004, untarped logs in full sun or shade had significantly lower adult emergence densities than tarped logs in the sun or shade. In conclusion, emergence, survival, and size of A. planipennis was significantly reduced if logs were cut early during larval development (July or August); splitting logs and storing them untarped in full sun or shade further reduced adult emergence. No treatment was 100% effective in preventing adult emergence.

Pine shoot beetle, Tomicus piniperda (Col., Scolytidae), responses to common green leaf volatiles

We tested the hypothesis that green leaf volatiles (GLVs) disrupt the response of overwintered pine shoot beetles, Tomicus piniperda (L.) to multiple‐funnel traps baited with the attractive host volatile α‐pinene. A combination of four GLV alcohols, 1‐hexanol (E)‐2‐hexen‐1‐ol (Z)‐2‐hexen‐1‐ol, and (Z)‐3‐hexen‐1‐ol, caused 54 and 36% reduction in the number of pine shoot beetles captured in two separate trapping experiments. Similarly, a combination of the four alcohols plus two GLV aldehydes, hexanal and (E)‐2‐hexenal, caused 38% reduction in the number of pine shoot beetles captured compared with α‐pinene alone. A blend of the two GLV aldehydes was not disruptive. None of the four GLV alcohols nor the two GLV aldehydes were disruptive when tested individually. The finding that the blend of four GLV alcohols reduced attraction of T. piniperda supports the general hypothesis that GLVs common to nonhost angiosperms are disruptive to conifer‐attacking bark beetles (Scolytidae).

Attack Densities of Tomicus piniperda and Ips pini (Coleoptera: Scolytidae) on Scotch Pine Logs in Michigan in Relation to Felling Date1

Established populations of an exotic bark beetle, the larger pine shoot beetle [Tomicus piniperda (L.)], were first reported in Ohio in July 1992. Subsequent surveys through July 1994 have found T. piniperda in six states in the United States and in one Canadian Province in the Great Lakes region. One-meter-long trunk sections were cut from Scotch pine (Pinus sylvestris L.) trees felled from February through July 1993 in a forested site in southern Michigan, laid horizontally, allowed to undergo natural attack by bark beetles and associates, and later dissected. In southern Michigan in 1993, T. piniperda initiated spring flight in late March; the pine engraver [Ips pini (Say)], a native pine bark beetle, initiated spring flight about one month later in late April. Tomicus piniperda attacks (galleries) were found in logs cut during February through May. Attack densities of T. piniperda were highest in February-cut logs, and declined with subsequent felling dates. The highest T. piniperda attack density recorded for an entire log section was 263 attacks/m 2 of bark area on one of the February-cut logs. Ips pini attack densities tended to increase with later felling dates. When I. pini attacked logs that had already been colonized by T. piniperda, I. pini galleries were mostly found on the upper log surface. When I. pini attacked logs with few or no T. piniperda, I. pini galleries were found on all log surfaces. By initiating spring flight several weeks before I. pini, T. piniperda is able to colonize much of the susceptible pine material and thereby may lower I. pini populations.

Tomicus piniperda (Coleoptera: Scolytidae) Shoot-Feeding Characteristics and Overwintering Behavior in Scotch Pine Christmas Trees

