Effect of ultraviolet on the environmental adaptability of Megalurothrips usitatus (Thysanoptera: Thripidae).

Megalurothrips usitatus Bagnall, an important pest of bean plants, is primarily managed with synthetic insecticides. M. usitatus has developed considerable resistance to various insecticides in multiple cowpea-growing areas in Hainan Province, China, posing challenges to its control in the field. Light control technology is a potentially effective physical control method for M. usitatus. The vision of thrips is highly sensitive to UV light, whereas other biological characteristics remain unknown. Therefore, this study evaluated the effects of ultraviolet light on the biological characteristics of M. usitatus. Results showed that the egg, larval, and pupal stages of M. usitatus were significantly shortened, and the emergence rate (79.59%) and adult survival rate (77.95%) were reduced under a devoid of UV light environment (UV-), compared with the full-spectrum light (control treatment group, CK) (p < 0.05). However, the single spawning quantity and total amount of spawning were significantly higher, and the sex ratio (57%) was the highest under UV- (p < 0.05). Single UV light (UV+) only affected the pupation rate. Also, the antioxidant enzymes, polyphenol oxidase, superoxide dismutase (SOD), and peroxidase activities were significantly and negatively correlated with the progression of generations under UV-, whereas catalase and SOD activities were significantly and positively correlated with the progression of generations under UV+. The UV- light conditions significantly interfered with the behavior selection of M. usitatus. The results of this study showed that the adaptability of M. usitatus populations would be greatly reduced in the absence of ultraviolet light, providing a theoretical basis for the control of M. usitatus populations.

60Co-γ Radiation Alters Developmental Stages of Zeugodacus cucurbitae (Diptera: Tephritidae) Through Apoptosis Pathways Gene Expression.

Radiation is considered as a promising insect pest control strategy for minimizing postharvest yield losses. Among various techniques, irradiation is a method of choice as it induces lethal biochemical or molecular changes that cause a downstream cascade of abrupt physiological abnormalities at the cellular level. In this study, we evaluated the effect of 60Co-γ radiation on various developmental stages of Zeugodacus cucurbitae Coquillett and subsequent carry-over effects on the progeny. For this purpose, we treated eggs with 30- and 50-Gy radiation doses of 60Co-γ. We found that radiation significantly affected cellular antioxidants, insect morphology, and gene expression profiles. Our results indicate that in response to various doses of irradiation reactive oxygen species, catalase, peroxidase, and superoxide dismutase activities were increased along with a significant increase in the malondialdehyde (MDA) content. We observed higher mortality rates during the pupal stage of the insects that hatched from irradiated eggs (50 Gy). Furthermore, the life span of the adults was reduced in response to 50 Gy radiation. The negative effects carried over to the next generation were marked by significantly lower fecundity in the F1 generation of the irradiation groups as compared to control. The radiation induced morphological abnormalities at the pupal, as well as the adult, stages. Furthermore, variations in the gene expression following irradiation are discussed. Taken together, our results signify the utility of 60Co-γ radiation for fruit fly postharvest management.

Influence of green light illumination at night on biological characteristics of the oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae).

The oriental armyworm, Mythimna separata is an important crop pest in eastern Asia. Nocturnal insects, including nocturnal moths, have phototactic behavior to an artificial light source. Phototactic behavior in insects is species-specific in response to different wavelengths of light sources. Our previous study showed that green (520 nm) light emitting diode (LED) light resulted in a significantly higher phototactic behavior in M. separata moths compared to the other wavelength LED lights. The goal of the present study is to investigate the influence of green light illumination on biological characteristics of different developmental stages in M. separata. Our results revealed that when different developmental stages of M. separata were exposed to the green light illumination in a dark period, several biological characteristics in all developmental stages except for egg stage were positively changed, but those of F1 generation M. separata which are next generation of the adults exposed to the green light did not significantly change compared with the control level. These findings suggest that green light illumination at night (or dark period) has a positive effect on the development and longevity of M. separata.

