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The Asian citrus psyllid (Diaphorina citri Kuwayama) is an insect pest capable of transmitting Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus greening in North America. D. citri also harbors three endosymbionts, Wolbachia, Candidatus Carsonella ruddii, and Candidatus Profftella armatura, which may influence D. citri physiology and fitness. Although genomic researches on these bacteria have been conducted, much remains unclear regarding their ecology and inter-population variability in D. citri. The present work examined the densities of each endosymbiont in adult D. citri sampled from different populations using quantitative PCR. Under field conditions, the densities of all three endosymbionts positively correlated with each other, and they are associated with D. citri gender and locality. In addition, the infection density of CLas also varied across populations. Although an analysis pooling D. citri from different populations showed that CLas-infected individuals tended to have lower endosymbiont densities compared to uninfected individuals, the difference was not significant when the population was included as a factor in the analysis, suggesting that other population-specific factors may have stronger effects on endosymbiont densities. To determine whether there is a genetic basis to the density differences, endosymbiont densities between aged CLas-negative females of two D. citri populations reared under standardized laboratory conditions were compared. Results suggested that inter-population variability in Wolbachia infection density is associated with the genotypes of the endosymbiont or the host. Findings from this work could facilitate understanding of D. citri-bacterial associations that may benefit the development of approaches for managing citrus greening, such as prevention of CLas transmission.

The stability of resistance to fenpropathrin was assessed using five populations of Diaphorina citri with varying initial resistances ranging from fully susceptible (SS) to fully resistant (RR). Furthermore, we quantified the relative expression of voltage-gated sodium channel (VGSC) genes in crosses of field-selected and laboratory-susceptible D. citri lines after eight months without insecticide selection. We found that resistance to fenpropathrin remained elevated up to eight months after exposure to fenpropathrin. A real-time quantitative PCR analysis using the susceptible baseline population revealed that levels of VGSC gene expression were significantly higher in the RS75 cross and the RR100 fully resistant line eight months after their last fenpropathrin exposure. Our results suggest that while fenpropathrin resistance is likely unstable under field conditions when interbreeding with susceptible individuals is possible, resistance can remain stable for at least 8 months if those populations are isolated. Further, insecticide rotation and the maintenance of susceptible reservoirs of individuals should mitigate fenpropathrin resistance in D. citri over time. The development of a VGSC gene biomarker may be a useful tool for monitoring pyrethroid resistance in D. citri going forward.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a major pest of citrus trees worldwide. A wide variety of insecticides are used to manage D. citri populations within citrus groves in Florida. However, in areas shared by citrus growers and beekeepers the use of insecticides may increase the risks of Apis mellifera  L. (Hymenoptera: Apidae) loss and contaminated honey. The objective of this research was to determine the environmental toxicity of insecticides, spanning five different modes of action used to control D. citri , to A. mellifera . The insecticides investigated were imidacloprid, fenpropathrin, dimethoate, spinetoram and diflubenzuron. In laboratory experiments, LD 50 values were determined and ranged from 0.10 to 0.53 ng/μl for imidacloprid, fenpropathrin, dimethoate and spinetoram. LD 50 values for diflubenzuron were >1000 ng/μl. Also, a hazard quotient was determined and ranged from 1130.43 to 10893.27 for imidacloprid, fenpropathrin, dimethoate, and spinetoram. This quotient was <0.447 for diflubenzuron. In field experiments, residual activity of fenpropathrin and dimethoate applied to citrus caused significant mortality of A. mellifera 3 and 7 days after application. Spinetoram and imidacloprid were moderately toxic to A. mellifera at the recommended rates for D. citri . Diflubenzuron was not toxic to A. mellifera in the field as compared with untreated control plots. Phenoloxidase (PO) activity of A. mellifera was higher than in untreated controls when A. mellifera were exposed to 14 days old residues. The results indicate that diflubenzuron may be safe to apply in citrus when A. mellifera are foraging, while most insecticides used for management of D. citri in citrus are likely hazardous under various exposure scenarios.

Endoparasitic hymenopteran Campoletis sonorensis can successfully parasitize twenty different lepidopteran larvae. During oviposition of the endoparasitoid egg into the lepidopteran larvae, venoms, ovarian proteins, and polydnavirus are all injected into the lepidopteran larvae. Temporal expressions of polydnaviral genes throughout parasitism maintain an inhibited larval immune response as well as developmental arrest. The Campoletis sonorensis Ichnovirus (CsIV) is a circular segment double stranded DNA genome dispersed within the genome of Campoletis sonorensis. There are 24 segments and 245707 base pairs in size. Dispersed within the CsIV genome are the presence of 5 (Cys-motif, Vankyrin, Vinnexin, N, and Rep) gene families. The cys-motif gene family contains 10 (VHv1.4, VHv1.1, WHv1.0, WHv1.6, AHv1.7, A'Hv1.7, UHv1.4, UHv1.7, FHv1.7, and LHv2.2) members distributed on seven superhelical (SH)segments (SHV, SHW, SHA, SHA', SHU, SHF, and SHL). The cys-motif genes located on segments SHV (VHv1.1 and VHv1.4), SHW (WHv1.0 and WHv1.6), and SHU (UHv1.4 and UHv1.7) are the most abundant genes within encapsidated virions, while SHA, SHA', SHF, and SHL are the least abundant segments with least cys-motif genes. The most abundant cys-motif gene WHv1.6 is 600 times more abundant than the low copy genes AHv1.7 and A'Hv1.7 combined. Transcription of infected tissues showed elevated levels of gene expression in hemocytes, nerve cord, and epidermal tissues.WHv1.6 was detectable in epidermis, hemocyte, fat body, gut, malpighan tubules and nerve cord at two and seven days post-parasitization. Time course parasitism showed signal at 6 hours post-parasitization and maintained throughout parasitism. Overlay experiments suggest that factors present in plasma may be required to mediate uptake of WHv1.6 into hemocytes. The ability for the cys-motif proteins to inhibit lepidopteran larval development through oral ingestion has been shown, however expression of CsIV cys-motif and related proteins in tobacco (VHv1.1,VHv1.4, WHv1.6, WHv1.0, and TSP14) yielded highly varied results. TSP14 in a field trial was able to reduce larval development and deter aphid infestations, however clip cage greenhouse results were hard to interpret. The expression of cys-motif genes VHv1.1, VHv1.4, VHv1.0, WHv1.6 from homozygous transgenic tobacco plants were not able repress neonate H.virescens larval feeding consistently or significantly. Keywords. Campoletis sonorensis Ichnovirus, Cys-motif Gene Family, Heliothis virescens, Myzus nicotiana , Polydnavirus