The effect of temperature on the development of the Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), was evaluated at eight constant temperatures (10, 15, 20, 25, 28, 30, 32.5 and 35°C), with relative humidity of 65% and a photoperiod of 14:10 (L:D) hours on two host plants, cauliflower, Brassica oleracea var. botrytis and cabbage, Brassica oleracea var. capitata. The low temperature threshold was estimated to be 7.06°C and 7.84°C and the thermal constant was 263.74 and 261.58 degree‐days for P. xylostella on cauliflower and cabbage, respectively, using the linear model. Data were fitted to various nonlinear temperature‐dependent models, and the low and high temperature thresholds, as well as the optimum temperature for development, has been estimated. Criteria of choice from the literature were used to evaluate models and to select the most suitable equation for P. xylostella development on each host plant. Conclusively, linear and Briere‐2 models are recommended for the description of temperature‐dependent development of P. xylostella on two host plants.

The effect of different soybean varieties (Glycine max 356, M4, M7, M9, Clark, Sahar, JK, BP, Williams, L17, Zane, Gorgan3 and DPX) on the life history and fecundity of the gram pod borer Helicoverpa armigera (Hubner) (synonym Heliothis armigera (Hubner), also known as the American or African bollworm) was determined at 25 Ϯ 1°C, 65 Ϯ 5% r.h. and a light : dark cycle of 16:8 h. The larval period ranged 17.30 to 26.20 days on M7 and L17, respectively. The longest development time was on L17, BP and Sahar (42.71, 40.29 and 39.20 days, respectively) and the shortest was on M7, M9, Williams and Clark (34.21, 36.06, 36.60 and 36.82 days, respectively). The development index of overall immature stages varied from 1.39 to 2.41, with the minimum on L17 and BP and the maximum on M7. The highest daily fecundity and total fecundity (118.92 and 582.70 eggs, respectively) and the lowest (37.88 and 177.10 eggs, respectively) were observed on DPX and 356, respectively. Cluster analysis of the biological parameters of H. armigera on different soybean varieties demonstrated that BP, Sahar and L17 were partially resistant to H. armigera. Knowledge of the extent of susceptibility or resistance of crop varieties and biology of a pest on that crop are fundamental components of integrated pest management (IPM) programs for many crops. Such information can help to detect and monitor pest infestation, variety selection and crop breeding.

The performance of two aphid parasitoids, Aphidius colemani Viereck and Aphidius matricariae (Haliday), against Aphis gossypii Glover on greenhouse cucumber (Cucumis sativus L.) and Myzus persicae (Sulzer) on sweet pepper (Capsicum annuum L.) were evaluated at various constant temperatures. Biological parameters of both parasitoids including developmental time, pupal survivorship, percentage of parasitism, and sex ratio of the progeny were studied at 5, 10, 15, 20, 25, 30, and 35 degrees C. At 25 degrees C, an average of 10.0 +/- 1.1 and 9.8 +/- 1.1 d was needed for A. colemani to complete its development from oviposition to adult eclosion on A. gossypii and M. persicae, respectively. The corresponding average times needed for A. matricariae were 11.9 +/- 0.9 and 11.5 +/- 1.1 d, respectively. The lower developmental thresholds for A. colemani reared on A. gossypii and M. persicae were estimated from linear regression equations to be 2.97 and 2.65 degrees C, respectively, whereas these values for A. matricariae were 3.37 and 3.51 degrees C, respectively. Parasitization rate of both parasitoid species, recorded as percent aphids mummified, increased almost linearly with increasing temperature to reach a maximum at 25 degrees C and decreased at 30 degrees C. The optimal temperatures for development of A. colemani and A. matricariae were approximately 30 and 25 degrees C, respectively, and high mortality occurred at higher temperatures. The Lactin 2 and Briere 1 developmental models were accepted based on their excellent goodness-of-fit to the data (residual sum of square and coefficient of determination) and estimable temperature thresholds and are strongly recommended for the description of temperature-dependent development of A. colemani and A. matricariae.

The functional response of two aphid parasitoids, Aphidius colemani Viereck and Aphidius matricariae (Haliday) (Hymenoptera: Aphidiidae), on the cotton aphid, Aphis gossypii Glover (Homoptera: Aphididae), was examined. Five constant temperatures (10, 15, 20, 25, and 30°C) and six host densities (2, 4, 8, 16, 32, and 64) were used during a 24-h period. At each temperature, 2-64 third-instar nymphs of A. gossypii were exposed to individual wasp mating pairs. A type II functional response model for both parasitoid wasps was fit separately for each temperature. The results showed that instantaneous attack rate (a) in A. colemani increased linearly as the temperature increases from 10 to 30°C, but in A. matricariae, (a) increased almost linearly with temperature to reach a maximum at 25°C, and then decreased at 30°C, displaying an asymmetrical domeshaped pattern. The highest instantaneous attack rate for A. colemani and A. matricariae were calculated 0.940 ± 0.144 day À1 at 30°C and 0.687 ± 0.157 day À1 at 25°C, respectively. Handling time (T h ) for A. colemani was inversely proportional to temperature and ranged from 0.093 ± 0.026 day at 10°C to 0.032 ± 0.004 day at 30°C, but in A. matricariae, (T h ) was between 0.078 ± 0.015 day at 10°C and 0.036 ± 0.014 day at 20°C. A. colemani achieved higher parasitism rate than A. matricariae at higher temperatures. This observation suggests that A. colemani maybe more effective for biological control of the cotton aphid during warmer periods.

Temperature-dependent development, survivorship and reproduction of the cotton aphid, Aphis gossypii on Cucumis sativus L. were evaluated at six constant temperatures (10, 15, 20, 25, 30 and 35°C). Developmental periods of immature stages varied from 20.70 days at 10°C to 3.81 days at 30°C. The population failed to survive at 35°C. As temperature increased, the intrinsic rate of increase (r m ) followed a typical asymmetrical dome-shape pattern, with maximum value of 0.419/day at 25°C. Survival of immature stages differed from 55.97% to 93.14% within the range of 10-30°C. The average adult longevity ranged from 8.56 days at 30°C to 17.00 days at 25°C. Three mathematical models were compared for accuracy in predicting the developmental rate of A. gossypii, and estimating its temperature thresholds and optima. The developmental threshold was estimated to be 6.19°C, and the thermal constant was 97.09 degree-days, using the linear model. The Briere 2 and Lactin 2 models were accepted for success to satisfy criteria of goodness-of-fit (residual sum of square and coefficient of determination) and estimable temperature threshold parameters and highly recommended for the description of temperature-dependent development of A. gossypii. No other data are available in using nonlinear models to describe the relationship between temperature and A. gossypii development.