Gladwin Joseph

RESPONSE OF SOME SCOLYTIDS AND THEIR PREDATORS TO ETHANOL AND 4-ALLYLANISOLE IN PINE FORESTS OF CENTRAL OREGON

Lindgren multiple funnel traps were set up in pine forests of central Oregon to determine the response of scolytid bark beetles to ethanol and 4-allylanisole (4AA). Traps were baited with two release rates of ethanol (4.5 or 41.4 mg/hr) and three release rates of 4AA (0, 0.6, or 4.3 mg/hr) in a 2 × 3 factorial design. All traps also released a 1:1 mixture of α- and β-pinene at 11.4 mg/hr. Of 13,396 scolytids caught, Dendroctonus valens made up 60%, Hylurgops spp. 18.5%, Ips spp. 16%, Hylastes spp. 1.8%, Ganthotrichus retusus 0.9%, and bark beetle predators another 2.8%. Increasing the release rate of ethanol in the absence of 4AA increased the number of most scolytid species caught by 1.5–3.7 times, confirming its role as an attractant. Ips latidens, Temnochila chlorodia, and clerid predators were exceptions and did not show a response to higher ethanol release rates. Release of 4AA at the lowest rate inhibited attraction of most scolytids, with a significant reduction in G. retusus, Hylastes macer, and Hylurgops porosus when compared to traps without 4AA. A high release rate of 4AA further inhibited responses for most beetles compared to low 4AA. Seven species were significantly deterred by high 4AA, including the latter three, and Hylastes longicollis, Hylastes nigrinus, Hylurgops reticulatus, and Ips latidens. Exceptions include Hylurgops subcostulatus, which was significantly attracted to both low and high 4AA, and I. pini, which was attracted to low and high 4AA in combination with low ethanol, but unaffected by either release of 4AA with high ethanol. Dendroctonus valens was significantly attracted to low 4AA and unaffected by high 4AA. Predators appeared to be less inhibited by 4AA than most bark beetles. Although 4AA can deter the attraction of some secondary bark beetles to ethanol in combination with α- and β-pinene, this inhibition could be weakened for certain species by increasing ethanol release rates. 4-Allylanisole may have some utility for managing the behavior of secondary bark beetles sensitive to this compound.

Sapwood and crown symptoms in ponderosa pine infected with black-stain and annosum root disease.

Abstract Crown growth parameters, extent of disease in roots, and volatile compounds from sapwood were measured for diseased and healthy ponderosa pine (Pinus ponderosa Dougl. ex Laws.). The pathogens were black-stain root disease, caused by Leptographium wageneri var. ponderosum (Harrington & Cobb), annosum root disease, caused by Heterobasidion annosum (Fr.) Bref., or both. Samples of sapwood collected near the root collar were heated in sealed vials and volatile compounds analyzed by gas chromatography. Acetaldehyde, acetone, ethanol, methanol, and 2-propanol were quantified. Acetaldehyde was selected by logistic regression to be the best predictor for distinguishing healthy from diseased trees. Acetaldehyde concentrations were significantly lower in healthy trees. Concentrations of methanol and acetaldehyde from sapwood were positively correlated to the percentage of non-functional root area caused by disease, while length of the terminal leader and water content of sapwood from near the root collar were negatively related. Crown growth parameters did not change significantly until more than one-third of the root system was diseased. The mean ethanol concentration from diseased trees was significantly higher than that from healthy trees. About half of the diseased pine contained high ethanol concentrations, with substantial variation in concentrations among cardinal positions sampled around the root collar. While high ethanol concentrations were associated with diseased trees, low ethanol concentrations were not a good indicator of health. All volatiles, except ethanol, were partially or entirely generated by thermal decomposition of sapwood constituents when heated in sealed vials during analysis. Nevertheless, some may be useful chemical markers for identifying trees with root disease before the disease reaches an advanced stage. Also, they might be useful in estimating what proportion of a root system is diseased and non-functional.

Ethanol and ambrosia beetles in Douglas fir logs exposed or protected from rain.

