scholarly journals Evidence for a Causal Relationship between the Solar Cycle and Locust Abundance

Agronomy ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 69
Author(s):  
Robert A. Cheke ◽  
Stephen Young ◽  
Xia Wang ◽  
Jamie A. Tratalos ◽  
Sanyi Tang ◽  
...  
Keyword(s):  
Solar Activity ◽  
White Noise ◽  
Schistocerca Gregaria ◽  
Southern Oscillation ◽  
Data Series ◽  
Desert Locust ◽  
Spectral Coherence ◽  
Migratory Locust ◽  
Geographical Regions ◽  
Sunspot Groups

Time series of abundance indices for Desert Locusts Schistocerca gregaria (Forskål 1775) and Oriental Migratory Locusts Locusta migratoriamanilensis (Meyen 1835) were analysed independently and in relation to measures of solar activity and ocean oscillation systems. Data were compiled on the numbers of territories infested with swarms of the Desert Locust from 1860–2015 and an inferred series that compensated for poor reporting in the 1860 to 1925 period. In addition, data for 1930 to 2014, when reports are considered to have been consistently reliable were converted to numbers of 1° grid squares infested with swarms and separated according to four different geographical regions. Spectral analysis to test the hypothesis that there are cycles in the locust dynamics revealed periodicities of 7.5 and 13.5 years for the inferred series that were significant according to the Ornstein-Uhlenbeck state-space (OUSS) test. Similar periodicities were evident in the 1° grid square data and in each of the regions but even though these were significantly different from white noise, they were not significant according to the OUSS criterion. There were no significant peaks in the Oriental Migratory Locust results with the OUSS test, but the data were significantly different from white noise. To test hypotheses that long term trends in the locust dynamics are driven by solar activity and/or oceanic oscillation systems (the Southern Oscillation Index (SOI), the North Atlantic Oscillation Index (NAO) and the Indian Ocean Dipole (IOD)), the original locust data series and their Kalman-filtered low frequency (LF) components were tested for causality using both spectral coherence tests and convergent cross mapping. Statistically significant evidence was found that solar activity measured by numbers of sunspot groups drive the dynamics, especially the LF components, of both species. In addition, causal links were inferred between both the SOI and NAO data and Desert Locust dynamics. Spectral coherence was also found between sunspot groups and the NAO, the IOD and LF SOI data. The data were also analysed showing that the LF SOI had causal links with the LF inferred Desert Locust series. In addition, the LF NAO was causally linked to the LF 1° grid square data, with the NAO for December-March being most influential. The results suggest that solar activity plays a role in driving locust abundance, but that the mechanisms by which this happens, and whether they are mediated by fluctuations in oceanic systems, is unclear. Furthermore, they offer hope that information on these phenomena might enable a better early warning forecasting of Desert Locust upsurges.

On Experiments in the Use of Poison Dusts against Adult Locusta migratorioides, Rch. & Frm., in the Sudan

1932 ◽  
Vol 23 (1) ◽  
pp. 65-68 ◽  
Author(s):  
H. H. King ◽  
W. Ruttledge
Keyword(s):  
Schistocerca Gregaria ◽  
First Year ◽  
Desert Locust ◽  
Migratory Locust ◽  
Large Numbers ◽  
Second Year

The Anglo-Egyptian Sudan has, so far as may be ascertained, always been liable to plagues of the migratory locust, Schistocerca gregaria, Forsk., generally referred to as the desert locust. In the summer of 1930 in addition to this species swarms of another migratory locust, Locusta migratorioides, Rch. & Frm., locally known as the hairy-chested locust, appeared. In most districts natives stated that they had never before seen this second species, but elderly inhabitants of Darfur and northern Kordofan recognised it as having occurred some forty-two years previously for two successive seasons; the first year in large numbers, the second in but small numbers. It was hoped that history would repeat itself and that the hairy-chested locust would be relatively scarce in its second year, but unfortunately this hope has not been realised; L. migratorioides was a more serious plague in 1931 than in the preceding year.

scholarly journals Effects of water extracts of frass from three locust species and various plants on oviposition and embryonic development in the desert locust, Schistocerca gregaria

2019 ◽  
Vol 28 (2) ◽  
pp. 195-204
Author(s):  
Seiji Tanaka ◽  
Toyomi Kotaki ◽  
Yudai Nishide ◽  
Amel Ben-Hamouda ◽  
Khemais Abdellaoui ◽  
...  
Keyword(s):  
Plant Species ◽  
Schistocerca Gregaria ◽  
Morphological Changes ◽  
Locusta Migratoria ◽  
Water Extract ◽  
Hatching Rate ◽  
Desert Locust ◽  
Leaf Extracts ◽  
Migratory Locust ◽  
Hatching Rates

The water extract of desert locust, Schistocerca gregaria, frass collected in the wild had an oviposition inhibitory (OI) effect when mixed with sand and presented to adults. Likewise, the leaves of six plant species, as well as frass produced by desert locusts fed with these plants, exerted OI effects when compared with the control sand wetted with water alone. In general, frass extracts had a greater OI effect than the extracts of leaves. The OI effect was also observed when adult desert locusts were exposed to extracts of frass produced by two other locusts, the Bombay locust, Nomadacris succincta, and the migratory locust, Locusta migratoria, fed with rescue grass, Bromus catharticus. Among the three species of locust, desert locust and migratory locust frass exerted a greater OI effect than Bombay locust frass. Frass samples extracted with hot and cool water produced similarly high OI effects, indicating that bacterial involvement during extraction is unlikely. Hatching rates of desert locusts were significantly reduced by extracts of all of the above mentioned frass when the extracts were mixed with sand and used to incubate the eggs. In contrast, the lethal effects of leaf extracts on the hatching rates varied depending on the plant species. The embryos became deformed within four days when three-day-old eggs were incubated in sand containing frass extracts from desert locusts fed with rescue grass, whereas no apparent morphological changes were observed when seven-day-old eggs were similarly tested, although their hatching rate was significantly reduced.

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