Effect of temperature variability on predatory mite, Hemicheyletia congensis (Cunliffe) (Acari: Actinidida: Cheyletidae) feeding on Petrobia tritici (Kandeel, El- Naggar & Mohamed) (Acari: Tetranychidae)

Abstract

Temperature is a vital environmental factor affecting the biological control agent, Hemicheyletia congensis (Cunliffe) (Acari: Cheyletidae). Biological aspects and life table parameters of H. congensis were studied under laboratory conditions at 20, 25 and 30°C and 65% R.H. It was fed on Petrobia tritici (Kandeel, El- Naggar & Mohamed) (Acari: Tetranychidae), a pest of wheat. Developmental durations of different stages decreased as temperature increased and were fitted to the linear regression model with R2 values ranged between 0.82 to 0.99 (mean 0.94) and zero developmental time between 5 and 12°C (mean 8.74°C).The maximum oviposition rate of 98.6 eggs/female was at 25°C followed by 86.2 at 30°C and 68.5 at 20°C. Life table parameters showed highest value for the Net reproductive rate (Ro)as 62.84 at 25°C. Highest intrinsic rate of natural increase (rm) was reached as 0.220 at 30°C while lower rm values as 0.109 and 0.165 at 20 and 25°C, respectively. The survival rate from egg to adult was 0.75, 0.90 and 0.80, at tested temperatures, respectively. Sex ratios were 0.70, 0.75 and 0.70 respectively. Time for population doubling was determined as 6.35, 4.20 and 3.15 days, respectively. H. congensis had the highest predation capacity at 25°C as 419.3 prey immatures per females and 299.7 for males, during predators’ life span. The number of prey consumed during predator total immatures averaged 50, 104.5 and 71 prey for predator female and 41.7, 104.2 and 62.1 prey for predator male, respectively. Results indicated the possibility of mass rearing of H. congensis at 25°C for further studies.