Seasonal Fluctuation in Population Density of Spider Mites (Acari: Tetranychidae) and Their Predators on Soybean Cultivated in Agrochemical Sprayed and Unsprayed Plots

Abstract

The seasonal fluctuation and species composition of spider mites and their predators on soybean were investigated in an agrochemical sprayed plot and an unsprayed control plot from 1999 to 2001 in Ibaraki, central Japan. Sprayed plots were treated with cypermethrin and fenitrothion (1999), acephate and imidacloprid (2000), and permethrin (2001). In both plots, spider mite populations showed three peaks in 1999 (June, August and October-November), and two in 2001 (August and September-November). In 2000, the populations peaked only once (August), because soybean flowered and fruited more than one month earlier than in other years and as a result, all leaves had dropped by late September. Of the spider mite species sampled, Tetranychus kanzawai Kishida, T. parakanzawai Ehara, T. pueraricola Ehara et Gotoh and T. urticae Koch (green form) dominated in both plots and at almost all times. Predators were phytoseiid mites, such as Gynaeseius liturivorus (Ehara), Amblyseius tsugawai Ehara, Neoseiulus californicus (McGregor), and N. womersleyi (Schicha), and insects like Scolothrips takahashii Priesner and Feltiella sp. The population density of G. liturivorus was positively related to the occurrence of phytophagous thrips until August when the thrips became scarce. Synchronized with spider mite density were phytoseiid mites other than G. liturivorus after August, and Scolothrips takahashii throughout the observation periods. Agrochemical spraying had an initial detrimental effect on phytoseiid mites and S. takahashii, but they had recovered by two-four weeks after spraying, suggesting that the effect of chemical spraying on predators was weak.

Development, Reproduction and Prey Consumption of the Thrips Predator Gynaeseius liturivorus (Ehara) (Acari: Phytoseiidae)

“…On grapevine, E. sojaensis population increases corresponding to S. dorsalis populatioin, but G. liturivorus was found in low frequencies (Shibao et al, 2004) despite its high predation ability on S. dorsalis in the present study. Contrary, on soybean, G. liturivorus population dominates among the species composition corresponding to the phytophagous thrips population in summer (Mori et al, 2008). Further basic studies on the population dynamics of G. liturivorus are needed on various plants and locations to elucidate whether G. liturivorus could be incorporated into thrips control programs.…”

“…G. liturivorus was recorded on tea (Camellia sinensis L.) (Hamamura, 1986;Santoso et al, 2004), grapevine (Vitis spp.) (Ashihara, 1995;Shibao et al, 2004) and soybean (Mori et al, 2008). Recently, Komi et al (2008a, b) found that G. liturivorus occured naturally on greenhouse vegetables in Kochi Prefecture in Japan, and it exhibited excellent prey consumption and oviposition rate when the 1st stadium larvae of melon thrips, Thrips palmi Karny were provided.…”

Age‐ and temperature‐dependent oviposition model of Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) with Tetranychus urticae as prey

“…2009), clementine (Abad‐Moyano et al. 2009, 2010a,b), soy bean (Mori et al. 2008), sweet pepper (Weintraub and Palevsky 2008), cucumber and pepper (Palevsky et al.…”

“…The population dynamics of N. californicus in association with its prey, T. urticae, have been studied in some agricultural crops such as strawberry (Fraulo and Liburd 2007;Sato et al 2007;Palevsky et al 2008;Cakmak et al 2009), clementine (Abad-Moyano et al 2009, 2010a, soy bean (Mori et al 2008), sweet pepper (Weintraub and Palevsky 2008), cucumber and pepper (Palevsky et al 2008), and apple (Pringle and Heunist 2006). However, the lack of a formal population model for N. californicus limits our understanding of this species' population dynamics.…”

<p><strong>Determination of seasonal changes of spider mite (Acari: Tetranychidae) densities and species composition on kudzu vine and soybean (Fabaceae) in Japan with the use of phosphoglucomutase zymograms*</strong></p>

“…Kudzu vine leaves almost totally covered the plots in mid-summer. For soybean, one agrochemical unsprayed plot was chosen in a soybean field as the study site; it was located in Ushiku (35°58'N; 140°10'E) in Ibaraki Prefecture (Mori et al, 2008). An area of 8 x 12.5 m was set up in this field and divided into 50 1.25 x 1.6 m subplots.…”