Effect of Uneven Acaricide Application on Effective Control of Spider Mites in Chrysanthemum Fields.

Abstract

The effect of uneven acaricide application on control of spider mites in chrysanthemum fields was examined by laboratory and field studies. The acaricide deposition index was measured using water-sensitive paper in chrysanthemum fields of five growers. The deposition was very high on the top face of the water-sensitive paper, but very low on the back. When two growers sprayed tebufenpyrad in their chrysanthemum fields, the density of spider mites did not decline in one field, and the result in the other field was unclear. When two growers sprayed milbemectin in their chrysanthemum fields, one grower could control the mite density, but the other could not. Resistance to acaricide was investigated using two strains of the Two-Spotted Spider Mite (green-form) collected from chrysanthemum fields examined for mite density. Both strains were resistant to tebufenpyrad, but susceptible to milbemectin. The mortality and fertility of mites were investigated by laboratory tests under different milbemectin deposition conditions. When the deposition index on the water-sensitive paper was 2 or more, the mite fertility was very low. Fertility was higher at an index of 1. We propose that both acaricide resistance and application deposition rate must be investigated for practical control of spider mites in chrysanthemum fields.

Quantifying pesticide efficacy from multiple field trials

“…If the contribution of resistance was significant, the effects of the mixed pesticides would be significantly higher than those of the single active‐ingredient pesticides since the resistant individuals to both ingredients must be rare in the field (Gould et al, ). We suspect that escape from exposure, and perhaps immigration, are the main reasons behind the survival (Kunimoto, Nishino, Otuji, & Inda, ).…”

Vertical Distribution of the Two-Spotted Spider Mite, Tetranychus urticae Koch (Green-Form), on Chrysanthemum Cuttings in Relation to Dipping Them in Acaricide Solution.

“…On the other hand,in the cuttings dipped in potassium oleate,the mite population began to increase within3weeks.Potassium oleate kills mites only at motile stages,and thus it is likely that a few eggs remained on the cuttings after the treatment.Thus,the proper acaricides should be selected for mite control.The following points should also be considered.First,many species of tetranychid mites are resistant to various acaricides (Kuwahara et al,1983;Goka,1998).In Nara Pref.,the two-spotted spider mite is known to have a low susceptibility to some acaricides (Kunimoto et al,1998a). Second,monitoring the mite number on weeds around chrysanthemum fields is indispensable.The two-spotted spider mite was commonly observed on weeds around the chrysanthemum field (Kunimoto et al,1997),and its migration from chrysanthemum to a kidney bean was also reported in Wakayama Pref.…”