The Analysis Of Reasons On Different Control Efficiency Of Seed Dressing With Imidacloprid Controlling Wheat Aphids Technology In The Whole Growth Period In Different Areas

The technology of wheat seed dressing with imidacloprid to control aphids in thewhole growth period, which has an good and long period efficience, has been rapidpopularization and application since it been put into actual production after research anddemonstration in many years by Plant Protection Institution of Hebei Academy ofAgriculture and Forestry Science and some other units. However, because of the differenceof sowing date, seed sowing rate, local climatic conditions, soil conditions, water andfertilizer conditions and so on from south to north in Hebei Province, the difference ofcontrol effect in different areas were occured. Therefore, in order to clear the differentcontrol efficiency about this technology in different regions, analyze the maininfluencing factors and finnaly improve this technology further, the wheat seed-dressingimidacloprid experiment did in three areas of Shijiazhuang, Baoding and Tangshan for thefurther development of appropriate technical details in the different regions of HebeiProvince. Specific findings are as follows:1.The comparation of control effect to aphids by seed dressing with imidaclopridduring the whole wheat growth period in different areasThe results of seed dressing with imidacloprid preventing and controlling wheataphids in different areas show that they all can prevent and control aphids in the wholegrowth period in different areas in Hebei. At the peak of wheat aphids, from May27thtoJune8th,the control effect to aphids of360ai g/100kg were both above86.86%inShijiazhuang and Baoding, and both more than95.59%of420ai g/100kg. However,compared with Shijiazhuang and Baoding, the control effect in Tangshan was less to wheataphids, in where the control effect of dressing dose of360ai g/100kg and420ai g/100kgwith imidacloprid were over80.12%and91.60%respectively at the peak of wheat aphids,June3thto June14th.The survey result of the occurrence conditions of natural enemies suggest that thistechnology has less impact on the natural enemies. In the same area, there were samespecies of natural enemies between different doses of seed dressing field with imidacloprid and the control field, and different areas had different dominant species of natural enemies.At the peak of occurrence amount of wheat aphids, dominant species of natural enemies ofwheat aphids are aphid parasites and lacewing in Shijiazhuang and Baoding,and aphidparasites and ladybirds are mainly in Tangshan. Aphid parasites accounted for90.21%ofthe total natural enemies in Shijiazhuang, aphid parasites and lacewing accounted for89.08%in Baoding, and aphid parasites and ladybirds accounted for75.00%inTangshan.The predator prey ratio were all in the controllable range of1:150or more inthe seed dressing fields of Shijiazhuang, Baoding and Tangshan, which showed less impacton the natural enemies of wheat aphids to a certain extent. Compared with conventionalcontrol method, this technology plays a role in the protection of natural enemies.The result of1000-grain weight in three areas shows that the1000-grain weight ofseed dressing field were all more increased than without dressing field. The1000-grainweight of seed dressing fields were significantly higher than not dressing fields inShijiazhuang area, and360ai g/100kg, the largest increased treatment, was higher than2.98%-2.99%in other dressing areas, but not significant between different dose of seeddressing. The1000-grain weight of420ai g/100kg treatment was significantly higher thanthe other treatments in seed dressing fields of Baoding area，which was more than3.04%-6.77%of the treatments of210ai g/100kg and360ai g/100kg and12.49%higher than non-pesticide control. In Tangshan area, only420ai g/100kg was significantlyhigher than other treatments.The results of the determination of imidacloprid residue in wheat plant in differentareas were different. In Baoding, the imidacloprid residue in wheat plant showed aobviously increase with the dose of seed dressing increasing. In Shijiazhuang andTangshan, the residue increased with the dose of seed dressing increasing from the lowdose to the middle dose, and then reduced from the middle dose to the high dose. Indifferent areas, the imidacloprid residue of Shijiazhuang and Baoding were all higher thanTangshan in wheat plant at the same dose levels of seed dressing.2.Analysis on influencing factors of control effect to wheat aphids after seed dressingwith imidacloprid in the whole growth period in different areasThe survey of aphids occurrence regularity conducted in Shijiazhuang, Baoding,Tangshan shows that the beginning date and the peak of aphids were all later, occurrenceamount were less and occurrence period were shorter in2013compared with2012inHebei Province. The peak of aphids occurrence was respectively reached on June2, June3,June9in Shijiazhuang, Baoding and Tangshan, and aphids on each hundred wheat plantswere followed by5888,1657and1390aphids per hundred plants. Aphids Occurrenceamount of Shijiazhuang was the largest, and Tangshan was the least. The pH value, organic matter, salinity of the soil in Shijiazhuang, Baoding, Tangshanof Hebei provice were measured, the water-fertilizer condition, planting pattern and seedsowing rate in these three areas were investigated and the temperature during aphidsoccurrence period were recorded. The results show that water-ertilizer conditions andplanting patterns were basically same in the three areas, and the pH value, organic matterand salinity of the soil were not significant difference. Compared the temperaturethroughout the growing period of wheat in these three areas, the results showed that thetemperature of Tangshan area was always the lowest. The temperature of Shijiazhuang washigher than Baoding in the early, but lower later, and has no difference overall.Preliminary judgment, the most basic reason that resulting in this control effectdifference is the different temprature of different areas. The relatively low temperature inTangshan area not only affected the occurrence period of aphids and the amount ofoccurrence, but also affected the absorptivity and efficacy of imidacloprid of wheat plant.