| Cotton seedling damping off caused by Rhizotonia solani is a major fungal disease.Seed coating and foliar spraying are common control methods in agricultural production.In recent years,the research on new seed coating agent and endogenous hormone has been rising gradually,which not only has a certain effect on the occurrence of cotton seedling diseases,but also is environmentally friendly.This study analyzed the control effect of three different agents on cotton seedling damping off and effect of cotton growth by seed coating and foliar spraying.Our study will provide reference for exploring the new low toxicity and high efficiency control agents,and provide experimental basis for the sustainable development of cotton.The main results are as follows:1、The control efficiency of 35%thiram·carboxin·thiamethoxam on cotton seedling damping offThe control efficiency of seed coating with 35%thiram·carboxin·thiamethoxam on cotton seedling damping off were studied and analyzed.The result showed that 750 g/100 kg seeds coated with 35%thiram·carboxin·thiamethoxam was showed the best control effect.The control efficiency was 91.75%and 86.63%at 13 days after full seeding in 2018 and 2019,there was significant difference from other two treatments with 500 g/100 kg and 625g/100 kg,and the control effect was higher than that of 12%weixiuling WP and 50%thiram WP.It is recommended that 35%thiram·carboxin·thiamethoxam seed-coating agent at the dosage of 750 g/100 kg seeds（effective ingredient 262.5 g/100 kg）be used in production,which has good control effect on cotton seedling Damping off,and the control effect is long,stable and safe.2、The control efficiency of 45 g/L metalaxyl·myclobutanil seed coating agent on cotton seedling damping offThe result showed that 500 g/100 kg seeds coated with 45 g/L metalaxyl·myclobutanil seed was the best control effect.The control efficiency was 75.45%at 6 days after full seeding,there was no significant difference from the treatment with 400 g/100 kg,but there was significant difference from other two treatments with 300g/100kg and 400g/L Weixiu·Fumei,151.63g/L metalaxyl and 11%azoxystrobin.Observation after treatment showed that there were no dwarfing,chlorosis,deformity and other abnormal phenomena in cotton seedlings,and there was no significant effect on other pests and no target organisms.The recommended dosage of 45 g/L metalaxyl·myclobutanil seed coating agent is 500 g/100 kg.3、The effects of novel plant endogenous hormones on cotton seedling damping off and cotton growthThe plant endogenous hormones（Jinshangtianhua）by foliar spraying had a certain control effect on cotton seedling damping off,and the control effect gradually decreased with the increase of dilution ratio.The results on two different application methods showed that the effect of foliar spraying was better than that of root irrigation.The results of application of endogenous hormones on the growth and development of cotton showed that the main root increased by 5.1 cm,SPAD increased by 1.1 cm,plant height increased by 3.7 cm,boll number increased by 1.2,seed cotton yield increased by 617.25～1238.7 kg·hm-2compared with the control.In addition,the effect of hail disaster on cotton yield was significantly reduced by the application of Jinshangtianhua,and the lint yield was basically the same as that of the control in the replanted cotton field after hail disaster.The above results showed that the endogenous hormone（Jinshangtianhua）not only had a good control effect on cotton seedling damping off,but also significantly affected the main agronomic traits of cotton,increased cotton yield and enhanced cotton stress resistance. |
