Biological Studies of the Oligonychus litchii (Trombidiformes:Tetranychidae) on Four Commercial Litchi Cultivars

Abstract

Litchi is one of the most important pillars of the fruit industry in Southeast Asia and mainland China. The litchi spider mite, Oligonychus litchii Lo & Ho (Prostigmata: Tetranychidae), is a major pest of litchi. To determine the influence of different litchi cultivars on the life cycle, fecundity, and longevity of O. litchii, life tables of O. litchii on 4 popular commercial litchi cultivars in China ('Baili,''Fezixiao,''Sanyuehong,' and'Nuomici') were constructed under laboratory conditions at 25 ± 1 °C, 65 to 80% RH, and photoperiod of 14: 10 h (L: D). Life stages of O. litchii consist of egg, larva, protonymph, deutonymph, and adult, with distinct body sizes and colors. The life table parameters were significantly influenced by litchi cultivars. Our results showed that the developmental time of immature O. litchii was significantly longer on Baili than on the other 3 litchi cultivars. The immature survival rates of O. litchii varied from 21.74% to 68.42%. Oligonychus litchii laid significantly more eggs on Nuomici (64.84 eggs per female) than on other cultivars. The population doubling time of O. litchii ranged from 4.56 to 22.42 d, and a significant varietal effect was seen. The mites feeding on Nuomici showed the lowest intrinsic rate of natural increase per d (rm = 0.14 female per female per d). In addition, the net reproductive rate (R0) and finite rate of increase (λ) of O. litchii had the highest value on Nuomici (22.86 female per female per generation, and 1.16 female per female per d, respectively). The comparison of rm, R0, and immature survival rate of O. litchii on host plants revealed that Nuomici is the most suitable cultivar, suggesting that Nuomici is more susceptible to the litchi spider mite than the other 3 litchi cultivars.