Economic threshold, injury levels and population density of Tetranychus urticae and Petrobia tritici infesting Wheat plants at Sharkia and Beheira Governorates, Egypt

Abstract

Assessment of the economic damage threshold (ETLs) and economic injury levels (EILs) of Tetranychus urticae and Petrobia tritici infested wheat (Giza 168) were studied at Sharkia and Beheira Governorates, during 2016/2017 season. Also, the population density of both mite species was achieved. Results cleared that the values of (ETLs) were less than (EILs) levels. The (ETLs) values of T. urticae on wheat plants at Beheira and Sharkia (as x1 &x2 peaks results) ranged 4-4.33 and 4.33-10 individuals /leaf, while the (EILs)values ranged 4.33-5 and 10.33- 13.33 Individuals /leaf for the two localities, respectively. In the same trend the ETLs of P.tritici on wheat plants at Sharkia and Beheira (as x1 &x2 peaks results) ranged 3.33-4.00 and 3.33 individuals. /leaf, while the EILs ranged 5-5.33 and 3.67-5.33 Individuals / leaf for the two localities, respectively. In addition, the results of population density of the two mite species showed that, there were two peaks for each species at the two study localities.The results of statistical analysis detected positive insignificant correlation was observed between the population of the two mite species and average temperature while it was negative and insignificant with average of R.H. %. The relatively high effect as partial regression (E.V. %) for tested climatic factors of 5.18% was recorded for average temperature on P.tritici at Sharkia Governorate, while the relatively high multiple correlation for the two tested climatic factors together was 17.07% recorded on P. tritici at Beheira Governorate.