Development of a Low-Cost and Effective Trapping Device for Apple Maggot Fly (Diptera: Tephritidae) Monitoring and Control in Mexican Commercial Hawthorn Groves.

Few efforts have been made in Mexico to monitor Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) in commercial hawthorn (Crataegus spp.) crops. Therefore, the main objectives of this study were to evaluate infestation levels of R. pomonella in feral and commercial Mexican hawthorn and to assess the efficacy of different trap-lure combinations to monitor the pest. Wild hawthorn was more infested than commercially grown hawthorn at the sample site. No differences among four commercial baits (Biolure, ammonium carbonate, CeraTrap, and Captor + borax) were detected when used in combination with a yellow sticky gel (SG) adherent trap under field conditions. However, liquid lures elicited a slightly higher, although not statistically different, capture. Cage experiments in the laboratory revealed that flies tended to land more often on the upper and middle than lower-bottom part of polyethylene (PET) bottle traps with color circles. Among red, orange, green, and yellow circles attached to a bottle trap, only yellow circles improved fly captures compared with a colorless trap. A PET bottle trap with a red circle over a yellow background captured more flies than a similar trap with yellow circles. An SG adherent yellow panel trap baited with ammonium carbonate was superior to the improved PET bottle trap (red over a yellow background) baited with different liquid proteins, but a higher proportion of females and no differences in fly detection were measured in PET traps baited with protein lures. These trials open the door for future research into development of a conventional nonadherent trap to monitor or control R. pomonella.

Niche differentiation and colonization of a novel environment by an asexual parasitic wasp.

How do asexual taxa become adapted to a diversity of environments, and how do they persist despite changing environmental conditions? These questions are linked by their mutual focus on the relationship between genetic variation, which is often limited in asexuals, and the ability to respond to environmental variation. Asexual taxa originating from a single ancestor present a unique opportunity to assess rates of phenotypic and genetic change when access to new genetic variation is limited to mutation. Diachasma muliebre is an asexual Hymenopteran wasp that is geographically and genetically isolated from all sexual relatives. D. muliebre attack larvae of the western cherry fruit fly (Rhagoletis indifferens), which in turn feed inside bitter cherry fruit (Prunus emarginata) in August and September. R. indifferens has recently colonized a new host plant with an earlier fruiting phenology (June/July), domesticated sweet cherries (P. avium), and D. muliebre has followed its host into this temporally earlier niche. We tested three hypotheses: 1) that all D. muliebre lineages originate from a single asexual ancestor; 2) that different D. muliebre lineages (as defined by unique mtDNA haplotypes) have differentiated on their ancestral host in an important life-history trait, eclosion timing; and 3) that early-eclosing lineages have preferentially colonized the new sweet cherry niche. We find that mitochondrial COI and microsatellite data provide strong support for a single ancestral origin for all lineages. Furthermore, COI sequencing revealed five mitochondrial haplotypes among D. muliebre, and individual wasps possessing one distinctive mitochondrial haplotype (haplotype II) eclosed as reproductive adults significantly earlier than wasps with all other haplotypes. In addition, this early-eclosing lineage of D. muliebre is one of two lineages that have colonized the P. avium habitat, consistent with the preferential colonization hypothesis. These data suggest that D. muliebre has evolved adaptive phenotypic variation despite limited genetic variation, and that this variation has subsequently allowed an expansion of some wasps into a novel habitat. The D. muliebre system may allow for in-depth study of adaptation and long-term persistence of asexual taxa.

A field test for host fruit odour discrimination and avoidance behaviour for Rhagoletis pomonella flies in the western United States.

Prezygotic isolation due to habitat choice is important to many models of speciation-with-gene-flow. Habitat choice is usually thought to occur through positive preferences of organisms for particular environments. However, avoidance of non-natal environments may also play a role in choice and have repercussions for post-zygotic isolation that preference does not. The recent host shift of Rhagoletis pomonella (Diptera: Tephritidae) from downy hawthorn, Crataegus mollis, to introduced apple, Malus domestica, in the eastern United States is a model for speciation-with-gene-flow. However, the fly is also present in the western United States where it was likely introduced via infested apples ≤ 60 years ago. R. pomonella now attacks two additional hawthorns in the west, the native C. douglasii (black hawthorn) and the introduced C. monogyna (English ornamental hawthorn). Flight tunnel tests have shown that western apple-, C. douglasii- and C. monogyna-origin flies all positively orient to fruit volatile blends of their respective natal hosts in flight tunnel assays. Here, we show that these laboratory differences translate to nature through field-trapping studies of flies in the state of Washington. Moreover, western R. pomonella display both positive orientation to their respective natal fruit volatiles and avoidance behaviour (negative orientation) to non-natal volatiles. Our results are consistent with the existence of behaviourally differentiated host races of R. pomonella in the west. In addition, the rapid evolution of avoidance behaviour appears to be a general phenomenon for R. pomonella during host shifts, as the eastern apple and downy hawthorn host races also are antagonized by non-natal fruit volatiles.

Effects of aerial spray volume, coverage, and sabadilla on Scirtothrips perseae (Thysanoptera: Thripidae).

