David L. Wood

The Pitch Canker Epidemic in California

Native Monterey pine (Pinus radiata D. Don) forests are currently found at three disjunct locations in coastal California and on two islands off the coast of Mexico. The mainland forests comprise, in total, approximately 4,500 ha (11), whereas the two island populations are limited to 150 ha on Cedros Island and fewer than 400 trees on Guadalupe Island (28). Collectively, these populations are significant ecological and recreational resources, but they are also a valuable repository of useful genetic traits for improved varieties of Monterey pine, which are widely used by the timber industry. In California, Monterey pine is important as a landscape tree, with an estimated 50 million standing trees as of 1985. Monterey pines were especially popular for plantings on freeway rights-of-way, where they served as visual and sound barriers for the adjacent properties. It was among such trees that a dieback problem became apparent in Santa Cruz County (Fig. 1) during the mid-1980s. In 1986, A. H. McCain, extension plant pathologist at University of California Berkeley, established that the affected trees were suffering from pitch canker (30), caused by Fusarium circinatum Nirenberg & O’Donnell (=Fusarium subglutinans (Wollenweb. & Reinking) Nelson, Toussoun, & Marasas f. sp. pini). Subsequent surveys showed the disease to be widespread in coastal Santa Cruz County, with a clearly disjunct infestation being found farther inland, in Alameda County (Fig. 1). Curiously, the disease was also found in Christmas tree farms in Los Angeles and San Diego counties, more than 450 km to the southeast (8).

Response to host volatiles by native and introduced populations of Dendroctonus valens (Coleoptera: Curculionidae, Scolytinae) in North America and China

Bark beetles (Coleoptera: Curculionidae, Scolytinae) have specialized feeding habits, and commonly colonize only one or a few closely related host genera in their geographical ranges. The red turpentine beetle, Dendroctonus valens LeConte, has a broad geographic distribution in North America and exploits volatile cues from a wide variety of pines in selecting hosts. Semiochemicals have been investigated for D. valens in North America and in its introduced range in China, yielding apparent regional differences in response to various host volatiles. Testing volatiles as attractants for D. valens in its native and introduced ranges provides an opportunity to determine whether geographic separation promotes local adaptation to host compounds and to explore potential behavioral divergence in native and introduced regions. Furthermore, understanding the chemical ecology of host selection facilitates development of semiochemicals for monitoring and controlling bark beetles, especially during the process of expansion into new geographic ranges. We investigated the responses of D. valens to various monoterpenes across a wide range of sites across North America and one site in China, and used the resulting information to develop an optimal lure for monitoring populations of D. valens throughout its Holarctic range. Semiochemicals were selected based on previous work with D. valens: (R)-(+)-α-pinene, (S)-(−)-α-pinene, (S)-(−)-β-pinene, (S)-(+)-3-carene, a commercially available lure [1:1:1 ratio of (R)-(+)-α-pinene:(S)-(−)-β-pinene:(S)-(+)-3-carene], and a blank control. At the release rates used, (+)-3-carene was the most attractive monoterpene tested throughout the native range in North America and introduced range in China, confirming results from Chinese studies. In addition to reporting a more effective lure for D. valens, we present a straightforward statistical procedure for analysis of insect trap count data yielding cells with zero counts, an outcome that is common but makes the estimation of the variance with a Generalized Linear Model unreliable because of the variability/mean count dependency.

Acetophenone as an anti-attractant for the western pine beetle, Dendroctonus Brevicomis LeConte (Coleoptera: Scolytidae).

Host location and colonization by bark beetles is dependent upon the relative and absolute amounts of attractant and antiattractant compounds available. Many investigations have lead to use of antiattractants for the management of these pests and have been especially focused on verbenone. However, recent studies have identified new antiattractants for several species of bark beetles. We report results of recent investigations of the response of western pine beetle, Dendroctonus brevicomis LeConte, to two recently identified antiattractants, acetophenone, and fenchyl alcohol, with verbenone as a standard of comparison, in northern California. Release of both acetophenone and verbenone resulted in significantly lower trap catches of D. brevicomis in aggregation pheromone-baited traps, while fenchyl alcohol was inactive. Acetophenone was the only antiattractant that did not reduce numbers of the most abundant predator of D. brevicomis, Temnochila chlorodia (Mannerheim), responding to the attractant pheromone of its prey. Aggregation pheromone-baited traps with acetophenone also had the highest predator/prey ratio. Our results suggest that acetophenone may be part of the intra- and interspecific interactions among sympatric species of bark beetles and may have application in their control.

