Toxicity of spinosad in protein bait to three economically important tephritid fruit fly species (Diptera: Tephritidae) and their parasitoids (Hymenoptera: Braconidae)

The feeding toxicity of the natural insecticide spinosad in Provesta protein bait was evaluated for three economically important fruit fly species, the Mediterranean fruit fly, Ceratitis capitata (Wiedemann); the melon fly, Bactrocera cucurbitae Coquillett; and the oriental fruit fly, Bactrocera dorsalis Hendel. Both females and males were evaluated. Spinosad was remarkably similar in toxicity to all three fruit fly species. Male C. capitata (24 h LC50 values and 95% fiducial limits = 2.8 [2.60-3.0] mg/liter spinosad) were significantly, although only slightly more susceptible to spinosadthan females (4.2 [3.8-4.6] mg/liter). Male (5.5 [4.7-6.6] mg/liter) andfemale (4.3 [3.7-4.9] mg/liter) B. cucurbitae were equally susceptible to spinosad. Female (3.3 [3.1-3.6] mg/liter) and male (3.1 [2.9-3.3] mg/liter) B. dorsalis also were equally susceptible to spinosad. Provesta bait containing spinosad also was evaluated against two parasitoids of tephritid fruit flies, Fopius arisanus (Sonan) and Pysttalia fletcheri (Silvestri). These parasitoids did not feed on the bait, so a contact toxicity test was conducted. Significant amounts of mortality were found only after exposure of parasitoids to spinosad-coated glass vials with concentrations > or =500 mg/liter spinosad. Parasitoids were less susceptible than fruit flies to such a degree that use of spinosad in bait spray should be compatible with these parasitoid species. Because the fruit flies tested in this study were so susceptible to spinosad, this product seems to be promising as a bait spray additive and a replacement for malathion for control of these species.     

Toxicity of Bacillus thuringiensis to laboratory populations of the olive fruit fly (Dacus oleae).

A survey of Bacillus thuringiensis recovered from the environments of olive groves in Greece was carried out. Of 80 soil samples, 24 were found to contain B. thuringiensis with parasporal crystal inclusions; these were tested for toxicity against the olive fruit fly (Dacus oleae). Mortality levels of larvae caused by the different isolates varied from 7 to 87%. Higher levels of mortality were observed if a mixture of relatively pure crystals and spores was used compared with the mortality resulting from either fraction alone. We were able to show that the toxicity of the most active isolate is likely to be specific for D. oleae.     

Toxicity of Bacillus thuringiensis to laboratory populations of the olive fruit fly (Dacus oleae).

A survey of Bacillus thuringiensis recovered from the environments of olive groves in Greece was carried out. Of 80 soil samples, 24 were found to contain B. thuringiensis with parasporal crystal inclusions; these were tested for toxicity against the olive fruit fly (Dacus oleae). Mortality levels of larvae caused by the different isolates varied from 7 to 87%. Higher levels of mortality were observed if a mixture of relatively pure crystals and spores was used compared with the mortality resulting from either fraction alone. We were able to show that the toxicity of the most active isolate is likely to be specific for D. oleae.     

Effect of insecticides on the diamondback moth (Lepidoptera: Plutellidae) and its parasitoid Diadegma insulare (Hymenoptera: Ichneumonidae)

Studies were conducted to evaluate the toxicity of insecticides to adult Diadegma insulare (Cresson) and its host the diamondback moth, Plutella xylostella (L.). Leaf-dip and direct-dip bioassays for diamondback moth larvae and residual bioassays for adults of diamondback moth and D. insulare were used to assess mortalities. Larval mortalities at field rates were significantly higher with carbaryl, permethrin, spinosad, and tebufenozide when compared with Bacillus thuringiensis, or imidacloprid in the larval-dip bioassay 72 h after treatment. In the leaf-dip and residual bioassays, both permethrin and spinosad caused 100% mortalities to diamondback moth larvae and adults, respectively, 72 h after treatment. Of all the materials tested, only B. thuringiensis and tebufenozide were not toxic to D. insulare 24 h after treatment. Spinosad was not toxic to D. insulare 30 min after treatment. However, 100% mortality was observed 8 h after treatment.     

