RESUMO

The sterile insect technique (SIT), an environmentally friendly means of control, is currently used against plant, animal, and human pests under the area-wide integrated pest management. It consists in the mass production, sterilization, and release of insects in an affected area where sterile males mate with wild females leading to no reproduction. Here, we review SIT in the Neotropics and focus on particular recent successful cases of eradication of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), as well as effective programs used against the Mexican fruit fly Anastrepha ludens (Loew), the New World screwworm fly Cochliomyia hominivorax (Coquerel)), and the Cactus moth Cactoblastis cactorum (Berg). We examine when SIT does not work and innovations that have made SIT more efficient and also highlight complimentary techniques that can be used in conjunction. We address potential candidate species that could be controlled through SIT, for example Philornis downsi Dodge & Aitken. Finally, we consider the impact of climate change in the context of the use of the SIT against these pests. Given the recent dramatic decline in insect biodiversity, investing in environmentally friendly means of pest control should be a priority. We conclude that SIT should be promoted in the region, and leadership and political will is needed for continued success of SIT in the Neotropics.

Assuntos

RESUMO

Anastrepha ludens (Loew) is one of the most important pests of citrus and mango crops in Mexico. A method used to control this pest is the sterile insect technique, which consists in the mass production, irradiation, and release of insects in affected areas. The production of insects begins with the establishment of colonies to produce eggs, which must be highly fertile to ensure an adequate production of larvae. However, female fecundity and fertility can be affected by adult density and sex ratio, thus an optimal sex ratio in mass-rearing cages must be used. The genetic sexing strain of A. ludens (Tapachula-7) allows the identification of the sex at the pupal stage, making it possible to establish rearing cages with different sex ratios. We determined if different sex ratios have an effect on egg production. Two sex ratios (4♀: 1♂ and 1♀: 1♂) were compared. Fecundity, fertility and survival at different ages were also determined. Higher fertility and fecundity per female were observed at a ratio of 4:1. However, females with higher fecundity had reduced survival probabilities. In conclusion, maintaining colonies with a lower proportion of males in cages ensures a greater fecundity and fertility. Further research is necessary to understand whether results can be attributed to lower male harassment in cages.

Assuntos

RESUMO

The aim of this study was to experimentally test for adult cross-resistance to hypoxia or anoxia in a desiccation-resistant population of Anastrepha ludens Loew. We compared desiccation resistant flies with unselected (control) flies by measuring the effect of pre-emergence hypoxia on some fitness parameters (emergence, flight ability, copulation success, latency to copulation, copulation duration, ovary size). Anoxia effects were determined using eye color changes during pupa development and fly emergence after re-oxygenation. Both strains were negatively affected in all measured parameters when exposed to hypoxia for more than 48 h. However, after hypoxia, control flies showed, in general, shorter latency to mate and longer copula duration than desiccation-resistant flies. Anoxia-induced arrest of pupa development, whereas returning to normoxia conditions induced resumption of development. Anoxia period length (longer than 72 h) increased mortality to 100% in the control line, whereas the desiccation-resistant line survived even at 120 h of anoxia. Thus, pre-release hypoxia must not exceed 24 h in order to maintain insect quality independently of fly type.

Assuntos

RESUMO

Phenotypic plasticity is thought to evolve in response to environmental unpredictability and can shield genotypes from selection. However, selection can also act on plastic traits. Egg-laying behaviour, including clutch size regulation, is a plastic behavioural trait among tephritid fruit flies. We compared plasticity in clutch size regulation among females of Anastrepha ludens populations stemming from environments that differed in the degree of predictability in egg-laying opportunities. Clutch size regulation in response to hosts of different sizes was compared among flies from (a) a wild, highly isolated population, (b) a wild population that switches seasonally from a small wild host fruit that varies greatly in abundance to an abundant large-sized commercial host, and (c) a laboratory population. Flies from all three populations adjusted clutch number and size according to host size. However, flies from the heterogeneous wild environment were more plastic in adjusting clutch size than flies from agricultural settings that also laid fewer eggs; yet both populations were more plastic in adjusting clutch size in line with host size when compared with laboratory females. When wild and orchard females encountered the largest host, clutch size was extremely variable and egg regulation did not follow the same trend. Heterogeneity in host availability in space and time appears to be as important as seasonal variation in host size in maintaining plastic clutch size regulation behaviour. In stable environments, there was a clear reduction in the plasticity of these traits.

