Development of probiotic diets for the olive fly: evaluation of their effects on fly longevity and fecundity

One possible control strategy against the olive fly, Bactrocera oleae, the most serious olive crop pest, is the Sterile Insect Technique (SIT) application. However, a number of problems associated with this method remain that decrease the effectiveness of SIT, including the quality of reared insects. Taking the importance of the relationship between the olive fly and bacteria into consideration, the effects of probiotic diets enriched with Pseudomonas putida on B. oleae longevity and fecundity were evaluated. First, we found that the probiotic bacterium, P. putida, is conveyed from diets to the oesophageal bulb as well as to the fly midgut after feeding on the probiotic diet. Subsequently, B. oleae adults fed on either: (a) a standard full protein and sugar diet; (b) a sugar only diet; (c) a probiotic standard full protein and sugar diet; or (d) a probiotic sugar diet. Flies fed on probiotic diets were supplied with an inoculated gel containing P. putida; non‐inoculated gel was provided to the flies fed on non‐probiotic diets. B. oleae males and females that fed on sugar diets did not survive as long as those that fed on protein diets. A comparison of the longevity of adults fed on full diet and sugar with their respective probiotic diets revealed no significant difference. Males fed on the sugar only diet survived longer than males fed on probiotic sugar diet, and females fed on the full protein and sugar diet survived much longer than females fed on the full probiotic diet. As regarding fecundity, both full diets resulted in a higher number of eggs laid per female. Females fed on the probiotic sugar diet laid a higher number of eggs than females that fed on sugar only. The inoculated gel of the probiotic sugar diet contained a significantly higher quantity of leucine, isoleucine and proline than the non‐inoculated gel of the sugar only diet. The possible role of dietary bacteria in relation to functional aspects of olive fly physiology is discussed.     

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.     

Influence of diet on synthesis and utilisation of lipids for reproduction by the tsetse fly Glossina morsitans

Fatty acid composition of lipids from adult Glossina morsitans was unaffected by an in vitro fed diet of cow blood which induces production of under-sized offspring compared to that of flies fed on a superior diet of pig blood. The commonest fatty acids were C_16:0, C_16:1 and C_18:1 and only small differences in proportions were detected between virgin and pregnant females. Rate of lipid accumulation by males and females was the same and was unaffected by diet, but males achieved a maximum of 2.5 mg on day 9 while both virgin and fertilised females reached a maximum of 5,0 mg on day 14 of adult life. Lipid content of pregnant flies then fell to 3.0 mg on the day of larviposition and accumulation began again. A cow blood diet reduced the extent to which the lipids were utilised for larval growth and this was reflected in an altered secretory activity cycle in the female uterine gland. However, no effect on the growth of adult fat body was detectable in such flies. Mating and fertilisation, which influence reproductive events through activity of the endrocine system do not seem to affect the acquisition of lipid reserves by female Glossina. However, they clearly exert considerable influence over distribution of such reserves between fat body and uterine gland, which distribution is also affected by diet.     

Cholesterol oxidase: an oöstatic and larvicidal agent active against the cotton boll weevil,Anthonomus grandis

The enzyme cholesterol oxidase (E.C. 1.1.3.6), purified from Streptomyces culture filtrate was previously found to have oral insecticidal activity on neonate larvae of the boll weevil (Anthonomus grandis grandis Boheman) from a laboratory population. In the present study, second instar larvae were also controlled by the enzyme at diet concentrations similar to those which control neonates (12 day LC₅₀ = 2.4 μg.ml^?1 in diet). Larvae from field-collected adults were similarly susceptible to cholesterol oxidase in the diet. When ingested by adult females during the mating/pre-oviposition period, cholesterol oxidase greatly reduced subsequent oviposition (83% reduction in eggs laid as compared to controls) and larval survival (97% reduction from controls). Dissection of treated adult females revealed poorly developed ovaries and few developing oöcytes. These studies were conducted to further evaluate the utility of cholesterol oxidase in a program to establish boll weevil-resistant transgenic cotton.     

