<strong>Effect of bran moisture content and initial population density on mass production of <em>Tyrophagus putrescentiae </em>(Schrank) (Acari: Acaridae)</strong>

Abstract

The mold mite, Tyrophagus putrescentiae (Schrank), is an alternative prey for the predatory mites used in biological control. In order to maximize the food supply and maintain the population of predators, it is very important to understand the effects of bran moisture content (BMC) and initial population density (IPD) on mass production of T. putrescentiae. In the current study, the population increase of T. putrescentiae under six BMCs and five IPDs were evaluated at optimal temperature and humidity with suitable photoperiod conditions. The results showed that the population growth rates of T. putrescentiae were significantly higher with higher BMC. The population increased by 8, 32, 72, 304 times within five weeks under different BMC which was 8.3%, 10%, 15%, 20%, respectively. Unfortunately, when BMC reached to 25%, there was a great amount of mildew growing other than the mites. In the case of IPD, about 10000 adult mites per 100 g bran resulted in the largest final population of T. putrescentiae. However, either lower or higher IPD led to a smaller final population. It was also concluded that population growth rate decreased while the initial density was increasing, ranging from 1,055, 601, 397, 266, 109 times under initial density of ~5,000, 10,000, 15,000, 20,000, 25,000 adult mites per 100 g bran, respectively. Besides, we also described a method in detail for the effective isolation and counting of mites from bran. We found that population growth grew to maximum (over 50,000 mites / bran per gram) under BMC of 20%, IPD of ~50 adults / bran per gram, temperature of 28±1 °C, 80±5% R.H. and photoperiod of all darkness, which could be the best condition for mass production of T. putrescentiae. Our results provide basic biological information for the mass rearing of the mold mite, which will maintain stable and controllable food source for the predatory mites.