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Larvae of Thagona tibialis (Walker) (Lepidoptera: Erebidae) have been reported to defoliate tropical almond plants, Terminalia catappa L. (Combretaceae), in urban areas of Belo Horizonte (2005), Viçosa (2006), Morro Reuter (2007), and Brasília (2012), Brazil. The origin of T. tibialis is uncertain, but it is now dispersed throughout urban areas of all Brazilian states that have T. catappa. This pest not only has the capacity for high infestation and defoliation rates on T. catappa, but it also can invade houses and cause allergies to humans because of larval hairs and adult scales that are easily dislodged. The objectives of this research were to describe the morphological and ecological characteristics of T. tibialis and to evaluate defoliation of T. catappa by T. tibialis larvae in Viçosa. The specimens collected for this study were a variant of T. tibialis that does not have dark dots on the forewings. Larvae were bluish-white, with orange sub-dorsal stripes and black spots throughout the body. Final instars were approximately 40 mm long. Adults exhibit sexual dimorphism. Females were always white, while males varied from white to light or dark brown. Eggs were round, except for the flattened base and micropyle regions, with the greatest diameters being 0.86 mm long and 0.62 mm wide. Larvae of T. tibialis injured from 3.6% to 98.9% of the leaves on T. catappa trees. From 78.2% to 96.9% of mature leaves and from 3.2% to 21.8% of young leaves were injured, indicating T. tibialis larvae prefer mature leaves of T. catappa.
Searching rate, mutual interference, and killing power were studied for two predator species, Coccinella undecimpunctata L. and Hippodamia tredecimpunctata L. (Coleoptera: Coccinellidae), provided with two prey species, Aphis gossypii (Glover) and Aphis punicae (Shinji) (Hemiptera: Aphididae), under laboratory conditions of 27 ± 2°C and 70 ± 5% RH. The searching rate of larvae and adult female C. undecimpunctata was higher than that of H. tredecimpunctata. Both C. undecimpunctata and H. tredecimpunctata exhibited higher searching rates when fed on A. gossypii than when fed on A. punicae. Larvae and adults of C. undecimpunctata showed higher searching rates than H. tredecimpunctata on both prey species. Mutual interference values for larval stage of both C. undecimpunctata and H. tredecimpunctata were higher than those for adults. For H. tredecimpunctata feeding on A. gossypii, respective values were 0.148, 0.190, 0.118, 0.070, and 0.069 for 1st, 2nd, 3rd, 4th larval instars and adults, respectively; while these values were 0.161, 0.167, 0.218, 0.140, and 0.058 on A. punicae, respectively. In conclusion, our laboratory data suggest that C. undecimpunctata might be a more efficient predator of A. gossypii and A. punicae compared with H. tredecimpunctata.
Formulations of neem (Neemix® 4.5) and spinosad (SpinTor® 2SC) were tested for their effects when mixed with the multicapsid nucleopolyhedrovirus virus (AgMNPV) from the velvetbean caterpillar, Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), for control of pickleworm larvae, Diaphania nitidalis (Stoll) (Lepidoptera: Pyralidae). In these experiments, neem had no additive effects in combination with AgMNPV. However, combinations of AgMNPV with spinosad as low as 1.0 × 10−6 of the original 22.8% suspension showed added efficacy against pickleworm larvae. These biorational insecticides are compatible with nucleopolyhedrovirues and may be useful in management of this primary pest of cucurbits.
The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and the hawthorn spider mite, T. viennensis Zacher, are two of the most important pest mites of apple trees (Rosaceae) in China. Because garlic straw, Allium sativum L. (Amaryllidaceae), is normally dumped on farmland, it potentially represents a cheap and readily available resource for pest management. The contact toxicity and repellent effects of garlic-straw extracts (20, 10, 5, 2.5, and 1.25 g/L) were tested against female adults of T. urticae and T. viennensis in the laboratory. The 20 g/L concentration caused 76.5% and 54.9% mortality 48 h after treatment on T. urticae and T. viennensis, respectively. The toxicity regression equations for garlic-straw extract on T. urticae and T. viennensis 48 h after treatment were y = 1.3 x 3.9 and y = 0.8 x 4.1, and the LC50 values were 7.2 g/L and 13.8 g/L, respectively. Repellency of T. urticae was 95.6% and 65.2% after 24 h at extract concentrations of 10 g/L and 20 g/L, respectively. The other concentrations of the garlic-straw extract had no significant repellent effects. However, each concentration of the garlic-straw extract had significant repellent effects on T. viennensis, and the repellent rates were higher than 90% for each concentration. Garlic straw or extracts from it may have potential uses for the sustainable management of T. urticae and T. viennensis.