Effects of triflumezopyrim on the reproduction of brown planthopper,Nilaparvata lugens

The brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), is a notorious pest on rice in Asia and has evolved serious resistance to traditional chemical insecticides in recent years. Triflumezopyrim, a newly commercialized mesoionic insecticide, exhibited an excellent control effect on sucking insects, including N. lugens. However, the effects of triflumezopyrim on the reproduction of N. lugens have not yet been fully elucidated. In this study, we investigated the impacts of different concentrations of triflumezopyrim (LC₁₀, LC₅₀ and LC₉₀) on the reproduction and the reproduction related genes of N. lugens exposure to the insecticide via systemic and contact route. The results indicated that the preoviposition periods of N. lugens females in the LC₅₀ and LC₉₀ triflumezopyrim-treated groups (♀ t × ♂ t) were prolonged in contact toxicity treatment, compared with control (acetone treatment). The fecundities for three pair combinations (♀ c ×♂ t, ♀ t ×♂ c and ♀ t ×♂ t) treated with LC₅₀ and LC₉₀ concentrations of triflumezopyrim showed a significant decrease compared to water/acetone-treated control via contact and systemic route. No significant effects of LC₁₀ triflumezopyrim on preoviposition period and fecundity were found in contact and systemic toxicity treatments. However, the triflumezopyrim did not influence the egg hatchability. By microscope observation, the LC₅₀ and LC₉₀ triflumezopyrim impended the ovarian development in females. qRT-PCR analysis showed that the vitellogenin (NlVg) relative expression level of female adults exposed to LC₅₀ and LC₉₀ triflumezopyrim decreased by 30.3 – 39.5% in two toxicity treatments. The titers of another reproduction related hormones juvenile hormone III (JH III) in LC₅₀ and LC₉₀ triflumezopyrim-treatments were 27.4% and 25.8% lower than control in contact toxicity treatment and 27.08% and 37.18% lower than control in systemic toxicity treatment. In summary, these results suggested that the median lethal and high lethal concentrations of triflumezopyrim inhibited the reproduction and reduced the expression of NlVg and JH III in N. lugens. This study provided a reference for the efficient and scientific utilization of triflumezopyrim in the field.     

Sublethal effects of abamectin on the development,fecundity, and wing morphs of the brown planthopper Nilaparvata lugens

The brown planthopper Nilaparvata lugens negatively affects rice yield by sucking nutrients from the rice stem and spreading viruses. In this study, the effects of sublethal concentrations of abamectin on development, fecundity, and wing morphs of N. lugens were investigated. Treatment with sublethal concentrations of abamectin showed no significant effects on the developmental period of F₀ nymphs. Although LC₁₀ and LC₂₅ treatments resulted in 10% and 25% mortality, the LC₂₅ treatment significantly prolonged the lifespan of macropterous and brachypterous females. Abamectin-treated brachypterous females showed significantly lower fecundity than control females. Furthermore, abamectin treatment showed no significant effects on the developmental period of F₁ nymphs. However, LC₂₅ treatment significantly inhibited the fecundity of brachypterous F₁ females and significantly reduced the proportion of macropterous F₁ females and brachypterous F₁ males. LC₂₅ treatment showed no significant effects on the fecundity of macropterous F₁ females. Considering the proportion of macropterous and brachypterous F₁ females, the relative fitness of the macropterous F₁ nymphs in the control, LC₁₀, and LC₂₅ treatment groups was 1, 1.02, and 0.84, respectively, and that of brachypterous F₁ nymphs was 1, 0.79, and 0.93, respectively. Sublethal concentrations of abamectin inhibited N. lugens emergence. The present findings indicate the potential of abamectin for N. lugens field control.     