Logs from the base of Douglas fir (Pseudotsuga menziesii) trees cut in October 1993 were randomly assigned to one of three treatment groups: (1) wet logs—cut from the fallen tree and left exposed to rain, (2) dry logs—cut from the fallen tree, placed on blocks, and protected from rain under a plastic tent, and (3) crown logs—left attached to the fallen tree with its branches intact and exposed to rain. The following May, ethanol concentrations were highest in the phloem and sapwood of wet logs (0.24 and 0.35 μmol/g fresh wt, respectively). Ethanol concentrations in tissues from dry and crown logs were similar to each other (ranging from 0.002 to 0.03 μmol/g fresh wt), but were significantly lower than in wet logs. It appears that rain absorbed by the outer bark of wet logs creates a barrier to gas exchange between living tissues and the atmosphere, which facilitates the development of hypoxic conditions necessary for ethanol synthesis and accumulation. Branches on crown logs exposed to rain help maintain low ethanol concentrations in the log tissues; we discuss several potential mechanisms to explain this response. By early September, the densities of Gnathothrichus spp. gallery entrance holes were high on wet logs (21.5/m2) and low on dry (2.5/m2) and crown logs (5.8/m2), indicating their preference for logs with higher ethanol concentrations. Protecting logs from rain will significantly reduce ethanol concentrations and the density of ambrosia beetle galleries. Leaving branches attached to logs will produce similar results, but its effectiveness may vary depending on the environmental conditions. Host selection by secondary scolytid beetles that use ethanol as a kairomone can be manipulated and possibly managed by controlling the production of ethanol in the host resource.

Ethanol Synthesis and Water Relations of Flooded Pseudotsuga menziesii (Mirb.) Franco (Douglas-Fir) Seedlings under Controlled Conditions

Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings were flooded in a controlled environment. Roots rapidly synthesized ethanol with the highest rates during the first 6 h. Ethanol readily diffused into the flooding solution and moved into the stem. Ethanol concentrations in the flooding solution (normalized g-1 dry mass of roots) were four to six times the concentrations in the stems or roots. Ethanol concentrations in the roots and stems were six to 16 times larger than in the needles. Stomatal conductance and water uptake continuously increased during the first 96 h of flooding, whereas ethanol concentrations in the roots and stem increased to their maximum at 6-24 h after flooding and then decreased. Supplying Douglas-fir shoots with ethanol concentrations at two to three times those measured in flooded seedlings had no effect on stomatal conductance. Ethanol synthesis and accumulation in Douglas-fir seedlings in response to flooding does not have a detrimental impact on stomatal conductance or water uptake.

Ethanol synthesis, nitrogen, carbohydrates, and growth in tissues from nitrogen fertilized Pseudotsuga menziesii (Mirb.) Franco and Pinus ponderosa Dougl. ex Laws. seedlings

Abstract Seedlings of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, and ponderosa pine, Pinus ponderosa Dougl. ex Laws., were grown in a controlled environment and fertilized with nutrient solutions containing 150 ppm (+N), or 0 ppm nitrogen (−N). These treatments greatly altered seedling growth, and the concentrations of N and carbohydrates in their tissues. Metabolically active tissues, such as roots, incubated with a limited supply of O2 became hypoxic faster and synthesized more ethanol than less active tissues, such as needles. All tissues that were incubated for 4 h in N2 synthesized ethanol. Needles incubated in N2 and light had much lower quantities of ethanol than needles in N2 and dark, suggesting that O2 from photosynthetsis limited internal anoxia. Most tissues from +N seedlings synthesized greater quantities of ethanol in N2 anoxia than tissues from −N seedlings, probably because they were able to produce more enzymes with a greater availability of N. However, this increase in ethanol synthesis between N treatments was most pronounced in the phloem. Ethanol and soluble sugar concentrations were negatively related in needles and positively related in roots of N+ seedlings, but not −N seedlings. Starch concentrations had no effect on the amount of ethanol produced by any tissue. Regardless of N treatments, all tissues from ponderosa pine produced more N2-induced ethanol than Douglas-fir, in part because its tissues contained different concentrations of soluble sugars and N as a consequence of phenological differences between the species. However, ponderosa pine tissues may also maintain greater quantities of anaerobic enzymes, or their isozymes than Douglas-fir.