八种新烟碱类杀虫剂对地熊蜂工蜂的毒性及风险评估

【目的】评价新烟碱类杀虫剂对地熊蜂Bombus terrestris工蜂的毒性和生态风险性,为温室施用新烟碱类杀虫剂提供科学依据。【方法】分别采用饲喂法和接触法测定了噻虫嗪、噻虫胺、啶虫脒、吡虫啉、烯啶虫胺、呋虫胺、噻虫啉和氟吡呋喃酮8种新烟碱类杀虫剂对地熊蜂成年工蜂的急性经口和急性接触毒性。同时评估了8种新烟碱类杀虫剂对地熊蜂工蜂的生态风险性。【结果】8种杀虫剂经饲喂法测定,噻虫胺对地熊蜂成年工蜂的毒性最高,24 h和48 h的LD 50值分别为0.0433和0.0330μg a.i./蜂;氟吡呋喃酮毒性最低,24 h和48 h的LD 50值分别为72.4119和67.9079μg a.i./蜂。接触法测定的毒性与饲喂法测得的结果一致,噻虫胺的毒性最高,24 h和48 h的LD 50值分别为0.0220和0.0192μg a.i./蜂;氟吡呋喃酮的毒性最低,24 h和48 h的LD 50值分别为141.7641和130.3062μg a.i./蜂。生态风险评估表明,啶虫脒、噻虫啉和氟吡呋喃酮对地熊蜂成年工蜂的经口毒性和接触毒性均表现为低风险,吡虫啉、烯啶虫胺和呋虫胺的毒性表现为中等风险。噻虫嗪和噻虫胺对地熊蜂成年工蜂的经口毒性表现为中等风险,而接触毒性则表现为高风险。【结论】检测的8种新烟碱类杀虫剂中啶虫脒、噻虫啉与氟吡呋喃酮对地熊蜂成年工蜂的毒性为低毒,而噻虫嗪、噻虫胺、吡虫啉、烯啶虫胺、呋虫胺这5种杀虫剂均为高毒。在设施蔬菜花期使用地熊蜂授粉时,建议禁用这5种中、高风险的新烟碱类杀虫剂,以避免对熊蜂授粉的危害,而另3种低风险药剂可根据田间试验情况合理施用。     

复配杀虫剂BtA对棉铃虫的杀虫效果及对天敌中红侧沟茧蜂蛹和成虫的触杀毒性(英文)

为了科学施药, 合理保护和利用天敌对棉铃虫Helicoverpa armigera进行综合防治, 本研究在室内测定和比较了复配杀虫剂BtA和7种常用杀虫剂（阿维菌素、 Bt、 β-氯氰菊酯、辛硫磷、定虫隆、氰戊菊酯和丁硫克百威）对棉铃虫的杀虫效果及对其天敌中红侧沟茧蜂Microplitis mediator蛹和雌成虫的触杀毒性。采用浸叶法测定杀虫剂在室内72 h内对棉铃虫3龄幼虫的杀虫效果, 结果表明： 与其他杀虫剂相比, BtA对棉铃虫幼虫具有更高的毒性和致死效应 (LC₅₀=0.7364 mg/mL)。将棉铃虫3龄幼虫接到用浓度4 mg/mL上述杀虫剂分别处理过的大白菜上24, 48和72 h, 发现其死亡率之间存在显著差异（P≤0.05）。但在72 h后, BtA和其他杀虫剂对棉铃虫幼虫的杀虫效果之间并无显著差异(P>0.05)。BtA施药后, 随着时间的延长, 棉铃虫幼虫的死亡率也在增加。另外, 通过杀虫剂对寄生蜂中红侧沟茧蜂蛹和雌成虫的触杀毒性的生物测定发现： 与β-氯氰菊酯、 氰戊菊酯和丁硫克百威相比, BtA对中红侧沟茧蜂蛹和雌成虫的毒性较低, 对其蛹和雌成虫致死率分别仅为13.82%和7.33%。本研究证明BtA对鳞翅目害虫具有中等毒性, 而对寄生蜂中红侧沟茧蜂则具有较低毒性。     

