Host preference in Pseudacteon phorid flies: response of P. tricuspis and P. curvatus to black, red and hybrid imported Solenopsis fire ants in multiple choice bioassays

Host preferences in both sexes of Pseudacteon tricuspis Borgmeier (Jaguariuna biotype) and Pseudacteon curvatus Borgmeier (Formosa biotype) and their relative attraction to the imported fire ants (IFA), Solenopsis invicta Buren (red IFA), Solenopsis richteri Forel (black IFA) and S. invicta × S. richteri hybrids (hybrid IFA) were investigated in two separate experiments utilizing multiple choice flight bioassays. The results of both experiments clearly showed that both sexes of the Jaguariuna biotype of P. tricuspis could distinguish among the three IFA species and demonstrated greater preference for hybrid IFA and red IFA. This conclusion is supported by a variety of data collected on the number of fly visits, attack rate, and hovering duration (Experiment 1), and on the number of trapped flies (Experiment 2), which showed that black IFA is the least preferred of the three species. Similar results were recorded for the Formosan biotype of P. curvatus, although the data were not as strongly conclusive. Females of this biotype spent a significantly greater amount of time in hovering mode over red IFA and hybrid IFA compared to black IFA, but the other data were not significant. The red IFA is the natural host of both phorid fly biotypes and our results suggest that both biotypes may have evolved a specialized relationship with red IFA including an ability to discriminate it from related fire ants. These results are discussed in relation to the possible role of fire ant chemicals in mediating host preferences in phorid flies, contributions of male phorid flies to fire ant biocontrol, and the practical implications of the key findings.     

Establishment and dispersal of the fire ant decapitating fly Pseudacteon tricuspis in North Florida

The decapitating fly Pseudacteon tricuspis Borgmeier was released at eight sites in North Florida between the summer of 1997 and the fall of 1999 as a self-sustaining biocontrol agent of the red imported fire ant, Solenopsis invicta Buren. Several releases used parasitized fire ant workers while most involved adult flies released over disturbed ant mounds. Establishment and dispersal of fly populations were monitored by disturbing about 10 fire ant mounds at each site and then inspecting them closely for hovering flies over a period of about 30 min. Overwintering populations of flies were successfully established at 6 of 8 release sites. Over several years, fly populations at these sites increased to levels as high or higher than those normally seen in their South American homeland. By the fall of 1999, flies had expanded out 1–6 km from five release sites and occupied about 125 km². By the fall of 2000 the five initial release sites plus one new site had fused into one large area about 70 km in diameter. The flies had expanded out an additional 16–29 km and occupied about 3300 km². By the fall of 2001 the flies had expanded out an additional 10–30 km and occupied approximately 8100 km². Fly dispersal was not related to wind patterns in the Gainesville area. Based on the above rates of dispersal and an establishment rate of 66%, we estimate that a state the size of Florida would require 5–10 releases spaced over a 3-year period to cover the state in 6–9 years.     

Pseudacteon decapitating flies (Diptera: Phoridae): Are they potential vectors of the fire ant pathogens Kneallhazia (=Thelohania) solenopsae (Microsporidia: Thelohaniidae) and Vairimorpha invictae (Microsporidia: Burenellidae)?

Fire ant decapitating flies in the genus Pseudacteon were tested for their potential as hosts or vectors of two microsporidian pathogens of the red imported fire ant, Solenopsis invicta. Decapitating flies that attacked or were reared from S. invicta workers infected by Kneallhazia (=Thelohania) solenopsae or Vairimorpha invictae were tested for either pathogen by polymerase chain reaction (PCR) tests or visual examination for spores using phase microscopy. Three species of fire ant decapitating flies acquired the pathogen, Kneallhazia solenopsae. K. solenopsae was detected in 58% of pooled samples of Pseudacteon obtusus flies and 44% of pooled samples of Pseudacteon cultellatus that developed in K. solenopsae-infected fire ant workers. K. solenopsae was also found in 17% of pooled samples of field-collected Pseudacteon curvatus. In contrast, the microsporidium V. invictae was not detected in P. obtusus reared from V. invictae-infected S. invicta workers. Neither K. solenopsae nor V. invictae were detected in any of the hovering or ovipositing flies in the laboratory exposures, indicating no mechanical acquisition of the microsporidia occurred during oviposition activity. Greater than 92% of the P. obtusus that developed in K. solenopsae-infected ants survived and emerged as adults, thus indicating no detrimental effects of the microsporidium on pupal development and emergence. These results indicate that Pseudacteon decapitating flies may be able to vector K. solenopsae but not V. invictae among fire ants. Further tests are planned to determine if flies containing K. solenopsae are capable of transferring this pathogen either during oviposition or by being consumed by fire ant larvae.     

