Investigation on biology and population dynamics of Flea beetles (Phyllotreta spp.)on canola in Saveh region .

At present , flea beetles are the main pests of Canola seedling across the country .In Saveh region ,based on the collection made during the study,Phyllotreta corrugata is the causative agent and damage winter canola at early stages feeding on preliminary leaves and cotyledons in Autumn but members of the other genus Psylliodes ,in addition to adult feeding at the time, continue on feeding petiole and stems of canola seedlings in spring at larval stage .Ph.corrugata reported from Saveh,Gorgan and Tarom could be injurious if agronomic control measure were not done properly , then chemical control may be inevitable. The adult are 1.8-3.2 mm in length ,tibia and tarsus along with antennal segments are russet and the remaining parts are metallic black to green and blue ,eggs are minute, oval ,bright yellow and 0.42-0.56 mm in length ,larvae are white to cream and initially their size is 0.85to 1.17 mm but increases up to 2.8 to 5.6 mm at the last stage ,head and thorax are blackbrown, legs are thin and there are black spots distributed on the body surface ,Pupa are visible. Observations made during 2002-2003 showed that these beetles over winter as adults (under herbal remnant located around the fields) and appear from early to late March in fields feeding on different cruciferous host plants. Adults feeding having been completed, they mate and oviposition occurs individually or in small groups on or one on below the soil surface around the host plant roots .Egg incubation periods larval and pupal developments last 6-11 ,18-28 and 9-15 days respectively under 23 5± and 60±5 % Rh .In Saveh new adult appear from early June when canola is harvested in the region .New adults feed on newly emerged canola and crucifer weeds, then so aestivated under plant remnants .In autumn when fresh canola seedlings are avail able ,aestivated adults start feeding on them which is continued till early Dec. based on the data collected by yellow sticky traps. Overall results reveal that Ph.corrugata is a monovoltine insect pest in Saveh region.