Andrew S. Jensen

Transgenic Bt potato and conventional insecticides for Colorado potato beetle management: comparative efficacy and non-target impacts

Field studies were conducted in 1992 and 1993 in Hermiston, Oregon, to evaluate the efficacy of transgenic Bt potato (Newleaf®, which expresses the insecticidal protein Cry3Aa) and conventional insecticide spray programs against the important potato pest, Leptinotarsa decemlineata (Say), Colorado potato beetle (CPB), and their relative impact on non‐target arthropods in potato ecosystems. Results from the two years of field trials demonstrated that Newleaf potato plants were highly effective in suppressing populations of CPB, and provided better CPB control than weekly sprays of a microbial Bt‐based formulation containing Cry3Aa, bi‐weekly applications of permethrin, or early‐ and mid‐season applications of systemic insecticides (phorate and disulfoton). When compared with conventional potato plants not treated with any insecticides, the effective control of CPB by Newleaf potato plants or weekly sprays of a Bt‐based formulation did not significantly impact the abundance of beneficial predators or secondary potato pests. In contrast to Newleaf potato plants or microbial Bt formulations, however, bi‐weekly applications of permethrin significantly reduced the abundance of several major generalist predators such as spiders (Araneae), big‐eyed bugs (Geocorus sp.), damsel bugs (Nabid sp.), and minute pirate bugs (Orius sp.), and resulted in significant increases in the abundance of green peach aphid (GPA), Myzus persicae (Sulzer) – vector of viral diseases, on the treated potato plots. While systemic insecticides appeared to have reduced the abundance of some plant sap‐feeding insects such as GPA, lygus bugs, and leafhoppers, early and mid‐season applications of these insecticides had no significant impact on populations of the major beneficial predators. Thus, transgenic Bt potato, Bt‐based microbial formulations and systemic insecticides appeared to be compatible with the development of integrated pest management (IPM) against other potato pests such as GPA because these CPB control measures have little impact on major natural enemies. In contrast, the broad‐spectrum pyrethroid insecticide (permethrin) is less compatible with IPM programs against GPA and the potato leafroll viral disease.

Effects of Transgenic Bacillus thuringiensis Potato and Conventional Insecticides for Colorado Potato Beetle (Coleoptera: Chrysomelidae) Management on the Abundance of Ground-Dwelling Arthropods in Oregon Potato Ecosystems

Abstract Field studies were conducted in 1992 and 1993 in Hermiston, Oregon, to evaluate nontarget impacts of transgenic Bt potato (Newleaf) expressing Cry3Aa protein derived from Bacillus thuringiensis (Bt) Berliner subsp. tenebrionis and conventional insecticides for control of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say). Pitfall traps were used to estimate the abundance of nontarget ground-dwelling arthropods in different treatment plots. There were no significant differences in the trap captures of major ground-dwelling coleopteran predators such as carabids (Coleoptera: Carabidae) and staphylinids (Coleoptera: Staphylinidae) among Bt and non-Bt potato fields treated with weekly sprays of a microbial Bt-based formulation containing Cry3Aa, biweekly applications of permethrin, early and mid season in-furrow applications of systemic insecticides (phorate and disulfoton), or no insecticides. While weekly sprays of permethrin significantly reduced the trap capture of ground-dwelling spiders (Araneae), there were no significant differences in the capture of spiders between Bt and non-Bt-potato fields treated with Bt sprays, systemic insecticides, or no insecticides. Significantly more springtails (Collembola: Entomobryidae and Hypogastruridae) were captured in potato fields treated with permethrin than with any other CPB control regime (transgenic Bt potato alone, microbial Bt formulation containing Cry3Aa, applications of systemic insecticides, or no action controls), among which there were no significant differences. The relevance of these findings to field evaluation of nontarget impacts of transgenic Bt crops is discussed.

