Tim T. Y. Wong

Augmentative releases of Diachasmimorpha tryoni (Hymenoptera: Braconidae) to suppress a mediterranean fruit fly (Diptera: Tephritidae) population in Kula, Maui, Hawaii

Abstract Diachasmimorpha tryoni (Cameron), a larval parasitoid, was mass-reared in the laboratory and was used to suppress a wild Mediterranean fruit fly, Ceratitis capitata (Wiedemann), population in a nonisolated area (13 km2) of Kula, Maui, Hawaii. Weekly releases of D. tryoni, averaging 272,000 parasitoids per release, were made from March 10 to June 22, 1988. Trap catches of male C. capitata adults began to decline 8 weeks after the first release, and catches remained low throughout the summer months. However, in the control area of Keokea, adult catches began to increase in April and reached a peak in early July that was similar to that of previous years. The percentage of parasitism of C. capitata by D. tryoni was significantly higher for the six weekly collections of infested peaches in Kula than in the control area of Keokea: an average of 47.0% parasitism in Kula compared with 14.2% in Keokea. Of the total parasitoids, a significantly higher percentage of D. tryoni was recovered in fruit samples from Kula than in those from Keokea. Moreover, the number of C. capitata per fruit was significantly lower in the treated area than in the control area

Deterrence of repeated oviposition by fruit-marking pheromone inCeratitis capitata (Diptera: Tephritidae)

During ovipositor dragging on the fruit surface following egg laying in hawthorne fruit,Ceratitis capitata (Wiedemann) females deposit an unidentified pheromone that deters repeated oviposition attempts in that fruit. The pheromone proved water soluble and, when collected and sprayed in aqueous solution onto uninfested fruits in laboratory cages, effectively deterred boring attempts byC. capitata females of wild origin for at least 6 days (termination of test). A laboratory population ofC. capitata cultured on artificial media for more than 200 generations deposited pheromone that proved equally as deterrent to wild fly oviposition as pheromone from wild flies. However, lab fly oviposition was not effectively deterred by the presence of pheromone. The ecological significance of the pheromone is discussed.

VISUAL ORIENTATION OF CERATITIS CAPITATA FLIES TO FRUIT MODELS

Wooden and rubber fruit models of different shapes, colors, and sizes were hung in fruiting coffee trees. Spheres (7.5 cm in diam) were much more attractive to Ceratitis capitata (Wiedemann) than cubes, cylinders, or rectangles of equivalent surface area. Black and yellow were the most attractive of eight colors, and white and grey were the least attractive. When an array of sphere sizes were tested, the attraction to flies increased as the size of yellow spheres increased from 1.5 to 18 cm diam. Trimedlure (tert‐butyl 4(5)‐chloro‐2‐methylcyclohexanecarboxylate) enhanced the attraction for males when added to 20.3 times 25.4‐cm yellow rectangles and to 7.5‐cm black spheres.

Behavioral responses of Ceratitis capitata flies to bait spray droplets and natural food

In studies carried out on field‐caged non‐fruiting host trees, we examined effects of environmental and adult physiological and experiential state factors on responses of released Mediterranean fruit flies, Ceratitis capitata (Wiedemann), to droplets of proteinaceous bait (PIB‐7) with or without 20% insecticide (malathion). We confirmed that fresh PIB‐7 is both attractive and phagostimulatory to proteindeprived medflies and found that presence of 20% malathion ultra low volume concentrate (ULVC) in PIB‐7 droplets does not significantly repel medflies from approaching droplets but does significantly deter feeding on them. A single relatively fresh deposit of bird feces, an important source of protein for medflies in natural environments, attracted several times more laboratory‐cultured and wild medflies than 20 droplets of 80% PIB‐7/20% malathion ULVC (about the average number of droplets per m2of plant canopy in aerial bait spray programs). Attraction to protein was significantly greater among wild medflies deprived of protein continuously from eclosion than among wild medflies that had recent (within 3 days) or continuous access to protein. Attraction to protein increased significantly with increasing age (2, 7 and 12 days) of protein‐deprived wild medflies. But we found no significant positive impact of recent brief experience of wild medflies with protein on degree of subsequent attraction to protein. In final experiments that mimicked the size, density and distribution of bait spray droplets on tree foliage typical for an aerial medfly control program, very few (4%) or no released protein‐deprived wild medflies found a bait droplet within the 15 min test period even though most found a single deposit of bird feces. We conclude that the effectiveness of aerial bait sprays against medflies might be enhanced substantially (and the proportion of infested area treated with bait spray reduced considerably) by (1) including synthetic equivalents of attractive components of bird feces in the spray mixture, and (2) adjusting spatial and temporal patterns of bait spray applications according to estimates of the composition and abundance of natural medfly food and the age structure of medfly adult populations in infested regions.

Reproductive behavior of Biosteres arisanus (Sonan) (Hymenoptera:Braconidae), an egg-larval parasitoid of the oriental fruit fly