辣椒碱对烟粉虱的生物活性及生长发育和生殖力的影响

在实验室条件下研究了辣椒碱对烟粉虱的生物活性及生长发育和生殖力的影响.结果表明:辣椒碱对烟粉虱各虫态均有杀虫活性,且随辣椒碱浓度的增大活性增强;辣椒碱浸叶法/浸虫法处理对烟粉虱成虫、卵和若虫的毒力(LC50分别为3525.79、1603.29和1526.27mg·L-1))均高于内吸法处理(LC50分别为5360.04、2359.19和5897.43 mg.L-1),两种处理方法下辣椒碱对烟粉虱卵的毒力均明显高于对成虫的毒力;2000和4000 mg·L-1浓度辣椒碱对烟粉虱成虫具有明显的拒食作用,烟粉虱在该两种浓度辣椒碱处理过的棉花叶上取食24 h的蜜露分泌量均显著低于取食非处理棉花叶后的蜜露分泌量;辣椒碱各试验浓度对烟粉虱成虫均表现出较强的产卵忌避作用,当辣椒碱处理浓度达4000 mg·L-1时,对烟粉虱的选择性产卵忌避率和非选择性产卵忌避率分别高达94.2％和83.0％.500、1000和2000 mg·L-1辣椒碱浸渍处理对烟粉虱存活卵和若虫的发育历期、成虫羽化率均没有影响,但辣椒碱4000mg·L-1处理明显延长烟粉虱若虫发育历期、降低成虫羽化率.不同浓度辣椒碱处理均明显抑制烟粉虱生殖力,且这种抑制作用随辣椒碱浓度的增大而增强.     

Immediate and delayed mortality of Rhyzopertha dominica (Coleoptera: Bostrichidae) and Sitophilus oryzae (Coleoptera: Curculionidae) adults exposed to spinosad-treated commodities

A series of tests was conducted to characterize differences in the mortality of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), and rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), exposed to three commodities treated with a liquid and dry spinosad formulation. In laboratory bioassays, adults of the two insect species were exposed to untreated wheat, Triticum aestivum L., corn, Zea mays L., and sorghum, Sorghum bicolor (L.) Moench., and to commodities treated with 1 mg (AI)/kg of liquid and dry spinosad formulations. Mortality was assessed from independent samples examined at specific time intervals to determine immediate mortality and after 24 h of recovery on untreated grain at 28 degrees C and 65% RH to determine delayed mortality. Comparison of the time required for 50% (LT50) and 95% (LT95) mortality indicated that R. dominica adults were consistently and significantly more susceptible (died quickly) than S. oryzae adults when exposed to spinosad-treated commodities. In general, the toxicity of liquid and dry spinosad formulations was similar against R. dominica or S. oryzae. The toxicity of spinosad to each species varied slightly among the three commodities, and there were no consistent trends to suggest that spinosad was more effective on one commodity versus another. LT50 values based on immediate mortality for R. dominica on all commodities ranged from 0.45 to 0.74 d; corresponding values based on delayed mortality ranged from 0.04 to 0.23 d, suggesting delayed toxic action of spinosad in R. dominica. LT50 values based on immediate and delayed mortality for S. oryzae on all three commodities treated with the two spinosad formulations were essentially similar and ranged from 2.75 to 4.56 d. LT95 values for R. dominica based on immediate mortality on spinosad-treated commodities ranged from 1.75 to 3.36 d, and those based on delayed mortality ranged from 0.49 to 1.88 d. There were no significant differences in LT95 values based on immediate and delayed mortality for S. oryzae on spinosad-treated commodities, and the LT95 values ranged from 7.62 to 18.87 d. The toxicity of spinosad was enhanced during a 24-h holding period after removal from spinosad-treated commodities only against R. dominica adults, and possible reasons for increased postexposure mortality of R. dominica adults after brief exposures to spinosad warrant further study.     

Insecticide enhancement with feeding stimulants in corn for western corn rootworm larvae (Coleoptera: Chrysomelidae)

Amounts of the insecticide thiamethoxam required for 50% mortality of western corn rootworm larvae, Diabrotica virgifera virgifera LeConte, were reduced 100-fold when extracts of germinating corn, Zea mays L., were used to entice neonate larvae to feed on it. In behavioral bioassays, neonate rootworm larvae fed vigorously on filter paper disks treated with liquid pressed from corn roots. Moreover, disks treated with an acetone extract of corn (dried and rewetted with water) also elicited strong feeding from larvae. Larvae wandered away from filter paper disks treated with distilled water without feeding. Dilutions of thiamethoxam were tested in the bioassay alone or with corn extract and the efficacy of this insecticide was improved by the addition of the corn extract. For solutions containing 10 ppm thiamethoxam, 95% larval mortality occurred after 30 min of exposure when corn extract was present, but only 38% mortality occurred when the same concentration of insecticide alone (no feeding stimulants) was tested. Larval mortality after 24 h was significantly higher for corn extract-treated disks with 0.01, 0.1, 1, or 10 ppm insecticide than for the same concentrations without corn extract. Thiamethoxam did not deter larval feeding on corn extract, even at the highest concentration of thiamethoxam tested.     