Helicopter applications using sabadilla (27-57 g [AI]/ha and 11.1-23.7 kg/ha sugar bait) in different volumes of water were made on avocado against Scirtothrips perseae Nakahara in Ventura County, CA. On small (2.8 m tall) trees, volumes of 374 and 795 liter/ha resulted in 3-18% and 19-43% spray coverage, respectively, on water-sensitive papers. On large (6.9-8.4 m tall) trees, these volumes resulted in only 1-3% and 6-11% coverage, respectively. On small trees, sabadilla in 374 liter/ha significantly reduced numbers of larvae 3 and 6 d after treatment (DAT). In contrast, on large trees, 374 liter/ha did not reduce larval numbers and was less effective than 561-1,964 liter/ha from 3-11 DAT. However, volumes of 1,543 and 1,964 liter/ha did not increase efficacy compared with 1,169 liter/ha. The results indicate that large trees require sabadilla in higher spray volumes for control of S. perseae, making applications on large trees more costly. The extra costs may not result in larval control beyond 11 d, making it especially critical to properly time applications on large trees.

Effects of aerial spray volume, coverage, and abamectin on Scirtothrips perseae (Thysanoptera: Thripidae).

Helicopter applications using abamectin in different spray volumes were made against Scirtothrips perseae Nakahara in Ventura County, CA. On small (2.2 m tall) trees, spray coverage on water-sensitive papers was 24-48% and 43-97% for 468 and 935 liter/ha volume treatments, respectively. On large (6.2-8.1 m tall) trees, spray coverage was lower and quite variable, from 1 to 28% and 10 to 70% for 468 and 935 liter/ha treatments, respectively. On small trees, 468, 701, and 935 liter/ha with a high abamectin rate (26 g [AI]/ha) were equally effective against larvae from 13 to 27 d after treatment (DAT). On medium (4.2 m tall) trees, 468 and 935 liter/ha with the high rate were equally effective from 23 to 113 DAT. On large (6.5-8.1 m tall) trees, 468 and 935 liter/ha with a low abamectin rate (13 g [AI]/ha) were ineffective in three tests. In a fourth large (6.8 m tall) tree test, 468 and 935 liter/ha with the high rate were effective at 3 and 37 DAT. In a fifth large (6.2 m tall) tree test, 468-1,403 liter/ha with the high and 935 liter/ha with the low rate were equally effective 2-22 DAT. After all effective treatments, thrips numbers were lower than in controls for 1-3 mo. However, stable and highest reductions in populations were sometimes delayed until 20-23 DAT even when coverage was high. The variability in spray coverage on the lower levels of large trees and the delayed effect may explain inconsistencies in the reporting of or in actual aerial application results.

Mechanism of extracellular ATP- and adenosine-induced apoptosis of cultured pulmonary artery endothelial cells.

Apoptosis may be important in the exacerbation of endothelial cell injury or limitation of endothelial cell proliferation. We have found that extracellular ATP (exATP) and adenosine cause endothelial apoptosis and that the development of apoptosis is linked to intracellular metabolism of adenosine [Dawicki, D. D., D. Chatterjee, J. Wyche, and S. Rounds. Am. J. Physiol. 273 (Lung Cell Mol. Physiol. 17): L485-L494, 1997]. In the present study, we investigated the mechanism of this effect. We found that exATP, adenosine, and the S-adenosyl-L-homocysteine (SAH) hydrolase inhibitor MDL-28842 caused apoptosis and decreased the ratio of S-adenosyl-L-methionine to SAH compared with untreated control cells. Using release of soluble [3H]thymidine as a measure of DNA fragmentation, we found that the effect of adenosine on soluble DNA release was potentiated by coincubation with homocysteine. These results suggest that the mechanism of exATP- and adenosine-induced endothelial cell apoptosis involves inhibition of SAH hydrolase. exATP-induced apoptosis was enhanced by an inhibitor of adenosine deaminase, whereas exogenous adenosine-induced apoptosis was partially inhibited by an adenosine deaminase inhibitor. These results suggest that adenosine deaminase may also be involved in the mechanism of adenosine-induced endothelial cell apoptosis. Adenosine and MDL-28842 caused intracellular acidosis as assessed with the fluorescent probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. The cell-permeant base chloroquine prevented adenosine-induced acidosis but not apoptosis. Thus, although intracellular acidosis is associated with adenosine-induced apoptosis, it is not necessary for this effect. We speculate that exATP- and adenosine-induced endothelial cell apoptosis may be due to an inhibition of methyltransferase(s) activity. Purine-induced endothelial cell apoptosis may be important in limiting endothelial cell proliferation after vascular injury.

Behaviors associated with egg and parasite deposition by gravid and Lambornella clarki-infected Aedes sierrensis.