Effect of semolina-jaggery diet on survival and development of Drosophila melanogaster

Drosophila melanogaster is an ideal model organism for developmental studies. This study tests the potential of semolina-jaggery (SJ) diet as a new formulation for bulk rearing of flies. Semolina and jaggery are organic products obtained from wheat endosperm and cane sugar, respectively. Semolina is a rich source of carbohydrates and protein. Jaggery has a high content of dietary sugars. Moreover, preparation of semolina jaggery diet is cost-effective and easy. Thus, the current study aimed to compare survival and developmental parameters of flies fed the SJ diet to flies fed the standard cornmeal-sugar-yeast (CSY) diet. SJ diet enhanced survival of flies without affecting fecundity; male flies showed increased resistance to starvation. A higher number of flies emerged at F₂ and F₃ generation when fed the SJ diet than when fed the control CSY diet. SJ diet did not increase fly body weight and lipid percentage. Therefore, SJ diet can be used for bulk rearing of healthy flies at par with the standard cornmeal-sugar-yeast diet.     

Bacterial symbiosis in Bactrocera oleae,an Achilles’ heel for its pest control

Investigations on microbial symbioses in Tephritidae have increased over the past 30 years owing to the potential use of these relationships in developing new control strategies for economically important fruit flies. Bactrocera oleae (Rossi)—the olive fruit fly—is a monophagous species strictly associated with the olive tree, and among all the tephritids, its symbionts are the most investigated. The bacterium Candidatus Erwinia dacicola is the major persistent resident endosymbiont in wild B. oleae populations. Its relationship with B. oleae has been investigated since being identified in 2005. This endosymbiont is vertically transmitted through generations from the female to the egg. It exists at every developmental stage, although it is more abundant in larvae and ovipositing females, and is necessary for both larvae and adults. Studying B. oleae–Ca. E. dacicola, or other B. oleae–microbe interactions, will allow us to develop modern biological control systems for area-wide olive protection and set an example for similar programs in other important food crops. This review summarizes the information available on tephritid–microbe interactions and investigates relationships among fruit flies, bacteria and host plants; however, its focus is on B. oleae and its strict association with Ca. E. dacicola to promote environmentally friendly control strategies for area-wide pest management.     

Potential risks of systemic imidacloprid to parasitoid natural enemies of a cerambycid attacking Eucalyptus

A community of insect herbivores has established on eucalyptus species in California following their introduction from Australia. A number of the species are under complete or partial biological control. A response to introduction of additional pest species into the complex has been the application of systemic insecticides to infested trees. Natural enemies that have been introduced to control the various pest species feed on the nectar of treated trees, and thus may be affected by these pesticides. In this study, Eucalyptus rudis trees were treated at label rates with the neonicotinoid systemic insecticide imidacloprid and nectar sampled at 5 months post-treatment during the spring bloom. The concentration of imidacloprid and its toxic metabolites in nectar was measured by ELISA at 660 ppb. Adults of the encyrtid egg parasitoid Avetianella longoi that were fed floral nectar collected from treated trees had significantly lower survival and reproductive fitness than adults fed nectar from untreated trees. In feeding bioassays, in which the adults were fed a range of concentrations of imidacloprid in sugar water, the LC₅₀ for A. longoi was 212 ppb imidacloprid. Bioassays were also conducted with the braconid larval parasitoid, Syngaster lepidus. The LC₅₀ for S. lepidus was 288 ppb imidacloprid. The insecticide appears to be concentrating in the nectar at higher levels than reported from other plant species and at concentrations exceeding the LC₅₀ for two important parasitoids. If tree treatments become widespread as a result of continual introductions of new eucalypt herbivores, established biological control programs could be at significant risk.     

