Sheri L. Smith

Detection and quantification of Leptographium wageneri, the cause of black-stain root disease, from bark beetles (Coleoptera: Scolytidae) in Northern California using regular and Real-time PCR

Black-stain root disease is a threat to conifer forests in western North America. The disease is caused by the ophiostomatoid fungus Leptographium wageneri (W.B. Kendr.) M.J. Wingf., which is assoc...

Thinning Jeffrey pine stands to reduce susceptibility to bark beetle infestations in California, U.S.A.

1 Bark beetles (Coleoptera: Curculionidae, Scolytinae) are commonly recognized as important tree mortality agents in coniferous forests of the western U.S.A. 2 High stand density is consistently associated with bark beetle infestations in western coniferous forests, and therefore thinning has long been advocated as a preventive measure to alleviate or reduce the amount of bark beetle‐caused tree mortality. 3 The present study aimed to determine the effectiveness of thinning to reduce stand susceptibility to bark beetle infestations over a 10‐year period in Pinus jeffreyi forests on the Tahoe National Forest, California, U.S.A. Four treatments were replicated three times within 1‐ha square experimental plots. Treatments included thinning from below (i.e. initiating in the smallest diameter classes) to a residual target basal area (cross‐sectional area of trees at 1.37 m in height) of: (i) 18.4 m2/ha (low density thin); (ii) 27.6 m2/ha (medium density thin); (iii) 41.3 m2/ha (high density thin); and (iv) no stand manipulation (untreated control). 4 Throughout the present study, 107 trees died as a result of bark beetle attacks. Of these, 71% (75 trees) were Abies concolor killed by Scolytus ventralis; 20.6% (22 trees) were Pinus ponderosa killed by Dendroctonus ponderosae; 4.7% (five trees) were P. jeffreyi killed by Dendroctonus jeffreyi; 1.8% (two trees) were P. jeffreyi killed by Ips pini; 0.9% (one tree) were P. jeffreyi killed by Orthotomicus (= Ips) latidens; 0.9% (one tree) were P. ponderosa killed by both Dendroctonus brevicomis and D. ponderosae; and 0.9% (one tree) were P. jeffreyi killed by unknown causes. 5 In the low density thin, no pines were killed by bark beetles during the 10‐year period. Significantly fewer trees (per ha/year) were killed in the low density thin than the high density thin or untreated control. No significant treatment effect was observed for the percentage of trees (per year) killed by bark beetles.

Evaluation of a commercially available ELISA kit for quantifying imidacloprid residues in Erthrina sandwicensis leaves for management of the Erythrina gall wasp, Quadrastichus erythrinae Kim.

The erythrina gall wasp (EGW), Quadrastichus erythrinae Kim 2004, was first detected in Hawaii in 2005 and has been infesting and killing Erythrina trees throughout the island chain since. It is believed EGW originated from Africa (Messing et al. 2009). Its host range appears to be limited to Erythrina; its geographic range already includes much of Asia and the Pacific. In North America, EGW has recently become established in south Florida and it is expected that introductions will occur to southern California (Smith et al. 2007). Observations indicate that a highly favored host is E. variegate L., but numerous species, including the Hawaiian endemic, E. sandwicensis O. Deg are severely injured and killed. Erythrina are warm-loving plants with about 115 species in the genus. It is expected that EGW will expand its geographic range to meet that of its host Erythrina with some restrictions due to climate (Li et al. 2006).

Efficacy of Systemic Insecticides for Control of the Invasive Goldspotted Oak Borer (Coleoptera: Buprestidae) in California

Abstract From 2009 to 2013, we tested four systemic insecticide formulations and five application methods against the invasive goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), in California. The insecticides were evaluated in three experiments: 1) 2009 remedial applications of emamectin benzoate (stem-injection) and imidacloprid (stem-injection and soil-injection); 2) 2009–2012 emamectin benzoate and imidacloprid initially applied at different times during the dormant season with varying injection technologies; and 3) 2013 dinotefuran applied to several tree diameter size classes. Adult leaf-feeding bioassays were used to assess the impact of systemic treatments against A. auroguttatus, whereas enzyme-linked immunosorbent assays determined the quantity of the active ingredient of insecticide residues in foliage. Imidacloprid (experiment 1) persisted at elevated levels in foliage of coast live oak, Quercus agrifolia Née, for 1.5 yr following stem injections. Stem injections of emamectin benzoate (experiment 2) sometimes significantly decreased survival in adults fed foliage from treated Q. agrifolia, and both the emamectin benzoate and imidacloprid treatments reduced adult feeding in some trials. Imidacloprid residues in Q. agrifolia and California black oak, Quercus kelloggii Newb., foliage remained at elevated levels (>10 µg/g) ∼2 yr postapplication. In 2013 (experiment 3), dinotefuran residues were highest in foliage collections 2 wk postapplication and greatest in smaller diameter oaks, but insecticide treatment had no effect on survival or frass production by adults fed foliage from treated trees. Systemic injections of emamectin benzoate and imidacloprid applied during the dormant season to uninfested or lightly infested oaks can reduce adult A. auroguttatus survival and maturation feeding.

An improved synthetic attractant for the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), in northeastern California

The mountain pine beetle, Dendroctonus ponderosae Hopkins 1902, is found in pine forests throughout the western U.S., north to northern British Columbia and Alberta, Canada and south to Mexico. It causes high levels of pine mortality throughout its range. Hosts include many species of Pinus (Pinaceae); in northern California, D. ponderosae is a pest of pine types dominated by P. ponderosa Douglas ex Lawson et C.Lawson, P. contorta Douglas ex Loudon, P. monticola Douglas ex D. Don, and in mixed conifer types where P. lambertiana Douglas is the principal host (Struble 1945). The extensive geographic range of D. ponderosae, and the variability in environments in which it occurs, create challenges for developing effective semiochemical tools for reducing beetle-caused tree mortality. Nonrandom genetic variation occurs among populations of D. ponderosae and has been attributed to both geography and host differences Variation has also been observed in D. ponderosae responses to host-produced pheromone synergists (Pitman & Vité 1969, Billings et al. 1976, Libbey et al. 1985, Miller & Lindgren 2000), leading to uncertainties in semiochemical deployment among locations and forest types. Semiochemical attractants (lures) can be used efficiently only when their effectiveness in different locations and host types is understood. For more than 20 years the standard lure for D. ponderosae has consisted of three components: two pheromones, trans-verbenol and exo-brevicomin, and myrcene, a host-based monoterpene synergist (Borden & Lacey 1985). This lure has generally caught greater numbers of D. ponderosae than other combinations of host compounds; however, most comparisons have been limited to British Columbia (e.g., Borden et al. 1987, Pureswaran & Borden 2005). In western U.S., uncertainty remains about the relative effect of individual monoterpenes for synergizing aggregation pheromones of D. ponderosae. This is especially true for terpinolene, which is commonly found as a minor component of oleoresin in hosts of D. ponderosae (e.g., Smith 2000), and has been found to catch similar numbers of beetles to myrcene in some forest types (Billings et al. 1976). Terpinolene appears to be less ubiquitous in western pines than myrcene, but in California is frequently present in the oleoresins of both P. ponderosa and P. lambertiana among others (Smith 2000, S. L. Smith et al. unpublished data). Because the effectiveness of terpinolene as a pheromone synergist for D. ponderosae has varied (Billings et al. 1976, Conn et al. 1983), its utility for particular applications (geographic regions and forest types) must be evaluated before …