Population Density of Certain Piercing-Sucking Insects Infesting Wheat and its Associated Coccinellid Predator in Relation to Sampling Methods

Abstract

Population trends of certain piercing-sucking insects infesting wheat i.e. Thrips sp L., Empoasca spp and its associated coccinellid predator Coccinella undecimpunctata was determined by using yellow sticky traps (YST), direct count and sweep net methods on wheat fields. The tested taxa exhibited one seasonal peak only/each. By using YST both Thrips sp and Empoasca spp showed that their peaks at March 5 with a general average of 242.5 and 12.25 individuals/ 1 YST, respectively. No or very few numbers of C. undecimpunctata were collected by this method. Concerning the direct count method, Thrips sp and C. undecimpunctata exhibited their peaks at February 26 with a general average of 10.50 and 19.50 individuals/10 wheat tillers, respectively. However, Empoasca spp is completely disappeared. By using sweep net both Thrips sp and Empoasca spp revealed that semi-equal peaks at early and mid-February, while C. undecimpunctata peak was appeared one to four weeks later. Concerning the effectiveness of the used sampling methods it is appeared that yellow sticky traps can be used successfully to determine thrips populations. However, the direct count inspection can be considered as the most suitable method for determining coccinellid population trends. On the other hand, sweep net can be used as a successful method for determining Thrips sp, Empoasca spp and C. undecimpunctata in wheat fields.