Assessment irradiation effects on different development stages of Callosobruchus maculatus and on chemical, physical and microbiological quality of cowpea seeds.

Irradiation is a physical, environmentally friendly treatment which does not leave any residues in the product. It is increasingly used as an alternative to methyl bromide and other chemical fumigants for disinfestation of insect pest in stored grains. In this research, we try to evaluate the effect of low gamma irradiation doses in the range of 50-1200 Gy on the different stages of Callosobruchus maculatus. It was found that no adults emerged after irradiation of eggs at 450 Gy. No emerging adults (F1 generation) have been shown when larvae or pupae were exposed to 650 Gy. Also, no emerging adult has been shown from the parental C. maculatus adults irradiated with 650 Gy. When suppression of F1 generation was used for the measuring effective irradiation dose and phytosanitary efficacy, 650 Gy was required for disinfestation of cowpea seed weevils. The irradiation dose level of 650 Gy was used for the large-scale confirmatory tests applied to 27,754 adults of C. maculatus in cowpea seeds resulting in non F1 adults' production with a confidence level of 93.77%. All the physical and chemical characteristics of cowpea seeds were non-significantly (P ≤ 0.05) affected by the irradiation dose of 650 Gy. Meanwhile, this irradiation dose very slightly reduced the microbial load of cowpea seeds. We recommend the generic dose 650 Gy as the phytosanitary irradiation dose for the cowpea seed weevil.

LARVAL X-RAY IRRADIATION INFLUENCES PROTEIN EXPRESSION IN PUPAE OF THE ORIENTAL FRUIT FLY, BACTROCERA DORSALIS.

The sterile insect technique (SIT) was developed to eradicate the new world screwworm from the southern United States and Mexico, and became a component of many area-wide integrated pest management programs, particularly useful in managing tephritid fruit flies. SIT is based on the idea of rearing and sterilizing male pests, originally by ionizing radiation, and then releasing into field, where they compete for and mate with wild females. Mating with sterile males leads to reduced fecundity to lower pest populations. There are concerns with the use and distribution of radioisotopes for SIT programs, which have led to developing X-ray irradiation protocols to sterilize insects. We considered the possibility that X-ray irradiation exerts sublethal impacts aside form sterilizing insects. Such effects may not be directly observable, which led us to the hypothesis that X-ray irradiation in one life stage creates alterations in biological fitness and protein expression in the subsequent stage. We tested our hypothesis by irradiating larvae of Bactrocera dorsalis. There are two major points. One, exposing larvae to X-ray treatments led to reduced adult emergence, fecundity, fertility, and flight capacity from the corresponding pupae and emerged adults. Two, the X-ray treatments led to substantial expression changes in 27 pupal proteins. We assorted the 67 spots representing these proteins into three groups, metabolism, development, and structure. Our interpretation is these X-ray induced changes in biological performance and protein expression indicate their adult counterparts may be disabled in their abilities to successfully compete for and mate wild females in native habitats.

Sterilization of Hulecoeteomyia japonica japonica (= Aedes japonicus japonicus) (Theobald, 1901) by high-energy photon irradiation: implications for a sterile insect technique approach in Europe.

Hulecoeteomyia japonica japonica (= Aedes japonicus japonicus) (Diptera: Culicidae) (Theobald 1901), a container-breeding invasive species in North America and Europe, is attracting particular attention for its high local abundances and possible roles in the transmission of human and animal pathogens. The preferential habitats of this species are forested and bushy areas, which renders control measures extremely inefficient. Use of the sterile insect technique (SIT) may contribute to the implementation of area-wide integrated pest management strategies, as has been successfully proven with other aedine mosquito species. The present study investigates the effects of irradiation at a dose of 40 Gy on fitness parameters in H. j. japonica. Irradiation was performed on 16-24-h-old pupae from a colonized strain (PA) using a TrueBeam linear accelerator. Males from the PA strain were crossed with females of the same colony or with field-collected females. Irradiation induced a slight increase in mortality in male pupae, but did not alter the survival and mating abilities of emerging adult males. Rates of blood feeding and fertility were lower when PA strain males were kept with field-collected females rather than PA females. Irradiated males induced reductions in fertility (residual fertility: 2.6%) and fecundity in mated females. The data indicate that the SIT is a suitable technique to enhance the control of this species.

