Search

The two-spotted spider mite, Tetranychus urticae, is a polyphagous agricultural pest that feeds on over a thousand plant species and more than 150 crops. Its status as an agricultural pest is exacerbated by its outstanding potential to evolve resistance to pesticides. The existence of multiresistant mite populations challenges mite management and creates a need for the development of pesticides with novel modes of action. In this study, we evaluated the acaricidal activity of Neo-Boost, a pesticide registered as a bactericide/fungicide/insecticide/miticide. Neo-Boost formulation contains three active ingredients: potassium silicate, sodium percarbonate and tetraacetylethylenediamine. In contact with water, the latter ingredients generate peroxyacetic acid, a potent contact bactericide and fungicide. Using the recommended field dose, we tested contact and residual effects of Neo-Boost on T. urticae egg, larval, and adult life stages. We found that Neo-Boost had no ovicidal effect. When tested on larvae, Neo-Boost caused 87% mortality over 48 hours post-treatment that was comparable to the positive control AGRI-mek SC (active ingredient abamectin), in addition to delaying larval developmental progression. On adult mites, Neo-Boost acted as a deterrent and caused 35% mortality (an intermediate effect compared to the positive control AGRI-mek SC). We also tested the proposed ability of Neo-Boost to induce a systemic response, however, it had no priming effect on treated tomato plants against mites. Of the individual Neo-Boost components tested, peroxyacetic acid and potassium silicate were not effective in any assay. However, sodium percarbonate, surfactant, and other non-listed components were sufficient for the full effectiveness of Neo-Boost formulations. Additionally, phytotoxicity of Neo-Boost was rare and minor when it occurred. Overall, despite the inefficiency of some compounds, the Neo-Boost formulation, either in its original or simplified formulation, may be useful for mite control on crops that are destined for fresh human consumption or medicinal use.

The two-spotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most polyphagous herbivores, feeding on more than 1,100 plant species. Its wide host range suggests that TSSM has an extraordinary ability to modulate its digestive and xenobiotic physiology. The analysis of the TSSM genome revealed the expansion of gene families that encode proteins involved in digestion and detoxification, many of which were associated with mite responses to host shifts. The majority of plant defense compounds that directly impact mite fitness are ingested. They interface mite compounds aimed at counteracting their effect in the gut. Despite several detailed ultrastructural studies, our knowledge of the TSSM digestive tract that is needed to support the functional analysis of digestive and detoxification physiology is lacking. Here, using a variety of histological and microscopy techniques, and a diversity of tracer dyes, we describe the organization and properties of the TSSM alimentary system. We define the cellular nature of floating vesicles in the midgut lumen that are proposed to be the site of intracellular digestion of plant macromolecules. In addition, by following the TSSM's ability to intake compounds of defined sizes, we determine a cut off size for the ingestible particles. Moreover, we demonstrate the existence of a distinct filtering function between midgut compartments which enables separation of molecules by size. Furthermore, we broadly define the spatial distribution of the expression domains of genes involved in digestion and detoxification. Finally, we discuss the relative simplicity of the spider mite digestive system in the context of mite's digestive and xenobiotic physiology, and consequences it has on the effectiveness of plant defenses.

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most polyphagous herbivores feeding on cell contents of over 1,100 plant species including more than 150 crops. It is being established as a model for chelicerate herbivores with tools that enable tracking of reciprocal responses in plant-spider mite interactions. However, despite their important pest status and a growing understanding of the molecular basis of interactions with plant hosts, knowledge of the way mites interface with the plant while feeding and the plant damage directly inflicted by mites is lacking. Here, utilizing histology and microscopy methods, we uncovered several key features of T. urticae feeding. By following the stylet path within the plant tissue, we determined that the stylet penetrates the leaf either in between epidermal pavement cells or through a stomatal opening, without damaging the epidermal cellular layer. Our recordings of mite feeding established that duration of the feeding event ranges from several minutes to more than half an hour, during which time mites consume a single mesophyll cell in a pattern that is common to both bean and Arabidopsis plant hosts. In addition, this study determined that leaf chlorotic spots, a common symptom of mite herbivory, do not form as an immediate consequence of mite feeding. Our results establish a cellular context for the plant-spider mite interaction that will support our understanding of the molecular mechanisms and cell signaling associated with spider mite feeding.

Inter-relationships ordinarily exist between mRNA expression of GABA-A subunits in the frontopolar cortex (FPC) of individuals that had died suddenly from causes other than suicide. However, these correlations were largely absent in persons that had died by suicide. In the present investigation, these findings were extended by examining GABA-A receptor expression patterns (of controls and depressed individuals that died by suicide) in the orbital frontal cortex (OFC), hippocampus, amygdala. locus coeruleus (LC),and paraventricular nucleus (PVN), all of which have been implicated in either depression, anxiety or stress responsivity. Results Using QPCR analysis, we found that in controls the inter-relations between GABA-A subunits varied across brain regions, being high in the hippocampus and amygdala, intermediate in the LC, and low in the OFC and PVN. The GABA-A subunit inter-relations were markedly different in persons that died by suicide, being reduced in hippocampus and amygdala, stable in the LC, but more coordinated in the OFC and to some extent in the PVN. Conclusions It seems that altered brain region-specific inhibitory signaling, stemming from altered GABA-A subunit coordination, are associated with depression/suicide. Although, it is unknown whether GABA-A subunit re-organization was specifically tied to depression, suicide, or the accompanying distress, these data show that the co-ordinate expression of this transcriptome does vary depending on brain region and is plastic.