First report and population dynamics of the Tobacco Thrips, Thrips parvispinus (Karny) (Thysanoptera: Thripidae) on ridged gourd, Luffa acutangula (L.) Roxy in selected export fields in southern Ghana

Thrips attack several crops causing considerable economic damage. To prevent this damage, sticky traps can be used to monitor their population for the timely execution of management interventions. Ridged gourd or turia (Luffa acutangula (L.) Roxy) is an important Asian vegetable exported regularly to the European Union market from Ghana. However, this vegetable has been intercepted severally at the point of entry because of thrips infestation. The current study is aimed at identifying and monitoring thrips population on turia using blue and yellow sticky traps in six export vegetable production sites in Ghana for two consecutive seasons and three trapping periods. The results showed that Thrips parvispinus (Karny) (Thysanoptera: Thripidae) was the commonest and only species of thrips found attacking turia. The highest and lowest mean number of thrips were recorded from the blue and yellow sticky traps during the dry and the late part of the major rainy seasons, respectively. Thrips population build-up was observed to reach its peak at the flowering stage of the crop. This is the first report of T. parvispinus in Ghana. The implications of this finding on the export of turia to the EU market has been discussed

Self-oscillation

Physicists are very familiar with forced and parametric resonance, but usually not with self-oscillation, a property of certain dynamical systems that gives rise to a great variety of vibrations, both useful and destructive. In a self-oscillator, the driving force is controlled by the oscillation itself so that it acts in phase with the velocity, causing a negative damping that feeds energy into the vibration: no external rate needs to be adjusted to the resonant frequency. The famous collapse of the Tacoma Narrows bridge in 1940, often attributed by introductory physics texts to forced resonance, was actually a self-oscillation, as was the swaying of the London Millennium Footbridge in 2000. Clocks are self-oscillators, as are bowed and wind musical instruments. The heart is a "relaxation oscillator," i.e., a non-sinusoidal self-oscillator whose period is determined by sudden, nonlinear switching at thresholds. We review the general criterion that determines whether a linear system can self-oscillate. We then describe the limiting cycles of the simplest nonlinear self-oscillators, as well as the ability of two or more coupled self-oscillators to become spontaneously synchronized ("entrained"). We characterize the operation of motors as self-oscillation and prove a theorem about their limit efficiency, of which Carnot's theorem for heat engines appears as a special case. We briefly discuss how self-oscillation applies to servomechanisms, Cepheid variable stars, lasers, and the macroeconomic business cycle, among other applications. Our emphasis throughout is on the energetics of self-oscillation, often neglected by the literature on nonlinear dynamical systems.Comment: 68 pages, 33 figures. v4: Typos fixed and other minor adjustments. To appear in Physics Report

Morphometric diagnosis of Glossina palpalis (Diptera: Glossinidae) population structure in Ghana

Abstract Objective This study aimed to identify isolated population(s) of Glossina palpalis in Ghana using geometric morphometrics to evaluate variations in wing-shape and size between populations of the fly from three regions. Results Wing shape of G. palpalis tsetse flies from the Northern, Western and Eastern Regions varied significantly between each other. Populations from the Northern and Western Regions varied the most (Mahalanobis Distance = 54.20). The least variation was noticed between populations from the Western and Eastern Regions (MD = 1.99). On morphospace, the Northern population clearly separated from the Eastern and Western populations both of which overlapped. Wing centroid size also significantly varied among populations. Reclassification scores were satisfactory reaching 100% for the Northern population. The Northern population of G. palpalis is possibly isolated from the Western and Eastern Region populations. Meanwhile, a panmictic relationship could be on-going between the Western and Eastern populations. We speculate that geographical distance and subspecific difference between populations are among factors responsible for observed pattern of wing shape variations among the studied populations. The implications of results regarding choice of control strategy and limitations of the study are discussed

Basic Developmental Characteristics of the Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), Reared under Laboratory Conditions

The life cycle of the invasive alien insect pest, fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), was studied using a colony established from field-collected larvae. Eggs, neonate larvae, and newly emerged adult moths were used in experiments to investigate the basic biology of the FAW. Adult females laid up to 1184 eggs with a mean of 469 ± 22 eggs per female. The incubation period of eggs and percentage hatchability were 2-3 days and 80–87%, respectively. The mean larval lengths from the first to the sixth instar were 4.63, 6.60, 9.76, 15.86, 25.13, and 27.81 mm, respectively. The mean larval weights were 0.003, 0.019, 0.045, 0.050, 0.060, and 0.067 g, respectively, for the six instars. The mean width of the head capsule of the sixth instar larva was 2.76 mm. The total larval duration throughout the six instar stages was 16–18 days, while the mean pupal weight was 0.25 ± 0.001 g and 0.35 ± 0.011 g for males and females, respectively. The mean pupal length was 14.3 ± 0.16 mm for males and 17.2 ± 0.14 mm for females. Pupal duration ranged from 8 to 14 days, with a mean of 10.35 ± 0.26 days, while the pupal emergence rate ranged from 60 to 94%, with a mean of 80.25 ± 1.28%. The life cycle of males lasted 33–44 days and that of females lasted 36–49 days under laboratory conditions. Adult copulation occurred between 8 and 11 pm, with the peak occurring at 9 pm. This study provides baseline information about the biology of the FAW. Apart from being an important reference point for future research on the FAW, the data provided would aid FAW management decision-making

First report and population dynamics of the Tobacco Thrips, Thrips parvispinus (Karny) (Thysanoptera: Thripidae) on ridged gourd, Luffa acutangula (L.) Roxy in selected export fields in southern Ghana

Thrips attack several crops causing considerable economic damage. To prevent this damage, sticky traps can be used to monitor their population for the timely execution of management interventions. Ridged gourd or turia (Luffa acutangula (L.) Roxy) is an important Asian vegetable exported regularly to the European Union market from Ghana. However, this vegetable has been intercepted severally at the point of entry because of thrips infestation. The current study is aimed at identifying and monitoring thrips population on turia using blue and yellow sticky traps in six export vegetable production sites in Ghana for two consecutive seasons and three trapping periods. The results showed that Thrips parvispinus (Karny) (Thysanoptera: Thripidae) was the commonest and only species of thrips found attacking turia. The highest and lowest mean number of thrips were recorded from the blue and yellow sticky traps during the dry and the late part of the major rainy seasons, respectively. Thrips population build-up was observed to reach its peak at the flowering stage of the crop. This is the first report of T. parvispinus in Ghana. The implications of this finding on the export of turia to the EU market has been discussed