Abstract Overwintering behavior of Tomicus piniperda (L.) was studied in a Scotch pine (Pinus sylvestris L.) Christmas tree plantation in Indiana (1992–1994) and a plantation in Michigan (1994). In general, adults feed inside shoots during summer, then move to overwintering sites at the base of trees in autumn. In early autumn, adults were most often found in shoot-feeding tunnels that were still surrounded by green needles, whereas few were in tunnels surrounded by yellow or brown needles. For all years and sites combined, the range in the percentage of recently tunneled shoots that contained live T. piniperda adults decreased from 89 to 96% in mid-October, to 15–66% in early November, to 2–10% in mid-November, and to 0–2% by late November to early December. In each year, the first subfreezing temperatures in autumn occurred in October, before most adults left the shoots. Of 1,285 T. piniperda-tunneled shoots, one to seven tunnels (mean = 1.6) and zero to three adults were found per infested shoot. Of these 1,285 attacked shoots, 55% of the shoots had one tunnel, 33% had two, 9% had three, 3% had four, and <1% had five to seven tunnels each. When two or more tunnels occurred in a single shoot, adults were most commonly found in the innermost (most basal) tunnel. For the 2,070 tunnels found in the 1,285 shoots, average shoot thickness at the tunnel entrance was 6.0 mm, average distance from the tunnel entrance to the shoot tip was 6.3 cm, and average tunnel length was 2.3 cm. Four Scotch pine Christmas trees were dissected in January 1993. Eighty percent of the tunneled shoots were in the upper quarter of the tree crown and 98% were in the upper half. For the four trees inspected in January, one live adult was found in a shoot and 85 adults were found in the outer bark along the lower trunk from 1 cm below the soil line to 19 cm above the soil line. No overwintering adults were found outside the trunk in the duff or soil near the base of each test tree. Implications of these results are discussed in terms of surveying, timing the cutting of Christmas trees, and cutting height for Christmas trees.

Tomicus piniperda (Coleoptera: Scolytidae) Emergence in Relation to Burial Depth of Brood Logs

Abstract The pine shoot beetle, Tomicus piniperda (L.), is an exotic pest of pines, Pinus spp., that was first found in the United States in 1992. A federal quarantine currently regulates movement of pine Christmas trees and pine nursery stock from infested to uninfested counties. The current national Pine Shoot Beetle Compliance Management Program requires T. piniperda-infested brood material to be disposed of by burning, chipping, or burial. The burial option requires that the infested pine material be buried at a depth of at least 30 cm. We tested this requirement by burying logs with similar levels of infestation at 0, 15, 30, 45, 61 and 76 cm and then monitoring for T. piniperda emergence. Logs were buried at two times during larval development (early and late) and in two soil types (sandy loam and loam). Emergence patterns from the two soil types were similar. Overall, 1,747 T. piniperda adults were collected from the 24 exposed control logs, but only 34 adults from the 120 buried logs, including 24 adults from logs buried at 15 cm, eight adults from 30 cm, one adult from 45 cm, and one adult from 61 cm. In comparing mean emergence density from buried logs with that of exposed logs, 98.6% mortality occurred at 15 cm, 99.5% at 30 cm, and >99.9% at ≥45 cm. Mean date of T. piniperda emergence to the soil surface was affected by burial depth and burial date, but not soil type.

Tomicus piniperda (Coleoptera: Scolytidae) Initial Flight and Shoot Departure Along a North-South Gradient

Abstract The exotic pine shoot beetle, Tomicus piniperda (L.) (Coleoptera: Scolytidae), established in the north central and northeastern United States (U.S.) and adjacent regions in Canada, is regulated by a federal quarantine that restricts movement of pine material during specific times of the year based on the beetle’s life history. Although climatic variation occurs across T. piniperda’s range, a single set of dates is used for timing the movement of pine logs. We monitored T. piniperda spring flight, fall shoot departure, and air and internal tree temperatures at three sites along a 300-km north-south gradient in Michigan and Indiana. We also estimated dates for initial spring flight (12°C threshold) and fall shoot departure (0°C threshold) across an 850-km gradient using historical temperature records (1901 to 1999). Average daily temperatures in fall 1997 (8 October to 12 December) and spring 1998 (20 February to 21 April) were 1.8 to 2.4°C colder, respectively, at the northern field site than at the southern field site. Fall shoot departure began at approximately the same time (day 289 to 290) at all three field sites, but complete shoot departure was extended by 3 wk at the southern site (day 336) compared with the northern site (day 317). T. piniperda adults were first captured in funnel traps on calendar day 86 at the northern site and on day 59 at the central and southern field sites. Peak flight occurred at approximately the same time (day 86) at all three sites. Within-shoot temperatures were very similar to air temperatures in the fall and aboveground inside-bark temperatures were similar to air temperatures in the spring. Average predicted dates based on historical temperature records varied by 31 d for initial shoot departure and 84 d for initial spring flight between northern Michigan and southern Indiana. Because considerable variation can occur in T. piniperda behavior across a broad geographic range, dates specified in the U.S. Federal quarantine should be adjusted according to local temperatures.