Comparison of laboratory colonies and field populations of Tamarixia radiata, an ectoparasitoid of the Asian citrus psyllid, using internal transcribed spacer and cytochrome oxidase subunit I DNA sequences.

The genetic diversity of Tamarixia radiata Waterston (Hymenoptera: Eulophidae) laboratory colonies derived from collections in China, northern Vietnam, Pakistan, and a mixed colony from Taiwan and southern Vietnam was evaluated using the internal transcribed spacer (ITS) region 1, ITS-2, and the 5' end of the cytochrome oxidase subunit I gene. The strains share the same ITS sequence, consistent with the morphological hypothesis that the collections represent a single species. The COI marker was variable and could distinguish the northern Vietnam and Pakistan colonies from each other and from the other colonies. Comparison of COI sequences from field-collected populations of Puerto Rico, Guadeloupe, and Texas indicates that Florida is not a likely source of the introduction into Puerto Rico but is a likely source of the introduction into Texas.

Phylogenetic and structural relationships of the PR5 gene family reveal an ancient multigene family conserved in plants and select animal taxa.

Pathogenesis-related group 5 (PR5) plant proteins include thaumatin, osmotin, and related proteins, many of which have antimicrobial activity. The recent discovery of PR5-like (PR5-L) sequences in nematodes and insects raises questions about their evolutionary relationships. Using complete plant genome data and discovery of multiple insect PR5-L sequences, phylogenetic comparisons among plants and animals were performed. All PR5/PR5-L protein sequences were mined from genome data of a member of each of two main angiosperm groups-the eudicots (Arabidoposis thaliana) and the monocots (Oryza sativa)-and from the Caenorhabditis nematode (C. elegans and C. briggsase). Insect PR5-L sequences were mined from EST databases and GenBank submissions from four insect orders: Coleoptera (Diaprepes abbreviatus and Biphyllus lunatus), Orthoptera (Schistocerca gregaria), Hymenoptera (Lysiphlebus testaceipes), and Hemiptera (Toxoptera citricida). Parsimony and Bayesian phylogenetic analyses showed that the PR5 family is paraphyletic in plants, likely arising from 10 genes in a common ancestor to monocots and eudicots. After evolutionary divergence of monocots and eudicots, PR5 genes increased asymmetrically among the 10 clades. Insects and nematodes contain multiple sequences (seven PR5-Ls in nematodes and at least three in some insects) all related to the same plant clade, with nematode and insect sequences separating as two clades. Protein structural homology modeling showed strong similarity among animal and plant PR5/PR5-Ls, with divergence only in surface-exposed loops. Sequence and structural conservation among PR5/PR5-Ls suggests an important and conserved role throughout the evolutionary divergence of the diverse organisms from which they reside.

Toxicity of sucrose octanoate to egg, nymphal, and adult Bemisia tabaci (Hemiptera: Aleyrodidae) using a novel plant-based bioassay.

The sweetpotato whitefly, Bemisia tabaci (Gennadius), B biotype, presents a unique problem for vegetable growers by serving as a vector of plant viruses and by inducing physiological disorders of leaves and fruit. An action threshold of a single whitefly is necessary because of the threat of disease in many areas and growers rely heavily on a single class of insecticides (neonicotinoids) for whitefly control. Additional control methods are needed to manage this pest in commercial vegetables. Extracts of wild tobacco contain natural sugar esters that have previously been shown effective in controlling many soft-bodied insects. We developed a novel tomato leaf bioassay system to assess a synthetic sugar ester derivative, sucrose octanoate, for insecticidal activity against the eggs, nymphs, and adults of B. tabaci. The LC50 values for sucrose octanoate against adults, second instars, and fourth instars of the whitefly were 880, 686, and 1,571 ppm, respectively. The LC50 against whitefly eggs was higher (11,446 ppm) but indicated that some egg mortality occurred at the recommended application rate of 0.8-1.2% (3,200-4,800 ppm [Al]). Toxicity of sugar esters to whitefly eggs has not been reported previously. The tomato leaf bioassay produced reliable and repeatable results for whitefly toxicity studies and predicted that effective nymph and adult whitefly control can be achieved with sucrose octanoate at application rates < or = 1% (4,000 ppm [AI]). Field efficacy studies are warranted to determine whether this biorational pesticide has application in commercial tomato production.

Sucrose octanoate toxicity to brown citrus aphid (Homoptera: Aphididae) and the parasitoid Lysiphlebus testaceipes (Hymenoptera: Aphidiidae).