Biological activity of Xanthium strumarium seed extracts on different cancer cell lines and Aedes caspius,Culex pipiens (Diptera: Culicidae)

Effects of methanol extracts of Xanthium strumarium on different cancer cell lines and on the mortality rates of Aedes caspius, Culex pipiens (Diptera: Culicidae) were investigated. Among the cell lines tested, the Jurkat cell line was the most sensitive to the methanol extract and ethyl acetate fraction, with reported LC₅₀ values of 50.18 and 48.73 μg/ml respectively. Conversely, methanol extracts were not that toxic to the A549 cell line though the toxicity increased on further purification. The percentage of growth inhibition was dose dependent for the methanol extract and ethyl acetate fraction. The ethyl acetate fraction showed higher toxicity to all cell lines tested when compared to the methanol extract. The results showed that methanol extracts of plant seeds caused 100% mortality of mosquito larvae at a concentration of 1000 μg/ml after 24 h of treatment. The LC₅₀ and LC₉₀ values of X. strumarium were found to be 531.07 and 905.95 μg/ml against Ae. caspius and 502.32 and 867.63 μg/ml against Cx. Pipiens, respectively. From the investigations, it was concluded that the crude extract of X. strumarium showed a weak potential for controlling the larval instars of Ae. caspius and Cx. pipiens. However, on further purification the extract lost the larvicidal activity. The ethyl acetate fraction showed higher toxicity to all cell lines tested when compared to the methanol extract. The ethyl acetate fraction investigated in this study appears to have a weak larvicidal activity but a promising cytotoxic activity. Future studies will include purification and investigation in further detail of the action of X. strumarium on Cancer Cell Lines and mosquitoes.     

Insecticidal activity of Citrus aurantium peel extract against Bactrocera oleae and Ceratitis capitata adults (Diptera: Tephritidae)

Citrus aurantium (L.) peel extracts in petroleum ether were evaluated for toxicity against olive fruit fly, Bactrocera oleae (Gmelin) and medfly, Ceratitis capitata (Wiedemann) adults. Bactrocera oleae flies were more susceptible to the extract than C. capitata in contact and residual bioassays. Fumigation bioassay had no effect. Both sexes of B. oleae were equally susceptible in both types of bioassays. However, males of C. capitata were more susceptible than the conspecific females. LD₅₀ values (concentration causing 50% mortality) after 96 h for the males and females of B. oleae were 44.8 and 40.1 μg/insect in contact bioassay through topical application. Whereas, LD₅₀ values for the males and females of C. capitata were 38.8 and 67.8 μg/insect respectively. LC₅₀ values after 96 h for the males and females of B. oleae were 18.8 and 17.8 μg/cm² in Petri dish residual bioassay. Whereas, LC₅₀ values for the males and females of C. capitata were 70.6 and 147.1 μg/cm² respectively.
Fractionation of the extract on a silica gel column with three different polarity solvents resulted in three fractions with only the intermediate polarity solvent fraction having substantial insecticidal activity. Toxicity of the mixtures of active and inactive fractions was equal to the original extract. Our results indicate that C. aurantium has potential for controlling insect pests.     

