| Seed coating was an encouraged treatment before crop planting in agriculture practices in our country.Chemicals in the coating-agents have a control for the diseases and pests either in the plants or the soil.Nowadays,seed coating has been widely applied in most of farms European and the USA,while in China,this coating technique was rarely used in oilseed rape,which is the most important oil crop in our country.This study was therefore conducted to be research the coating treatment on the seeds of oilseed rape,which would be a guidance for the agriculture processes.The results are shown as follows:1.Effects of coating agents on germination and seedling-growth of oilseed rapeThe results showed that 300 mg ai·L-1 is the highest dose which the oilseeds could tolerant to germinate successfully;however,if the coated seeds were rinsed after a treating time shortened to no longer than 2 h,the side-effect of the chemicals in the coating agents could be eliminated.According the presences of the germinated seeds and the following seedlings,ten tested varieties in this study could be divided into three types: type I,which has the highest tolerance to coating agents,concludes zheping4 and zhongshuang11;type III,which is the most sensitive,concludes zhongheza488 and qinyou79;and others belongs to type II.2.Effects of imidacloprid as a seed-coating agent on germination of oilseedCoating treatment with imidacloprid at doses in the recommended range has no significant effect on the accumulative germination ration on the oilseed rape;but coating with imidacloprid could inhibited the activities of α-amylase at the early stage for a short time.So the needed revertose was lack,which lead to a lowered germination,and inhibited the germination potential.However,such alterations appeared to be not significant as the seedlings grew up.It is therefore suggested that coating with chemicals at an appropriate dose could have a somewhat effect on seed germination,but not significant;which was reflected by the unchanged accumulative germination.3.Effects of imidacloprid as a seed-coating agent on seedlings’ growthCoating treatment with imidacloprid at dose of 600 mg ai·L-1 had a significantly adverse effect on the seed germination and seedlings’ growth,but the inhibition was weakened as the seedlings grew up.When the seedlings grew to the six-leaf stage,the treated seedlings were not different from the controls.The repressed of root development at the early stage was repaired to a normal level,when six leaves were developed.4.Effects of imidacloprid as a seed-coating agents on the pestsThe total leaf area of the treated seedlings was significantly increased,and the pest-infested leaf area was significantly decreased.Average pest per seedlings was also significantly decreased.Treatment with imidacloprid at the effective dose targeting to aphids could have somewhat effects on the whiteflies and thrips.Such influences could make an acceleration of these pests’ population growth,and a fastened resistance development.5.Effects of imidacloprid as a seed-coating agents on the aphidsTreating with imidacloprid as a seed-coating agents could killed no more than 50% aphids on the plants,but had a significant avoidance effect on the aphids and their offspring.On the other hand,data of EPG confirmed that the ingested food of aphids on the treated plants were decreased,which suggested that diffusion coefficient of virus could be inhibited. |
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