Studying on susceptibility of some alfalfa varieties to alfalfa seed chalcid (Bruchophagus roddi Guss.)

    The alfalfa seed chalcid, Bruchophagus roddi (Guss) is one of the most serious alfalfa seed pests in Iran. There are differences in susceptibility to B. roddi between alfalfa cultivars. The present study was carried out to examine susceptibility of some alfalfa clones to a alfalfa seed chalcid. The experiments were arranged as a Randomized Complete Block Design (RCBD) with 25 treatments (25 alfalfa cultivars) repeated in three replicates and fulfilled in Ismaeil Abad Station, Ghazvin, Iran. Sampling was conducted in four phases from 12^th Aguest to 21^st September with an interval of 10 days. Analysis of variance was individually carried out for each phase, combined analysis were also done for all phases. Comparison of the treatment means using Duncan test showed that there was significant differences (P<0.01) in number of seeds per pod produced by the treatments, Gharayonje variety with 6.183 and variety of Kouzareh with 4.379 had the most and least average of seeds per pod, respectivly. The significant differences were also observed in undamaged seeds, sampling times and interaction, as variety of Kefandoa with 91.46% and variety of Rahnani with 79.45% had the most and less of undamaged seeds respectivly. In comparison of sampling times, there were also significant differences in seed damage between sampling time. The least damage (2.90%) was observed in the seeds harvested in first sampling (mid-August), however the highest percentage damage (20.37%) caused by the pest occurred in third sampling (early September). The results showed that in the early September, the wasp activity reaches its peak. Therefore it can be concluded that mid-August is the best harvesting time to reduce the pest damage to the seed crops.