Study on host preference and leaf damage of Spodoptera littoralis larvae in four sugar beet cultivars under laboratory conditions

Spodoptera littoralis (Boisduval) is one of the major pests of sugar beet in southern parts of Iran and host plant resistance is an important component of its integrated management. Because of some problems in experimentation under natural field conditions, this study was conducted to evaluate the resistance of 4 sugar beet cultivars ("6/7mu", "Rasul ", "Shiran", "4/7 Hybrid") using leaf discs and detached leaves under laboratory conditions. Host preference of neonate larvae was evaluated using leaf discs (5 mm diam) placed on a filter paper within a petri dish (0 cm diam) and replicated five times (0 larvae per replicate). Leaf damage was examined by detached leaves, embedded in percentage agar-agar in a plastic jar (500 ml capacity) infested with 5 larvae, using a randomized complete block design with 4 replicates. The experiments terminated when the of the more than 90 percentages first leaf was damaged. Results showed that there was no significant difference among cultivars for host preference of neonate larvae while they differed for leaf damage significantly (P<0.05). The cultivars "6/7 mn" and "4.7 hybrid" with mean of 5.5 and "Shirin" with mean of 8.5 showed the lowest and highest leaf damage, respectively. The cultivars did not show significant differences in larval survival and larval weight. Based on the results, sugar beet detached leaf assay can be used as a rapid, inexpensive technique to evaluate sugar beet germplasm.