Comparative Study of Life Histories, Laboratory Rearing, and Immature Stages of \u3ci\u3eEuschistus Servus\u3c/i\u3e and \u3ci\u3eEuschistus Variolarius\u3c/i\u3e (Hemiptera: Pentatomidae)

A comparative study was conducted of the field life histories of Euschistus servus and E. varialarius in southern Illinois, their life cycles under controlled laboratory conditions, and their immature stages. The results indicate that E. servus is bivoltine and E. variolarius is univoltine. Adults of both species emerged from overwintering sites during early April, began feeding and copulating on leaves of common mullein (Verbascum thapsus) and surrounding vegetation, and reproduced shortly thereafter. Neither eggs and first instars of either species, nor second instars of E. variolarius, were collected in the field. Seasonal occurrences of the adults and subsequent immature stages are discussed for each species. No individuals were found after the first week of November. Both species were reared on green beans (Phaseolus vulgaris) under a 16L:8D photoperiod and constant temperature of 23 ± 0.06° C. The incubation period averaged 5.8 days for E. servus and 5.4 days for E. variolanus. Durations of the 5 subsequent stadia averaged, respectively, 5, 6, 6.7, 9.3, and 11.5 days for E. servus, and 4.9,5.7,7.8,9.7, and 13.3 days for E. varialarius. Comparisons of incubation period and stadia between the two species showed that only the stadia for the first instars were not statistically different. Total developmental period was longer for E. varialarius than for E. servus. The external anatomy of the egg and each of the five nymphal instars is described for each species

The Stink Bugs (Hemiptera: Heteroptera: Pentatomidae) of Washington State

Froeschner (1988) recorded 23 species of stink bugs (Hemiptera: Heteroptera: Pentatomidae) from Washington State. Based on material primarily housed in the M. T. James Entomological Collection at Washington State University, the number of species is increased to 51. Three species recorded by Froeschner (1988) were not found in our collections: Apateticus crocatus (Uhler), Chlorochroa rossiana Buxton and Thomas, and Tepa rugulosa (Say). Species recorded from Washington State for the first time are: Apoecilus bracteatus (Fitch), Perillus bioculatus (Fabricius), Podisus maculiventris (Say), P. pallens (Stål), P. placidus Uhler, P. serieventris Uhler, Zicrona caerulea (Linnaeus), Halyomorpha halys (Stål), Brochymena quadripustulata (Fabricius), B. sulcata Van Duzee, Acrosternum hilare (Say), Aelia americana Dallas, Banasa euchlora Stål, B. tumidifrons Thomas and Yonke, Chlorochroa congrua Uhler, Coenus delius (Say), Cosmopepla uhleri Montandon, Dendrocoris pini Montandon, Euschistus servus (Say), E. tristigmus (Say), E. variolarius (Palisot), Holcostethus limbolarius (Say), Neottiglossa sulcifrons Stål, N. undata (Say), Prionosoma podopioides (Uhler), Tepa yerma (Rolston), Trichopepla grossa (Van Duzee), and Amaurochrous vanduzeei Barber and Sailer

Incidence of the Beet Leafhopper-Transmitted Virescence Agent Phytoplasma in local Populations of the Beet Leafhopper, Circulifer tenellus, in Washington State

Phytoplasma diseases are increasingly becoming important in vegetable crops in the Pacific Northwest. Recently, growers in the Columbia Basin and Yakima Valley experienced serious outbreaks of potato purple top disease that caused significant yield loss and a reduction in tuber processing quality. It was determined that the beet leafhopper-transmitted virescence agent (BLTVA) phytoplasma was the causal agent of the disease in the area and that this pathogen was transmitted by the beet leafhopper, Circulifer tenellus Baker (Hemiptera: Cicadellidae). To provide the most effective management of phytoplasmas, timing of insecticide applications targeted against insects vectoring these pathogens should be correlated with both insect abundance and infectivity. Beet leafhoppers were collected from a potato field and nearby weeds in Washington throughout the 2005, 2006, and 2007 growing seasons and tested for BLTVA by PCR to determine the incidence of this phytoplasma in the insects. In addition, overwintering beet leafhoppers were collected throughout Columbia Basin and Yakima Valley and tested for BLTVA to investigate if these insects might constitute a source of inoculum for this phytoplasma from one season to the next. Results showed that 29.6% of overwintering leafhoppers collected near potato fields carried the phytoplasma. BLTVA-infected leafhoppers were also found in both potatoes and nearby weedy habitats throughout the growing season. PCR testing indicated that a large proportion of beet leafhoppers invading potatoes were infected with the phytoplasma, with an average of 20.8, 34.8, and 9.2% in 2005, 2006, and 2007, respectively. Similarly, BLTVA infection rate in leafhoppers collected from weeds in the vicinity of potatoes averaged 28.3, 24.5, and 5.6% in 2005, 2006, and 2007, respectively. Information from this study will help develop action thresholds for beet leafhopper control to reduce incidence of purple top disease in potatoes

