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The sugarcane aphid, Melanaphis sacchari (Zehntner) (Heteroptera: Aphididae), was recently recognized as a pest of grain sorghum, Sorghum bicolor (L.) Moench, in the southeastern United States. The objectives of the study reported herein were to evaluate the suitability of using a consensus-based scouting network and determine the timing of insecticide applications for management of sugarcane aphid in grain sorghum. The timing of insecticide applications was (1) application at 25 aphids per leaf, (2) application at 50 aphids per leaf, (3) a delayed application 1 week after occurrence of 50 aphids per leaf, or (4) not treated. Results showed that a single application of flupyradifurone at 15.4 g(AI)/ha consistently reduced populations to nearly zero for the remainder of the season, while aphid populations in the nontreated plots reached a peak of 300–400 aphids per leaf. Aphid populations on the upper leaves reached 50 aphids per leaf in nontreated plots 1 week after reaching the treatment threshold on the lower leaves. All plots receiving insecticide applications had similar estimated yields, which were >5 times greater than yields in nontreated plots. Results from the consensus-based scouting network showed that first detections and reported first commercial applications generally occurred within 1 week (range of 3–11 d) of the actual populations quantified in the research trials. These data suggest that initiating scouting for sugarcane aphid populations following notification of activity in the area through consensus reporting would provide adequate warning for preventing economic losses to sugarcane aphid.
The sugarcane aphid, Melanaphis sacchari (Zehntner), is an economically important invasive insect pest of sorghum, Sorghum bicolor (L.) Moench, production in the southern United States. Studies were conducted to: (1) assess the fecundity of Lysiphlebus testaceipes (Cresson) parasitizing M. sacchari in the greenhouse, and (2) examine the temporal synchrony between L. testaceipes and M. sacchari in the field during 2017 and 2018. Results indicate that after 96 h, the number of M. sacchari increased approximately 90-fold from a single adult in the greenhouse study. The percentage of mummification observed in the greenhouse study was 15.2 ± 3.3%. Of those mummies, L. testaceipes adults emerged from 88.7 ± 4.4%, with 38.6 ± 8.4% of those males. Field observations showed that L. testaceipes appeared in the sentinel fields in late July to August. The percentage of mummies observed in the June- and July-planted plots of 2017, and June-planted plots of 2018 were 4.5 × 10–4 ± 1.5 × 10–4%, 7.4 × 10–4 ± 4.4 × 10–4%, and 4.4 × 10–5 ± 1.7 × 10–5%, respectively. Even though parasitization of M. sacchari by L. testaceipes was observed in both field and greenhouse, the lack of wasps before late July and low rate of parasitization in the field suggest that this species is not well synchronized with M. sacchari populations. Additional natural enemies (e.g., other parasitoids, predators, and entomopathogens) or other adaptations will be necessary before this pest is managed using biological control in Georgia.
This article presents the status of Anopheles mosquito species and malaria parasite occurrences in North Africa. Because information is dispersed among numerous sources, we assimilated the information into a synthesis of the current status and potential of the disease in the region. Malaria transmission has been interrupted in North Africa, but the risk of re-emergence remains high. Indeed, competent vectors are present across the region, and the number of imported cases is increasing. The dominant parasite among imported cases is Plasmodium falciparum Welch in Tunisia, Algeria, and Morocco and Plasmodium vivax Grassi & Feletti in Libya and Egypt. In northwestern Africa (Tunisia, Algeria, Morocco), vectors formerly responsible for malaria transmission are Anopheles labranchiae Falleroni and Anopheles sergenti Theobald, whereas Anopheles pharoensis Theobald and Anopheles sergenti are the main malaria vectors in Egypt. Anopheles multicolor Cambouliu and An. sergenti are the major potential vectors of malaria transmission in Libya. In 2014, malaria caused by P. falciparum (1 case) and P. vivax (23 cases) were documented in Aswan Governorate, Egypt, indicating probable re-emergence of transmission, although these cases are considered as imported. In Algeria, local cases caused by P. falciparum in 2013 suggested probable re-emergence of malaria transmission. Four cases of airport malaria were noted for the first time in Tunisia during summer 2013 and were caused by P. falciparum. The presence of competent malaria vector species, together with high numbers of imported malaria cases each year, underscores the risk of re-emergence of autochthonous transmission in all countries of North Africa.
