Charmaine D. Sylva

Mediterranean fruit fly (Dipt., Tephritidae) suppression in persimmon through bait sprays in adjacent coffee plantings*

Abstract:  Oriental persimmon, Diospyros kaki L., in Upper Kula on the island of Maui (Hawaii) is attacked by the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). Recent suppression trials using mass trapping with a synthetic food‐based bait, initiated in alternate host crops before the start of persimmon season, had shown promise as a means of reducing C. capitata population levels. However, this did not adequately suppress C. capitata population where there were adjacent plantings of coffee, Coffea arabica L., a favoured alternate host, which bears fruits before and during the persimmon season. To improve C. capitata population suppression, we applied a spinosad‐based bait spray to coffee plants, starting before persimmon fruits became susceptible to oviposition by the Mediterranean fruit fly. The bait spray suppressed the C. capitata population and led to reduced infestation of both coffee cherries and persimmon fruits. Percentage parasitization of C. capitata in coffee cherries by established biological control agents, primarily Fopius arisanus (Sonan), was not significantly different in unsprayed vs. sprayed plots even after 11 weekly sprays. These results suggest that mass trapping, combined with spinosad‐based bait sprays, are control components that are compatible with biological control and can be combined in an integrated pest management system for C. capitata.

Comparative Evaluation of Spinosad and Phloxine B as Toxicants in Protein Baits for Suppression of Three Fruit Fly (Diptera: Tephritidae) Species

Abstract Spinosad and phloxine B are two more environmentally friendly alternative toxicants to malathion for use in bait sprays for tephritid fruit fly suppression or eradication programs. Laboratory tests were conducted to assess the relative toxicity of these two toxicants for melon fly, Bactrocera cucurbitae Coquillett; oriental fruit fly, Bactrocera dorsalis Hendel; and Mediterranean fruit fly, Ceratitis capitata (Wiedemann) females. Field tests also were conducted with all three species to compare these toxicants outdoors under higher light and temperature conditions. In laboratory tests, spinosad was effective at much lower concentrations with LC50 values at 5 h of 9.16, 9.03, and 4.30 compared with 250.0, 562.1, and 658.9 for phloxine B (27, 62, and 153 times higher) for these three species, respectively. At 16 ppm spinosad, LT50 values were lower for all three species (significantly lower for C. capitata and B. dorsalis) than 630 ppm phloxine B LT50 values. At 6.3 ppm spinosad, the LT50 value for C. capitata (3.94) was still significantly less than the 630 ppm phloxine B LT50 value (6.33). For all species, the 100 ppm spinosad concentrations gave LT50 values of <2 h. In comparison among species, C. capitata was significantly more sensitive to spinosad than were B. cucurbitae or B. dorsalis, whereas B. cucurbitae was significantly more sensitive to phloxine B than were C. capitata or B. dorsalis. LC50 values were reduced for both toxicants in outdoor tests, with greater reductions for phloxine B than for spinosad for B. dorsalis and B. cucurbitae. Fly behavior, though, is likely to keep flies from being exposed to maximum possible outdoor light intensities. Comparable levels of population suppression for any of the three species tested here will require a much higher concentration of phloxine B than spinosad in the bait.

Active Ingredients in Cade Oil That Synergize Attractiveness of α-Ionol to Male Bactrocera latifrons (Diptera: Tephritidae)

Abstract Cade oil, a commercially available essential oil produced by destructive distillation of juniper, Juniperus oxycedrus L., twigs, is known to synergize the attractancy of α-ionol to male Bactrocera latifrons (Hendel). Through chemical fractionation and outdoor olfactometer-based bioassays, seven compounds in cade oil were identified that potentially could provide some level of synergism. Tests with sterile laboratory flies showed that four of the seven compounds (eugenol, isoeugenol, 2-methoxy-4-ethylphenol, and 2-methoxy-4-propylphenol), together with a closely related compound not found in cade oil, 2-methoxy-4-methylphenol, are capable of synergizing the attractiveness of α-ionol to male B. latifrons under field conditions. The similarity in structures of these five synergistic compounds shows that there is a response to a core 2-methoxyphenol structure, with fly response little affected by some variation in the composition of the side chain on the number 4 carbon. Because identified synergists were structurally similar, only one compound, eugenol, was selected for further field studies. In an 8-wk weathering test, using released sterile flies, traps baited with α-ionol + eugenol had catches comparable with catches at traps baited with α-ionol + cade oil, with catches generally increased with a higher eugenol loading. For both eugenol and cade oil, catches tended to be better when these synergists were deployed on separate wicks from the α-ionol. Eugenol and α-ionol, however, were unable to provide attraction comparable with that of cade oil and α-ionol in tests with wild fly populations.

