Biological control of twospotted spider mite, <Emphasis Type="Italic">Tetranychus urticae</Emphasis>, with predatory mite, <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>, in strawberries

Greenhouse and field experiments were conducted from 2005 to 2007 to determine the effectiveness of different release times with the predatory mite, Neoseiulus californicus (McGregor), for control of the twospotted spider mite (TSSM), Tetranychus urticae Koch, in strawberries (Fragaria x ananassa Duchesne). The effect of N. californicus releases over time and on development of TSSM populations during a growing season were evaluated. Our hypothesis was that repeated applications of N. californicus, which is currently recommended by biological control companies, might be unnecessary to attain season-long control of TSSM. In greenhouse trials, three treatments consisting of releases of N. californicus at five-day intervals: day 0, day 5, and day 10, and an untreated control were evaluated. The treatment releases significantly reduced TSSM below the control within five days of each release. Neoseiulus californicus significantly reduced TSSM in treatments with high densities (leaflets with ≥ 40 TSSM) below that of treatments with lower densities (leaflets with ≤ 10 TSSM) demonstrating that if released at a predator: prey ratio of 1:10, timing of release does not alter the effectiveness of N. californicus in controlling TSSM. However, we found that if the ratio of predator: prey remains adequate, N. californicus is a more efficient predator at high TSSM densities. Field studies included three treatments consisting of releases of N. californicus at one-month intervals. All treatments significantly reduced TSSM compared with the control plots (no releases). Releases applied early in the season sustained TSSM significantly below those in the control plots for the whole season. Our results indicate that one release of N. californicus is able to sustained control of TSSM in strawberry throughout a growing season if released when TSSM populations are low early in the season in the southeastern United States.     

Tn10 transposase mutants with altered transpososome unfolding properties are defective in hairpin formation

Transposition reactions take place in the context of higher-order protein-DNA complexes called transpososomes. In the Tn10 transpososome, IHF binding to an "outside end" creates a bend in the DNA that allows the transposase protein to contact the end at two different sites, the terminal and subterminal binding sites. Presumably this helps to stabilize the transposase-end interaction. However, the DNA loop that is formed must be unfolded at a later stage in order for the transposon to integrate into other DNA molecules. It has been proposed that transpososome unfolding also plays a role in transposon excision. To investigate this possibility further, we have isolated and characterized transposase mutants with altered transpososome unfolding properties. Two such mutants were identified, R182A and R184A. Both mutants fail to carry out hairpin formation, an intermediate step in transposon excision, specifically with outside end-containing substrates. These results support the idea that transpososome unfolding and excision are linked. Also, based on the importance of residues R182 and R184 in transpososome unfolding, we propose a new model for the Tn10 transpososome, wherein both DNA ends of the transpososome make subterminal contacts with transposase.     

Structure of the Small Dictyostelium discoideum Myosin Light Chain MlcB Provides Insights into MyoB IQ Motif Recognition

Dictyostelium discoideum MyoB is a class I myosin involved in the formation and retraction of membrane projections, cortical tension generation, membrane recycling, and phagosome maturation. The MyoB-specific, single-lobe EF-hand light chain MlcB binds the sole IQ motif of MyoB with submicromolar affinity in the absence and presence of Ca²⁺. However, the structural features of this novel myosin light chain and its interaction with its cognate IQ motif remain uncharacterized. Here, we describe the NMR-derived solution structure of apoMlcB, which displays a globular four-helix bundle. Helix 1 adopts a unique orientation when compared with the apo states of the EF-hand calcium-binding proteins calmodulin, S100B, and calbindin D_9k. NMR-based chemical shift perturbation mapping identified a hydrophobic MyoB IQ binding surface that involves amino acid residues in helices I and IV and the functional N-terminal Ca²⁺ binding loop, a site that appears to be maintained when MlcB adopts the holo state. Complementary mutagenesis and binding studies indicated that residues Ile-701, Phe-705, and Trp-708 of the MyoB IQ motif are critical for recognition of MlcB, which together allowed the generation of a structural model of the apoMlcB-MyoB IQ complex. We conclude that the mode of IQ motif recognition by the novel single-lobe MlcB differs considerably from that of stereotypical bilobal light chains such as calmodulin.     