Monitored releases of Rhinoncomimus latipes (Coleoptera: Curculionidae), a biological control agent of mile-a-minute weed (Persicaria perfoliata), 2004–2008

Mile-a-minute weed, Persicaria perfoliata (L.) H. Gross, is an invasive annual vine of Asian origin that has developed extensive monocultures, especially in disturbed open areas in the Mid-Atlantic region of the United States. A host-specific Asian weevil, Rhinoncomimus latipes Korotyaev, was approved for release in North America in 2004, and weevils have been reared at the New Jersey Department of Agriculture Beneficial Insect Laboratory since then. By the end of 2007 more than 53,000 weevils had been reared and released, mostly in New Jersey, but also in Delaware, Maryland, Pennsylvania, and West Virginia. The beetles established at 63 out of 65 sites (96.9%) where they were released between 2004 and 2007, with successful releases consisting of as few as 200 weevils. Weevils were recorded at 30 additional non-release sites in New Jersey, where they had dispersed at an average rate of 4.3 km/year. Standardized monitoring of fixed quadrats was conducted in paired release and control sites at eight locations. Significant differences in mile-a-minute weed populations in the presence and absence of weevils were found at three locations, with reduction in spring densities to 25% or less of what they had been at the start within 2–3 years at release sites, while weed densities at control sites were largely unchanged. Mile-a-minute weed populations at a fourth site were similarly reduced at the release site, but without control data for comparison due to rapid colonization of the paired control site. At the other four locations, all on islands, mile-a-minute weed populations were reduced at both release and control sites without large weevil populations developing, apparently due to environmental conditions such as late frost and extreme drought.     

Dispersal and competitive impacts of a third fire ant decapitating fly (Pseudacteon obtusus) established in North Central Florida

Self-sustaining classical biological control agents offer hope for permanent wide-area control of imported Solenopsis fire ants in the United States because escape from abundant natural enemies left behind in Argentina is a likely reason for unusually high fire ant densities in the United States. The fire ant decapitating fly Pseudacteon obtusus Borgmeier (Diptera: Phoridae) was released as a biocontrol agent of the red imported fire ant (Solenopsis invicta Buren) in Gainesville, FL because it is a common parasitoid of this ant in Argentina and because it has a higher propensity of attacking fire ants along foraging trails than the two Pseudacteon species previously released. Field surveys of a rapidly expanding P. obtusus population (8–12 km/yr) proved that this fly was capable of thriving and successfully competing with the much more abundant Pseudacteon curvatus Borgmeier. However, Pseudacteon tricuspis Borgmeier, the first decapitating fly released, was effectively excluded from most sample sites when faced with competition from both P. curvatus and the similar-sized P. obtusus. Despite clear evidence for competitive exclusion, P. tricuspis abundance at sample sites was positively correlated with the abundance of its two competitors—probably because of moderate to strong covariability in the suitability of sample sites for all three congeners. The addition of P. curvatus, the second parasitoid released, increased total parasitism pressure on fire ant populations by about 10-fold. The addition of P. obtusus, the third species, did not measurably improve total guild parasitism rates on imported fire ants in North Central Florida (as assessed by roadside trap counts), but the performance of this species will likely vary with habitat, region, and climate.     

Effect of habitat complexity on biological control by the red imported fire ant (Hymenoptera: Formicidae) in collards

A potentially important and understudied biological control agent in US agroecosystems is the red imported fire ant, Solenopsis invicta Buren. Red imported fire ants may be particularly important biological control agents because we can manipulate their abundance with changes in habitat complexity. The effect of habitat complexity on biological control by fire ants was determined using plots of collards intercropped with white clover (complex habitat) and simple collard monocrops. The most economically significant pests of collards are larvae of the diamondback moth (DBM), Plutella xylostella (L.). Predation of DBM larvae by fire ants was more rapid and efficient in the intercrop than the monocrop. Red imported fire ants were 23% less abundant in the intercrop than the monocrop, however, suggesting that fire ants had a greater per capita effect on DBM survival in the complex habitat. Red imported fire ant predation of DBM larvae was significantly affected by larval density. Red imported fire ants also reduced the survival of leaf beetles, another economically significant pest taxa, by 45%. Furthermore, collard leaf damage tended to be inversely related to fire ant density and fire ants were more effective at reducing crop damage in the complex intercrop. Our study indicates the ability of red imported fire ants to be effective biological control agents and suggests that increasing habitat complexity can enhance red imported fire ant efficacy and herbivore control.     