Assessment of Corn Pollen as a Food Source for Two Tephritid Fruit Fly Species

Abstract The melon fly, Bactrocera cucurbitae (Coquillett) is a serious pest of cucurbit crops. Although melon fly females oviposit in cucurbit crops, both males and females are frequently associated with a range of nonhost plants, including both crops such as corn (Zea mays C. Linnaeus) and wild plants such as castor bean (Ricinus communis C. Linnaeus) that occur within the cropping area or along the crop borders. This association with nonhost plants has been used for control purposes through the technique of spraying protein baits incorporating a toxicant on these nonhost plants. Association of melon flies to corn has not been reported to be tied to any phenological stage of corn. We report field studies that show that melon flies, as well as oriental fruit flies, B. dorsalis (Hendel), may show increased population levels in corn at the time of, and subsequent to, flowering and pollen shed and suggest that this population increase may be tied to pollen consumption. Before this, pollen had not been reported to be an important food source for the tropical Bactrocera spp.

Assessment of Navel Oranges, Clementine Tangerines, and Rutaceous Fruits as Hosts of Bactrocera cucurbitae and Bactrocera latifrons (Diptera: Tephritidae).

Export of Citrus spp. fruits may require risk mitigation measures if grown in areas with established tephritid fruit fly (Diptera: Tephritidae) populations capable of infesting the fruits. The host status of Citrus spp. fruits is unclear for two tephritid fruit fly species whose geographic ranges have expanded in recent years: melon fly, Bactrocera cucurbitae (Cocquillett), and Bactrocera latifrons (Hendel). In no choice cage infestation studies, B. latifrons oviposited into intact and punctured Washington navel oranges (Citrus sinensis [L.] Osbeck) and Clementine tangerines (C. reticulata L. var. Clementine), but eggs rarely developed to the adult stage. B. cucurbitae readily infested intact and punctured tangerines, and to a lesser extent punctured oranges, but did not infest intact oranges. Limited cage infestation and only a single literature report of field Citrus spp. infestation suggest that risk mitigation of Citrus spp. for B. latifrons is not needed. Risk mitigation options of Citrus spp. for B. cucurbitae, including heat and cold treatments and systems approaches, are discussed.

Field Trapping Bactrocera latifrons (Diptera: Tephritidae) with Select Eugenol Analogs That Have Been Found to Attract Other ‘Non-Responsive’ Fruit Fly Species

Bactrocera latifrons (Hendel) (Diptera: Tephritidae) is a pest fruit fly species native to Oriental Asia which has invaded and established in Hawaii and Tanzania and has been recovered in detection trapping in California. It is largely non-responsive to the male lures cuelure and methyl eugenol. Alpha-ionol + cade oil is a moderately effective male B. latifrons attractant, but is not as attractive as cuelure or methyl eugenol are to other fruit fly species. An improved attractant is therefore desired. With the recent success in finding other non-responsive fruit fly species attracted to isoeugenol, methyl-isoeugenol, or dihydroeugenol in Australia and other countries, we wanted to assess whether B. latifrons might also respond to these “eugenol analogs.” Working with wild B. latifrons populations in Hawaii, we assessed the relative catch of B. latifrons in traps baited with the eugenol analogs with catch in traps baited with alpha-ionol, alpha-ionol + cade oil, or alpha-ionol + eugenol. Catch was significantly higher in traps baited with alpha-ionol + cade oil relative to traps with any of the other baits. There was, though, some male B. latifrons catch in traps baited with dihydroeugenol or isoeugenol but none in traps baited with methyl-isoeugenol.

Natural Field Infestation of Mangifera casturi and Mangifera lalijiwa by Oriental Fruit Fly, Bactrocera dorsalis (Diptera: Tephritidae):

Mango, Mangifera indica (Anacardiaceae), is a crop cultivated pantropically. There are, however, many other Mangifera spp (“mango relatives”) which have much more restricted distributions and are poorly known but have potential to produce mango-like fruits in areas where mangoes do not grow well or could be tapped in mango breeding programs. Because of the restricted distribution of many of the Mangifera spp, there has also been limited data collected on susceptibility of their fruits to infestation by tephritid fruit flies which is important to know for concerns both for quality of production and for quarantine security of fruit exports. Here, we report on natural field infestation by the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae), of two mango relatives native to Indonesia: Mangifera casturi and Mangifera lalijiwa. Rates of infestation of fruits of these two Mangifera spp by tephritid fruit flies have not previously been reported.

Natural Field Infestation of and by Oriental Fruit Fly, (Diptera: Tephritidae)

Mango, Mangifera indica (Anacardiaceae), is a crop cultivated pantropically. There are, however, many other Mangifera spp (“mango relatives”) which have much more restricted distributions and are poorly known but have potential to produce mango-like fruits in areas where mangoes do not grow well or could be tapped in mango breeding programs. Because of the restricted distribution of many of the Mangifera spp, there has also been limited data collected on susceptibility of their fruits to infestation by tephritid fruit flies which is important to know for concerns both for quality of production and for quarantine security of fruit exports. Here, we report on natural field infestation by the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae), of two mango relatives native to Indonesia: Mangifera casturi and Mangifera lalijiwa . Rates of infestation of fruits of these two Mangifera spp by tephritid fruit flies have not previously been reported.