The Population Dynamics, Thermal Activity Thresholds And Olfactory Behavior Of The Aphid Parasitoids (Aphidius Avenae And Aphidius Gifuensis)

Wheat aphids are the momentous pest in the wheat fields of China, even all over the world. Hymenopterous parasitoids are great significance for natural control of aphid populations. However, in order to take advantage of Aphidius in aphid control, this paper made a primary study on the population dynamics, thermal activity thresholds and the olfactory behavior to alarm pheromone (E-β-Farnesene EβF) and sex pheromone (Z,E-Nepetalactone NEP) of the aphid parasitoids(Aphidius avenae Haliday and Aphidius gifuensis Ashmead).1. Through the two consecutive years’survey, we identified that the composition and proportion of different species of aphid parasitoids in the wheat field of Tai’an and Langfang. In the whole investigation period in2010and2011of Tai’an, from April28th to May28th, the ratio of A. avenae was68.87%and55.03%respectively, while Aphidius gifuensis was27.62%and41.30%respectively. But in Langfang, from May2nd to June7th in2010and2011, the ratio of A. avenae was93.43%and94.77%respectively. A. gifuensis was an aphidius that predominately specializes in the parasitism of aphids feeding on wheat before wheat filling stage, while A. avenae was the dominant species during wheat milk ripe stage in Tai’an. Aphidius avenae was the dominant species in Langfang. In Tai’an area, aphid parasitoids adults were found at the end of April. Mummy aphids were found at the beginning of May. During wheat filling stage, the number of mummy aphids increased dramatically. Then the population of A. avenae reached a peak. Because of the fewer aphids, the number of mummy aphids was decreased significantly, as well as the number of aphid parasitoids. The wheat growth period was delayed in Langfang than that in Shandong area due to the geographical differences, as well as the occurrence and damage of aphids. The occurrence and the burst of aphid parasitoids were delayed about1week than that in Tai’an.2. The SCPs of female A. gifuensis from the higher latitude regions of Langfang were significantly lower than those from lower latitudes of Tai’an area. Female A. gifuensis from Langfang have stronger ability to coldness than those from Tai’an. Female A. avenae were more thermally tolerant than female A. gifuensis at heat coma, activity recovery and WTmin temperature (P<0.05). Female A. gifuensis had stronger ability to coldness than female A. avenae. The WTmin and activity recovery temperature of female A. gifuensis were significantly lower than those of female A. avenae. 3.100times diluted EβF had extremely significant attraction on female A avenae (P<0.01), and it had significant attraction on male A. avenae (P<0.05), while it hadn’t significant attraction on male and female A. gifuensis.1000times diluted EβF had extremely significant attraction on male and female A. gifuensis (P<0.01).100times diluted NEP had significant attraction on female A. gifuensis (P<0.01), while it had significant attraction on male A. gifuensis (P<0.05), and these4different concentrations of NEP on A. avenae had no significant attraction.Tai’an and Langfang belong to Huanghuaihai wheat area in China. The experimental sites were chosen in Tai’an and Langfang. A systematic comparison was done between these two species of wheat aphid parasitoids, occurrence, cold resistance, thermal activity thresholds and the olfactory behavior to EβF and NEP. All of these can provide some preliminary theoretical basis in seasonal dynamics population of aphid parasitoids in wheat field from different regions; predict the occurrence trend, build natural enemies resources database, field application of pheromone and biological control by using natural enemies.