Acaricidal activity of Juglans regia leaf extracts on Tetranychus viennensis and Tetranychus cinnabarinus (Acari: Tetranychidae)

Leaf extracts of the walnut, Juglans regia L., were evaluated under laboratory conditions to determine their acaricidal activity on the mites Tetranychus cinnabarinus (Boisduval) and Tetranychus viennensis Zacher (Acari: Tetranychidae). Extracts had both contact and systemic toxicity to these mites. The four solvents tested for preparing crude extracts were petroleum ether, chloroform, ethyl acetate, and methanol. Methanol was the most efficient solvent, with an extraction rate from 17.06 + 0.80 to 20.27 +/- 0.28%. Petroleum ether was the least effective solvent, with extraction rates from 2.30 +/- 0.13 to 2.71 +/- 0.13%. However, the crude extracts with petroleum ether resulted in the highest mite mortality (79.04 +/- 0.52%) in a slide dip bioassay. Mites mortalities from the concentrated extracts prepared by chloroform, ethyl acetate, methanol, or distilled water were significantly lower than petroleum ether. The mean lethal concentrations (LC50) of the extracts from petroleum ether, chloroform, ethyl acetate, methanol, and distilled water to the two mite species were 0.73 +/- 0.04, 1.66 +/- 0.28, 4.96 +/- 0.35, 7.45 +/- 0.67, and 9.91 +/- 0.32 mg/ml, respectively. After liquid chromatography and thin-layer chromatography, the concentrated extracts of petroleum ether were separated into eight fractions and tested for acaricidal activity. Fraction 6 produced significantly higher mite mortality rates than the other groups, killing approximately 90% of both species.     

Laboratory evaluation of entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae against puparia and adults of Ceratitis capitata (Diptera: Tephritidae)

Laboratory experiments were done to measure the pathogenicity of 10 autochthonous isolates of Beauveria bassiana (Balsamo) Vuill. and of five Metarhizium anisopliae (Metsch.) Sorok. toward puparia and adults of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Although all isolates applied via inoculation of the fungal suspensions on the ventral surface of the abdomen were pathogenic to adults, with mortality rates ranging from 30 to 100% and average survival times (ASTs) from 6.5 to 8.6 d, when C. capitata puparia were immersed in the conidial suspensions, only B. bassiana Bb-1333 and EABb 01/103-Su and M. anisopliae EAMa 01/58-Su isolates caused >50% mortality of puparia. In a second series of bioassays conducted on five selected isolates, adults were sprayed with four 10-fold concentrations ranging from 1.0 x 10(5) to 1.0 x 10(8) colony-forming units (cfu)/ml. The median lethal concentrations (LC50) of the four most virulent isolates ranged from 4.9 x 10(5) to 2.0 x 10(6) cfu/ml with estimated time to kill 50% of the insects ranging from 4.6 to 5.3 d. The effect of a sublethal dose (ca. LD50) of either B. bassiana EABb 01/103-Su or M. anisopliae EAMa 01/58-Su isolate was studied by reciprocal crossing. Treatment with B. bassiana reduced fecundity and fertility at 6, 8, and 10 d after treatment, with fecundity and fertility reductions ranging from 20.0 to 71.2% and from 33.6 to 60.0%, respectively. These reductions occurred in pairing combinations of treated females with either treated or nontreated males. M. anisopliae was more effective in reducing fecundity and fertility at 6 d after treatment, with the reduction varying from 58.4 to 72.1% and from 28.6 to 45.9%, respectively. In addition, the first oviposition was significantly delayed for 1 d in females treated by either fungal species. The above-mentioned five selected isolates were assayed against C. capitata puparia treated as late third instars in sterilized soil at 25'C under three moisture conditions (-0.1, -0.01, and -0.0055 MPa). At -0.01 MPa, all isolates were low pathogenic to C. capitata puparia, whereas significant differences in the puparia mortality occurred between isolates at -0.1 and -0.0055 MPa. The highest pupal mortalities ranged from 52.5 to 70.0%, as a function of soil moisture and were caused by EAMa 01/58-Su and Bb-1333 isolates.     

Sunlight-activated insecticides: historical background and mechanisms of phototoxic activity

Several photosensitizing agents, which are activated by illumination with sunlight or artificial light sources, have been shown to be accumulated in significant amounts by a variety of insects when they are administered in association with suitable baits. The subsequent exposure of such insects to UV/visible light leads to a significant drop in survival. Of the photosensitizers tested so far, xanthenes (e.g. phloxin B) and porphyrins (e.g. haematoporphyrin) appear to be endowed with the highest photoinsecticidal activity. In particular, porphyrins absorb essentially all the UV/visible light wavelengths in the emission spectrum of the sun; hence they are active at very low doses. Thus, 1 h irradiation of Ceratitis capitata, Bactrocera oleae (also known as Dacus oleae) or Stomoxys calcitrans which ingested a few nanomoles of porphyrin per fly with light intensities of the order of 1000 microE s(-1) m(-2) causes about 100% death in laboratory tests. Present evidence suggests that such photosensitizers act on the membranes of the midgut with consequent feeding inhibition, as well as on the neuromuscular sheath. No apparent onset of photoresistance has been observed. The rapid photobleaching of xanthenes and porphyrins when illuminated by visible light, as well as the lack of significant toxicity of such compounds in the dark, minimizes the risk of an important environmental impact of such photoinsecticidal agents.     