Laboratory longevity and competitiveness of Dacus ciliatus Loew (Diptera: Tephritidae) following sub-sterilizing gamma irradiation.

The effect of a sub-sterilizing gamma radiation dose on Dacus ciliatus adults was investigated to assess the suitability of the sterile insect technique (SIT) as an alternative method to control this pest. Late pupae (48 h prior to adult emergence) from a laboratory strain were irradiated with 120 Gy of gamma rays emitted by a 60Co source. Following adult emergence, the mortality of irradiated and non-irradiated cohorts was recorded. Over a period of 50 days after emergence, no significant negative effects of irradiation upon the longevity of male or female laboratory flies were observed. A laboratory competitiveness study (Fried test), using irradiated laboratory and wild males at a ratio of 3:1 was conducted to assess the ability of irradiated males to reduce the egg hatch rates of a wild population. The overall competitiveness was found to be ca. 0.32, suggesting a reduced, but satisfactory, quality of irradiated laboratory as compared with wild males. Based on the above findings, we calculated and proposed effective male release ratios for field application of SIT against D. ciliatus.

Gamma Irradiation as a Phytosanitary Treatment of Bactrocera tau (Diptera: Tephritidae) in Pumpkin Fruits.

The fruit fly Bactrocera tau (Walker) is an important quarantine pest that damages fruits and vegetables throughout Asian regions. Host commodities shipped from infested areas should undergo phytosanitary measures to reduce the risk of shipping viable flies. The dose-response tests with 1-d-old eggs and 3-, 5-, 7-, 8-d-old larvae were initiated to determine the most resistant stages in fruits, and the minimum dose for 99.9968% prevention of adult eclosion at 95% confidence level was validated in the confirmatory tests. The results showed that 1) the pupariation rate was not affected by gamma radiation except for eggs and first instars, while the percent of eclosion was reduced significantly in all instars at all radiation dose; 2) the tolerance to radiation increased with increasing age and developmental stage; 3) the estimated dose to 99.9968% preventing adult eclosion from late third instars was 70.9 Gy (95% CL: 65.6-78.2, probit model) and 71.8 Gy (95% CL: 63.0-87.3, logit model); and iv) in total, 107,135 late third instars cage infested in pumpkin fruits were irradiated at the target dose of 70 Gy (62.5-85.0, Gy measured), which resulted in no adult emergence in the two confirmatory tests. Therefore, a minimum dose of 85 and 72 Gy, which could prevent adult emergence at the efficacy of 99.9972 and 99.9938% at the 95% confidence level, respectively, can be recommended as a minimum dose for phytosanitary treatment of B. tau in any host fruits and vegetables under ambient atmospheres.

Postharvest irradiation treatment for quarantine control of Drosophila suzukii (Diptera: Drosophilidae) in fresh commodities.

Irradiation is a postharvest quarantine treatment option for exported commodities such as stone fruits and small fruits to prevent movement of the new invasive pest spotted wing drosophila, Drosophila suzukii (Walker) (Diptera: Drosophilidae). The effects of irradiation on larval and pupal development and adult reproduction in D. suzukii were examined. Larvae (first, second, and third instars) and pupae (1-2-d-old, 3-5-d-old, and 7-8-d-old) on diet were irradiated at target doses of 20, 30, 40, and 50 Gy in replicated factorial experiments and survival to the adult stage was recorded. Tolerance to radiation increased with increasing age and developmental stage. Males and females were equally susceptible. A radiation dose of 40 Gy applied to first- and second-instar larvae prevented adult emergence. The late-stage pupa was the most radiation-tolerant stage that occurs in fruit, and individuals irradiated at this stage readily emerged as adults; therefore, prevention of F1 adults was the desired treatment response for large-scale validation tests with naturally infested fruit. In large-scale tests, a radiation dose of 80 Gy applied to late-stage pupae in sweet cherries or grapes resulted in no production of F1 adults in > 33,000 treated individuals, which meets the zero tolerance requirement for market access. A minimum absorbed dose of 80 Gy is recommended for quarantine control of D. suzukii.