Aggressive Behavior in Olive Fruit Fly Females: Oviposition Site Guarding against Parasitic Wasps

Among Tephritidae flies, the females display agonistic behavior to maintain single oviposition sites and reduce larval competition for food. In the olive fruit fly, Bactrocera oleae, female-female aggressive interactions are characterized by reciprocal wing waving, chasing, head butting and boxing with forelegs. Little is known on tephritid aggressive behaviors directed towards natural enemies, with special reference to parasitoids attacking their young instars. In this study, we quantified the aggressive behavior of B. oleae females guarding their oviposition site against the braconid parasitoid Psyttalia concolor. The fly aggressive behavior displayed against the parasitoids was compared that directed towards paper dummies mimicking P. concolor adults. When a P. concolor female came close (<20 mm) to a B. oleae female guarding the oviposition site, the 91.67% of the flies displayed wing-waving, the 63.34% chased the parasitoid, the 45% showed head-butting, while boxing was observed only in the 26.67% of the aggressions. When paper dummies were tested, only the 66.67% of the flies displayed wing-waving, the 8.33% performed chasing, followed by head butting (5.00%) and boxing (3.33%). B. oleae displayed longer aggression bouts towards live wasps over dummies. Overall, this is the first evidence pointing out that tephritid aggressive acts, besides their role in intraspecific interactions, were also highly effective to displace parasitic wasps from the fly oviposition site. Further research on potential consequences on fitness traits arising from the above-discussed behaviors, as well as on parasitoid learning-mediated responses to tephritid aggressions, is urgently required.     

Effects of B-azolemiteacrylic on life-history traits and demographic parameters of two-spotted spider mite,Tetranychus urticae (Acari: Tetranychidae)

The present study was conducted to evaluate sublethal effects of B-azolemiteacrylic on the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Female adults of T. urticae were exposed to LC₁₀ and LC₃₀ of the acaricide, and the effects on treated females and their offspring were evaluated. The results showed that the fecundity of F₀ female adults treated with LC₁₀ and LC₃₀ of B-azolemiteacrylic was reduced by 30.9 and 39.2%, respectively. Longevity and oviposition period of the females were significantly reduced as well. The developmental duration of egg and deutonymph stage of the F₁ generation were not significantly different from that of the control. The protonymph stage after LC₃₀ treatment lasted significantly longer, whereas the larva, deutonymph and female stage were significantly shorter than the control. The oviposition period of the F₁ generation was significantly shortened, the fecundity of each female decreased significantly, and the ratio of female-to-male was reduced too. Moreover, the average generation period of T. urticae after LC₁₀ and LC₃₀ treatments was shorter than that of the control, and the net production rate (R₀), intrinsic rate of increase (r_m) and finite rate of increase (λ) were all reduced by 33.3, 7.5 and 1.9% (LC₁₀ treatment) and by 51.3, 14.8 and 3.6% (LC₃₀ treatment), respectively. The population doubling time was prolonged by 7.5 and 14.8% after LC₁₀ and LC₃₀ treatments, respectively, compared with the control. These results indicate that B-azolemiteacrylic may effectively inhibit the development rate of the F₀ and F₁ populations of T. urticae, which will help design integrated strategies for the comprehensive control of T. urticae and rational use of pesticides in the field.

     

Effect of semolina-jaggery diet on survival and development of Drosophila melanogaster

Drosophila melanogaster is an ideal model organism for developmental studies. This study tests the potential of semolina-jaggery (SJ) diet as a new formulation for bulk rearing of flies. Semolina and jaggery are organic products obtained from wheat endosperm and cane sugar, respectively. Semolina is a rich source of carbohydrates and protein. Jaggery has a high content of dietary sugars. Moreover, preparation of semolina jaggery diet is cost-effective and easy. Thus, the current study aimed to compare survival and developmental parameters of flies fed the SJ diet to flies fed the standard cornmeal-sugar-yeast (CSY) diet. SJ diet enhanced survival of flies without affecting fecundity; male flies showed increased resistance to starvation. A higher number of flies emerged at F₂ and F₃ generation when fed the SJ diet than when fed the control CSY diet. SJ diet did not increase fly body weight and lipid percentage. Therefore, SJ diet can be used for bulk rearing of healthy flies at par with the standard cornmeal-sugar-yeast diet.     

