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Abstract
5. In Egypt and many other countries cereal grains are considered a valuable source of protein and carbohydrates which are required for human nutrition. The rice weevil, Sitophilus oryzae (L.) is one of the most injurious pest of stored grains all over the world due to its ability to fly and attack grains in both field and store.
The present work was carried out in Plant Protection Department, Faculty of Agricultural, Zagazig University during three successive years of 2005, 2006 and 2007 on rice weevil,
S. oryzae (L.). The ecological studies included the effect of varietal resistance of thirteen cereal varieties belonging to five types of grains on some biological aspects and certain infestation parameters of rice weevil under no-choice and free-choice rearing, as well as the relationship between some chemical constituents, morphological and anatomical characteristics of tested varieties and studied aspects and parameters. In addition, the effect of Neemazal T/S formulation (1% Azadirachitin) on rice weevil mortality by spraying each of wheat and rice grains, inner surface of containers (cloth bags and plastic cups) and containers plus grains. The obtained results can be summarized in the following points :
1. Varietal Resistance
1.1. Under no-choice rearing
1.1.1. Effect of varieties on some biological and infestation parameters
Thirteen grain varieties belonging to five grain types were evaluated to infestation with the rice weevil at constant conditions of 30 ± 1 ˚C. and 70 ± 5% R.H. . The tested varieties were Single cross, T.W.C. 352, T.W.C. 327, T.W.C. 325 (maize); Giza 15, Dorado (sorghum); Giza 168, Sakha 93, Gemeza 7 (wheat); Giza 177, Sakha 101 (milled and husked rice) and Sakha 104 (milled rice) and Giza 2000 (barley). The obtained results showed that the differences between tested varieties in respect to number of F1 emerged adults and susceptibility index proved to be statistically highly significant, whereas the other parameters clarified insignificant variations. Barley – Giza 2000 variety was the least susceptible showing the longest least developmental period (58.00 days) and the lowest values of 1.31, 0.40, 0.82 (rel. low), 1.00 and 1.14 for mean number of F1 adult progeny, susceptibility index, % infested grains, mean number of holes per infested grain and % weight loss, successively. On the other hand, sorghum – Giza 15 and Dorado as well as maize – Single cross and T.W.C. 352 indicated high levels of susceptibility having the corresponding values in the ranges of 38.57 – 41.86 days, 23.38 – 43.33 adults/female, 4.43 – 5.31, 13.58 – 64.78%, 1.00 – 1.50 and 2.32 – 10.94% for the abovementioned biological and infestation parameters, respectively. The differences between the tested grain types, proved to be statistically insignificant for mean developmental period and significant for the other parameters. According to susceptibility index, barley grains were the most resistant showing the lowest value of 0.40, whereas sorghum grains proved to be the most susceptible indicating the highest index value of 5.15. The other studied biological and infestation parameters nearly confirm the previous conclusion.