Assuntos

RESUMO

Tephritid pests controlled through the sterile insect technique (SIT) are mass-reared and subsequently released in affected areas. Several quality parameters are currently used to test adults, but none take into account interactions with a predator. When sterile males are released in the field, they will need to avoid predators until they reach sexual maturity and survive long enough to mate with wild females. Spiders are one of the most common predators that flies may encounter in release sites. In this study, we evaluated the antipredator behavior of a mass-reared sterile unisexual strain ('Tapachula-7') of the Mexican fruit fly Anastrepha ludens (Diptera: Tephritidae) against their spider predators. We sampled spiders in citrus trees to determine which families could be more common. We established the baseline activity rates of sterile Tapachula-7 (Tap-7) flies in comparison with wild flies. We also tested the behavior of the fertile and sterile bisexual strain and wild flies against hunting spiders (Family Salticidae) and orb building spiders (Family Tetragnathidae). We recorded 18 spider families, with Salticidae being the most dominant. Tap-7 flies diminished their activity in comparison with wild males at 1800 h but showed similar activity levels earlier in the day. When exposed to orb-web spiders (Leucauge venusta), Tap-7, fertile and sterile males from the bisexual strain had similar rates of survival, but Tap-7 males showed lower survival than wild males. Against hunting spiders (Phidippus audax), wild males had higher probability of defensive wing displays, but there was no difference in spider attack rates. In general, sterile Tap -7 males performed as well as males from the bisexual strain, although they had lower survival than wild males. This could be due to either mass-rearing and/or irradiation effects. We recommend the use of the defensive wing display behavior as a quality parameter and propose a rapid and effective method to evaluate fly activity. The efficiency of SIT will be improved if released sterile males have the same antipredator repertoire as their wild counterparts.

Assuntos

RESUMO

Fruit flies (Diptera: Tephritidae) are major pests worldwide. The sterile insect technique, where millions of flies are reared, sterilized by irradiation and then released, is one of the most successful and ecologically friendly methods of controlling populations of these pests. The mating behaviour of irradiated and non-irradiated flies has been compared in earlier studies, but there has been little attention paid to the anti-predator behaviour of mass-reared flies, especially with respect to wild flies. Tephritid flies perform a supination display to their jumping spider predators in order to deter attacks. In this study, we evaluated the possibility of using this display to determine the anti-predator capabilities of mass-reared irradiated, non-irradiated flies, and wild flies. We used an arena setup and observed bouts between jumping spiders (Phidippus audax Hentz) and male Mexican fruit flies (Anastrepha ludens Loew). We show that although all flies performed a supination display to their predator, wild flies were more likely to perform a display and were significantly more successful in avoiding attack than mass-reared flies. We suggest that this interaction can be used to develop a rapid realistic method of quality control in evaluating anti-predator abilities of mass-reared fruit flies.

Assuntos

RESUMO

Commercially ripe 'Hass' avocados, Persea americana Mill, artificially exposed to wild Anastrepha ludens (Loew) (Diptera: Tephritidae) females 24 h after harvest were placed in a cold storage facility to determine the effect of low temperature on larval survival and adult viability. Fruit were left for 3, 6, 9, and 12 d in a cold room at 5 degrees C followed by a 20-25-d period at ambient temperature to allow for larval development and pupation. Hass avocados and grapefruit, Citrus paradisi Macfadyen, maintained at ambient temperature served as controls. Overall, only 0.23% of the Hass avocados and 19.30% of the grapefruit were infested. The number of infested fruit increased with decreasing exposure time to cold. Puparia from cold-treated Hass avocados were significantly smaller than those stemming from cold-treated grapefruit. Hass avocados exposed for 12 d to 5 degrees C yielded no puparia, and those exposed for 6 and 9 d yielded 22 and two puparia, respectively, but no adults. Although Hass avocados exposed to cold temperature for 3 d yielded adults that reached sexual maturity (N = 16), females laid inviable eggs. Grapefruit exposed to cold for 12 d yielded normal-sized puparia (but no adults), whereas those exposed over 9 d yielded females able to lay viable eggs. We conclude that exposing fruit to cold storage after packing and during transport represents an effective risk-mitigating procedure in the highly improbable event that a gravid A. ludens female might lay eggs in a commercially ripe Hass avocado that had been left unprotected in a packinghouse.

