Sarah L. Bates

Impact of Leptoglossus occidentalis (Hemiptera: Coreidae) on Douglas-Fir Seed Production

Abstract We investigated the effect of feeding by the western conifer-seed bug, Leptoglossus occidentalis Heidemann, on seed production in developing cones of coastal Douglas-fir, Pseudostuga menziesii (Mirb.) Franco, with respect to seed bug life stage and sex (nymphs, adult females, and adult males) and timing of feeding (early, mid-, and late season cone development). Feeding by females on caged cones for a 2-wk period during late season cone development reduced the proportion of full seeds in cones by ≈70% compared with caged control cones. There was no significant difference among nymphs, adult females, and adult males with respect to the proportion of empty or partially fed-upon seeds produced during the same feeding period. Feeding by nymphs for 2 wk early in the season resulted in a threefold increase in the number of unextractable seeds fused to cones compared with the control. Weight measurements of harvested seeds indicated that radiography is an accurate tool to distinguish among Douglas-fir seeds that have sustained light, moderate, or severe damage. Determining the full impact of L. occidentalis on conifer seed production will require the development of a reliable method to distinguish between naturally aborted seeds and seeds emptied through feeding by seed bugs.

Life table for Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae) and prediction of damage in lodgepole pine seed orchards

Abstract  1 Fecundity, egg hatch and nymphal survivorship of Leptoglossus occidentalis Heidemann were determined and used to develop a damage prediction formula for seed bugs in lodgepole pine seed orchards.

Measuring the Impact of Leptoglossus occidentalis (Heteroptera: Coreidae) on Seed Production in Lodgepole Pine Using an Antibody-Based Assay

Abstract We measured the impact of Leptoglossus occidentalis on seed production in lodgepole pine, Pinus contorta variety latifolia Engelmann, using an antibody marker developed to detect residual saliva in fed-on seeds. Nymphs, adult females, and adult males were caged on cones during early, mid- and late season cone development. Individual analysis of 12,887 seeds extracted from 365 cones revealed that 37.3% seeds tested positive for seed bug saliva. The antibody assay was 38 times more effective than radiography at detecting seed bug damage. Radiography can detect partially emptied seed but cannot discriminate between aborted seeds and those emptied by seed bugs. The antibody marker was least sensitive in detecting early season damage compared with mid- and late season damage. We hypothesize that residual saliva in seeds fed on early in the season was either absorbed by the damaged seed or degraded over time. Early season feeding resulted in the greatest number of seeds fused to cone scales and the extraction efficiency for cones exposed to feeding during this time was reduced by 64% compared with control cones. Adding fused seeds to antibody-positive seeds raised the proportion of damaged seeds to 48.3%. At all stages of cone development, adult females were the most destructive life stage, damaging up to two seeds per day late in the season. When seed losses were adjusted to damage per degree-day, female damage was greatest early in the season, while males caused the same amount of damage regardless of cone development period. The results of the antibody assay provide baseline data for developing damage prediction formulae, and establish L. occidentalis as a potentially serious pest in lodgepole pine seed orchards.

Abortion and Seed Set in Lodgepole and Western White Pine Conelets Following Feeding by Leptoglossus occidentalis (Heteroptera: Coreidae)

Abstract Leptoglossus occidentalis Heidemann is a serious pest of second-year cones in conifer seed orchards. We investigated the impact of this insect on first-year pine conelets. L. occidentalis adults and nymphs were caged on conelets of lodgepole pine, Pinus contorta var. latifolia Engelmann, and western white pine, Pinus monticola Dougl. ex D. Don. Abortion in lodgepole pine conelets was negligible, but feeding by nymphs reduced seed production by 75% compared with unexposed controls. Mortality of nymphs on lodgepole pine conelets was almost 100%, suggesting that conelets of this species are not a suitable food source for L. occidentalis. When nymphs had access to second-year cones, seed set in conelets was unaffected, and survival of nymphs greatly improved. Seventy-five percent of western white pine conelets exposed to L. occidentalis nymphs aborted, compared with none in unexposed controls. Seed set in surviving cones was reduced by 47%. Conelet abortion fell to 10% when nymphs were provided with an alternative food source. In pine seed orchards, damage to conelets probably is caused primarily by nymphs remaining on trees after second-year cones have been harvested.

Bacillus thuringiensis protein production, signal transduction, and insect control in chemically inducible PR-1a/cry1Ab broccoli plants.