Susceptibility of Selected Potato Varieties to Zebra Chip Potato Disease

Zebra chip (ZC), an emerging and serious disease of potato has caused millions of dollars in losses to the potato industry in the United States, Mexico, Central America, and New Zealand. The disease has recently been associated with a previously undescribed species of liberibacter tentatively named “Candidatus Liberibacter solanacearum” transmitted to potato by the potato psyllid, Bactericera cockerelli (Šulc). At present, applications of insecticides targeted against the potato psyllid are the only means to manage ZC. Given the low psyllid density and short inoculation access period required to induce the disease, insecticides may not act fast enough to prevent transmission of liberibacter to potato by the psyllid and development of ZC. Identification and development of ZC-resistant or tolerant varieties may offer the most efficient and sustainable way to manage this potato disease. Susceptibility of selected potato varieties to ZC was evaluated under controlled field cage conditions in 2009 and 2010 in WA by inoculating potato plants with “Ca. L. solanacearum” using infective potato psyllids and monitoring them for ZC symptom development. All potato varieties evaluated in both years of the study were determined to be very susceptible to the disease, with almost 100% of the inoculated plants developing severe ZC foliar and tuber symptoms. Potato yield in all tested varieties was significantly affected by ZC, with yield losses ranging from 49.9% to 87. 2%. Information from this research suggests that there is an urgent need to develop new potato varieties that are resistant or tolerant to this damaging potato disease

Latent Period and Transmission of “Candidatus Liberibacter solanacearum” by the Potato Psyllid Bactericera cockerelli (Hemiptera: Triozidae)

"Candidatus Liberibacter solanacearum" (Lso) is an economically important pathogen of solanaceous crops and the putative causal agent of zebra chip disease of potato (Solanum tuberosum L.). This pathogen is transmitted to solanaceous species by the potato psyllid, Bactericera cockerelli (Šulc), but many aspects of the acquisition and transmission processes have yet to be elucidated. The present study was conducted to assess the interacting effects of acquisition access period, incubation period, and host plant on Lso titer in psyllids, the movement of Lso from the alimentary canal to the salivary glands of the insect, and the ability of psyllids to transmit Lso to non-infected host plants. Following initial pathogen acquisition, the probability of Lso presence in the alimentary canal remained constant from 0 to 3 weeks, but the probability of Lso being present in the salivary glands increased with increasing incubation period. Lso copy numbers in psyllids peaked two weeks after the initial pathogen acquisition and psyllids were capable of transmitting Lso to non-infected host plants only after a two-week incubation period. Psyllid infectivity was associated with colonization of insect salivary glands by Lso and with Lso copy numbers >10,000 per psyllid. Results of our study indicate that Lso requires a two-week latent period in potato psyllids and suggest that acquisition and transmission of Lso by psyllids follows a pattern consistent with a propagative, circulative, and persistent mode of transmission

Absence of photoperiod effects on mating and ovarian maturation by three haplotypes of potato psyllid, Bactericera cockerelli (Hemiptera: Triozidae)

We examined the effects of photoperiod on reproductive diapause of three haplotypes of potato psyllid, Bactericera cockerelli (Hemiptera: Triozidae), collected from three geographic locations: south Texas (Central haplotype), California (Western haplotype), and Washington State (Northwestern haplotype). Psyllids were reared from egg hatch to adult eclosion under short- and long-day conditions, to determine whether short-days led to a lack of mating, delays in ovarian development, and accumulation of fat by female psyllids. Our expectation was that a reproductive response to short-days would be more likely to be exhibited by psyllids of the northern-latitude haplotype (Northwestern) than psyllids of the other two haplotypes. We also examined whether this species exhibited a photoperiod-controlled polymorphism in body size, as observed in other psyllid species, by comparing six body and wing measures of psyllids reared under short- and long-day conditions. Virtually 100% of females of each haplotype exhibited both egg maturation and mating at both long- and short-day conditions, providing no evidence that this species exhibits a photoperiod-induced reproductive diapause. Fat was present in most psyllids, although with higher probability of presence in short-day females than long-day females. Phortoperiod had no effect on body size. We found differences among haplotypes in body size, with psyllids from Washington State (Northwestern haplotype) having larger wings and longer tibiae than psyllids of the two southern populations. Our photoperiod results, combined with overwintering observations for this species and for other Triozidae, prompted us to hypothesize that potato psyllid -- at least in the Pacific Northwest growing region -- overwinters in a temperature-controlled quiescence rather than in a true diapause