We report the toxicological effects of a new biorational, synthetic sucrose octanoate (AVA Chemical Ventures L.L.C., Portsmouth, NH), on brown citrus aphid, Toxoptera citricida (Kirkaldy), nymphs and adults and to its native parasitoid Lysiphlebus testaceipes (Cresson). Sucrose octanoate topically applied was equally toxic to brown citrus aphid adults and nymphs with LC50 and LC90 values ranging from 356 to 514 and 1029 to 1420 ppm, respectively. Mortalities of both stages did not differ significantly over time during the 3-24-h sampling period. Dry residues of sucrose octanoate exhibited similar levels of toxicity to both nymphs and adults. Mortality ranged from 60 to 70% at 6,000 ppm 4 h after exposure. L. testaceipes was not harmed by treatments as high as 4,000 ppm of sucrose octanoate as long as the parasitoid had mummified before treatment. Based on these results, sucrose octanoate would be a useful biorational in citrus integrated pest management programs.

Effect of neem seed extract on feeding, growth, survival, and reproduction of Diaprepes abbreviatus (Coleoptera: Curculionidae).

A commercially available neem seed extract, Neemix 4.5, containing 4.5% azadirachtin (AZA), was assessed for biological activity against the root weevil Diaprepes abbreviatus (L.), an important exotic insect pest of Florida citrus. Laboratory bioassays against neonatal and 3-wk-old larvae fed sliced carrot treated with Neemix produced dose-dependent larval mortality and reduced fresh weights among survivors of treatments. The weight response was greater than the mortality response for both larval age groups. Neonates treated with 45 mg/liter AZA weighed 60% less than those in the control after 4 wk. Three-week-old larvae treated with 45 mg/ liter AZA weighed 30% less than those in the control after 5 wk. When neonates were exposed to insect diet incorporated with Neemix, reductions in larval survival and weight were observed at concentrations as low as 4.8 mg/liter AZA after 6 wk. Larval growth was inhibited by >97% with 42.9 mg/liter AZA in the diet. A soil drench containing 30 mg/liter AZA reduced the survival and weight gain of neonates added to potted citrus and provided protection to the roots in a greenhouse experiment. A concentration of 90 mg/liter AZA was required to provide protection of citrus roots against 4-wk-old larvae. Reproductive effects were observed when adult weevils were fed foliage treated with Neemix. The numbers of larvae hatching per egg mass were reduced by 27% and 68% at 30 and 90 mg/liter AZA, respectively. These results suggest that Neemix should be further evaluated for use in integrated pest management (IPM) programs of citrus.

Efficacy of various ground-applied pyrethroids against adult Anopheles quadrimaculatus in the rice growing region of Arkansas.

Ground-applied ULV, cold aerosol, insecticide sprays were evaluated against caged adult female Anopheles quadrimaculatus. Treatments included 2 rates each of resmethrin, permethrin and a water-based permethrin formulation. Mortality at 24 h posttreatment was not significantly (P greater than or equal to 0.05) different between the resmethrin and water-based permethrin treatments. Both rates of permethrin were significantly (P less than 0.05) less effective than the other treatments.

Long-term residual activity of methoprene against Psorophora columbiae larvae in rice plots.

A slow-release, briquet formulation of methoprene produced long-term residual activity against Psorophora columbiae larvae in 37.2 m2 (400 ft2) rice plots. An application rate of 1 briquet/9.3 m2 (1/100 ft2) provided significantly (P less than 0.05) greater reduction of adult mosquito emergence (98.2%) than did a rate of 1 briquet/18.6 m2 (1/200 ft2) (89.6%) during 5 insecticidal activity assessments conducted over a period of 58 days. No significant (P greater than 0.05) differences in activity were detected between treated plots which were continuously flooded and those periodically drained and reflooded.

Activity of lambda-cyhalothrin applied as an ultralow volume ground treatment against Anopheles quadrimaculatus adults.

Lambda-cyhalothrin was evaluated as an ultralow volume ground adulticide treatment at rates of 0.25, 0.5 and 1.0 g/ha. Resmethrin, a standard adulticide, was applied at a rate of 1.96 g/ha. All treatments provided greater than or equal to 95% control up to 50 m from the spray route. The highest rate of lambda-cyhalothrin and the resmethrin standard provided greater than or equal to 95% control up to 200 m, which is twice the distance normally assessed in this type of testing. Control was reduced at 200 m for the 0.25 and 0.5 g/ha rates of lambda-cyhalothrin, which provided 73 and 88% mortality, respectively. Lambda-cyhalothrin appears to have the insecticidal activity required for operational mosquito control.

Efficacy of Bacillus sphaericus formulations against Psorophora columbiae larvae in small rice plots.