Evaluating biological control of fire ants using phorid flies: effects on competitive interactions

The effects of the parasitic phorid fly, Pseudacteon tricuspis Borgmeier, on the competitive interactions between the red imported fire ant, Solenopsis invicta Buren, and a native North American ant, Forelius pruinosus (Roger), were investigated in the laboratory. P. tricuspis is a highly host-specific endoparasitoid of S. invicta workers that is currently being reared and released as a biological control agent of S. invicta in the US. We tested the effect of P. tricuspis on the colony growth rate of S. invicta when S. invicta was forced to compete with F. pruinosus for a protein resource (freeze-killed crickets) in laboratory competition arenas. In addition to colony growth rate, we quantified the effect of the phorid flies on the foraging rate of S. invicta. Though S. invicta significantly reduced its foraging rate in the presence of the phorid flies, we did not detect an effect of the flies on colony growth rate. Possible explanations for these results include behavioral compensation by S. invicta for the presence of the flies. We present these laboratory results in light of a literature search indicating that laboratory tests of biological control agent efficacy are good predictors of field efficacy. We conclude that P. tricuspis alone is unlikely to suppress S. invicta populations in the field by reducing their competitive ability.     

Colonization and hyperparasitism ofCotesia rubecula (Hym.: Braconidae), a newly introduced parasite ofPieris rapae,in Virginia

A Yugoslavian strain ofCotesia rubecula (Marshall) (Hymenoptera: Braconidae) was released in spring broccoli for control of the imported cabbageworm,Pieris rapae (L.), in Montgomery Co., Virginia, in 1987.C. rubecula reproduced and parasitized imported cabbageworm larvae in fall broccoli in 1987. It was found in moderate numbers in the summer and fall crops in 1988, and by fall had dispersed 0.8 km from the original release site. However, noC. rubecula were detected in our broccoli plots in Montgomery Country in 1989 or 1990. The hymenopteran hyperparasitesIsdromas lycaenae (Walker)(Ichneumonidae), Spilochalcis torvina (Cresson) (Chalcididae), andTetrastichus galactopus (Ratzeburg) (Eulophidae) were found attackingC. rubecula. Hyperparasites emerged from 31.8% and 41.1% of theC. rubecula cocoons in 1987 and 1988, respectively.T. galactopus was the most numerous hyperparasite in 1987, butS. torvina was dominant in 1988. Hyperparasite activity was low during early spring, but increased in July in both years. By August 1988, only hyperparasites emerged from theC. rubecula cocoons collected in the field. In spite ofC. rubecula's success in overwintering, hyperparasites, especiallyS. torvina, may be a limiting factor in the establishment ofC. rubecula in southwestern Virginia.      

Fire ant alarm pheromone and venom alkaloids act in concert to attract parasitic phorid flies, Pseudacteon spp.

Pseudacteon tricuspis, Pseudacteon obtusus and Pseudacteon curvatus are three species of parasitic phorid flies (Diptera: Phoridae), which have been introduced as classical biological control agents of imported, Solenopsis fire ants (Hymenoptera: Formicidae) in the southern USA. Previous studies demonstrated the behavioral response of P. tricuspis to the venom alkaloids and alarm pheromone of the fire ant, S. invicta. In the present study, we compared the responses of P. tricuspis, P. obtusus and P. curvatus to Solenopsis invicta alarm pheromone, venom alkaloids, or a mixture of both chemicals in four-choice olfactometer bioassays. The main hypothesis tested was that the fire ant alarm pheromone and venom alkaloids act in concert to attract Pseudacteon phorid flies. Both sexes of all three Pseudacteon species were attracted to low doses of the fire ant alarm pheromone or venom alkaloids (i.e. 1 ant worker equivalent) alone. However, the flies were significantly more attracted to a mixture of both chemicals (i.e., 1:1 mixture of alarm pheromone + alkaloids) than to either chemical. The results suggest an additive rather than a synergistic effect of combining both chemicals. Comparing the fly species, P. tricuspis showed relatively greater attraction to cis alkaloids, whereas the alkaloid mixture (cis + trans) was preferred by P. obtusus and P. curvatus. In general, no key sexual differences were recorded, although females of P. tricuspis and P. obtusus showed slightly higher response than conspecific males to lower doses of the alarm pheromone. The ecological significance of these findings is discussed, and a host location model is proposed for parasitic phorid flies involving the use of fire ant alarm pheromone and venom alkaloids as long range and short range attractants, respectively.     