Evaluating irradiation dose for sterility induction and quality control of mass-produced fruit fly Bactrocera tryoni (Diptera: Tephritidae).

The sterile insect technique has been routinely used to eradicate fruit fly Bactrocera tryoni (Froggatt) incursions. This study considers whether fly quality in a mass-rearing facility can be improved by reducing irradiation doses, without sacrificing reproductive sterility. Pupae were exposed to one of five target irradiation dose ranges: 0, 40-45, 50-55, 60-65, and 70-75 Gy. Pupae were then assessed using routine quality control measures: flight ability, sex ratio, longevity under nutritional stress, emergence, and reproductive sterility. Irradiation did not have a significant effect on flight ability or sex ratio tests. Longevity under nutritional stress was significantly increased at 70-75 Gy, but no other doses differed from 0 Gy. Emergence was slightly reduced in the 50-55, 60-65, and 70-75 Gy treatments, but 40-45 Gy treatments did not differ from 0 Gy, though confounding temporal factors complicate interpretation. Reproductive sterility remained acceptable (> 99.5%) for all doses--40-45 Gy (99.78%), 50-55 Gy (100%), 60-65 Gy (100%), and 70-75 Gy (99.99%). We recommend that B. tryoni used in sterile insect technique releases be irradiated at a target dose of 50-55 Gy, providing improved quality and undiminished sterility in comparison with the current 70-75 Gy standard while also providing a substantial buffer against risk of under dosing.

Drosophila oogenesis as a bio-marker responding to EMF sources.

The model biological organisms Drosophila melanogaster and Drosophila virilis have been utilized to assess effects on apoptotic cell death of follicles during oogenesis and reproductive capacity (fecundity) decline. A total of 280 different experiments were performed using newly emerged flies exposed for short time daily for 3-7 d to various EMF sources including: GSM 900/1800 MHz mobile phone, 1880-1900 MHz DECT wireless base, DECT wireless handset, mobile phone-DECT handset combination, 2.44 GHz wireless network (Wi-Fi), 2.44 GHz blue tooth, 92.8 MHz FM generator, 27.15 MHz baby monitor, 900 MHz CW RF generator and microwave oven's 2.44 GHz RF and magnetic field components. Mobile phone was used as a reference exposure system for evaluating factors considered very important in dosimetry extending our published work with D. melanogaster to the insect D. virilis. Distance from the emitting source, the exposure duration and the repeatability were examined. All EMF sources used created statistically significant effects regarding fecundity and cell death-apoptosis induction, even at very low intensity levels (0.3 V/m blue tooth radiation), well below ICNIRP's guidelines, suggesting that Drosophila oogenesis system is suitable to be used as a biomarker for exploring potential EMF bioactivity. Also, there is no linear cumulative effect when increasing the duration of exposure or using one EMF source after the other (i.e. mobile phone and DECT handset) at the specific conditions used. The role of the average versus the peak E-field values as measured by spectrum analyzers on the final effects is discussed.

Upscaling irradiation protocols of Aedes albopictus pupae within an SIT program in Reunion Island.

The implementation of the sterile insect technique against Aedes albopictus relies on many parameters, in particular on the success of the sterilization of males to be released into the target area in overflooding numbers to mate with wild females. Achieving consistent sterility levels requires efficient and standardized irradiation protocols. Here, we assessed the effects of exposure environment, density of pupae, irradiation dose, quantity of water and location in the canister on the induced sterility of male pupae. We found that the irradiation of 2000 pupae in 130 ml of water and with a dose of 40 Gy was the best combination of factors to reliably sterilize male pupae with the specific irradiator used in our control program, allowing the sterilization of 14000 pupae per exposure cycle. The location in the canister had no effect on induced sterility. The results reported here allowed the standardization and optimization of irradiation protocols for a Sterile Insect Technique program to control Ae. albopictus on Reunion Island, which required the production of more than 300,000 sterile males per week.

