Investigation on the resistance of onion cultivars to Thrips tabasi Lind. in Hormozgan Province, Iran

Subject Areas : entomology and othea arthropods

J. Abbasi ¹ , M. Fallahzadeh ² , S. Bagheri ³

1 - Department of Entomology, Agricultural Faculty, Islamic Azad University, Jahrom, Iran/ Plant Protection Managment Office of Fars, Iran
2 - Department of Entomology, Jahrom Branch, Islamic Azad University, Iran
3 - Department of Plant Protection, Safiabad Agricultural and Natural Resources Research Center, Dezful, Iran

Received: 2012-05-17 Accepted : 2012-12-14 Published : 2012-11-21

Keywords:

Abstract :

Sensitivity and tolerance rate of common cultivars were evaluated in complete randomized block design with six treatments (Local Red, Local White, Savanasuit, Primavera, Early White Grano and Riobravo) to Thrips tabaci Lind. Of onion and four replications in the field condition in Hormozgan province. Sensitivity of cultivars was evaluated based on number of larvae and adults. Every two weeks adults and larvae of the plant were separated and counted using washing method. The tolerance rate in two experiments (treated and untreated) was evaluated based on thrips and yield at the end of the season. Soil applications of Imidiacolopride 35% suspension were used to eliminate the pest from plants in treated experiment. Results showed that there was no significant difference among treatments in term of number of adults. There were significant differences among treatments in terms of larvae and sum of the adults and larvae. Local Red and White cultivars with average of 22.88 and 21.18 thrips/plant (sum of adults and larvae) were the most sensitive and Primavera and Savanasuit cultivars with 8.8 and 11.17 thrips/plant were the most tolerant cultivars. Thus Local Red and White cultivars are the more sensitive, Primavera and Savanasuit cultivars are relatively resistant and Early White Grano and Riobravo cultivars are semi susceptible. Also there were significant differences in yield between treated and untreated experiments. So, in both experiments (treated and untreated) cultivar Riobravo with the average yield of 41667 and 51000 kg/ha had the highest tolerance. Despit relatively large population of thrips on Riobravo variety (similar to susceptible cultivars Local Red and Local White), this cultivar produced the highest amount of yield (24% more) compare to unsprayed most tolerant.