Northern bobwhite quail, Colinus virginianus (L.) (Galliformes: Odontophoridae), population declines are well documented, but pinpointing the reasons for these decreases has proven elusive. Bobwhite population declines are attributed primarily to loss of habitat and land use changes. This, however, does not entirely explain population declines in areas intensively managed for bobwhites. Although previous research demonstrates the negative impact of red imported fire ant (Solenopsis invicta Buren) (Hymenoptera: Formicidae) on northern bobwhites, the mechanisms underlying this effect are largely unknown. To meet the protein demands of early growth and development, bobwhite chicks predominantly consume small insects, of which ants are a substantial proportion. Fire ants alter ant community dynamics by often reducing native ant diversity and abundance while concurrently increasing the abundance of individuals. Fire ants have negative effects on chicks, but they are also a large potential protein source, making it difficult to disentangle their net effect on bobwhite chicks. To help investigate these effects, we conducted a laboratory experiment to understand (1) whether or not bobwhites consume fire ants, and (2) how the benefits of this consumption compare to the deleterious impacts of bobwhite chick exposure to fire ants. Sixty bobwhite chicks were separated into two groups of 30; one group was provided with starter feed only and the second group was provided with feed and fire ants. Bobwhite chicks were observed feeding on fire ants. Chicks that fed on fire ants had reduced survival and weight gain. Our results show that, while fire ants increase potential food sources for northern bobwhite, their net effect on bobwhite chicks is deleterious. This information will help inform land managers and commercial bobwhite rearing operations.
Three aphid species (Hemiptera: Aphididae) typically infest winter canola, Brassica napus L. (Brassicales: Brassicaceae), fields in central Oklahoma. They are the turnip aphid, Lipaphis pseudobrassicae (Davis), the cabbage aphid, Brevicoryne brassicae L., and the green peach aphid, Myzus persicae (Sulzer). The expansion of canola acreage in Oklahoma and the ubiquitous nature of aphid infestations in the crop indicate the need to understand the role of natural enemies in controlling aphid infestations. This study determined the parasitoid species attacking aphids in canola during the flowering through pod development growth stages, when aphid populations often build to the point requiring insecticide treatment. Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae) was the dominant parasitoid species. Individuals of all three aphid species were parasitized by D. rapae. Percent parasitism ranged from 0 to 45% depending on aphid species, field, and sample date. An Aphelinus sp. (Hymenoptera: Aphelinidae) was recovered from cabbage aphids from one field on a single sample date. Parasitism of turnip aphid on 20 May 2013 (17–45%) was greater than parasitism for cabbage aphid (2–12%) on that date. Parasitism of green peach aphid was not significantly different from that of cabbage aphid. Parasitism of cabbage aphid and green peach aphid initially increased but then decreased over the course of the study, while parasitism of turnip aphid continued to increase over time.
Reduviid species (Hemiptera: Reduviidae) are efficient predators of the sucking pest Helopeltis antonii Signoret (Hemiptera: Miridae) on cashew, Anacardium occidentale L. (Anacardiaceae). Six species of harpactorine reduviids (Hemiptera: Reduviidae: Harpactorinae) were found feeding on H. antonii in cashew in India. They were Endochus albomaculatus Stål, Epidaus bicolor Distant, Euagoras plagiatus Burmeister, Irantha armipes Stål, Panthous bimaculatus Distant, and Sphedanolestes signatus Distant. These species were reared under laboratory conditions [24–32°C, 89–94% RH, 12:12 h (L: D)] on larvae of the greater wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae). The incubation period, stadial period, nymphal mortality, fecundity, longevity, and sex ratio were studied for these six species. Panthous bimaculatus laid the highest number of eggs and exhibited prolonged incubation period. The incubation period was the shortest in E. plagiatus. The nymphal survival rate was highest in E. plagiatus and lowest in E. albomaculatus. Post-embryonic development from first nymphal instar to adult significantly varied in the six species. The sex ratios of I. armipes, S. signatus, and P. bimaculatus were female-biased, while the sex ratios of E. plagiatus, E. bicolor, and E. albomaculatus were male-biased. Longevities of both female and male adults of the six reduviid species also significantly varied. The aggressiveness of prey capturing and rostral thrusting varied among species. Post-copulatory cannibalism of males by females was observed only in E. bicolor. Numerous desirable biological traits suggest that E. plagiatus can be effectively mass cultured.
Sweet potato leaf curl virus (SPLCV), which is transmitted by the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), species complex, can severely affect yields of sweetpotatoes, Ipomoea batatas (L.) Lam. (Convolvulaceae). This virus is endemic in sweetpotato fields at the U.S. Vegetable Laboratory (USVL), Charleston, S.C. In 2010 and 2011, experiments were conducted to determine if repeated insecticide applications were useful for protecting ‘Beauregard’ sweetpotato from SPLCV infection. In 2010, plots were untreated or treated twice weekly with imidacloprid. A row of SPLCV-infected sweetpotato genotype ‘W-258’ was planted between ‘Beauregard’ plots to serve as a source of whiteflies and SPLCV. A similar test was performed in 2011, except that the plots were sprayed only once a week, and a rotation of four insecticides (in the order of imidacloprid, pyriproxyfen, acetamiprid, and pymetrozine) was used. Yellow sticky traps were placed horizontally in the center of each plot at canopy height to monitor whitefly abundance. Leaf samples were taken every other week to test for SPLCV infection using real-time polymerase chain reaction (PCR) techniques. Over the two-year period, there were significantly fewer whiteflies on sticky cards in the sprayed treatment for only two of the 36 weekly samples, indicating that insecticides were largely ineffective in reducing whitefly populations moving into these plots. By the end of the growing season each year, all of the unsprayed plots were infected with SPLCV as determined by real-time PCR. However only about one-half of the sprayed plots were infected with SPLCV. This indicates that insecticides could be useful in protecting sweetpotatoes from SPLCV. The insecticide sprays would likely be more effective under normal production practices where sources of the virus are not in such close proximity to the uninfected crop.