Random mutations induced by a sub-sterilizing dose of gamma ray on Aedes albopictus male pupae and transmission to progeny.

The application of the Sterile Insect Technique (SIT) to mosquito control is based on the systematic release of large numbers of adult males that have been previously sterilized by irradiation. Ionizing radiation doses inducing full sterility also cause somatic damages that reduce the capacity of the treated males to compete with wild males. The optimal dose inducing high levels of male sterility and minimal impact on competitiveness can be assessed by establishing a dose-response curve. Sub-sterile males are, to a variable degree, still fertile and might be able to transmit to the progeny and following generation(s) sub-lethal random mutations resulting from irradiation. To investigate this, we treated Ae. albopictus male pupae with a sub-sterilizing (2-4 % of egg hatching) dose of gamma rays and explored expressed mutated genes in treated males and their progeny using RNA-seq. Single nucleotide polymorphisms (SNPs) were called using two independent pipelines. Only SNPs common to both pipelines (less than 5 % of the total SNPs predicted) were considered reliable and were annotated to genes. Over 600 genes with mutations likely induced by irradiation were found in the treated Ae. albopictus males. A part of the genes found mutated in irradiated males were also found in (and therefore probably passed on to) males of the F1 and F2 progeny, indicating that genetic variations induced by irradiation may be transmitted along generations. The mutated genes in irradiated males did not seem to significantly affect biological processes, except in one case (i.e., oxidative phosphorylation). Only in four cases (i.e., oxidative phosphorylation, UDP-glucose metabolic process, proton transmembrane transport and riboflavin metabolism) we found biological processes to be significantly affected by mutated genes that were likely transmitted to the male progeny. Our results suggest that random mutations induced by a sub-sterilizing dose of gamma ray in Ae. albopictus male pupae and transmitted to the male progeny of the irradiated mosquitoes do not affect biological processes potentially harmful, from a public-health point of view.

Gamma-Irradiated Female Aedes aegypti Mosquitoes Exhibit Greater Susceptibility to Mayaro Virus.

Mayaro virus (MAYV) is an alphavirus endemic in many parts of Central and South America transmitted to humans by Aedes aegypti. Currently, there is no vaccine or treatment of Mayaro infection, and therefore it is essential to control transmission by reducing populations of Ae. aegypti. Unfortunately, Ae. aegypti are extremely difficult to control with traditional integrated vector management (IVM) because of factors such as growing resistance to a dwindling list of registered insecticides and cryptic immature and adult habitats. The sterile insect technique (SIT) by irradiation is gaining traction as a novel supplemental tool to IVM. The SIT is being used operationally to release large numbers of sterilized colony-reared male mosquitoes in an intervention area to overwhelm females in the natural population, eventually causing population decline because of high frequencies of unfertilized eggs. However, little is known about the effect of irradiation on vector competence for mosquito-borne viruses such as MAYV in females that may be accidentally reared, irradiated, and released alongside males. In this investigation, we exposed female Ae. aegypti pupae to radiation and evaluated vector competence after inoculation with MAYV. Infection and dissemination rates of irradiated (10 and 40 Gy) Ae. aegypti were higher than those of non-irradiated cohorts at 7 and 14 days after infection. Although these results indicate a need to maintain effective sex sorting prior to irradiation and release of Ae. aegypti, our results are consistent with several previous observations that vectorial capacity and vector competence are likely lower in irradiated than in nonirradiated females.

Maintenance of imaginal disc plasticity and regenerative potential in Drosophila by p53.