The complete nucleotide sequence of the mitochondrial genome of the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae)

The complete mitochondrial genome of the oriental fruit fly Bactrocera dorsalis s.s. has been sequenced, and is here described and compared with the homologous sequences of Bactrocera oleae and Ceratitis capitata. The genome is a circular molecule of 15,915 bp, and encodes the set of 37 genes generally found in animal mitochondrial genomes. The structure and organization of the molecule is typical and similar to the two closely related species B. oleae and C. capitata, although it presents an interesting case of putative intra-molecular recombination. The relevance of the growing comparative dataset of tephritid complete mitochondrial genomes is discussed in relation to the possibility to develop robust assays for species discrimination in quarantine and agricultural monitoring practices, as well as basic phylogeography/population genetic studies.     

Comparative evaluation of spinosad and phloxine B as toxicants in protein baits for suppression of three fruit fly (Diptera: Tephritidae) species

Spinosad and phloxine B are two more environmentally friendly alternative toxicants to malathion for use in bait sprays for tephritid fruit fly suppression or eradication programs. Laboratory tests were conducted to assess the relative toxicity of these two toxicants for melon fly, Bactrocera cucurbitae Coquillett; oriental fruit fly, Bactrocera dorsalis Hendel; and Mediterranean fruit fly, Ceratitis capitata (Wiedemann) females. Field tests also were conducted with all three species to compare these toxicants outdoors under higher light and temperature conditions. In laboratory tests, spinosad was effective at much lower concentrations with LC50 values at 5 h of 9.16, 9.03, and 4.30 compared with 250.0, 562.1, and 658.9 for phloxine B (27, 62, and 153 times higher) for these three species, respectively. At 16 ppm spinosad, LT50 values were lower for all three species (significantly lower for C. capitata and B. dorsalis) than 630 ppm phloxine B LT50 values. At 6.3 ppm spinosad, the LT50 value for C. capitata (3.94) was still significantly less than the 630 ppm phloxine B LT50 value (6.33). For all species, the 100 ppm spinosad concentrations gave LT50 values of < 2 h. In comparison among species, C. capitata was significantly more sensitive to spinosad than were B. cucurbitae or B. dorsalis, whereas B. cucurbitae was significantly more sensitive to phloxine B than were C. capitata or B. dorsalis. LC50 values were reduced for both toxicants in outdoor tests, with greater reductions for phloxine B than for spinosad for B. dorsalis and B. cucurbitae. Fly behavior, though, is likely to keep flies from being exposed to maximum possible outdoor light intensities. Comparable levels of population suppression for any of the three species tested here will require a much higher concentration of phloxine B than spinosad in the bait.     

Effects of in vivo exposure to DEET on blood feeding behavior and fecundity in Anopheles quadrimaculatus (Diptera: Culicidae)

This study determined the effects of contact with DEET on guinea pig skin on mortality, probing time, blood feeding rate, engorgement time, and fecundity responses in female Anopheles quadrimaculatus Say. Exposure, in this manner, to 10% DEET (in ethanol) for 5 min, resulted in 98% mortality in mosquitoes after 24h. The median probing time (PT(50)) required by females, when exposed to 0.1%, 1.0%, and 10% DEET, was significantly (P<0.0001) longer (12.5, 12.1, and 19.1s, respectively) than the 6.8s required by females to probe ethanol-treated skin (control). Similarly, mean blood feeding rates in populations of females exposed to 1.0% DEET for < or = 5 min (14.4%) was 6x lower (P<0.001) (85.5%) than in females exposed to ethanol-treated skin, whereas the mean engorgement time on skin treated with 1.0% DEET (66.3s) was significantly shorter (P<0.0001) than for females feeding on the control guinea pigs (105.9s). The mean number of mature o?cytes per female (fecundity) in treatment (1.0% DEET) and control mosquitoes was not significantly different. The responses to DEET observed in this study suggest that repeated exposure of female A. quadrimaculatus populations to this repellent, in laboratory bioassays, could result in confounding of toxicant and repellent effects and inaccurate estimates of DEET repellency.     

