Temperature-dependent parasitism in Trichogramma brassicae (Hym.: Trichogrammatidae), modeling finite parasitism rate

Abstract

Parasitism rate of Trichogramma brassicae Bezdenko at laboratory conditions with six constant temperatures of 15, 20, 25, 30, 32 and 35 ± 1 °C, relative humidity of 65 ± 5% and a light period of 16 h. was evaluated on the eggs of gelechiid moth Sitotroga cerealella (Olivier). Parasitism rate of T. brassicae was significantly affected by different temperatures. The highest (40.257 hosts) and the lowest (3.731 hosts) values of net parasitism rate (C0) was obtained at 32 and 15 °C, respectively. The transformation rate of host population to parasitoid offspring (Qp) was equal to 1 at all temperatures. The values of stable parasitism rate (ψ) increased from 0.074 to 0.451 (host/parasitoid) with increasing temperature from 15 to 30 °C, but the values for this parameter at 32 and 35 °C significantly decreased. The highest recorded value for finite parasitism rate (ω) was obtained at 30 °C (0.654 day-1). The temperature thresholds for finite parasitism rate of T. brassicae were estimated by nonlinear models of Briere-1 and Lactin-2. The Lactin-2 better fitted the related data (SSE = 0.004833, R2adj = 0.977, AIC = -38.7438). The obtained values for the lower temperature threshold (Tmin), optimum temperature (Topt) and upper temperature threshold (Tmax) of parasitism activity of this parasitoid were 13.20, 31.20 and 35.40 °C, respectively.

Keywords

• biological control
• parasitism rate
• temperature thresholds
• trichogramma
• modeling