Red spider mites, Tetranychus merganser Boudreaux (Acari: Tetranychidae), is an agricultural pest that causes economic losses in papaya and nopal crops in Mexico. The aim of this research was to assess antibiosis and antixenosis as resistance mechanisms in seven host plants (Thevetia ahouai, Carica papaya, Phaseolus vulgaris, Moringa oleifera, Pittosporum tobira, Helietta parvifolia, Capsicum annuum var. glabriusculum) to red spider mites. Antixenosis was evaluated by non-preference for oviposition and feeding, antibiosis by infinitesimal rate of increase, finite rate of increase and doubling time, and the percentage of spider mites mortality. Oviposition and damage by feeding of T. merganser were significantly greater on C. papaya than on the other host plants. The growth rate of the spider mite was significantly lower in P. tobira and T. ahouai than in the other host plants. The percentage of hatched eggs of T. merganser was significantly higher in P. vulgaris than in the other plant species. Based on the demographic parameters, survival, food intake, and oviposition, these results indicated that compared with C. papaya, P. tobira and T. ahouai were more resistant. These results may be due to the fact that they were plants species of different families. The resistant plants can be studied as alternatives in the management of T. merganser.

<!-- *** Custom HTML *** --> The red spider mite, Tetranychus merganser Boudreaux (Acari: Tetranychidae), is an important agricultural pest in Australia, China, Thailand, the United States, and Mexico because feeding causes severe damage and defoliation of plants. The aim of the study was to evaluate effects of Equisetum arvense L. ethanolic extract on biological parameters of T. merganser in a laboratory. Different concentrations (10, 50, 100, 250, 500, and 1,000 µg/ml) of ethanolic extract were applied to T. merganser females. E. arvense extract did not kill T. merganser, but increased the number of eggs by 19.9, 22.5, and 21.2% compared with a check at 24, 48, and 72 hours, respectively. It also augmented the growth rate and finite rate of increase, and decreased doubling time of the red spider mite. The effects require further study because the plant extracts could have considerable implications for natural enemies and also might be suitable for mass production of red spider mites for other experiments in a laboratory.