Redefinition of the aphid genus Sitobion Mordvilko (Hemiptera: Aphididae) based on cladistic analyses, with emphasis on North American species

A hypothesis of monophyly for the aphid genus Sitobion is tested using cladistics. A diverse sample of thirty Sitobion species from Africa, Asia, Europe and North America were included, along with six species of Macrosiphum, eight new species similar to some Sitobion, one species of Illinoia, and Dysaphis tulipae (Boyer de Fonscolombe) as outgroup. A matrix of forty‐seven taxa and forty‐eight characters was analysed in paup, resulting in a set of thirty‐nine equally parsimonious cladograms. Despite a high degree of homoplasy in the data, the results show that Sitobion is not a monophyletic group. The endemic North American species, along with two pteridophyte‐feeding species from Europe, clearly belong to a separate lineage from the other Eurasian and African species. The endemic North American species are more closely related to the type species of Macrosiphum and Illinoia than to Sitobion avenae (Fabr.), the type species of Sitobion. Two species are placed as junior synonyms of Sitobion alopecuri (Takahashi): Macrosiphum (Sitobion) salicicornii Richards, syn.n. and Sitobion sylvestri Hille Ris Lambers; syn.n. Twelve species previously listed in Sitobion are placed in Macrosiphum with six new combinations: Macrosiphum adianti (Oestlund);Macrosiphum clydesmithi Robinson, comb.n.;Macrosiphum cystopteris Robinson;Macrosiphum dryopteridis (Holman), comb.n.;Macrosiphum equiseti (Holman), comb.n.;Macrosiphum insularis (Pergande);Macrosiphum lambi Robinson, comb.n.;Macrosiphum ptericolens Patch;Macrosiphum pteridis Wilson, Macrosiphum rhamni (Clarke);Macrosiphum walkeri Robinson, comb.n.;Macrosiphum woodsiae Robinson, comb.n. Two synonyms are reinstated as valid species: Macrosiphum occidentalis (Essig) and Macrosiphum pteridis Wilson.

Population Dynamics of the Beet Leafhopper (Hemiptera: Cicadellidae) in the Columbia Basin as Influenced by Abiotic Variables

ABSTRACT Beet leafhoppers (Circulifer tenellus Baker) have been identified as the vector for a plant-pathenogenic phytoplasma known as beet leafhopper-transmitted virescence agent. Beet leaf-hopper-transmitted virescence agent causes purple top disease in potatoes, which can reduce yields and tuber quality. A trapping network, composed of ≈100 sites, monitors leafhoppers in the Columbia Basin of Oregon and Washington through a collaborative effort of regional researchers and stakeholders. Yellow sticky cards were used to determine the timing and spatial distribution of beet leafhoppers in the Columbia Basin; insects were counted weekly from early April through late October in 2006, 2007, and 2008. Weather data collected from a network of weather stations in Oregon and Washington were used in a nonparametric multiplicative regression analysis to determine which abiotic environmental variables might influence beet leafhopper populations. Weather conditions (mean temperature, dew point, precipitation, and wind speed) for 2006–2008 were also characterized using CIs established based on weather data from 1998 to 2004 for each weather variable. Several abiotic environmental factors significantly correlated with beet leafhopper populations, including temperatures the preceding fall and winter, elevation, and precipitation. Beet leafhopper populations appear to be highly variable across the region, with low numbers at a majority of the sites and only a limited number of high populations in localized areas.

The adult and larva of a new species of Podothrombium (Acari: Trombidiidae) associated with aphids in oregon

Abstract Podothrombium sylvicolum Zhang sp. nov. is described from Oregon, USA. An adult of this species was collected from a plant, Montia siberica (L.) Howell, infested with aphids (Sitobion sp.). The larvae and protonymphs of P. sylvicolum were subsequently reared in the laboratory. P. sylvicolum larvae were ectoparasitic on aphids (Sitobion sp.) in the laboratory and on other species of aphids in the field. This study is the first report on larval, protonymphal and adult instars of a Podothrombium species. A key to world species of Podothrombium (larvae) is provided.