The transmission of Leishmania tropica (Wright) (Protozoa: Sarcomastigophora: Trypanosomatidae) was studied in a historic focus of the cutaneous leishmaniasis disease in southeast Tunisia. The sandfly Phlebotomus sergenti (Parrot) (Diptera: Psychodidae), the confirmed vector of L. tropica in humans, was the most abundant Phlebotomus species found in homes. Phlebotomus chabaudi s.l. (Croset) was the dominant species in the natural rocky habitats favored by the North African gundi, Ctenodactylus gundi (Rothman), which is a known putative rodent reservoir of L. tropica. Leishmania tropica MON-8 (Rioux, Lanotte and Pratlong) was the species isolated and identified from gundi, humans, and P. sergenti in the disease focus area. Based on these results, the North African gundi may serve at least as a maintenance host for L. tropica in this area of southeast Tunisia, even though L. tropica is commonly stated to be anthroponotic. These results also suggest that there may be two transmission cycles of L. tropica in this region, with P. sergenti transmitting L. tropica among humans inside and in peridomestic habitats and P. chabaudi s.l. transmitting the disease agent among gundi in their natural habitats. Phlebotomus chabaudi s.l. also may transmit to humans when humans venture into areas inhabited by gundi host reservoirs.
The Hybrid Single Particle Lagrangian Integrated Trajectory Model and meteorological graphics software (Grads and ArcGIS) were used to analyze source areas and migratory trajectories of a population of Locusta migratoria migratoria (L.) (Orthoptera: Acrididae) in the Tacheng region of Xinjiang, China that borders with eastern Kazakhstan. The source areas of these locusts migrating into the Tacheng region are distributed near Lake Alakol, Lake Zaisan, eastern Lake Balkhash, the Irtysh River, and Ayaguz River in Kazakhstan. Locusts follow nine migratory trajectories in their invasion of Tacheng. On the respective migration dates, a westerly wind, northerly wind, or northwesterly wind, the latter being the prevailing wind direction, occurred at 950 hPa over the source areas. At migration heights of 300, 500, and 800 m above mean sea level, the air temperatures ranged from 25.0–31.0°C, 21.5–26.0°C, and 21.0–25.0°C, respectively. The concept of insect migration pattern in Central Asia is proposed, but a series of theoretical and empirical studies will be needed to provide support for this postulation.
The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is a major pest of cotton (Gossypium spp.) that overwinters in an adult diapause. Diapause is primarily induced by adult diet, but late-season cotton, postharvest regrowth, and volunteer cotton also support reproduction, especially in the subtropics and tropics where conditions permit cotton fruiting during the fallow season. When cotton plants escape crop destruction efforts they may produce fruit and become heavily infested by overwintered weevils. The ecological implications of these plants to survival of overwintered weevils have not been studied. We examined the physiological and survival responses of trap-captured overwintered weevils to starvation and to square (reproduction-promoting) and boll (diapause-inducing) diets. Few newly captured overwintered weevils exhibited fat body hypertrophy or gonadal characters of diapause. Square feeding rapidly induced a high level of reproductive development in both weevil sexes but little fat accumulation. Compared with the square diet, a boll diet promoted more gradual reproductive development in female weevils, but also stimulated in both weevil sexes the development of hypertrophied fat bodies similar to those associated with diapause. Although diapause was not reinduced by the boll diet, resulting accumulations of fat allowed substantially greater host-free longevity compared with overwintered weevils that were not fed. The contributions of diapause and fallow-season reproduction to boll weevil overwintering survival are commonly recognized. Findings of this study identify an additional mechanism by which overwintered boll weevils may utilize fallow-season cotton to enhance survival, and reinforce the importance of eliminating cotton during the fallow season.
The effects of long-term laboratory rearing on the performance of Telenomus remus Nixon (Hymenoptera: Platygastridae), an egg parasitoid of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), were investigated by comparing a laboratory-reared strain with a wild strain of the parasitoid. Restriction fragment length polymorphism revealed no genetic variation between the two strains. The wild strain exhibited a higher level of egg parasitism, a longer reproductive period, and a higher level of fecundity than did the laboratory-reared strain while developmental time and female longevity did not differ between the strains. Furthermore, host search efficiency and flight ability were superior in the wild strain compared to the laboratory strain, but oviposition behavior did not differ. Our results indicate that, over time, laboratory rearing may select for individuals that are less fertile, less aggressive, and have lower flight activity than their wild counterparts, which also exhibit a higher parasitism performance and superior potential for population increase in a shorter period of time. Implications for biological control using T. remus and strategies to avoid losses of parasitism efficiency are discussed.