Lethal and sublethal toxicity of fipronil and imidacloprid on Psyttalia concolor (Hymenoptera: Braconidae)

Psyttalia concolor (Szèpligeti) (Hymenoptera: Braconidae) is a koinobiont endoparasitoid of several species of tephritid (Diptera) larvae, such as Bactrocera oleae (Gmelin) and Ceratitis capitata (Wiedemann). Here, we report on the effects of imidacloprid and fipronil on P. concolor females, when different routes of exposure were evaluated: residual contact (cover and bait sprays) and via treatment of host species. Moreover, the persistence of the bait formulated compound also was studied. For each experiment, lethal (mortality) and sublethal effects (parasitization rate or longevity) were studied. Fipronil produced 100% mortality irrespective of exposure route, and it was very persistent, because 34-d-old residues still produced this high mortality rate, being as toxic or even more toxic than the reference product dimethoate. Toxicity of imidacloprid depends on the mode of exposure, although always remained less toxic than dimethoate. Imidacloprid caused high mortality or sublethal effect to the progeny in cover sprays and when applied via treated host, being harmless in bait sprays application. In conclusion, our results suggest that fipronil should not be used in the field when the parasitoid is present. On the contrary, although imidacloprid is physiologically active against females of P. concolor, ecological selectivity may result through the use of bait treatment.     

Growth inhibitory and antifeedant activity of extracts from Melia dubia to Spodoptera litura and Helicoverpa armigera larvae

The growth inhibitory activity and deterrency of Melia dubia (Meliaceae) extracts to Spodoptera litura and Helicoverpa armigera were investigated. Artificial diet bioassays using neonate larvae of both S. litura and H. armigera indicated that dichloroethane (DCE) and methanol (Me) extracts of M. dubia inhibited growth in a dose dependent manner. DCE and Me-5II fractions also resulted in 50% deterrency at concentrations of 22.5 and 16.8 micrograms/cm2 respectively against S. litura larvae in a leaf disc-choice test. The DCE-5 fraction was found to be more toxic to larvae (LC50 of 0.65%) than the Me-5II (LC50 of 0.8%), 72 hr after topical application. Both fractions lack contact toxicity, but the deterrent effect persisted for at least 60 hr under laboratory conditions. Although salannin was isolated from the DCE fraction to show antifeedant activity, the physico-chemical characteristics of the active fractions DCE-5 and Me-5II were not identical with either salannin or azadirachtin.     

Response of melon fly (Diptera: Tephritidae) to weathered SPLAT-Spinosad-Cue-Lure

Studies were conducted in Hawaii to measure attraction of male melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), to SPLAT-Cue-Lure (C-L) and SPLAT-Melo-Lure (M-L) (raspberry ketone formate). Direct field comparisons of SPLAT-C-L and SPLAT-M-L at low (5%) and high (20%) concentrations indicated few differences in attraction over a 15-wk period. Subsequently, only SPLAT-Spinosad-C-L (5%) was compared with Min-U-Gel C-L with naled (standard used in California) in weathering studies. Treatments were weathered for 1, 2, 4, and 8 wk in Riverside, CA, and shipped to Hawaii for attraction/toxicity tests under field and semifield conditions by using released males of controlled ages, and for feeding tests in the laboratory. In terms of attraction, SPLAT-Spinosad-C-L compared favorably to, or outperformed the current standard of Min-U-Gel-C-L with naled. In terms of toxicity, the cumulative 24-h mortality did not differ between the two insecticide-containing C-L treatments in field cage studies after 8 wk. However, in feeding studies in which individual males were exposed for 5 min to the different C-L treatments after 4 wk of weathering, SPLAT-Spinosad-C-L demonstrated reduced mortality compared with the Min-U-Gel-C-L with naled, suggesting reduced persistence of the spinosad material. Spinosad has low contact toxicity and when mixed with SPLAT and C-L offers a reduced risk alternative for control of B. cucurbitae and related C-L-responding species, without many of the negative effects to humans and nontargets of broad-spectrum contact poisons such as naled.