Effect of Imidacloprid and Thiamethoxam on Vitality of Stored Wheat Grains and Sucking Pests in Beginning of Growing Season

The research was carried out at the Center for Research and Studies of Biological Control and in the field of the Faculty of Agriculture at Damascus University in 2017. The study aimed to investigate the effect of treating wheat grains T. aestivum with one of the two insecticides imidacloprid and thiamethoxam on the viability of the grains after treating them according to the usage rates recommended by the manufacturer for field use and storing them for different periods of time from one month to ten months. The results showed that there were no significant differences in the percentage of wheat germination between the different treatments at each time, it was 80.5, 77, 82.5% after storage the treated grains for one month and it was 83, 80, 78% after ten months of storage, in the treatment of the control and imidacloprid and thiamethoxam, respectively. The results also showed that there were no significant differences in the root length of wheat seedlings between the different treatments at each time. It was 8.8, 9.3 and 9.4 cm after the treated grains storage for one month and it was 8.85, 10.71, 9.50 cm after ten months of the treated grains storage in the treatment of the control, imidacloprid and thiamethoxam, respectively. The results showed that there were no significant differences in the length of wheat seedlings between the different treatments at all times. It was 8.8, 8.35, 8.75 cm after the treated grains storage for one month and it was 7.08, 8.80, 7.82 cm after ten months of storage in the control , imidacloprid ,. thiamethoxam treatment, respectively. The results also showed that there were no significant differences in the dry weight of wheat plants between the different treatments at each time, as it was 0.053, 0.026, 0.025 g after the treated grains storage for one month and it was 0.017, 0.014, 0.017 g after ten months of storage in the control , imidacloprid and thiamethoxam treatment, respectively. (Schizaphis graminum : Aphidae: Homoptera) and green leaf hopper insects (EmpoascadecipiensPaoli: Homoptera: Cicadellidae) appeared on wheat plants when cultivated in the field after their grains were treated with water only and stored for different time periods from 1 to 6 months.The results showed an increase in the number of insects in the field on wheat plants over time, regardless of the period of storing grains. After 15 days of planting, the number of aphids in the field reached 0.2, 0.6, 1.1 insects / 10 plants, and the number of green leaf hopper was 1.4, 1.5, 2 Insect / 10 plants when planting grains treated with water only and stored for a month, 3 months and 6 months, respectively. After 64 days after planting, the number of grasses aphids reached 25, 27, 35 aphids / 10 plants, and the number of green leaf hopper insects reached 7,7,7 insects / 10 plants when the grains were stored for one, 3, 6 months. The effect of residual toxicity of imidacloprid and thiamethoxam insecticides in treated wheat grains and stored for different periods of time on the number of insects was also studied. The results showed that the treatment of wheat grains with imidacloprid and thiamethoxam showed great protection for wheat plants from infection with insects after 15 days of planting, significant differences appeared in the number of aphids between treatment of the control and treatment with insecticides at a significant level of 5% regardless of the time of storage of grains, whereas, the average of insects number in the control treatment when storing the treated grain for a month was 0.2 insects / 10 plants, while it was 0 - 0 insects / 10 plants, when treated with imidacloprid and thiamethoxam respectively. Similarly, the average of insects number in the control treatment when storing the treated grains for a period of six months was 1.1 insects / 10 plants, while it was0 - 0.2 insects / 10 plants when treated with Imidacloprid and thiamethoxam respectively. After 64 days of planting wheat grains treated with imidacloprid and thiamethoxam and stored for different periods of time, the results showed that the significant differences between the different treatments at all storage times increased due to the increase in the number of insects on all plants atall treatments. The results also showed the residual toxicity effect of wheat grains treated with imidacloprid and thiamethoxam and stored for different periods of time on the number of green leaf hopper insects. It was noted that the treatment of wheat grains with imidacloprid and thiamethoxam showed great protection for wheat plants from infection with green leaf hopper insects after 15 days of planting. Significant differences appeared in the number of hopper insects between the control treatment and the insecticide treatment at a significant level of 5% regardless of the storage time of the treated grains, and imidacloprid was the best compared to the rest of the treatments. It was observed that the effectiveness of both insecticides continued for a period of up to five months and lost their effectiveness upon storage for six months. Both insecticides achieved protection for plants from insect infestation, but the levels of protection varied, as imidacloprid was the best, followed by thiamethomxam. It was also noticed that despite storing the treated grains for a long period of time that reached six months, the number of aphids and green leaf hoppers on plants in the treatment of imidacloprid and thiamethoxam was the lowest compared to the control