Bacillus sphaericus formulations were evaluated against Psorophora columbiae larvae in small rice plots. All formulations tested provided good control (greater than 84%) for all rates tested at 2 days posttreatment. At 10 days posttreatment, fair control (greater than 70%) was recorded for ABG-6232 (0.184 kg/ha), ABG-6262; 27-242-BA (0.766 and 2.298 liters/ha), and ABG-6262; 29-293-BA (2.298 liters/ha). At 7 days posttreatment mortality was below 66%. Control did not exceed 27% at 15 days posttreatment for any formulation tested. Application rates for all formulations tested had little relationship with observed mortality, and control levels often were greater at the lower dosages tested. Bacillus sphaericus provided an effective means for controlling Ps. columbiae, but additional research is needed to determine the lower limit of effective treatment dosages and spore persistence in the rice field environment.

Evaluation of Bacillus sphaericus 2362 against Culex quinquefasciatus in septic ditches.

Four application rates of Bacillus sphaericus strain 2362 were tested for efficacy in septic ditches against Culex quinquefasciatus 2nd-4th instar larvae. Trials were conducted over a 2-year period. In 1987, all dosages applied to dairy effluent ditches resulted in substantial reductions after 48 h. Differences among dosages did not differ significantly (P greater than or equal to 0.05). After 5 days, mosquito larval numbers increased with dosage rates of 0.6, 0.9 and 1.2 liters/ha. Residual control was maintained, however, at 2.4 liters/ha for 17 days. In 1988, B. sphaericus applied to domestic sewage effluent ditches at rates of 1.2 liters/ha, and 2.4 liters/ha induced greater than 79% suppression for a period of 15 days, and the 1.2 liters/ha rate induced greater than 79% suppression for a period of 20 days. A rate of 0.9 liters/ha provided good to excellent control (greater than 88%) for a period of 10 days. A rate of 0.6 liters/ha produced less than 50% suppression after 48 h.

Efficacy of various Bacillus thuringiensis var. israelensis formulations against Psorophora columbiae larvae as assessed in small rice plots, 1984-88.

Granular, liquid and briquette formulations of Bacillus thuringiensis var. israelensis were tested in small rice plots during 1984-88 against Psorophora columbiae larvae. Vectobac AS, Skeetal G, Teknar HPD, ABG 6172, ABG 6188, ABG 6193, ABG 6197, ABG 6199, ABG 6138F and ABG 6221 provided excellent control at high dosages and good control (generally greater than 85%) at relatively low concentrations. ABG 6221 and ABG 6172 provided excellent control at low concentrations. Additional testing of these formulations will be required to ascertain specific lower limits such that more economical larval mosquito control can be obtained.

Activities of four insect growth regulator formulations of fenoxycarb against Psorophora columbiae larvae.

Four formulations of fenoxycarb were evaluated at dosages of 0.022 and 0.011 kg ai/ha against Psorophora columbiae larvae in rice plots. Granular formulations, at both rates, provided moderate to excellent control of larvae introduced within 24 h posttreatment. A 1.0% fenoxycarb/200 ITU B.t.i. granule provided 86.2% reduction of emergence from larvae introduced at 120 h posttreatment. Aside from this formulation residual activity was lacking. The liquid formulation performed moderately well at the high rate against larvae introduced within 24 h; however, residual activity rapidly diminished.

Efficacy of fenoxycarb (Pictyl) against Psorophora columbiae in Arkansas ricefields.

The IGR, fenoxycarb was effective against mosquitoes in both small rice plots and commercial ricefields in southeast Arkansas at the rate of 10 g AI/ha. It adequately controlled Psorophora columbiae populations. This compound shows excellent promise as a tool in effective IPM schemes against Ps. columbiae larvae in Arkansas rice fields by acting as a direct control, and possibly by indirectly increasing their vulnerability to natural controls.

Combination ground and aerial adulticide applications against mosquitoes in an Arkansas riceland community.

Simultaneous ground and aerial adulticide applications were evaluated against riceland mosquitoes in Stuttgart, AR, during July 1985. Naled was aerially applied at 52.6 ml/ha over 10.4 km2 surrounding the city. Ground ULV applications of a mixture of malathion, HAN and resmethrin/PBO (1:1:0.0625) were applied within the city at a rate of 221.8 ml/min at 24 kph. Adult populations of Anopheles quadrimaculatus and Psorophora columbiae were reduced at 24 hr but resurgence of Ps. columbiae was evident at 48 hr posttreatment. Posttreatment data indicated that movement of both mosquitoes occurred along the path of prevailing wind.