The introduction of the fire ant parasitoid Pseudacteon nocens in North America: challenges when establishing small populations

Several species of parasitoid phorid flies (Pseudacteon spp., Diptera: Phoridae) have been released into the United States as potential biological control agents for the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Here we report the first successful introduction and spread of Pseudacteon nocens Borgmeier at a site in Texas, USA. Pseudacteon nocens is an important natural enemy since it is a widespread and often abundant parasitoid of S. invicta in Argentina, where it attacks larger fire ant workers eliciting a strong defensive response. Several years of effort to establish this species previously failed, and here we provide a model to better understand the likelihood of founding new populations when introducing sequential batches of flies in field or laboratory cultures. We also report on a novel method of establishing new populations of phorids in the field using pupae burial boxes to overcome constraints of releasing adult flies or infected worker ants.     

Releases of Trichogramma platneri (Hymenoptera: Trichogrammatidae) in Apple Orchards under a Sterile Codling Moth Release Program

Based on the premise that augmented host numbers may help multiply and support parasitoid populations, the egg parasitoid Trichogramma platneri Nargarkatti was released in apple orchards which were participating in a sterile codling moth, Cydia pomonella (L.), release program. Nonviable eggs resulting from matings involving at least one sterile codling moth partner can be successfully parasitized by T. platneri. Grain moth-reared, as well as codling moth-reared, T. platneri were released either in the spring or in the spring and summer oviposition period(s) of wild codling moth. Sentinel codling moth eggs were hung weekly, for 3-day periods, from May until September to determine fluctuations in T. platneri populations both during and between releases. Low numbers of wild or nonviable codling moth eggs or other susceptible host eggs resulted in sufficient eggs to maintain low spring- or summer-introduced T. platneri populations. T. platneri reduced codling moth damage in trees in which the Trichogramma were released.     

Myrmica specioides Bondroit: a new invasive ant species in the USA?

Ants are among the most successful invasive species. The establishment of the infamous red imported fire ant Solenopsis invicta (Fabricius) has caused a considerable amount of damage to both the economy and the native ecosystem of the Southern United States. We report the first record of a newly introduced ant species, Myrmica specioides Bondroit, to the state of Washington. It possesses the characteristics of a potential pest ant: high aggressiveness, polygyny, and the tendency to reach high local abundances. This early record might facilitate the control of introduced populations before they can develop into a genuine nuisance.     

Field assessment of a frond-feeding weevil, a successful biological control agent of red waterfern, Azolla filiculoides, in southern Africa

Azolla filiculoides (red waterfern) is a small, floating fern native to South America, that has invaded aquatic habitats, predominantly water resevoirs in southern Africa. A frond-feeding weevil, Stenopelmus rufinasus Gyllenhal (Coleoptera: Curculionidae), was imported from Florida, USA, and released as a biological control agent against this weed in South Africa at the end of 1997. To date, 24,700 weevils have been released, which has resulted in local extinction of red waterfern at 81% of the 112 release sites. The weevil has not failed to control a single site. Several sites were, however, lost due to flooding or drainage of dams. The surface area of weed controlled totalled 203.5 ha. On average, A. filiculoides was controlled in infested sites in 6.9 (±4.3) months. The weed recolonized at 22 of the sites (through either spore germination or dispersal by waterfowl), but the weevils subsequently spread to all of these sites and successfully caused local extinction of the weed at 18 of the sites. Five years after the release of the weevil, the weed no longer poses a threat to aquatic systems in southern Africa. In comparison to other biological control programs of aquatic weeds, the program against A. filiculoides in southern Africa ranks among the most successful cases anywhere in the world.     

