Kenneth A. Bloem

Impact of Moth Suppression/Eradication Programmes Using the Sterile Insect Technique or Inherited Sterility

Numerous lepidopteran species have been investigated as candidates for control using the sterile insect technique (SIT) or inherited sterility (IS). However to date only two programmes are operational — the pink bollworm containment programme in the San Joaquin Valley, California, USA, and the codling moth suppression programme in British Columbia, Canada. Both of these programmes have been highly successful in controlling the pest populations, reducing insecticide use, and improving interactions between growers and the general public. However, other benefits, including the positive economic impacts of these programmes, have not been fully quantified. Methods to reduce the cost of lepidopteran programmes might include combining the SIT/IS with other pest control tactics such as mating disruption or the release of natural enemies, the development of genetic sexing strains, or the application of molecular technologies to develop genetic markers and genetic sterility. In future the greatest potential for impact of lepidopteran SIT/IS programmes may be in combating key invasive threats such as the eradication of an outbreak of the painted apple moth in New Zealand.

Inherited sterility in Cactoblastis cactorum (Lepidoptera: Pyralidae)

Newly emerged male and female adult cactus moths, Cactoblastis cactorum (Berg), were treated with increasing doses of gamma radiation, and the moths were outcrossed to fertile counterparts. Fecundity of the moth pairs was not affected by increasing doses of radiation. The minimum dose at which treated females were found to be 100% sterile when mated to untreated males was 200 Gy. Fertility of treated males declined with increasing doses of radiation to approach 0% near 500 Gy. Inherited effects resulting from irradiation of P males and females were expressed in the F1 generation as increased developmental time from oviposition to larval eclosion, increased egg mortality, and increased neonate to adult stage mortality. A shift in the F1 sex ratio in favor of males was not observed.

Applications of F1 sterility for research and management of Cactoblastis cactorum (Lepidoptera: Pyralidae)

The unintentional arrival of the cactus moth, Cactoblastis cactorum (Berg), in Florida has raised concerns for the safety of native and rare Opuntia species in the Florida Keys and the potential spread of C. cactorum to the Opuntia-rich areas of the western United States and Mexico. In addition to threatening the biodiversity of these native ecosystems, such non-target effects would generate negative publicity that could heighten public concern over the use of exotic natural enemies and jeopardize future biological control programs against weeds. In this paper we discuss the use of inherited (F1) sterility in Lepidoptera to study, predict, and manage the expanding populations of C. cactorum. Research areas in which the use of F1 sterility would be most applicable include (1) elucidation of the host range of C. cactorum for key native Opuntia species from across the U.S., (2) prediction of the geographic range of C. cactorum in the U.S. and Mexico, and (3) delineation of the impact of native natural enemies on the spread of C. cactorum. The use of F1 sterility for control of C. cactorum would be most appropriate for (1) eradication of C. cactorum from areas of new introductions, or from isolated and/or environmentally sensitive areas such as the Florida Keys, (2) establishment of a barrier by means of release of irradiated moths along the leading edge of the C. cactorum geographical range, and (3) provisioning sterile C. cactorum in the field as hosts for released natural enemies to increase their initial survival and establishment.

Season-Long Releases of Partially Sterile Males for Control of Codling Moth (Lepidoptera: Tortricidae) in Washington Apples

Abstract Season-long field studies were conducted in Washington apple orchards that compared the following: (1) twice per week releases of partially sterile codling moths, Cydia pomonella (L.), treated with either 100 or 250 Gy, and (2) combinations of mating disruption plus the release of partially sterile (100 Gy) codling moths, to control wild codling moth populations. No significant differences in the level of fruit damage at either midseason or harvest were found between any of the treatments, or between the treatments and the inside controls. Damage in all plots was <0.1%. In both studies, trap data suggest that the movement of the 100 Gy-treated moths into the other treatments and the inside controls may have masked treatment effects. However, fruit damage was significantly lower in all treatment plots when compared with control plots located outside of the treatment areas. Results indicated that the release of partially sterile male (and fully sterile female) codling moths does not result in increased fruit injury and that the lower dose of radiation used to partially sterilize males results in insects that are more active, disperse greater distances and are generally more competitive.