Egg- and Lambornella clarki-deposition behaviors by the treehole mosquito Aedes sierrensis were monitored inside laboratory deposition containers using a video camera. Gravid and infected mosquitoes were seen probing the substrate and in the water with their abdominal tips. Both eggs and parasites were recovered from the containers. Gravid and infected mosquitoes performed the same or similar types of behaviors, but gravid mosquitoes spent significantly higher percentages of time engaged in exploratory probing movements than did infected mosquitoes. Gravid mosquitoes also spent significantly less percentage time resting and more percentage time grooming than did infected mosquitoes. It appears that, compared to gravid mosquitoes, infected mosquitoes spent less relative time in certain behaviors that may not benefit the parasite.

Free flight of Lambornella clarki-infected, blood-fed, and gravid Aedes sierrensis (Diptera: Culicidae).

Total flight times and flight numbers of Lambornella clarki Corliss & Coats-infected and uninfected nonblood-fed (control), blooded, and gravid Aedes sierrensis (Ludlow) were monitored in laboratory experiments using a free-flight acoustical system. Mean flight time and number of males were not affected by L. clarki infection, but mean flight time of infected females was significantly less than those of control and gravid females. Flight numbers of infected and control females did not differ significantly. Blood feeding initially suppressed flight, but flight dramatically increased with increasing time after the blood meal. There was an increase in flight that corresponded to increased parasite presence inside the ovaries in young, but not older, females.

Tethered flight capabilities and survival of Lambornella clarki-infected, blood-fed, and gravid Aedes sierrensis (Diptera: Culicidae).

Flight capabilities and survival of Lambornella clarki Corliss & Coats-infected, control, blood-fed, and gravid Aedes sierrensis (Ludlow) were monitored using a tethered flight mill system and by recording deaths at various times after initiation of these tests. Flight capabilities of infected and control males as measured by total number of flights, total time spent flying, total distance flown, average flight speed, and percentage time flying were similar. Flight capabilities of females with parasites, with fresh blood meals, and with fully developed eggs did not differ significantly. Flight capabilities of 1- to 2-d-old starved infected and starved control females also did not differ significantly. Although flight capabilities did not differ significantly, infected males died earlier than control males. For females, blooded individuals lived longest, followed by controls, and then gravid and infected individuals. These results and results of glycogen analyses of mosquito thoraces indicate that the parasite primarily affected resources needed by the mosquito for survival and not those for flight.

Diel sugar-feeding and host-seeking rhythms in mosquitoes (Diptera: Culicidae) under laboratory conditions.

Mosquito sugar-feeding and host-seeking rhythms were recorded in the laboratory using remote sensors. In all five species studied, the two rhythms were nearly synchronous. In Anopheles quadrimaculatus Say, Culex quinquefasciatus Say, and Aedes triseriatus (Say), host-seeking activity increased slightly earlier than sugar feeding in the evening. The evening sugar-feeding period was longer than the evening host-seeking period in Aedes aegypti (L.), but the two periods were of similar duration in Aedes albopictus (Skuse). In the morning, the only clear difference between the two behaviors occurred in Cx. quinquefasciatus, which had a host-seeking peak but lacked a sugar-feeding peak. When exposed concurrently to both host and sugar stimuli, sugar feeding practically ceased in Ae. albopictus and Ae. aegypti. In the presence of host stimuli, the sugar-feeding rhythms of An. quadrimaculatus, Cx. quinquefasciatus, and Ae. triseriatus differed from those obtained in the absence of host stimuli by having an earlier onset of evening activity, a relatively smaller evening activity peak, and a more irregular activity pattern during early scotophase, respectively. We concluded that inseminated, nulliparous females have nonspecific appetitive feeding periods, and that the order in which sugar and blood are sought largely may be a function of factors other than differences in diel rhythms.

Simultaneous field comparison of evening temporal distributions of nectar and blood feeding by Aedes vexans and Ae. trivittatus (Diptera: Culicidae) in Ohio.

Nectar- and blood-feeding time distributions of Aedes vexans (Meigen) and Aedes trivittatus (Coquillett) were determined from collections of mosquitoes attempting to feed on flowers and human bait during six nights in an Ohio field. Distributions of nectar and blood feeding were different in Ae. vexans on three of five nights when analyses were possible, and they were different in pooled Ae. trivittatus data. Higher proportions of blood feeders appeared in earlier time intervals, but both nectar and blood feeding had broadly overlapping peaks and distributions. These results suggest that the nectar- and blood-feeding rhythms are probably in phase in Ae. vexans females, and that possibly the earlier onset of blood feeding reflects a strategy taking advantage of blood when it is available. Male Ae. vexans had later peak nectar-feeding times than females. Nectar feeding in males may be delayed by mating activity early in the activity period.

Tests of Sabethes cyaneus leg paddle function in mating and flight.

Both sexes of the mosquito Sabethes cyaneus have conspicuous midleg paddles of unknown function. These paddles are displayed prominently by males during courtship. However, we found that paddle removal reduced successful mating of females, not males. Males without paddles approached and courted females normally, but females without paddles were rarely approached by males. Paddle removal appeared not to alter flight, and paddleless females oviposited in the manner characteristic of Sabethes, suggesting that the paddles do not aid in hovering or rapid reverse flight. We conclude that paddles of females are used in attracting males but that their function in males remains undetermined.