New Geographic Records for the Nearctic Psyllid Bactericera maculipennis (Crawford) with Biological Notes and Descriptions of the Egg and Fifth-Instar Nymph (Hemiptera: Psylloidea: Triozidae)

Abstract. The Nearctic psyllid Bactericera maculipennis (Crawford) (Hemiptera: Psylloidea: Triozidae) is one of only five known species of Psylloidea worldwide whose host plants include species of Convolvulaceae (Solanales). Current checklists of North American Psylloidea report B. maculipennis only from California and Utah. Our surveys of field bindweed, Convolvulus arvensis L. (Convolvulaceae), an Old World plant introduced into North America, show that B. maculipennis is considerably more widespread than indicated by historical accounts. We update the psyllids geographic range to include four states (Washington, Idaho, Oregon, Montana) not previously included in contemporary checklists. The egg and fifth instar nymph are described. We provide characters of the egg and nymph that distinguish this species from a congeneric species, Bactericera cockerelli (Šulc), occasionally found on field bindweed. Photographs of the male and female terminalia are provided. Bactericera maculipennis developed successfully on field bindweed and on several species of Ipomoea (Convolvulaceae) in laboratory assays. Overwintering females collected from leaf litter and dead or dormant stems of C. arvensis at locations in Central Washington mated and began to oviposit within 7 days of removal from the field, suggesting that B. maculipennis overwinters in a temperature-controlled quiescence rather than in a true reproductive diapause. Eggs and nymphs of B. maculipennis were found on stems of C. arvensis well into November in Central Washington, suggesting that this psyllid also may overwinter in pre-adult stages, as indicated by literature accounts from the 1940s and 1950s. Lastly, we propose that successful colonization of the invasive and exotic weed C. arvensis by B. maculipennis has allowed the psyllid to expand its geographic range well beyond historical boundaries. This conclusion is based upon the scarcity of native Convolvulaceae within regions in which the psyllid is newly recorded, combined with the now extensive distribution of the invasive C. arvensis in North America.

New North American Records for the Old World Psyllid Heterotrioza chenopodii (Reuter) (Hemiptera: Psylloidea: Triozidae) with Biological Observations

Abstract. n The Palearctic psyllid Heterotrioza chenopodii (Reuter) (Hemiptera: Psylloidea: Triozidae) belongs to a complex of psyllids having plants in the Amaranthaceae (including the former Chenopodiaceae) as hosts. Geographic records for this introduced species in North America date from 1988, and include a number of coastal regions in eastern Canada, the Northeastern U.S., inland Virginia, coastal British Columbia, California, and wetland habitats near Lincoln, Nebraska. We updated North American records for H. chenopodii to include inland Washington and Oregon, southwestern Idaho, northcentral California, western Colorado, and southern and central Alberta. Psyllids were collected from Atriplex micrantha (Amaranthaceae) and unidentified Atriplex species, and from yellow sticky cards that had been placed in potato fields to monitor arthropod pests of potatoes. Traits of the adult psyllid, fifth-instar nymph, and egg used in identifying specimens are summarized.We provide the first photographs of the egg, fifthinstar nymph, and terminalia of the adult male psyllid. Rearing trials showed that H. chenopodii developed on A. micrantha, A. hortensis, Chenopodium album, C. berlandieri, and garden beet, Beta vulgaris, but failed to develop on Amaranthus tricolor. Development was most rapid on the two Atriplex species. Heterotrioza chenopodii has been shown in Europe to exhibit photoperiod-controlled dimorphism in wing size, producing a long-winged form in spring and summer, and a short-winged form in autumn. We confirmed in rearing trials and by field collections that populations of H. chenopodii from central Washington State also exhibit this dimorphism. Short-winged forms began replacing long-winged forms in field populations between late August and early October.