Studies on free choice feeding preference of Tribolium castaneum beetle and larval development in wheat products were conducted under laboratory conditions (28±2°C and 60±5% RH). The results revealed that significantly higher number of beetles preferred flour grade-2 (30.00) followed by flour grade-1 (15.14), maida (9.71) and bran (9.43) for feeding. Feeding preference of beetle was the lowest for dry and tempered wheat. (2.14 and 2.43 respectively). After release, the neonate larvae developed rapidly in all treatments. However, all 50 larvae took 24 days to become imago in flour grade 1, 2 and bran; 25 days in maida and fine and 28 days in suji. The larval development was delayed in wheat grains and only 23.33 and 37.00 larvae matured to adult stage in dry and tempered wheat respectively in a period of 70 days. The developing larvae caused the highest weight loss to flour grade-l (3.41%) and the lowest to dry wheat (0.41%). The correlations (r) between different parameters of T. castaneum and wheat products were positive and significant. Factors affecting storage losses in wheat products are discussed.

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Feeding Preference and Development of Tribolium castaneum (Herbst.) in Wheat Products

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.

Wheat cultivars affecting life history and digestive amylolytic activity of Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae).

Wheat is one of the most important cultivated crops in all almost all countries of the world. Hybrids have significantly increased the productivity and quality of this major crop. The aim of this study was to evaluate wheat genotype resistance to Angoumois grain moth, Sitotroga cerealella (Oliv.) (Lepidoptera: Gelechiidae). Twelve wheat genotypes were tested against Sitotroga cerealella at 28±2°C, relative humidity 65±5% and photoperiod L: D 12: 12 hours in the laboratory. The results, evaluated on the basis of percent weight loss, damage, grain size and chemical composition of the grains, revealed that none of the genotypes was completely resistant to the infestation by this pest. However, their response varied significantly. Genotype IBW -97103 (weight loss, 12.19%) had significant resistance followed by IBW-97083 (17.43%), Bakhtawar-92 (19.48%), F-Sarhad (19.66%), IBW-97406 (27.19%), IBW-97114 (27.32%), IBW-97259 (29.40%), IBW-97110 (29.70%), IBW-96405 (30.94%), IBW-97366 (31.02%), IBW-97112 (36.14%) and WS-94194 (40.93%). The coefficient of correlation between percent weight loss and other parameters was significant, except for grain size. The coefficient of correlation between weight loss and chemical constituents was also significant, except for ash content. From the study it was concluded that prolonged storage of the most susceptible genotypes to S. cerealella should be avoided and the most resistant varieties, namely BW-97103< IBW-97083< Bakhtawar-92, should be cultivated. Key word: Wheat genotype, angoumois grain moth, chemical analysis of grains, resistance to moth, Sitotroga cerealella.

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Appraisal of different wheat genotypes against Angoumois grain moth, Sitotroga cerealella (Oliv.).

Grains of seven elite maize genotypes were evaluated for their comparative resistance to lesser grain borer, Rhyzopertha dominica (F). and Angoumois grain moth, Sitotroga cerealella (Olivier) on free choice basis under laboratory conditions (28±2°C and 60±5% RH). Progeny of emerging adults and weight loss of grains were taken as parameters to check resistance. The results indicated that adult progeny of both species and weight loss of grains were significantly low in White Monsanto ex-Cargil and Yellow Pioneer. However, significantly high number of adults were developed in yellow 2303, Waxy and Yellow 6525 Cargil with higher weight loss of grains. The correlation between adult progeny and grain weight loss in maize genotypes was significantly positive. Whereas the correlation between progeny of insect species was non-significant showing their independent development. The results suggested that resistant varieties could be incorporated in maize breeding programme to decrease the postharvest losses of grains.

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Susceptibility of Maize Grains to Storage Insects

Throughout the year, there was an abundance of fruit flies in Cue-lure baited traps. Two peaks; in summer and kharif (Autumn) coincided with the 14 SW and 43 SW respectively. In kharif, maximum bitter gourd fruit damage (62.70%) occurred in the 45 SW. A second peak, with 49.70% fruit damage was observed during the 15 SW period. The temperature (maximum and minimum) showed a significant positive correlation with adult abundance, fruit damage and pupal population. The temperature recorded dur- ing the preceding first, second and third weeks had a slightly greater impact than the temperature of the current week in which the fruit fly abundance had been checked. Other abiotic factors had a non-significant effect on fruit fly adult activity, fruit damage and pupal population.

http://www.plantprotection.pl/pdf-93536-27536?filename=Role of abiotic factors.pdf

S. U. Khattak

Papers

Relative susceptibility of wheat cultivars to Sitotroga cerealella (Oliver)

Combined infestation and losses caused by three storage insects in Pak-81 wheat variety.

Annual population incidence of oriental fruit fly (Dacus dorsalis) Hendel in a fruit orchard at Peshawar, Pakistan.