Following irradiation (IR), the DNA damage response (DDR) activates p53, which triggers death of cells in which repair cannot be completed. Lost tissue is then replaced and re-patterned through regeneration. We have examined the role of p53 in co-regulation of the DDR and tissue regeneration following IR damage in Drosophila. We find that after IR, p53 is required for imaginal disc cells to repair DNA, and in its absence the damage marker, γ-H2AX is persistently expressed. p53 is also required for the compensatory proliferation and re-patterning of the damaged discs, and our results indicate that cell death is not required to trigger these processes. We identify an IR-induced delay in developmental patterning in wing discs that accompanies an animal-wide delay of the juvenile-adult transition, and demonstrate that both of these delays require p53. In p53 mutants, the lack of developmental delays and of damage resolution leads to anueploidy and tissue defects, and ultimately to morphological abnormalities and adult inviability. We propose that p53 maintains plasticity of imaginal discs by co-regulating the maintenance of genome integrity and disc regeneration, and coordinating these processes with the physiology of the animal. These findings place p53 in a role as master coordinator of DNA and tissue repair following IR.

Exposure of insect cells to ionising radiation in vivo induces persistent phosphorylation of a H2AX homologue (H2AvB).

The response of eukaryotic cells to ionising radiation (IR)-induced double-strand DNA breaks is highly conserved and involves a DNA repair mechanism characterised by the early phosphorylation of histone protein H2AX (producing the active form γH2AX). Although the expression of an induced γH2AX variant has been detected in Drosophila melanogaster, the expression and radiation response of a γH2AX homologue has not been reported in economically important fruit flies. We use Bactrocera tryoni (Diptera: Tephritidae, Queensland fruit fly or 'Q-fly') to investigate this response with a view to developing molecular assays to detect/quantify exposure of fruit flies to IR and consequent DNA damage. Deep sequencing confirmed the presence of a H2AX homologue that we have termed H2AvB (i.e. variant Bactrocera) and has an identical sequence to a histone reported from the human disease vector Glossina morsitans. A linear dose-response of γH2AvB (0-400 Gy IR) was observed in whole Q-fly pupal lysates 24h post-IR and was detected at doses as low as 20 Gy. γH2AvB signal peaked at ~20min after IR exposure and at 24h post-IR the signal remained elevated but declined significantly by 5 days. Persistent and dose-dependent γH2AvB signal could be detected and quantified either by western blot or by laser scanning cytometry up to 17 days post-IR exposure in histone extracts or isolated nuclei from adult Q-flies (irradiated as pupae). We conclude that IR exposure in Q-fly leads to persistent γH2AvB signals (over a period of days) that can easily be detected by western blot or quantitative immunofluorescence techniques. These approaches have potential as the basis for assays for detection and quantification of prior IR exposure in pest fruit flies.

Mating competitiveness of Aedes albopictus radio-sterilized males in large enclosures exposed to natural conditions.

Mating competitiveness trials have been conducted in large net-screened enclosures (8 by 5 by 2.8 m) built in a natural shaded environment, in the summers of 2006, 2007, 2008, and 2009 in northern Italy. Aedes albopictus (Skuse) males were radio-sterilized by applying gamma radiations at doses in the range 30-60 Gy. Gamma radiation was administered to aged pupae at the rate of 2.3 Gy/min. Reared radiated males (originally collected in Rimini, Forli, Bologna, Matera, Pinerolo) and hybrid radiated males were tested against wild fertile males (originated from eggs collected in Rimini and Cesena) and reared fertile males, in multiple comparisons for mating competitiveness with reared or wild females. The ratio was kept constant at 100-100_100 (fertile males-radiated males_virgin females). Mating competitiveness was estimated through the calculation of the hatching rate of the eggs laid in oviposition traps positioned inside enclosures. No clear effect of the strains tested (reared, wild, or hybrid) was found. Results demonstrated that reducing the radiation dose from 60 to 30 Gy increases males' competitiveness. Laboratory investigations conducted after controversial results in the 2006 preliminary trials, showed that radiation induces precociousness in adult male emergence.

