The life history and digestive α-amylase activity of the Angoumois grain moth, Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae) were studied on six wheat cultivars (Arg, Bam, Nai 60, Pishtaz, Sepahan and Shanghai) at 25 ± 1°C, relative humidity of 65 ± 5% and a photoperiod of 16:8 (L:D) h. A delay in the developmental time of S. cerealella immature stages was detected when larvae were fed on cultivar Sepahan. The maximum survival rate of immature stages was seen on cultivar Bam (93.33 ± 2.10%), and the minimum rates were on cultivars Nai 60 (54.66 ± 2.49%) and Sepahan (49.33 ± 4.52%). The highest realized fecundity and fertility were recorded for females which came from larvae fed on cultivar Bam (93.30 ± 2.10 eggs/female and 91.90 ± 3.10%, respectively); and the lowest ones were observed for females which came from larvae fed on cultivar Sepahan (49.30 ± 4.50 eggs/female and 67.4 ± 11.1%, respectively). The heaviest male and female weights of S. cerealella were observed on cultivar Bam (2.97 ± 0.02 and 4.80 ± 0.01 mg, respectively). The highest amylolytic activity of the fourth instar was detected on cultivar Bam (0.89 ± 0.04 mg maltose min−1), which had the maximum mean hundred-wheat weight (5.92 ± 0.19 g). One α-amylase isozyme was detected in the midgut extracts from the fourth instar larvae fed on different wheat cultivars, and the highest intensity was found in larvae fed on cultivar Bam. Correlation analyses showed that very high correlations existed between the immature period, fecundity and fertility on one side and inhibition of α-amylase, soluble starch content and hundred-wheat weight on the other. According to the obtained results, cultivar Sepahan is an unfavorable host for the feeding and development of S. cerealella.

Intraspecific competition in the rice weevil, Sitophilus oryzae (L.) and the angoumois grain moth, Sitotroga cerealella (Oliv.) in grain sorghum was studied in laboratory experiments. Progeny production per female of each of the two species when reared separately, decreased as the initial parent population density increased. The number of progeny produced by Sitophilus oryzae increased to a peak, and then declined sharply with a further increase in initial parent population density, characteristic of a scramble competition. In contrast, the progeny produced by Sitotroga cerealella increased with an increase in parental density to reach a fairly constant maximum (flat topped curve), characteristic of a contest competition. It is concluded that intraspecific competition will not limit the potential of the grain moth S. cerealella of becoming a major pest of stored sorghum.

The susceptibility of the different stages of Sitotroga cerealella (Olivier) to gamma radiation was studied. The stages arranged in a descending order according to the values of gamma radiation LD50 are: adults (190.100 krad) for females and 183.200 krad for males, pupae (6.039 krad), 3 days old eggs (5.570 krad), one week old larvae (4.800 krad), 1-day-old eggs (4.181 krad) and 2 weeks old larvae (3.056 krad).

Experiments were carried out to study the effect of sublethal doses of gamma radiation (10–100 krad) on fecundity, longevity and sterility of adults of Silotroga cerealella. The results indicate that fecundity of females decreased as the dosage increased from 10–90 krad. At 100 krad no eggs were deposited. Raising the dose to 100 krad resulted in shortening the longevity to about half the longevity of the untreated moths. When irradiated females mated with similarly irradiated males, a dosage of 20 krad caused 97.17% sterility. A dose of 28 krad induced 96.69% sterility when normal females were mated with irradiated males, while 94.14% sterility resulted when normal males were mated with irradiated females.