Sublethal effects of abamectin on the biological performance of the predatory mite, <Emphasis Type="Italic">Phytoseius plumifer</Emphasis> (Acari: Phytoseiidae)

Traditionally estimating pesticide effects by measuring only lethal effect may underestimate the total negative effect on beneficial arthropods and sublethal effects should be assessed to estimate the total effect of their applications. In this study, sublethal effect of the acaricide abamectin (Vermectin^® 1.8% EC, Giah, Iran) on the predatory mite Phytoseius plumifer (Canestrini &; Fanzago) (Acari: Phytoseiidae) fed on Tetranychus urticae Koch was assessed in laboratory conditions. The adult predators were exposed to the residues of the acaricide on fig leaves and the LC₅₀ value was determined based on a concentration–response analysis. The results showed that sublethal concentrations (LC₁₀, LC₂₀ and LC₃₀) of abamectin severely affected the fecundity and longevity of the treated females of P. plumifer. Furthermore, reproductive and life table parameters of the subsequent generation were affected. The results indicated that adverse effects of abamectin on population growth of P. plumifer were significant, so the results from this study can be used to develop approximate guidelines for the use of abamectin in order to minimize their impact on P. plumifer and related natural enemies.     

Lethal and sublethal effects of spiromesifen,spirotetramat and spirodiclofen on Tetranychus urticae Koch (Acari: Tetranychidae)

Lethal and sublethal effects of spirotetramat, spiromesifen and spirodiclofen were assessed on Tetranychus urticae Koch. Leaf disc bioassay was used in all experiments. In this study, toxicity of these compounds was tested on T. urticae eggs and adults. Ovicidal activity was observed in all of the compounds tested, but only spirodiclofen was considerably effective against adult mites. Up to 24?h-old adult females were placed on leaf discs treated with sublethal concentrations (LC₁₀ or LC₂₅). Twenty-four hours after exposure to treated discs, 20 females showing no visible symptoms of poisoning were transferred to untreated leaf discs. The leaf discs were changed daily for up to five days. The number of eggs laid during this period was recorded. The survival rate, total number of laid eggs per female and egg hatching rate were calculated. All above-mentioned parameters were slightly lower in treated females compared with controls.     

The effect of the granulovirus (PapyGV) on larval mortality and feeding behaviour of the Pandemis leafroller,Pandemis pyrusana (Lepidoptera: Tortricidae)

An indigenous betabaculovirus (PapyGV) of the Pandemis leafroller, Pandemis pyrusana (Kearfott), was studied in the laboratory and greenhouse to determine how the virus affected leafroller mortality and foliar damage. Probability of mortality increased with virus concentration as observed after 7 and 10 days of feeding on virus treated diet in neonates and second instar larvae. LC₅₀ estimates for neonates at 7 and 10 days was 2743 and 389 occlusion bodies (OBs)/mm². For second instars, LC₅₀ was 139,487 and 813 OBs/mm² at 7 and 10 days. There was no biologically significant mortality response to increasing virus concentrations by fourth instar larvae; however, when fourth instar larvae were infected with virus on diet and then fed apple leaves, the leaf area consumed declined up to 50% with higher virus concentrations. In a greenhouse study, neonate larvae that fed on seedlings treated with water showed >90% survival and 80% pupation rate of larvae after being transferred to diet. In contrast, larvae that fed on apple seedlings sprayed with 3×10⁶ OBs/ml showed poor survival when transferred to diet after acquiring the virus and failed to reach the pupal stage. This virus shows promise for population regulation and can produce reduction in feeding damage.     