Spatial pattern dynamics of oak mortality and associated disease symptoms in a California hardwood forest affected by sudden oak death

Sudden oak death is a disease affecting coastal forests in California and southern Oregon. The spatial pattern of disease dynamics is important for forest and landscape pathology; in this work we investigated the interaction across landscape scales of disease symptomology in coast live oaks, Quercus agrifolia, (trunk bleeding, presence of beetles, and presence of the fungus Hypoxylon thouarsianum) and tree mortality through time. We used two-dimensional spatial analysis tools with data gathered in point-centered-quarter format in 2001 and 2004 to quantify the population density of the disease through time; to examine the spatial pattern of tree mortality across scales through time; and to examine the spatial co-occurrence of disease symptoms with crown mortality through time. Early in the study period dead trees were strongly clustered at smaller scales (~300 m) and after three years this clustering was less pronounced. Bleeding on trees occurred in clusters away from dead trees, particularly in 2004, likely indicating a new cohort of infected trees. The presence of H. thouarsianum was strongly related to overstory mortality through time. Beetle-infested trees co-occurred with mortality in 2001. By 2004, they occurred throughout the forest, and were less strongly correlated with overstory tree mortality, suggesting a future peak of tree mortality.

Suppression of Dendroctonus Brevicomis by Using a Mass-Trapping Tactic

Bark beetles (Scolytidae that feed on phloem and cambium) are a major pest of coniferous forests throughout the northern hemisphere (Rudinsky, 1962). Many bark beetle species use aggregative pheromones to colonize temporary habitats where they feed, mate, and reproduce (Wood, 1972; Borden, 1974). These pheromones offer exciting possibilities for pest suppression because they attract both sexes and because aggregation is essential for reproduction (Wood, 1972; Wood and Bedard, 1977).

A Blend of Ethanol and (−)-α-Pinene were Highly Attractive to Native Siricid Woodwasps (Siricidae, Siricinae) Infesting Conifers of the Sierra Nevada and the Allegheny Mountains

Woodwasps in Sirex and related genera are well-represented in North American conifer forests, but the chemical ecology of native woodwasps is limited to a few studies demonstrating their attraction to volatile host tree compounds, primarily monoterpene hydrocarbons and monoterpene alcohols. Thus, we systematically investigated woodwasp-host chemical interactions in California’s Sierra Nevada and West Virginia’s Allegheny Mountains. We first tested common conifer monoterpene hydrocarbons and found that (−)-α-pinene, (+)-3-carene, and (−)-β-pinene were the three most attractive compounds. Based on these results and those of earlier studies, we further tested three monoterpene hydrocarbons and four monoterpene alcohols along with ethanol in California: monoterpene hydrocarbons caught 72.3% of all woodwasps. Among monoterpene hydrocarbons, (+)-3-carene was the most attractive followed by (−)-β-pinene and (−)-α-pinene. Among alcohols, ethanol was the most attractive, catching 41.4% of woodwasps trapped. Subsequent tests were done with fewer selected compounds, including ethanol, 3-carene, and ethanol plus (−)-α-pinene in both Sierra Nevada and Allegheny Mountains. In both locations, ethanol plus (−)-α-pinene caught more woodwasps than other treatments. We discussed the implications of these results for understanding the chemical ecology of native woodwasps and invasive Sirex noctilio in North America. In California, 749 woodwasps were caught, representing five species: Sirex areolatus Cresson, Sirex behrensii Cresson, Sirex cyaneus Fabricius, Sirex longicauda Middlekauff, and Urocerus californicus Norton. In West Virginia 411 woodwasps were caught representing four species: Sirex edwardsii Brullé, Tremex columba Linnaeus, Sirex nigricornis F., and Urocerus cressoni Norton.

Robert Milton Silverstein 1916–2007

On February 26, 2007, Robert Milton Silverstein died peacefully, surrounded by his family, at the age of 90. He was an internationally recognized expert on the chemistry of insect communication. His pioneering studies led to the development of the field of chemical ecology. Born in Baltimore, MD, he grew up in Tottenville, Staten Island. He earned a B.S. in Chemistry at the University of Pennsylvania and an M.S. and a Ph.D. at New York University. During WWII, Milt served in the Army Medical Corps and was sent to the Pacific Theater, where he rose to the rank of Captain. He married Olive Jorgenson in 1943. They began a family and, in 1948, moved to California. Milt worked for 21 years at the Stanford Research Institute (SRI), where he made significant contributions in analytical methods, chemical synthesis, and flavor and fragrance chemistry. While at SRI, he began his ground-breaking studies in chemical ecology and wrote the first edition of his textbook, J Chem Ecol (2007) 33:1128–1130 DOI 10.1007/s10886-007-9297-y

Frequently Asked Questions on Pitch Canker

Author(s): Storer, Andrew J; Wood, David L; Gordon, Thomas R | Abstract: Pitch canker can kill branches on Monterey pines, and sometimes kills the entire tree. Use the color photos in this electronic publication to identify pitch canker, and learn what you can do to check its spread.