Assuntos

RESUMO

The Mexican fruit fly Anastrepha ludens (Loew) (Diptera: Tephritidae) is a polyphagous pestiferous insect with a geographical range encompassing highly variable environmental conditions. Considering that cryptic species have been recently found among South American representatives of the same taxonomic group as A. ludens, we tested whether or not some populations of A. ludens have evolved assortative mating as an isolating mechanism that maintains intrapopulation genetic differences and behavioral adaptations to local conditions. Males and females stemming from widely separated locations with similar environmental conditions and males and females stemming from populations within individual-flight range, but collected in different hosts (a native and an exotic one), mated randomly amongst themselves when placed in a field cage. Despite the fact that sibling males and females from two distinct populations also mated randomly amongst themselves, siblings engaged in significantly longer copulations than non-siblings, indicating that perhaps adults discriminated mates with similar genetic compositions. Our results have important practical implications as A. ludens is the most devastating pest of citrus in Mexico and Central America, and large-scale releases of sterile flies are used to control it.

Assuntos

RESUMO

We determined the efficacy of three potential oviposition deterrents in reducing fruit infestation by Anastrepha obliqua in tropical plum and mango orchards. These were: (1) Extracts of feces of Mexican fruit fly, Anastrepha ludens, known to contain the A. ludens host marking pheromone (HMP) and (2) two fully synthetic simplified analogues of the naturally occurring compound, which we have named desmethyl A. ludens HMP (DM-HMP) and Anastrephamide. Two applications of feces extracts 2 or 3 wk before fruit color break reduced A. obliqua infestation in plums by 94.1, 75.9, and 72% when measured 8, 14, and 25 d, respectively, after application. The natural A. ludens-HMP containing extract retained its effectiveness despite considerable rainfall (112.5 mm) and high A. obliqua populations. The synthetic desmethyl HMP derivative (DM-HMP) also reduced infestation in plums by 53.3 and 58.7% when measured, 18 and 26 d, respectively, after application. Finally, applications of Anastrephamide resulted in fruit loss cut by half and an 80% reduction in numbers of fly larvae per fruit. Our results confirm previous findings indicating that there is interspecific cross-recognition of the HMP in two of the most pestiferous Anastrepha species and open the door for the development of a highly selective, biorational Anastrepha management scheme.

Assuntos

RESUMO

Oocyte counts, used as a measure of egg load, were compared among three different age groups (15, 30 and 45 days) of two polyphagous species of tephritid fruit flies, Anastrepha ludens and Anastrepha obliqua, which were exposed to varying conditions of diet (sucrose vs sucrose and protein), availability of oviposition substrate (present vs absent), adult female density (1, 2 and 4 females/cage), and semiochemical context (presence vs absence of male pheromones and fruit volatiles). In both species, oocyte counts were higher in older females and for females fed sucrose and protein than for females fed sucrose only. The presence of artificial oviposition substrates influenced oocyte counts in A. obliqua, but not in A. ludens. Female density influenced oocyte counts in both species. Females maintained in groups had higher egg loads than isolated females. Finally, preliminary evidence suggests that semiochemical context influenced oocyte counts. Counts were highest for females in a room containing both fruit volatiles and male pheromone, lowest for females in a room containing neither volatiles nor pheromone, and intermediate for females in rooms containing either volatiles or pheromone but not both. Our results suggest that egg load is influenced by environmental factors in different ways in these two species. Egg load in A. obliqua, a species whose host fruits are highly ephemeral, is responsive to access to the host resource. By contrast, in A. ludens, a species infesting less ephemeral fruit, female density and age played a more important role than host stimuli. The role of ovarian maturation and oviposition in mediating these effects, as well as implications for mass rearing and pest management, are discussed.