Assessment of Simultaneous Application of SIT and MAT to Enhance Bactrocera Fruit Fly Management
Closed for Proposals
Project Type
Coordinated Research ProjectProject Code
D41027
CRP
2190
Approved Date
2018.06.21Project Status
ClosedStart Date
2018.12.03Expected End Date
2024.12.31Completed Date
2024.12.31Participating Countries
Australia, Bangladesh, Brazil, China, Czech Republic, France, Israel, India, Kenya, Mauritius, Malaysia, New Zealand, Pakistan, Thailand, United States of America, Viet Nam, South AfricaDescription
The Sterile Insect Technique (SIT), which is likewise an environment friendly technique involves the mass-rearing of male insects, sterilizing them by ionizing radiation and releasing them in the target area in numbers large enough to outcompete their wild counterparts. Sterile male insects mating with wild female insects will have result in no off-spring and the release of sterile males in adequate sterile to wild male over-flooding ratios suppresses the wild population in the targeted area. In certain cases, this population suppression can lead to eventual eradication of the target population. Furthermore, as the SIT acts in an inverse density dependent manner, it becomes therefore more effective when the wild population is reduced. The male annihilation technique (MAT) has been used to suppress Bactrocera pest species as part of an integrated pest management approaches, and even successfully applied to eradicate populations in some isolated situations such as of islands or outbreaks.? Integration of the male annihilation technique (MAT) with the SIT has so far been sequential, rather than simultaneous, with the SIT applied after a significant reduction of the wild population with the MAT; the reason being to avoid the mass-trapping of the released sterile males in the lured traps with the semichemical Methyl Eugeno; which would significantly reduce the efficacy of the SITThe development of cost-effective semiochemical treatments and delivering systems that improve sterile male sexual performance and reduce their response to male annihilation technique (MAT) formulations is highly desirable so that MAT and Sterile Insect Technique could be integrated. Even though the incorporation of semiochemical supplements for Bactrocera species appears feasible, practical and standard procedures to implement them at an operational scale still need to be developed and validated. Thus, exploring the potential of such an approach is essential in view that the simultaneous MAT and SIT application has considerable potential to drastically increase sterile to wild male overflooding ratios and therefore SIT cost-effectiveness. The combination of male replacement plus male enhanced performance increases what can be achieved with the same number of sterile flies: treating a wider area or enabling more rapid suppression or eradication. Furthermore, due to the increased cost-effectiveness, decisions to invest in SIT may be facilitated in situations where this would not otherwise be feasible. The CRP objective is to explore the potentially synergistic relationship between MAT and SIT when applied simultaneously to dramatically improve the efficacy of Bactrocera fruit fly management. The assessment of semiochemicals to enhance Bactrocera spp. SIT application against these pest fruit flies will include:Assessment of the effect of exposure of major Bactrocera pest species to semiochemicals on earlier sexual maturation and improved male sexual performance, as well as reduced response of exposed sterile males to MAT traps. Evaluation of key parameters in large field cages such as wild fly sex ratio, degree of lure response of sterile flies, sterile:wild over-flooding ratio and bisexual release to determine their influence on the effectiveness of simultaneous MAT and SIT.Field evaluation of simultaneous MAT and SIT within a pilot or operational setting that includes compatible management practices.
Objectives
The objective of the project is to is to explore the potentially synergistic relationship between male annihilation technique (MAT) and sterile insect technique (SIT) when applied simultaneously to dramatically improve the efficacy of Bactrocera fruit fly management.
Specific Objectives
Assess the effect of exposure of major Bactrocera pest species to semiochemicals on earlier sexual maturation and improved male sexual performance, as well as reduced response of exposed sterile males to MAT traps.
Evaluate key parameters in large field cages such as wild fly sex ratio, degree of lure response of sterile flies, sterile:wild over-flooding ratio and bisexual release to determine their influence on the effectiveness of simultaneous MAT and SIT.
Evaluate in the field the simultaneous MAT and SIT within a pilot or operational setting that includes compatible management practices.
Assess the effect of exposure of major Bactrocera pest species to semiochemicals on earlier sexual maturation and improved male sexual performance, as well as reduced response of exposed sterile males to MAT traps.