In an effort to develop a chemically inducible system for insect management, we studied production of Cry1Ab Bacillus thuringiensis (Bt) protein and control of the diamondback moth (DBM), Plutella xylostella L., in inducer-treated and untreated tissues of a broccoli line transformed with a PR-1a/cry1Ab expression cassette. Spraying leaves of these plants with the inducer acibenzolar-S-methyl (= 1,2,3 benzothiadiazole-7-thiocarboxylic acid-S-methyl-ester) (ASM) triggered expression of the cry1Ab gene and produced a high level of Cry1Ab protein within 2–3 days. Cry1Ab protein persisted in leaves for at least 8 weeks, providing prolonged protection from P. xylostella attack. Signals generated in inducer-treated leaves were transferred to untreated newly emerged leaves or heads, as seen by production of Cry1Ab protein and/or protection from insect damage in these plant parts. Signal transduction proceeded in an attenuated manner up to the sixth newly emerged leaf. No Cry1Ab protein was detectable by ELISA in uninduced young leaves, but small amounts of the protein were present in uninduced leaves older than 3 weeks and caused some insect mortality. Such basal expression of Bt genes without induction may favor the evolution of resistant insect populations and therefore limits the application of the PR-1a/cry1Ab system for insect management. However, the rapid production and steady maintenance of a high level of transgenic protein upon induction, the signal transduction observed, and the fact that the chemical inducer can be used in field conditions make the PR-1a promoter attractive for chemical regulation of other agriculturally or pharmaceutically important genes for which low expression in the absence of induction is not a concern.

Specific biochemical marker-based techniques for the identification of damage to Douglas-fir seed resulting from feeding by the western conifer seed bug, Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae)

Specific biochemical marker-based techniques were tested for their ability to distinguish between seeds of Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco, that were filled or unfilled (aborted) at maturity and those that were damaged or emptied by the western conifer seed bug, Leptoglossus occidentalis Heidemann. A polyclonal antibody raised against salivary gland extracts from L. occidentalis successfully identified residual salivary proteins on Western blots containing proteins from Douglas-fir seeds that had sustained various degrees of seed bug feeding damage. In a single blind experiment, the polyclonal antibody correctly identified 100% of undamaged control, 97% of unfilled control (aborted), and 98% of seed bug damaged seeds. Polyclonal antibodies raised against insoluble alfalfa crystalloid storage protein (11S globulin) detected the depletion of 11S globulin and the subsequent appearance of its hydrolyzed fragments in the soluble protein fraction of Douglas-fir seeds that were fed-upon by the seed bug. Feeding by L. occidentalis nymphs caused ca. 98% depletion of insoluble protein, but only ca. 53% reduction in the amount of soluble protein in seeds that appeared empty on radiographs. By comparison, unfilled (aborted) seeds contained significantly less insoluble and soluble protein than empty seeds that were fed-upon by L. occidentalis; moreover, no crystalloid (11S globulin) breakdown products were generated. The biochemical markers described in this study are reliable tools that can be used to identify conifer seeds that have sustained light to severe damage from L. occidentalis feeding.

Biochemical Assay Detects Feeding Damage to Loblolly Pine Seeds Caused by the Leaffooted Pine Seed Bug (Hemiptera: Coreidae)

A large number of proteins in salivary gland extracts of the leaffooted pine seed bug, Leptoglossus corculus Say, were strongly recognized by a polyclonal antibody-based assay developed for detecting saliva of the western conifer seed bug. Lepfoglossus occidentalis Heide- mann, in lodgepole pine, Pinus contorta var. lafifolia Engelmann, seeds. An average of approxi- mately 85% of loblolly pine, Pinus faeda L., seeds exposed to feeding by L. corculus for 1 to 4 weeks in the laboratory contained detectable amounts of salivary proteins when the antibody assays were performed weekly on samples (n = 10) of seed. In comparison, radiography of exposed seed detected an average of approximately 63% damaged seed over the same 4-wk period, indicating that the antibody assay increased sensitivity of damage detection by approxi- mately one-third. Depletion of insoluble polypeptides and proliferation of soluble polypeptides 523.5 kDa was apparent after SDS-PAGE and quantitative assays were performed on proteins extracted from seeds that were damaged by exposure to L. corculus feeding. Our data suggest that the antibody-based test could be used to obtain accurate estimates of seed losses attrib- utable to L. corculus feeding in southern pine seed orchards.