Evaluation of adjuvants to improve control of spotted‐wing drosophila in organic fruit production

Spotted‐wing drosophila, Drosophila suzukii (Matsumura), is a key pest of berry crops in the United States. It is managed intensively using insecticides, but organic fruit growers have few effective chemical control options. Spinosad is the most effective organically approved product for control of D. suzukii, while other organic options have not shown high levels of control. Adjuvants are products added to pesticides to improve effectiveness, and these may function as stickers, spreaders or surfactants improving the spray coverage of insecticides on surfaces and thereby increasing the likelihood that pests will contact residues. We conducted experiments evaluating organically approved biopesticides in combination with three adjuvants including poly‐1‐p‐menthene, alcohol ethoxylate and polyether‐polymethylsiloxane‐copolymer polyether to determine whether addition of adjuvants improved efficacy and residual activity of these products. Alcohol ethoxylate and poly‐1‐p‐menthene showed some inherent insecticidal activity against D. suzukii in laboratory assays. Adjuvants increased mortality of some insecticides but not to a level that would provide adequate fruit protection. Poly‐1‐p‐menthene had a negative effect when combined with hydrogen peroxide + PAA and sabadilla alkaloids. Mortality in semi‐field bioassays was quite low except for spinosad. Polyether‐polymethylsiloxane‐copolymer polyether had a negative effect on the efficacy of spinosad. The adjuvants did not extend residual activity of the insecticides. Adjuvants did not provide the expected benefits of increased performance against D. suzukii when combined with organic biopesticides. Other methods for enhancing these insecticides will need to be explored to provide organic growers with more effective chemical control options for this invasive pest.     

Mutations in the gene encoding tight junction claudin-14 cause autosomal recessive deafness DFNB29

Tight junctions in the cochlear duct are thought to compartmentalize endolymph and provide structural support for the auditory neuroepithelium. The claudin family of genes is known to express protein components of tight junctions in other tissues. The essential function of one of these claudins in the inner ear was established by identifying mutations in CLDN14 that cause nonsyndromic recessive deafness DFNB29 in two large consanguineous Pakistani families. In situ hybridization and immunofluorescence studies demonstrated mouse claudin-14 expression in the sensory epithelium of the organ of Corti.     

Evaluation of various deployment strategies of imidacloprid-treated spheres in highbush blueberries for control of Rhagoletis mendax (Diptera: Tephritidae)

Biodegradable, ammonium-baited spheres treated with the neonicotinoid insecticide Provado (imidacloprid) at 2% (AI) were evaluated for controlling blueberry maggot flies, Rhagoletis mendax Curran. Three strategies for sphere deployment in highbush blueberries, Vaccinium corymbosum L., were compared with untreated control plots in 1999 and once again compared against control plots and organophosphate insecticide sprays in 2000. The patterns of sphere deployment were as follows: (1) perimeter deployment in which spheres were hung individually and spaced equally around the perimeter of experimental plots; (2) cluster deployment in which four groups of three spheres were hung in equally spaced perimeter locations of experimental plots; and (3) uniform deployment in which spheres were placed 10 m apart (in a grid-like pattern) within experimental plots. In 1999, there were no significant differences in fruit injury levels based on observed R. mendax oviposition scars and reared larvae among plots containing imidacloprid-treated spheres in perimeter, cluster, and internal-grid patterns. However, all plots containing spheres had significantly lower fruit infestation levels (<2%), compared with unsprayed control plots with no spheres deployed, which had infestation levels (>20%). In 2000, there were no significant differences in fruit injury based on observed R. mendax oviposition scars between plots containing imidacloprid-treated spheres in the three deployment strategies tested and plots that received Guthion (Azinphosmethyl) spray applications. However, significantly fewer R. mendax larvae were reared from berries collected from plots that received two applications of Guthion compared with plots in which imidacloprid-treated spheres were deployed. Irrespective of sphere deployment strategies, all sphere-treated and sprayed plots had significantly lower injury levels (<1.5%), based on numbers of reared larvae compared with berries collected from the control plots (>4.0%). Based on captures of flies on unbaited Pherocon AM boards placed in the center of treatment plots, we observed a suppression of R. mendax in plots containing imidacloprid-treated spheres compared with control plots. The potential of using imidacloprid-treated spheres as a behavioral control integrated pest management tactic for blueberry maggot flies is discussed.     