Phenology and parasitism rates in introduced populations of <Emphasis Type="Italic">Pseudacteon tricuspis</Emphasis>, a parasitoid of <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

We documented patterns of seasonal abundance and rates of parasitism in introduced populations of Pseudacteon tricuspis Borgmeier, a phorid parasitoid of the red imported fire ant, Solenopsis invicta Buren. Adult P. tricuspis populations were censused at monthly intervals for 1 year at three sites in northern Florida. Censuses were conducted by aspirating phorids attracted to disturbed S. invicta mounds. Pseudacteon tricuspis adults were present in every month at all sites, although abundances varied greatly among sites and over time. The highest densities of flies (up to 453 censused at 10 disturbed S. invicta mounds in 30 min) were observed in November, and changes in abundance over time were positively correlated among sites. Sex ratios were usually male biased. Parasitism rates were evaluated by collecting workers from field colonies and monitoring them in the laboratory for evidence of parasitism. Parasitism rates were very low – always less than 1%. The average parasitism rate per colony over 16 colonies and 2 years was 0.058%. No pupariation occurred within the first 8 days of collection, suggesting parasitism by P. tricuspis induced behavioral changes in parasitized workers that precluded such workers from our collections. If so, true field parasitism rates may be several times higher than measured here, yet still low in an absolute sense. These low parasitism rates can be reconciled with observed adult phorid densities by considering the large number of host ants present at the study sites.     

Efficacy of spider and ant predators on the cotton fleahopper [Hemiptera: Miridae]

The efficacy of predators of immature cotton fleahoppers,Pseudatomoscelis seriatus (Reuter), was calculated using field and laboratory cage confinement tests for consumption rate. The predators tested were the striped lynx spider,Oxyopes salticus Hentz; the black and white jumping spider,Phidippus audax (Hentz); the celer crab spider,Misumenops celer Hentz; and the red imported fire ant,Solenopsis invicta Buren. The spider predators were evaluated in a cotton field using predator-prey confinement cages on cotton plants. Average percent control (sensuAbbott 1925) of fleahoppers byO. salticus, P. audax, andM. celer were 42%, 66% and 32% respectively. The rate of fleahopper consumption by red imported fire ants was measured in the laboratory using various numbers of ants and fleahoppers. Daily percent control by ants ranged from 0.5% (single ant and fleahopper) to 100% (colony linked). The functional response of the 4 arthropod species to different prey numbers is illustrated and discussed as is the relative potential usefulness of natural enemies to suppress fleahoppers on cotton.      

Post-Release Host-Specificity Testing of Pseudacteon tricuspis, a Phorid Parasitoid of Solenopsis Invicta Fire Ants

Inherent in any biological control program is the risk of nontarget effects. Pseudacteon tricuspisBorgmeier, a parasitoid phorid fly, has been introduced to the United States from South America as a potential biocontrol agent of the red imported fire ant, Solenopsis invictaBuren. We conducted tests of host specificity on introduced populations of P. tricuspis, which are attracted to alarm pheromones released by their hosts during events such as mound disturbances and interspecific interactions. We monitored disturbed mounds of S. invicta and its close congener, S. geminata(F.), during the expansion of P. tricuspis across north Florida and after populations had been established for ~3 years. We also tested host acceptance in established populations of P. tricuspis by offering trays containing S. invicta, S. geminata, and 14 additional ant species representing 12 different non-Solenopsis genera. Although P. tricuspiswas commonly observed to hover over and attempt to oviposit on S. invicta, we never observed any parasitization attempts on any other ant species. As predicted by laboratory tests, released populations of P. tricuspis appear to be highly host specific and pose no obvious threat to nontarget species.     