The egg-larval parasitoid Biosteres arisanus (Sonan) is a candidate for classical and augmentative biological control programs directed against seven tephritid pest species in many tropical and subtropical areas of the world. Aspects of its reproductive behavior were examined in the laboratory to facilitate its mass production. Mean longevity (±SEM) of host-deprived and ovipositing females was 15.3 ± 0.2 and 18.6 ± 0.2 days, respectively, when reared in groups of 200 ♀♀. However, when reared individually, ovipositing females lived for 21.4 ± 2.1 days. Ovarian maturation peaked at an average of 121.1 ± 5.5 mature eggs per female on the sixth posteclosion day and declined thereafter as the females aged. Mean number of eggs deposited per day was 16.5 ± 1.3 and mean fecundity was 88.4 ± 11.3 eggs per female. Mean potential fecundity (eggs deposited and eggs remaining in ovaries at death) was 133.4 ± 12.8 eggs. When host clutch size increased, B. arisanus female increased its oviposition activity per day. However, percentage parasitism of host eggs remained <50% and, as a result, superparasitism was minimized to <1%. No oviposition preference was detected when Bactrocera dorsalis (Hendel) and Ceratitis capitata (Wiedemann) eggs were presented to B. arisanus females. Size of cage provided for mating and light intensity each had a significant influence on the number of inseminated B. arisanus females. With an exposure period of 6 diurnal h, mean percentage of inseminated females was 77.4 ± 4.3 and 3.0 ± 3.0% when mating occurred in 8.3 and 0.02-m3 outdoor screened cages, respectively. Progeny of B. arisanus was exclusively males when females mated indoors. Increasing the number of inseminated females in the rearing cages significantly increased female oviposition activity.

Learning in oviposition site selection by Ceratitis capitata flies

Significant differences in propensity to attempt oviposition into various types of fruit were found among Mediterranean fruit flies, Ceratitis capitata, from the same wild population. Evidence presented suggests repeated exposure to one host fruit type conditions females to that host, and influences female response to other hosts in future encounters. Reversibility of conditioning was also demonstrated. Learning to refuse a novel host type is indicated as being more important than learning to accept a familiar host type in medfly conditioning to hosts.

STRATEGIES FOR COLONIZATION AND MAINTENANCE OF THE MEDITERRANEAN FRUIT FLY

Colonies of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) were established from field‐collected pupae and reared for 12 generations (G) using 3 different methods; given special care (C). eased from special care into mass rearing (E), and forced directly into mass rearing (F). The respective average numbers of viable pupae per ♀ increased from 1.5, 1.7, and 2.0 at G1 to 6.3, 6.6, and 8.5 at G12. The number of viable eggs per fertile ♀, though varying greatly depending on generation, never had an increasing or decreasing trend. Thus, since the fertility of individual ♀ ♀ remained relatively constant, improved yields were primarily due to an increase in the proportion of reproducing females. Furthermore, switching the E colony to the F regimen after G5 was as detrimental as initial colonization.

Intra‐tree foraging behavior of Ceratitis capitata flies in relation to host fruit density and quality

We examined the intra‐tree foraging behavior of individually‐released, wild‐population Mediterranean fruit flies (medflies), Ceratitis capitata (Wiedemann), on field‐caged host trees bearing each of three different densities (0, 3, or 12 per tree) of non‐infested host fruit (kumquat) or each of two levels of fruit quality (12 non‐infested fruit or 12 fruit infested with eggs and covered with host marking pheromone). With increasing den: ity of non‐infested fruit, medflies tended to remain longer in trees, visit more fruit before leaving, oviposit more often, accept a proportionately smaller number of fruit visited, and emigrate sooner after the last egg was laid (i.e. have a shorter Giving‐Up‐Time). Medflies spent much less time, oviposited much less often, and exhibited a longer Giving‐Up‐Time on trees harboring pheromone‐marked fruit than non‐infested fruit. Variation in temperature within the range at which experiments were conducted (25–36 °C) had little detectable influence on foraging behavior. We compare our findings with published findings on the intra‐tree foraging behavior of another tephritid fly, Rhagoletis pomonella (Walsh), and with current foraging behavior theory. We discuss implications of our findings with respect to medfly management strategies, particularly fruit stripping in eradication programs and use of synthetic marking pheromone for control.

Interactions Between Augmentatively Released Diachasmimorpha longicaudata (Hymenoptera: Braconidae) and a Complex of Opiine Parasitoids in a Commercial Guava Orchard

A study was conducted to determine the eVect of augmentatively releasing mass-reared Diachasmimorpha longicaudata (Ashmead) on a complex of four co-existing parasitoid species which attack the oriental fruit fly, Bactrocera dorsalis (Hendel). The species belonging to this complex are the egg-pupal parasitoid, Biosteres arisanus (Sonan) and the larval-pupal parasitoids, Biosteres vandenboschi (Fullaway), D. longicaudata and Psyttalia incisi (Silvestri). The study site was a 160-ha commercial orchard of common guava, Psidium guajava L. (cv. Beaumont) located on Kauai island. One year before the release of D. longicaudata, B. arisanus was the dominant parasitoid, accounting for 91.1% of the parasitoids recovered. Despite releases of large numbers of D. longicaudata (600000-800 000 parasitized puparia/ week), B. arisanus continued to account for 90% of all parasitoids recovered from the oriental fruit fly. The larval parasitoid P. incisi may have been reduced as a result of D. longicaudata releases. D. longic...

Host-marking pheromone and use of previously established oviposition sites by the mediterranean fruit fly (Diptera: Tephritidae)

Under controlled conditions, the Mediterranean fruit fly, Ceratitis capitata(Wiedemann) preferred to initiate oviposition into preexisting, naturally formed oviposition punctures in a host fruit, kumquat (Fortunella japonica),over establishing new sites on the fruit. This preference was expressed despite the presence of naturally deposited host-marking pheromone (HMP)shown previously to deter oviposition. An almost-identical preference for existing punctures was expressed when females were presented with fruit bearing artificially made punctures on which HMP had been naturally deposited. Using artificial punctures and HMP extracts, the occurrence of punctures was manipulated independently of the presence of HMP.Under field-cage conditions, we found that (1) punctures stimulated egg-laying on kumquats, regardless of HMP treatment; (2) HMP extract inhibited egg-laying, regardless of the occurrence of punctures; and (3) the extent to which HMP inhibited egg-laying was greater on fruit free of punctures than on fruit bearing them. The physiological, evolutionary, and pest management implications of these results are discussed.