Effect of flour and pasta debris on larval development of Rhyzopertha dominica

The development of Rhyzopertha dominica (F.) larvae on different types of flour and on pasta debris was evaluated under laboratory condition. Tests were carried out on wheat flour, semolina, wheat bran, corn meal, corn starch, rice flour, buckwheat flour, chickpea flour, almond flour, chestnut flour, potato starch, and pasta debris. Two layers of flour or pasta debris, 3 and 6 mm high, were placed in Petri dishes and 20 first instar larvae were put into the middle of the substrate. Four replicates were carried out for each combination of substrate, particle size, and thickness of the layer. The emergence of adults was assessed daily. Chestnut flour and semolina permitted the development of larvae in a period of time similar to that observed in cereal kernels while chickpea flour and wheat flour were less appropriate food; in fact, only 25% of larvae underwent complete development into adults. In the case of corn meal, rice flour, and wheat bran, only 5% of adults emerged, while larvae were unable to develop on corn starch and potato starch. Although R. dominica is a well-known pest of pasta, pasta debris was less suitable for the development of larvae, as few adults emerged and a longer development time was observed. A three-millimeter layer of suitable food was sufficient for the development of larvae, although a higher number of adults was observed in the 6 mm layer.