Pilot field trials with Aedes albopictus irradiated sterile males in Italian urban areas.

The pilot field studies here presented are part of a long-term research program aimed to develop a cost-effective sterile insect technique (SIT) methodology to suppress Aedes albopictus (Skuse) populations. Aedes albopictus is a mosquito species mainly developing in man-made containers and with an island-like urban and suburban distribution. These two features make the application of the sterile insect technique a possible control strategy. Five trials have been performed in three small towns from 2005 to 2009 (Emilia-Romagna region, northern Italy). Reared male pupae, sexed by a sieving technique allowing the recovery of approximately 26-29% of males, were exposed to gamma rays and immediately released in the field. Adult population density was estimated based on a weekly monitoring of egg density in the ovitraps, whereas induced sterility was estimated by measuring the hatching percentage of weekly collected eggs in SIT and control areas. Results showed that sterile males released at the rate of 896-1,590 males/ha/wk induced a significant sterility level in the local population. In addition, when the sterility level achieved values in the range of 70-80%, a similar reduction also was found for the egg density in the ovitraps. We could estimate that the minimum egg sterility value of 81% should be maintained to obtain suppression of the local population. Immigration of mated females was not a main issue in the small villages where trials have been run.

Remating behavior in Anastrepha fraterculus (Diptera: Tephritidae) females is affected by male juvenile hormone analog treatment but not by male sterilization.

The sterile insect technique (SIT) has been proposed as an area-wide method to control the South American fruit fly, Anastrepha fraterculus (Wiedemann). This technique requires sterilization, a procedure that affects, along with other factors, the ability of males to modulate female sexual receptivity after copulation. Numerous pre-release treatments have been proposed to counteract the detrimental effects of irradiation, rearing and handling and increase SIT effectiveness. These include treating newly emerged males with a juvenile hormone mimic (methoprene) or supplying protein to the male's diet to accelerate sexual maturation prior to release. Here, we examine how male irradiation, methoprene treatment and protein intake affect remating behavior and the amount of sperm stored in inseminated females. In field cage experiments, we found that irradiated laboratory males were equally able to modulate female remating behavior as fertile wild males. However, females mated with 6-day-old, methoprene-treated males remated more and sooner than females mated with naturally matured males, either sterile or wild. Protein intake by males was not sufficient to overcome reduced ability of methoprene-treated males to induce refractory periods in females as lengthy as those induced by wild and naturally matured males. The amount of sperm stored by females was not affected by male irradiation, methoprene treatment or protein intake. This finding revealed that factors in addition to sperm volume intervene in regulating female receptivity after copulation. Implications for SIT are discussed.

The case for a generic phytosanitary irradiation dose of 400 Gy for Lepidoptera that infest shipped commodities as pupae.

The pros and cons of a generic phytosanitary irradiation dose against all Lepidoptera pupae on all commodities are discussed. The measure of efficacy is to prevent the F1 generation from hatching (F1 egg hatch) when late pupae are irradiated. More data exist for this measure than for others studied, and it is also commercially tenable (i.e., prevention of adult emergence would require a high dose not tolerated by fresh commodities). The dose required to prevent F1 egg hatch provides a liberal margin of security for various reasons. A point at issue is that correctly irradiated adults could be capable of flight and thus be found in survey traps in importing countries resulting in costly and unnecessary regulatory action. However, this possibility would be rare and should not be a barrier to the adoption of this generic treatment. The literature was thoroughly examined and only studies that could reasonably satisfy criteria of acceptable irradiation and evaluation methodology, proper age of pupae, and adequate presentation of raw data were accepted. Based on studies with 34 species in nine families, we suggest an efficacious dose of 400 Gy. However, large-scale confirmatory testing (> or = 30,000 individuals) has only been reported for one species. A dose as low as 350 Gy might suffice if results of more large-scale studies were available or the measure of efficacy were extended beyond prevention of F1 egg hatch, but data to defend measures of efficacy beyond F1 egg hatch are scarce and more would need to be generated.