ARSTRACT Spatial genetic variability of the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), was studied by collecting samples from 31 locations in the United States, Argentina, Panama, and Puerto Rico, and then using amplified fragment length polymorphism to detect genetic variation. Analysis of molecular variance showed significant genetic variation in fall armyworm among all (28%) sample locations and individuals within (71%) sample locations; genetic variation of fall armyworm was minimal between sample locations grouped into regions. The pairwise fixation index (FST) comparisons showed significant genetic differentiation (0.288) among the 31 locations. However, dendrograms of results from cluster analysis did not provide support of a high level of genetic structuring among regions. The isolation by distance analysis for all sample locations showed the absence of significant correlation between genetic dissimilarity and geographic distance except for fall armyworm samples collected within Argentina. Moreover, the estimate of modest gene flow (Nm >1) may prevent gene fixation within regions. These results indicate that fall armyworm shows little genetic differentiation and high genetic diversity over its range, important information for the development of management strategies and monitoring the development of resistance to management techniques.
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Lepidopteran stem borers are the main pests of cereals in Ethiopia. In recent years, habitat management techniques, which aim at increasing plant biodiversity through mixed cropping, have gained increased attention in stem borer control. In the present study, the profitability of mixed cropping of maize with haricot beans at different ratios and the effect on infestation of maize by stem borers, yield and borer parasitism were studied in Melkassa and Mieso, Ethiopia, in a field experiment under natural infestation. In Melkassa, pest infestations were too low for the cropping system to affect pests, plant damage and yields significantly, whereas in Mieso, where the pest densities were high, intercropping of maize with beans at ratios of 1:1 to 2:1 significantly decreased borer densities compared with pure maize stands. Chilo partellus (Swinhoe) and Cotesia flavipes. (Cameron) were the major stem borer and parasitoid species, respectively, recorded both at Melkassa and Mieso. Borer parasitism was higher at Mieso than at Melkassa and tended to increase with the increase of the haricot bean ratio in the intercropping system. Land equivalent ratios of >1 indicated higher land use efficiency in mixed compared with sole cropping, even if pest densities were low.
Post application persistence of two entomopathogenic nematode (EPN) species, Heterorhabditis bacteriophora strain HK3 and Steinernema carpocapsae strain DD136, was studied against soil-dwelling late second instar larvae (L2) of western flower thrips (WFT) Frankliniella occidentalis (Thysanoptera: Thripidae). The nematodes were applied at 200 and 400 infective juveniles (IJ) cm −2 , and L2 WFT were introduced at 0 (same day), 3, 6, 9 or 12 days after nematode application (DANA). Heterorhabditis bacteriophora caused higher thrips mortality than S. carpocapsae in most of the tests and both species persisted for at least 6 days, causing WFT mortality of up to 76 and 37.8%, respectively. In a separate experiment, H. bacteriophora and S. feltiae (Filipjev) Sylt were applied at 200 and 400 IJ cm −2 once (10, 15, or 20 days) or twice (10 and 15, 10 and 20, or 15 and 20 days) after introduction of ten female and two male WFT adults onto bean plants (Phaseolus vulgaris). An early repeated application (10 and 15 days after adult WFT release) of H. bacteriophora at 200 IJ cm −2 resulted in significantly lower numbers WFT than a single applications at 400 IJ cm −2 indicating that better WFT control can be achieved if the same concentration is split over time. However, an early application (10 days after adult WFT release) of H. bacteriophora at 400 IJ cm −2 controlled WFT better than late applications, indicating that time of EPN application is additionally very crucial in WFT control. For S. feltiae, higher WFT mortality was recorded when nematodes were repeatedly applied on days 10 and 15 than in any other applications at a given concentration. Thus, an early application of an efficient and relatively more persistent nematode species, e.g., H. bacteriophora HK3, at a lower concentration but in a repeated manner, can result in higher thrips control than a single application at the higher concentration.
Habitat management techniques to control maize stem borers were tested in eastern (Melkassa and Mieso) and western (Sibu-Sire) Ethiopia. These techniques consisted of using mixed cropping of maize with haricot beans at different maize:bean ratios and a ''push-pull'' (PP) strategy utilizing Napier grass as a trap plant around maize plots as the ''pull'' and Desmodium in between maize rows as a deterrent or ''push''. In Melkassa, pest infestations were too low for the cropping system to significantly affect pests, plant damage and yields while in Mieso, where the pest densities were high, intercropping of maize with beans at ratios of 1:1 to 2:1 significantly decreased borer densities compared to pure maize stands. Chilo partellus (Swinhoe) and Cotesia flavipes (Cameron) were the major stem borer and parasitoid species, respectively, recorded both at Melkassa and Mieso. Borer parasitism was higher at Mieso than at Melkassa and it tended to increase with the increase of haricot bean ratio in the intercropping system. Land equivalent ratios of >1 indicated higher land use efficiency in mixed compared to sole cropping, even if pest densities were low. Establishment of Desmodium and Napier grass in PP trials varied from site to site, and poor establishment was observed in plots with low soil pH. Where yields varied significantly, they were lower in the PP than the sole maize plots. Borer densities were low and digitalcommons.unl.edu B e l ay & F o s t e r i n C r o p P r o t e c t i o n 2 9 ( 2 0 1 0 ) 2 mostly not affected by the cropping system. However, in the second season when borer density was relatively high, higher levels of infestation and leaf feeding scores were recorded in the control than push-pull plots.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.