Evaluate key parameters in large field cages such as wild fly sex ratio, degree of lure response of sterile flies, sterile:wild over-flooding ratio and bisexual release to determine their influence on the effectiveness of simultaneous MAT and SIT.
Evaluate in the field the simultaneous MAT and SIT within a pilot or operational setting that includes compatible management practices.
Impact
Due to their attractiveness to males of some Bactrocera and Zeugodacus species, ME and CL are highly effective lures in traps that are also used for “male annihilation technique” (MAT). The MAT is a behavioural control tactic that involves the attraction and killing of target insects. Such is the attractiveness of ME and CL for males of some species, MAT is highly effective for their suppression and even eradication in some circumstances. For this reason, MAT can be used prior to sterile insect technique (SIT) programmes to reduce the abundance of wild males (Vargas et al., 2014). Sterile males are then released to replace the wild males in the population, which ensures a high ratio of sterile to wild males in the treatment area and improved population suppression due to limited competition. This sequential application of MAT followed by SIT was believed to be necessary because if MAT and SIT were to be used simultaneously, released sterile males could be attracted to MAT baits to the same extent as wild males.
However, it has been proposed that MAT and SIT may be applied at the same time. This simultaneous application may be possible due to the effects of semiochemical exposure on subsequent attractiveness of male dacines to the same or other phenylpropanoids/ phenylbutanoids. Evidence to date suggests that males need to be exposed to one of these chemicals only once in their life to accrue reproductive benefits. Thereafter, the response of males to lures is suppressed. For example, exposing B. dorsalis to ME for as little as 30 minutes when sexually mature can lead to reduced capture probability of males by approximately 80% (Shelly, 1994). This effect can last for over 30 days. Interestingly, it may not even be necessary to feed a lure to sterile males before release to reduce their attraction to it. In B. tryoni, feeding on RK in an agar block diet containing sucrose and hydrolysed yeast for 48 hours after adult eclosion led to reduced attraction to cue-lure in the laboratory, and traps baited with CL in field cages and a commercial orchard. Mathematical modelling suggests that the release of sterile males pre-treated with phenylpropanoids should reduce their attraction to MAT baits, while simultaneously improving their mating success with wild females due to improved sexual performance and lower levels of competition from wild males. As such, the simultaneous application of MAT and SIT is proposed to lead to a situation where “male replacement” occurs, with wild males being suppressed by MAT and wild females mating with sterile males that remain in the field. However, further empirical data are required to demonstrate the effectiveness of the simultaneous application of MAT and SIT.
In order to develop operational strategies for simultaneous MAT with SIT, the underlying genetics, behaviour and physiology of the lure effects must be documented. Previous research is clear that these effects are not consistent across species and must be independently researched for each species of concern. Even for the well-studied B. dorsalis, it is now clear that the modified pheromone effect is only one part of a larger story. However, when comparing such studies, it is often difficult to determine how much of the variation across species is due to biological variation, and how much is due to different experimental approaches. Overcoming this problem is an essential role for this CRP..
The progress made with the increase the knowledge on (1) understand the differential sensitivity of different lure types to different fly species and use this information to inform recommendations for the field application of MAT against target species. (2) determine how exposure of larvae or adults to different lures modifies their subsequent development rate and propensity to response to lures (either the same lure or different lures).and (3) on provide behavioural, physiological and ecological insights that will improve modelling of the field phenology of the pests and the integration of MAT and SIT for their sustainable control in contributing to turn the insect control morecos-effective and being optimized the technology (SIT +MAT) to be transfered through the TC mechanism to our Member States.
Relevance
The development of cost-effective semiochemical treatments and delivery systems that improve sterile male performance and reduce their response to semiochemicals is highly desirable so that MAT and SIT could be integrated. Even though the incorporation of semiochemical treatments/supplements appears feasible, practical and standard procedures of implementation at an operational scale still need to be developed and validated. Thus, exploring the potential of such approaches is essential in view that the simultaneous MAT and SIT application has considerable potential to improve sterile to wild male overflooding ratios and therefore SIT cost-effectiveness. The combination of male replacement plus male enhanced performance increases what can be achieved with the same number of sterile flies: treating a wider area or enabling more rapid suppression or eradication. Furthermore, due to the increased cost-effectiveness, decisions to invest in SIT may be facilitated in situations where this would not otherwise be feasible.