11种不同类型杀虫剂对卷蛾分索赤眼蜂繁殖的亚致死效应

在实验室条件下通过药膜法研究了11种不同类型的杀虫剂对卷蛾分索赤眼蜂Trichogrammatoidea bactrae Nagaraja成蜂的毒性, 并研究了杀虫剂对其繁殖的亚致死效应, 旨在评估各药剂对卷蛾分索赤眼蜂成蜂的安全性, 为小菜蛾Plutella xylostella防治过程中杀虫剂的合理施用提供科学依据。研究结果表明, 卷蛾分索赤眼蜂成蜂对阿维菌素最敏感, 致死中浓度LC₅₀和亚致死浓度LC₃₀分别为0.1984和0.1660 mg/L, 其次为氟虫腈（0.2027和0.1903 mg/L）、溴虫腈（0.3069和0.2038 mg/L）、多杀霉素（1.3630和1.0481 mg/L）、杀螟丹（8.1042 和6.7891 mg/L）、高效氯氰菊酯（10.3647和5.8035 mg/L）和丁醚脲（11.5318 和9.9212 mg/L）。经亚致死浓度LC₃₀的阿维菌素、溴虫腈、杀螟丹、丁醚脲、多杀霉素和氟虫腈处理后, 卷蛾分索赤眼蜂的寿命（1.00~1.67 d）显著缩短, 寄生卵量（0~21.70粒/雌）明显降低, 种群参数（净生殖力R₀、内禀增长率r_m、周限增长率λ和世代平均历期T）明显低于对照（P<0.05）。田间推荐浓度的茚虫威、氟啶脲、苏云金杆菌Bacillus thuringiensis、虫酰肼对卷蛾分索赤眼蜂寿命及产卵量均没有不利影响, 但能通过缩短其世代平均历期T, 从而使净生殖力R₀、内禀增长率r_m和周限增长率λ增加。而经亚致死浓度LC₃₀的高效氯氰菊酯处理后, 卷蛾分索赤眼蜂的寿命（3.77 d）显著延长, 寄生卵量（55.47粒/雌）明显提高, 种群参数明显高于对照(P<0.05)。结果说明, 氟啶脲、茚虫威、苏云金杆菌和虫酰肼对卷蛾分索赤眼蜂较安全; 丁醚脲对卷蛾分索赤眼蜂成蜂的寄生能力影响极大, 在田间施用时应当尽量避开卷蛾分索赤眼蜂成蜂的盛发期。     

Ethanol extract of Cassia siamea L. increases life span in Drosophila melanogaster

The stem of Cassia siamea L. (Fabaceae) has been used in traditional Thai medicine as a longevity remedy. The objective of this study was to investigate the effect of ethanolic stem extract of C. siamea (CSE) on the life span of Drosophila melanogaster. The results showed that a diet containing 10 mg/mL CSE could significantly extend the mean life span of D. melanogaster by 14% compared with the control diet (P < 0.01). The maximum life span was 74, 78, and 84 days in control, CSE (5 mg/mL) and CSE (10 mg/mL) groups, respectively. Supplementation of CSE at 10 mg/mL also significantly increases the activity of superoxide dismutase (SOD) and catalase (CAT) at days 25 and 40 compared with the control diet. Treatment of CSE at 5 and 10 mg/mL significantly increased the climbing ability of D. melanogaster both on days 25 and 40 compared with the control flies. Paraquat and H₂O₂ challenge test showed that flies fed with CSE at 10 mg/mL had a longer survival time than the control flies (P < 0.01). This study provides supportive evidence that supplementation with CSE prolonged life span and reduced oxidative stress in D. melanogaster.     