Diel Flight Pattern and Flight Performance of Cactoblastis cactorum (Lepidoptera: Pyralidae) Measured on a Flight Mill: Influence of Age, Gender, Mating Status, and Body Size

Abstract Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) is an invasive herbivore that poses a serious risk to Opuntia cacti in North America. Knowledge of the flight behavior of the cactus moth is crucial for a better understanding of natural dispersal, and for both monitoring and control. We used computer-linked flight mills to investigate diel flight activity and flight performance in relation to gender, age, mating status, and body size. Maximal flight activity for both mated and unmated moths occurred during twilight, whereas flight activity was low during photophase. The total distance flown and the number of initiated flights within a diel cycle were higher in both unmated and mated females than in males, but the longest single flight was similar in both genders. These findings suggest that pheromone trap captures of males likely indicate the simultaneous presence of females and that mated females might even be in areas where males are not detected yet. Flight performance heterogeneity was large, with a small portion of the population (both males and females) performing long unbroken flights, whereas the majority made short flights. Females had higher pupal and adult body size and shorter longevity than males. A few individuals, particularly young mated females, flying long distances may be important for active spread of a population and the colonization of new habitats. Implications of this study in the control of the cactus moth by using the sterile insect technique are discussed.

Improving the cost-effectiveness, trade and safety of biological control for agricultural insect pests using nuclear techniques

Abstract If appropriately applied, biological control offers one of the most promising, environmentally sound, and sustainable control tactics for arthropod pests and weeds for application as part of an integrated pest management (IPM) approach. Public support for biological control as one of the preferred methods of managing non-indigenous and indigenous pests is increasing in many countries. An FAO/IAEA Coordinated Research Project (CRP) addressed constraints related to costly production systems for biological control agents, and the presence of accompanying pest organisms during their shipment. These constraints can be alleviated using nuclear techniques such as ionizing radiation or X-rays to reduce production and handling costs (e.g., by expanding the period of host suitability, increasing shelf life, avoiding unnecessary sorting steps before shipment, etc.), and to eliminate the risk of shipping fertile host or prey pest individuals or other hitchhiking pests. These nuclear techniques can also help to reduce the risks associated with the introduction of exotic biological control agents, which can become pests of non-target organisms if not carefully screened under semi-natural or natural conditions. Radiation is also a very useful tool to study host-parasitoid physiological interactions, such as host immune responses, by suppressing defensive reactions of natural or factitious hosts. Applied at a very low-dose, radiation may be used to stimulate reproduction of some entomophagous insects. Additionally, radiation can be applied to semi- or completely sterilize hosts or prey for deployment in the field to increase the initial survival and build-up of natural or released biological control agents in advance of seasonal pest population build-up. Finally, the work carried out under this CRP has demonstrated the feasibility of integrating augmentative and sterile insect releases in area-wide IPM programmes, and to utilise by-products from insect mass-rearing facilities in augmentative biological control programmes. This special issue provides an overview of the research results of the CRP.

CACTOBLASTIS CACTORUM (Lepidoptera: pyralidae): Observations of Courtship and Mating Behaviors at Two Locations on the Gulf Coast of Florida

Abstract Cactoblastis cactorum (Berg) has become an invasive pest of Opuntia spp. along the coastal areas of southeastern United States from the panhandle of Florida to South Carolina. Spread of this insect into cactus dominated natural areas of the United States and Mexico and into agricultural opuntia fields of Mexico is raising concerns within international governments and conservation organizations. Interest is growing in using the Sterile Insect Technique (SIT) to manage C. cactorum populations. Information on courtship and mating behaviors of this insect is important in the development and application of SIT. We conducted mating table studies and determined that this moth exhibits simple rather than elaborate mating behaviors and that courtship and mating take place briefly during morning twilight. Typically, females initiate calling, males respond to females, and copulation are complete before sunrise. Successfully mated females attract males within a short period (mean of 5.2 min), while unsuccessful females continue calling for about 40 minutes. Mating pairs remain in copula for a mean of 31.8 min. Generally, mated females are busy ovipositing the first few nights after mating, not exhibiting additional mating behaviors. A release of marked males revealed that males stay near the release site and can be recovered and identified for subsequent population estimate studies. This study on courtship/mating behavior is helpful to the ongoing C. cactorum research to develop a successful SIT program, identify the female calling pheromone, improve monitoring traps, and develop a technique to estimate adult moth population abundance.