In 2013–2015, Mexico implemented a program of exploration and evaluation of native parasitoids of the spotted-wing drosophila Drosophila suzukii (Matsumura). Those efforts identified Pachycrepoideus vindemmaie Rondani and Trichopria drosophilae Perkins as native parasitoid species. Biological and population parameters, including oviposition preference on locally occurring species of Drosophilidae, were subsequently studied and quantified. Trichopria drosophilae required fewer days than P. vindemmiae in the larval stage, pupal stage, and development time of egg to adult, as well as exhibitied a higher intrinsic rate of increase (rm), finite rate of increase (λ), mean generation time (T), and doubling time (Dt), but its net reproduction rate (Ro) was lower. On the other hand, both parasitoids showed no differences in female longevity, sex ratio, and duration of egg stage. In the oviposition preference tests, D. suzukii pupae were equally preferred as those of Zaprionus indianus Gupta, but more than Drosophila melanogaster Meigen. These results indicate that local T. drosophilae has a higher potential to contribute to the ecological management of the invasive D. suzukii in Mexico than P. vindemmiae.
Several isolates of the recently described bacterial species Chromobacterium phragmitis Blackburn et al. were obtained from water collected from low-salinity tidal marshes in Maryland and Virginia. Bacteria were cultured in a liquid medium and applied to artificial diets in the laboratory. One of two Maryland isolates, IIBBL 113-1, was highly toxic to larvae of the cabbage looper Trichoplusia ni (Hübner) and the diamondback moth, Plutella xylostella (L.). The other Maryland isolate, IIBBL 112-1T, and the Virginia isolates were less toxic to these species. Maryland isolates were toxic to larvae of the seedcorn maggot Delia platura (Meigen), while a Virginia isolate, IIBBL 274-1, was of intermediate toxicity against D. platura. The C. phragmitis isolate IIBBL 113-1 was toxic to adults of the red flour beetle Tribolium castaneum (Herbst), while other C. phragmitis isolates had no activity against this species.
The codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is a key “fruit-feeding” pest of apples and is known for developing resistance to various insecticidal products applied in apple orchards. Laboratory studies were conducted to determine insecticide resistance in codling moth populations collected from various apple orchards in Pennsylvania. In particular, male moths of C. pomonella were collected from commercial and abandoned fruit orchards and were tested for their sensitivity levels to azinphos-methyl and methomyl via adult topical bioassays. Larval sensitivity also was examined for different insecticides (e.g., acetamiprid, novaluron, rynaxypyr) via diet-surface topical bioassays. Adult C. pomonella populations expressed significant differences in their sensitivity to azinphos-methyl and methomyl. Concurrent estimates of azinphos-methyl insecticide effectiveness (i.e., adult topical assays) of moths in monitoring traps showed increased tolerance in individuals captured in commercial orchards rather than in abandoned orchards. Results of larval bioassays showed differences in sensitivity to various insecticide compounds as well as differences between compounds based on the timing of mortality. After the initial assessment, however, all insecticides (except fenpropathrin) exhibited greater toxicity with increasing time.
The efficacy of D-glucose labeled with 13C6 (D-glucose-13C6) in the study of amino acid metabolism in insects was determined by incorporating either D-glucose-13C6 or unlabeled D-glucose into larval and adult diets of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Feeding treatments were: (a) labeled glucose diet for larvae + unlabeled glucose diet for adults; (b) unlabeled glucose diet for larvae + labeled glucose diet for adults; (c) labeled glucose diet for larvae + labeled glucose diet for adults; and (d) unlabeled glucose diet for larvae + unlabeled glucose diet for adults. Amino acid content of extracts from unmated adults and mated adults was determined with gas chromatography-mass spectrometry (GC-MS). L-alanine, L-aspartic acid, L-cysteine, L-glutamic acid, L-glycine, L-isoleucine, L-leucine, L-methionine, L-proline, L-phenylalanine, L-serine, L-threonine, L-tyrosine, and L-valine were identified from the insect extracts. In the treatment that fed unlabeled glucose larval and adult diets (control), amino acid content was lower after mating than before mating except for L-cysteine (e.g., 13-fold increase). Amino acid content in insects fed D-glucose-13C6 also decreased after mating except for L-valine, L-leucine, L-tyrosine, and L-isoleucine, all of which remained comparatively equal before and after mating, and L-threonine which increased almost 12-fold after mating. Only trace amounts of L-tyrosine and L-isoleucine were detected before and after mating in those fed labeled diets. These results suggest that stable isotopes can be used as labels for insect metabolic studies.
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