Seasonality ofOrmia depletaand Limits to Its Spread

Ormia depleta(Wiedemann) (Diptera: Tachinidae), a South American fly that homes on the calling songs of its hosts, was brought from Piracicaba, Brazil; colonized; and released in Florida for the biological control ofScapteriscusspp. mole crickets. It became established at some release sites and rapidly spread through most of peninsular Florida. The seasonal distributions of phonotactic females in Florida differed from the single summer peak recorded at Rio Claro and Piracicaba, Brazil (23° S). Near Bradenton (27° N), spring and fall peaks with a summer hiatus were quickly established and remain evident. At two sites near Gainesville (30° N), a strong fall peak and a modest-to-none spring peak developed. Peaks of phonotactic females seem to follow times of peak host availability and sometimes coincide with minima of host availability. Limits to geographical expansion ofO. depletaare poorly understood. At Gainesville, the site of earliest introduction, establishment was rapid and soundtrap catches increased for the first 3 years, exceeding 1000 per year at one site. Catches then declined for 3 years, almost reaching zero in 1994. On the other hand, annual sound-trap catches ofO. depletaat Bradenton exceeded 1000 in <2 years and have remained above that level for 5 years. Winters in Gainesville are more severe than those in Bradenton, but minimum winter temperatures in Gainesville were substantially lower duringO. depleta's increase than during its decline. Perhaps mild winters cause the flies to become active early—only to starve for lack of adequate winter nectar sources.O. depletamay yet spread to the northern limits of itsScapteriscushosts as present populations adapt to new environments. Or farther spread may require that new strains be introduced from more southerly sites in South America.     

Multivariate analyses of the factors affecting the distribution,abundance and social form of Louisiana fire ants, <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

We surveyed 165 sites to determine the ecological factors influencing the distribution, abundance, and occurrence of polygyny in the red imported fire ant (Solenopsis invicta) in Louisiana. On average, sites had 220 nests/ha, 14% of mounds were polygyne, and 22% of sites had ≥ one polygyne mound. The density of nests and ants per site both increased with the proportion of mounds that were polygyne and the organic and phosphorous content of the soil but decreased with longitude, latitude, and the silt: clay, calcium and sodium content of the soil. Ant density also declined with ambient relative humidity. These multivariate models explained ~25% of the variation in nest and ant density per site. Mean mound size per site increased with the phosphorous content of the soil and the number of nests at the site suggesting that prospective queens may select sites that are conducive to produce large mounds. Mean nest size, however, decreased with the proportion of nests that were polygyne and soil potassium while mounds in forests were typically larger than those in residential areas. Overall, this model accounted for 29% of the variation in mean nest size per site. Polygyne sites were patchily distributed across Louisiana. The probability of a site being polygyne declined with mean monthly temperature for 1999 – 2003 and distance to the nearest commercial waterway suggesting that shipping activities may have played a role in the introduction of polygyne colonists to an area. Forested sites were also less likely to be polygyne than those in residential areas. Finally, the density of polygyne nests and ants increased with latitude whereas that of the monogyne form generally declined with latitude. The abundance of both social forms was also greater when they occurred alone. These data are consistent with the hypothesis that monogyne and polygyne S. invicta compete with one another. Received 28 July 2006; revised 2 March 2007; accepted 29 May 2007.     

Biological Control of Anastrepha spp. (Diptera: Tephritidae) in Mango Orchards through Augmentative Releases of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae)

Diachasmimorpha longicaudata (Ashmead) parasitoids were released by air on a weekly basis over 1600 ha of commercial mango orchards, backyard orchards, and patches of native vegetation, at a density of ca. 940 parasitoids/ha. Releases were made during 2 consecutive years, beginning at flower onset and lasting until the end of the production cycle. Two areas, 7 km apart, were compared. In one area parasitoids were released, whereas the other area was used as a control. During the 2nd year treatments were reversed. Fruit was sampled in commercial mango orchards and in backyard orchards to assess levels of parasitism in fruit fly larvae. Highly significant differences in percentage parasitism were found in release and control zones in backyard orchards. Furthermore, trapping results indicated that D. longicaudata releases were associated with ca. 2.7-fold suppression of Anastrepha spp. populations in backyard orchards. Results suggest that suppression might be affected by environmental conditions and by the parasitoid:fly ratio achieved. Anastrepha obliqua McQuart populations were suppressed more effectively by use of parasitoids than those of Anastrepha ludens Loew, perhaps due to the type of host fruits used by each species. Augmentative parasitoid releases in marginal areas surrounding commercial orchards (backyard orchards, wild vegetation) can substantially suppress fly populations. Through this approach, the number of flies that later move into commercial orchards can be significantly reduced. Such a strategy, when combined with sound orchard management schemes, can allow growers to produce clean fruit without the need to resort to the widespread use of insecticides.