Examining the spatial distribution of flower thrips in southern highbush blueberries by utilizing geostatistical methods

Flower thrips (Frankliniella spp.) are one of the key pests of southern highbush blueberries (Vaccinium corymbosum L. x V. darrowii Camp), a high-value crop in Florida. Thrips' feeding and oviposition injury to flowers can result in fruit scarring that renders the fruit unmarketable. Flower thrips often form areas of high population, termed "hot spots", in blueberry plantings. The objective of this study was to model thrips spatial distribution patterns with geostatistical techniques. Semivariogram models were used to determine optimum trap spacing and two commonly used interpolation methods, inverse distance weighting (IDW) and ordinary kriging (OK), were compared for their ability to model thrips spatial patterns. The experimental design consisted of a grid of 100 white sticky traps spaced at 15.24-m and 7.61-m intervals in 2008 and 2009, respectively. Thirty additional traps were placed randomly throughout the sampling area to collect information on distances shorter than the grid spacing. The semivariogram analysis indicated that, in most cases, spacing traps at least 28.8 m apart would result in spatially independent samples. Also, the 7.61-m grid spacing captured more of the thrips spatial variability than the 15.24-m grid spacing. IDW and OK produced maps with similar accuracy in both years, which indicates that thrips spatial distribution patterns, including "hot spots," can be modeled using either interpolation method. Future studies can use this information to determine if the formation of "hot spots" can be predicted using flower density, temperature, and other environmental factors. If so, this development would allow growers to spot treat the "hot spots" rather than their entire field.     

Effect of trap height and within-planting location on captures of cranberry fruitworm (Lepidoptera: Pyralidae) in highbush blueberries

Abstract 1 Winged traps baited with synthetic sex pheromone lures [(E,Z)‐8,10‐pentadecadien‐1‐ol and (E)‐9‐pentadecen‐1‐ol acetate] were evaluated for their effectiveness in monitoring cranberry fruitworm, Acrobasis vaccinii Riley, in highbush blueberry, Vaccinium corymbosum L., plantings. Trap effectiveness was compared at different heights within the bush canopy and different locations within plantings. 2 In our trap height study, three positions were evaluated: (i) at the top of bush canopy (15 cm below the uppermost branch); (ii) centrally within bush canopy (60 cm below the uppermost branch); and (iii) at the bottom of the bush, 20 cm above ground level. Traps placed 15 and 60 cm below the uppermost branch captured significantly more male moths compared with traps placed 20 cm above ground level at two organic sites. 3 In our trap location study, four treatments were evaluated based on trap location relative to adjacent woodlands: (i) in trees within 1 m of the woodland boundary; (ii) in blueberry bushes adjacent to woodlands, 15 m from the woodland boundary; (iii) in blueberry bushes in the centre of the planting, 75 m from the woodland boundary; and (iv) in blueberry bushes furthest away from woodlands, 150 m from the woodland boundary. Traps located within 1 m of woodland boundary captured significantly more male moths compared with traps located centrally (15 and 75 m) within plantings.     

Evaluation of non-target effects of OMRI-listed insecticides for management of Drosophila suzukii Matsumura in berry crops

The spotted wing drosophila, Drosophila suzukii Matsumura, is an invasive pest of many fruit crops throughout North America, South America and Europe. The presence of this destructive pest has led to an increase in the number of insecticide applications. While conventional growers have an arsenal of different insecticides at their disposal, organic growers have a limited selection of effective options and rely heavily on applications of Entrust^®, the organic formulation of spinosad. An important part of research is to develop more tools for organic growers and evaluate the effects of insecticides intended to target D. suzukii on natural enemies in the system. The effects of six organic pesticides alone and in combination with three adjuvants and two phagostimulants were tested in laboratory bioassays on three common natural enemies in berry production systems including two predators, Chrysoperla rufilabris and Orius insidiosus, and a parasitoid wasp, Aphidius colemani. Under the IOBC toxicity rating scale, spinosad was rated consistently from slightly harmful to harmful across natural enemy species and residue age (the effects of pesticides over time). Sabadilla alkaloids caused mortality to O. insidiosus equal to that of spinosad. All tested pesticides were at least slightly harmful to A. colemani, and the adjuvant polyether-polymethylsiloxane-copolymer polyether caused mortality that was not significantly different from spinosad. In general, neither the addition of adjuvants nor phagostimulants increased the mortality of the insecticides tested. The exception was polyether-polymethylsiloxane-copolymer polyether, but it is unclear whether it increased the toxicity of the pesticides or was simply toxic itself since it caused high mortality to A. colemani when applied alone. Sublethal effects were measured for two predatory species by measuring eggs laid and % egg hatch. Minimal sublethal effects were observed in C. rufilabris. In contrast, all tested insecticides caused reduced egg hatch in O. insidiosus compared with the control.