DEVELOPMENT OF THE MOST EFFECTIVE TRAP TO MONITOR THE PRESENCE OF THE CACTUS MOTH CACTOBLASTIS CACTORUM (LEPIDOPTERA: PYRALIDAE)

Abstract Various trap specifications were evaluated to identify the most effective trap for capturing wild male Cactoblastis cactorum (Berg). All traps were baited with virgin female C. cactorum and, except for the first comparison of trap type, a standard wing trap was used in all experiments. Although wing traps captured more males than did the other trap types (delta or bucket), the differences were not significant. However, significantly higher numbers of males were captured in wing traps placed 2 m above ground than traps at 1 m or 0.5 m, and wing traps baited with four virgin females caught significantly more males than wing traps baited with a single female. Differences in number of males captured by young and old females were not significant, but more than twice as many males were captured in traps baited with one-day-old females than traps baited with four day old females. In addition, there were no significant differences in number of males caught in unpainted, white, wing traps and wing traps painted one of eight different colors (flat white, black, dark green, fluorescent green, yellow, fluorescent yellow, orange, or blue), although, more males were captured in the unpainted wing traps. The results presented here suggest that the best trap currently available to monitor C. cactorum is a standard (unpainted) wing trap, placed at a height of 2.0 m aboveground, and baited with four newly emerged females.

DEVELOPMENT OF TRAPPING METHODS WITH A SYNTHETIC SEX PHEROMONE OF THE PINK HIBISCUS MEALYBUG, MACONELLICOCCUS HIRSUTUS (HEMIPTERA: PSEUDOCOCCIDAE)

Abstract The pink hibiscus mealybug, Maconellicoccus hirsutus (Green), threatens numerous crops of economic importance and could spread from populations in California and Florida to 33 other states. Field experiments conducted in Florida evaluated 3 commercially available trap designs baited with synthetic female sex pheromone for efficiency in trapping adult male M. hirsutus as well as ease in processing. Delta traps and double-sided sticky cards captured more males than Jackson traps. The Delta and Jackson traps were more effective at minimizing the capture of non-target insects. The effect of lure age on males captured was also evaluated by pre-aging lures outdoors for 0 to 8 months before testing. Fewer males were caught in Delta traps as the age of the lure increased, with significantly fewer caught in traps that had been pre-aged for 2 months. Monitoring of male flight activity throughout diel cycle with baited Delta traps indicated that males were most active around dusk. The field experiments also showed that the pheromone traps often capture males in areas where no visual indication of an infestation is evident. The pheromone trap may serve as a valuable tool to detect new infestations of pink hibiscus mealybug.

LABORATORY EVALUATION OF INSECTICIDES FOR CONTROL OF THE INVASIVE CACTOBLASTIS CACTORUM (LEPIDOPTERA: PYRALIDAE)

Abstract We conducted laboratory assays of nine products registered for use on ornamental plants in Florida for their ovicidal and larvicidal activity against the invasive cactus moth Cactoblastis cactorum. One-hundred percent mortality (or 0% survival) of 1-day-old eggs was obtained when eggstick sections were treated with cypermethrin, spinosad, or imidacloprid. These products were equally as effective when assayed against eggs that were fully embryonated (28 days old), when cladodes of Opuntia stricta were exposed to neonates 24 hours after dipping, or to cladodes that were dipped and stored for 30 days before exposure. When Bacillus thuringiensis (Dipel®) was used to prevent neonate penetration into treated cladodes of O. stricta, 100% mortality (or 0% survival) was recorded in the laboratory.