SUSCEPTIBILITY OF SOME DRY DATE VARIETIES TO INFESTATION WITH THE SAW-TOOTHED GRAIN BEETLE, ORYZAEPHILUS SURINAMENSIS (L.)

Abstract

ABSTRACT The saw-toothed grain beetle, Oryzaephilus surinamensis (L.) is considered one of the mostserious insect pests which attack different stored products in all over the world. This study wascarried out in the Laboratory of Plant Protection Department, Faculty of Agriculture, Zagazig University, Egypt to study the susceptibility of six dry date, Phoenix dactylifera (L.) varieties (Malkabi, Skooty, Pertomoda, Shamia, Dekina and Gondella) to infestation with the saw-toothed grain beetle under non-choice and free-choice conditions. Parameters of evaluation among the tested varieties as regards resistance were mean complete developmental period, number of F1 emerged adults, susceptibility index and weight loss % after one and three months of storage. Results showed that the shortest mean complete developmental period of the insect was 28.33 days on Skooty variety, while the longest one was 33.67 days on Gondella variety in free–choice bioassay method. Dekina variety was the most preferred variety to the insect since their fruits produced the highest mean insect number of progeny (73.67 adults), whereas Skooty variety recorded the lowest mean (25.67 adults). Values of susceptibility index (SI) ranged between 4.38% for Gondella and 10.69% for Skooty. After one month of storage the percentage of wet weight lossranged between 1.83 in Pertomoda and 10.83% in Malkabi, while after three months of storage the lowest rate was 5.83 % in Gondella variety and the highest one (25.67%) was detected in Malkabi variety. The relative wet weight loss percent reached the highest value (30.80%) in Malkabi variety and the lowest one was 5.20% in Pertomoda after one month of storage. After three months of storage, Malkabi date variety recorded the maximum value of the relative wet weight loss(28.84%), whereas the minimum value (6.55%) was recorded in Gondella variety. The results clear that all tested dry date varieties were infested with O. surinamensis and no immune variety wasfound free from the insect infestation with preferable some tested varieties to the insect.