Evaluation of the Different Irrigation Time on Agriolimax agrestis Damage in Lettuce Fields of Tehran Province

One of the effective managing methods for slugs control is cultural method. A field study on the effect of different irrigation times on slug (Agriolimax agrestis)(Stylommatophora: Limacidae) damage in lettuce plants was carried out in the Varamin region in 2009. Treatments consisted of irrigation at various times: 1- irrigation in the morning, 2-irrigation after sunset 3-irrigation after sunset with Fericol bait (5gr/m²) and 4-irrigation after sunset with Methaldehyde bait (2.5gr/m²). The experiment conducted in a randomized complete block design with four replications. Each replicate consisted of three rows of 3 m length and 50 cm width and with in row plant spacing of 25 cm with a total of 36 plants /plot. The results indicated that maximum damages (based on the feeding of leaves) and minimum lettuce yield obtained for irrigation after sunset treatment with 52.82±3.4 percent of damaged plants with a lettuce yield 20.12 ton per hectare. Minimum damages with maximum yield found with treatment 4 with 10.53±2.8 percent damages with lettuce yield of 39.3 ton per hectare. Treatments 1 and 3 were with 10.92±2.7 and 10.71±2.3 percent damage and lettuce yield of 39.01 and 39.17 ton/ha respectively. There was no significant differences between the lettuce yields in the treatments 1, 3 and 4 at level of 5% (P>0.05) and were placed in group A. Also, it seems that changing irrigation times (treatment 1) is one of useful strategies in IPM method for controlling and reducing slug damage to lettuce plants which it has lettuce yield near to treatments 3 and 4.