Repellent,antifeedant and toxic effects of Ageratum conyzoides (Linnaeus) (Asteraceae) extract against Helicovepra armigera (Hübner) (Lepidoptera: Noctuidae)

Repellent, antifeedant and toxic effect of crude hexane extract of Ageratum conyzoides were investigated against Helicoverpa armigera. In orientation bioassay, the extract exhibited dose-dependent repellency against neonates. Extract significantly increased the mortality and decreased growth of different larval stages when administrated orally in artificial diet. EC₅₀ value was at 0.11% for larval growth inhibition. Toxicity of the extract was manifested by high mortality of first instar larvae after 7 days of feeding on diet containing 0.05–0.4% of extract with LC₅₀ of 0.17%. Under choice bioassay, extract showed strong antifeedant activity against fifth instar larvae with DI₅₀ of 0.21%. In nutritional bioassay, extract significantly reduced RCR, RGR, ECI and ECD of fifth instar larvae with increased AD. When RGR were plotted against RCR, the growth efficiency of larvae fed on treated diet was significantly lower than the control fed larvae suggesting the antifeedant and toxic effect of extract.     

Toxicity of acephate to larvae of gypsy moth as a function of host plant and bioassay method

We examined toxicity of acephate to third-instar gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), under different conditions of administration method, availability of food to larvae during bioassay, host plant, and activity of detoxifying enzymes. Larvae that had been fed field-collected foliage of white alder (Alnus rhombifolia Nutt.) were less susceptible 48 h after treatment with topically applied acephate if they were allowed to continue feeding on foliage during the bioassay period (LD₅₀= 60.6 μg/g larva ) than if they were not (LD₅₀= 13.5 μg/g larva ). All surviving larvae were replaced on their original food plant after the 48-h bioassay; of these, 14.4% of the larvae not fed during treatment died before pupation, compared with 1.3% of the larvae fed alder during treatment. The LD₅₀ obtained for topically treated larvae reared and treated on Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, (51.1 μg/g larva) was comparable to that obtained for larvae fed alder (60.0 μg/g larva) throughout treatment. Larvae treated orally with acephate, however, were slightly more susceptible when reared on Douglas-fir (LC₅₀, 20.3 ppm ) than when reared on alder (LC₅₀, 27.0 ppm ). Post-treatment mortality in orally treated larvae was 10.3% in those fed alder and 9.5% in those fed Douglas-fir. Higher cytochrome P-450 activities in larvae reared on Douglas-fir apparently did not enhance tolerance to acephate. Both sexes of orally treated larvae took significantly longer to pupate than did controls on both foliage types, as did topically treated males fed Douglas-fir. Pupal weight generally was slightly, but not always significantly, higher in treated than untreated larvae under all dietary and treatment regimes.     

Laboratory evaluation of the chemosterilant lufenuron against the fruit flies Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons

Four species of tephritid fruit flies, Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons were evaluated for toxic, developmental, and physiological responses to the chemosterilant lufenuron. No significant mortality of laboratory strains of the first three species was observed after their exposure up to 50 μg/mL of lufenuron in agar adult diet, whereas B. latifrons adults fed with 50 μg/mL of lufenuron in the diet caused significant mortality compared to the control. Fertility of C. capitata adults fed on 50 μg/mL lufenuron-fortified diet between 7 and 12 days of age was approximately 46% of the no lufenuron control. Fertility of B. dorsalis and B. latifrons adults fed on 50 μg/mL lufenuron-incorporated diet was about 45% and 62% of the control, respectively. Lufenuron did not significantly affect fertility of B. cucurbitae adults. Lufenuron did not affect fecundity of C. capitata and B. dorsalis. Fecundity of B. cucurbitae and B. latifrons was not evaluated due to difficulty to count the eggs laid deep in the agar diet. Larvae fed on a liquid larval diet with ≤ 0.1 μg/mL of lufenuron were also evaluated. Pupal recovery, adult emergence, adult fliers, mating, egg hatch, and egg production of C. capitata were significantly decreased, while for B. dorsalis, pupal recovery, larval duration and adult emergence were affected. No effect of lufenuron on B. cucurbitae larvae was observed. B. latifrons was not performed because shortage of eggs at the time of this research. Lufenuron is a potential agent for management and control of C. capitata and B. dorsalis.