Effects of nitrogen and Douglas-fir allelochemicals on development of the gypsy moth,Lymantria dispar

Two experiments were conducted to examine the influence of foliar nitrogen, terpenes, and phenolics of Douglas-fir on the development of gypsy moth larvae. In the first experiment, foliar concentrations of nitrogen and allelochemicals were manipulated by fertilizing 3-year-old potted seedlings with 0 or 200 ppm nitrogen. Concentrations of foliar nitrogen (0.33–2.38%) were negatively correlated with the phenolics (15.8–24.4 mg/g). Sixth-instar larvae previously reared on current-year Douglas-fir needles were allowed to feed on these seedlings. Pupal weights (312.8–995.6 mg) were positively correlated with levels of foliar nitrogen, negatively correlated with amounts of foliar phenolics, and uncorrelated with terpene concentrations. In the second experiment, terpene and phenolic extracts from Douglas-fir foliage were incorporated at natural levels into artificial diets with high and low levels of protein nitrogen. Neonate larvae grew faster and were larger on the high nitrogen control diet (4.1–4.5%), however, fourth instars performed better on the control diet with low nitrogen levels (2.5–2.7%). Foliar terpenes incorporated into diet had little effect on neonate fitness, but may induce subtle physiological changes in later instar larvae. Phenolics, alone or in combination with terpenes, excessively suppressed growth and survival, with no individuals living through the fourth instar, regardless of the nitrogen level. Incorporating foliar phenolic extracts into artificial diet caused unnatural levels of toxicity and failed to clarify the effects of Douglas-fir phenolics on gypsy moth fitness. Foliar nitrogen is a key factor influencing gypsy moth development on Douglas fir, but may be mitigated to some degree by phenolics.

Ethanol and Water in Pseudotsuga menziesii and Pinus ponderosa Stumps

Douglas fir (Pseudotsuga menziesii), west of the Oregon Cascades, and ponderosa pine (Pinus ponderosa), east of the Cascades, were cut during the fall in conjunction with various forest management practices. Trees cut varied in size and age, and the stumps were exposed to disparate winter temperatures and precipitation patterns. Nevertheless, the stumps showed similar responses in their synthesis and accumulation of ethanol. The following spring, ethanol concentrations in above-ground tissues of both species ranged from 3 to 116 times higher than in their corresponding root tissues. We suggest that this difference results from the above-ground tissues being more hypoxic than roots because they were exposed to more water from precipitation and warmer temperatures. Ethanol concentrations in the above-ground tissues of ponderosa pine stumps were about two to six times higher than in Douglas fir, and root tissues from pine stumps usually contained more ethanol after anaerobic incubation than roots from Douglas fir. Ethanol and volatile terpenes released from stumps can attract various beetle species that not only vector root diseases, but can also damage or kill seedlings and saplings. Understanding the dynamics of ethanol synthesis and accumulation in stumps and slash might contribute to new alternatives for managing these insects.

Physiology and growth of Douglas-fir seedlings treated with ethanol solutions

Applying 1, 5, 10, and 20% solutions of ethanol to the roots of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings three times a week was deleterious to their physiology and growth. Ethanol concentrations of 10% or higher were lethal within a week of treatment initiation, while the 5% solution was lethal to seedlings at 8 weeks. Seedlings treated with the 1% solution were alive at 8 weeks, but showed signs of physiological decline. If Douglas-fir seedlings have a tolerance threshold for ethanol solutions applied to their roots, it appears to be at a concentration below 1%. Ethanol moved up the stems and into needles, yielding concentrations in the stems 9 times higher than in needles. Ethanol vapors in the atmosphere surrounding seedlings readily diffused into needles, but not into stems. After 1 week of treatments, net photosynthesis, stomatal conductance, and transpiration declined as ethanol concentrations increased. However, seedlings treated with the control (0%) and 1% ethanol solutions had the same xylem water potentials, which were higher than for seedlings treated with the 5% solutions. High ethanol concentrations (]1%) may have damaged membranes involved in photosynthesis and stomatal function thereby causing the observed decline in net photosynthesis and stomatal conductance. At concentrations] 5%, water uptake was impaired, suggesting that root membranes may have been damaged.

White alder and Douglas-fir foliage quality and interegg-mass influences on larval development of gypsy moth,Lymantria dispar.

Individual families of gypsy moth collected from a single population exhibited different degrees of fitness when fed diets of white alder, a suitable broadleaf host, and Douglas-fir, an unsuitable conifer host. Members of families on diets of Douglas-fir had significantly lower survival, longer larval periods, lower pupal weights, and shorter pupal periods than members of the same families fed alder. Foliar nutritional quality, including nitrogen level and allelochemical composition (terpenes and phenols), was considered the key factor responsible for these differences. Growth parameters differed significantly for families within diet treatments, indicating that the genetic resources of a family did affect performance somewhat. The influence of a familys genetic resources on larval survival was most notable when larvae were under the greatest nutritional stress.