Assessing Potato Psyllid Haplotypes in Potato Crops in the Pacific Northwestern United States

The potato psyllid, Bactericera cockerelli (Šulc), is a vector of the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso) that has been linked to the economically devastating zebra chip disease of potato. To date, four haplotypes of the potato psyllid have been identified and include Central, Western, Northwestern, and Southwestern haplotypes. Zebra chip was reported in potato crops in the Pacific Northwestern United States for the first time in 2011, and the Lso-infected psyllids collected from zebra chip-affected fields were identified as the Western haplotype. Additional studies have reported a mix of the Western and Northwestern psyllid haplotypes in the Pacific Northwest. The present study further examined psyllid population dynamics over the duration of the 2012 potato season in the Pacific Northwest by haplotype analysis of 864 potato psyllids collected from potato fields in Washington, Oregon, and Idaho. In the Yakima Valley of Washington and the lower Columbia Basin of Washington and Oregon, the Northwestern haplotype was predominant (78%), and was detected earlier in the season than the Western haplotype. Interestingly, in south-central Idaho, all four psyllid haplotypes were identified, but the predominant haplotype was the Western haplotype (77%). Here, Northwestern psyllids were detected early in the season from June to mid-August, whereas Central psyllidswere detected in late July and thereafter. These results suggest that haplotype composition of psyllid populations in potato fields throughout the 2012 growing season in south-central Idaho differed greatly from those in Washington and Oregon. Additionally, all psyllids were analyzed for the presence of Lso, and no Lso-positive psyllids were found in Washington and Oregon, whereas Lso-positive psyllids were found in south-central Idaho. These Lso-positive psyllids consisted of the Western, Northwestern, and Central haplotypes

Zebra Chip Disease of Potato: Biology, Epidemiology, and Management

Zebra chip (ZC), a new and economically important disease of potato (Solanum tuberosum L.), has been documented to occur in commercial potato fields in the United States, Mexico, Central America, and New Zealand. This disease has caused millions of dollars in losses to the potato industry. Whole crops might be rejected because of ZC, often leading to abandonment of entire fields. Plant growth and yield are severely affected by the disease. Additionally, chips or fries processed from ZC-infected tubers exhibit dark stripes that become markedly more visible with frying, and hence are commercially unacceptable. The disease causes serious losses to the fresh market, tablestock and export potato industry as well. ZC-infected tubers usually do not sprout and if they do, produce hair sprouts or weak plants. Finally, there are indications that ZC symptoms might develop in tubers during storage. ZC has been associated with a previously undescribed species of liberibacter, tentatively named “Candidatus Liberibacter solanacearum”, also known as “Ca. L. psyllaurous”. The bacteriumis transmitted to potato by the potato psyllid, Bactericera cockerelli (Šulc). All commercial potato cultivars appear to be susceptible to ZC, and management tactics targeted against the potato psyllid are currently the only means to effectively manage the disease. Furthermore, there are concerns about quarantine and trade issues in psyllid-affected regions because some countries may require that shipments of potatoes from certain growing regions be tested for the disease before the shipments are allowed entry. ZC history, geographic distribution, biology, epidemiology, and management are discussed herein

Haplotypes of “\u3ci\u3eCandidatus\u3c/i\u3e Liberibacter solanacearum” suggest long-standing separation

Three haplotypes of the recently discovered bacterium species “Candidatus Liberibacter solanacearum” are described and related to geographic ranges. The first two are associated with Zebra Chip/Psyllid Yellows of potatoes and other solanaceous plants, vectored by the tomato/potato psyllid Bactericera cockerelli in North and Central America and New Zealand. The third is associated with diseased carrots in Finland and vectored by the carrot psyllid Trioza apicalis. The haplotypes are described by SNPs on the 16s rRNA, 16s/23s ISR and 50s rplJ and rplL ribosomal protein genes. These SNPs are inherited as a package across the three genes. Haplotype “a” has been found primarily from Honduras and Guatemala through western Mexico to Arizona and California, and in New Zealand. Haplotype “b” is currently known from eastern Mexico and northwards through Texas to south central Washington. These haplotypes show some range overlap in Texas, Kansas and Nebraska. The haplotypes are not yet known to elicit biological differences in the plant or insect hosts. These apparently stable haplotypes suggest separate bacterial populations of long standing