EFFECT OF PLANTING DATES AND SPACES ON THE INFESTATION OF CUCUMBER VARIETIES WITH TWO-SPOTTED SPIDER MITE, TETRANYCHUS URTICAE KOCH

Abstract

Field experiments were conducted to study the effectiveness of three cucumber planting dates (March, 15th; April, 15th and May, 15th), three planting spaces (20, 30 and 40 cm) between cucumber seeds and three varieties of cucumber (Al-Zaeim, El-Nemse and Prince) on the population densities of Tetranychus urticae Koch during 2015 and 2016 seasons. The results indicated that, the three variables (planting dates, spaces and varieties) had pronounced effects on the numbers of T. urticae movable stages on cucumber plants. The population density of T. urticae movable stages was affected significantly by the tested planting date, the earliest planting date (March, 15th) harboured the lowest population of T. urticae movable stages (6.62 and 4.78 individuals/inch2) in the two seasons, respectively. Cucumber plants cultivated at the longest planting space (40 cm) infested by the lowest rate of T. urticae movable stages (6.22 and 4.42 individuals/inch2) in the two seasons, respectively. The tested cucumber varieties showed significant differences in the infestation rates by T. urticae movable stages. Al-Zaeim variety was the least infested by T. urticae movable stages (9.27 and 6.12 individuals/inch2) for the two seasons, respectively. The results revealed that the lowest seasonal mean of infestation was 1.08 and 0.36 individuals/inch2 during the two tested seasons, respectively on cucumber plant (Al-Zaeimvariety) sown at the largest space (40 cm) during earliest planting date (March, 15th). While the highest infestation levels (37.03 and 35.33 individuals/inch2 in the two seasons, respectively) occurred on cucumber plants (Prince variety) planted at the closest planting space (20 cm) during last planting date (May, 15th).