Numerical responses of the predatory mites,Cheyletus eruditus(Trombidiformes: Cheyletidae) andCheyletus malaccensis, toLiposcelis decolor(Psocodea: Liposcelididae)

Abstract

Predatory mites display diverse ecological mechanisms to suppress pest population density below certain thresholds known to cause economic loss. The current study explored the numerical responses of the predatory mites, Cheyletus eruditus (Schrank) (Trombidiformes: Cheyletidae) and Cheyletus malaccensis Oudemans, to Liposcelis decolor (Pearman) (Psocodea: Liposcelididae). The numerical responses of these 2 cheyletid mites to nymphs, adult males, and adult females of L. decolor were determined under laboratory conditions at 24 ± 1 °C, 85 ± 5 RH, and 0:24 (L:D) photoperiod. Oviposition rate, oviposition efficiency, and efficiency of conversion of ingested (ECI) food resources were the key numerical response parameters assessed. The present study revealed a general trend of a strong negative and positive correlation between oviposition rates and increase in prey densities (number of prey per 16.98 cm2) for C. eruditus and C. malaccensis, respectively. The oviposition efficiency was mostly similar for both predatory mites and was inversely related to prey density. Generally, ECI (%) decreased considerably with increasing prey density across different prey types for both predators, however, C. malaccensis was more efficient than C. eruditus in utilizing prey biomass. Given the relatively weak numerical responses, we recommended further assessment of these predatory mites before recommending their use for managing stored-product insect pests in the United States.

Ecological Interactions of Predatory Mites, Cheyletus eruditus (Schrank) (Trombidiformes: Cheyletidae) and Cheyletus malaccensis Oudemans, and Prey, Liposcelis decolor (Pearman) (Psocodea: Liposcelididae), under Different Thermo-Hygrometric Regimes

“…The most significant result of this study was that C. eruditus and C. malaccensis were found to effectively prey on L. decolor and suppress its population in a wide range of ecological conditions. Our data have confirmed observations by several reports that both predatory mites are good potential natural enemies of most pestiferous insects in stored products, including psocids in the genera Liposcelis and Lepinotus [ 6 , 7 , 23 , 29 , 30 , 31 , 32 , 33 ]. In the Czech Republic, for example, C. eruditus (Cheyletin ® ) is the only commercialized predatory mite approved for use to manage mite pests in food storage systems such as in a stored-grain mass and in grain residues, debris in empty stores, or seed stores in [ 1 , 34 ].…”

“…Rearing methods for C. eruditus and C. malaccensis were as described in [ 6 , 23 ]. These methods are modified from a mass rearing protocol for C. eruditus as described by [ 24 ].…”

“…These methods are modified from a mass rearing protocol for C. eruditus as described by [ 24 ]. Only adult female (♀) predatory mites were used for this study and were selected based on what is described in [ 6 , 21 , 23 , 25 ].…”

“…Experimental arenas consisted of two 6.0 cm diameter Petri dishes (forming a total cylindrical surface area of 113.04 cm 2 ; the total migration area of the individual predator in a closed cylinder) (60 × 15 mm, Style Polystyrene, Becton Dickinson and Company, Franklin Lakes, NJ, USA). Other aspects of the arenas were as described in [ 6 , 23 ]. The total migration area of individual prey was 47.12 cm 2 .…”

“…For example, susceptible laboratory strains of L. decolor can tolerate higher concentrations of phosphine up to 249.76 ppm [ 22 ]. Previous data [ 6 , 23 ] on the foraging behaviors of C. eruditus and C. malaccensis showed that these cheyletids had the potential to suppress L. decolor population under the same temperature (24 ± 1 °C) and RH (85 ± 5%) conditions. Given that the general performance of an effective biocontrol agent is a function of multiple ecological interactions among many biotic and abiotic variables, the evaluation of predator–prey interaction based on other variables such as predatory-to-prey ratio and thermo-hygrometric factors is necessary to investigate.…”