The Ecological Regulation Of Soybean Planted Adjacent To Potato And Maize On Piercing-sucking Pests In Soybean Field

Soybean is an important oil crop planted in our country,its yield and quality are closely related to the pests in soybean fields.So far,using chemical method is still the most important part in soybean field's pest control,and it also causes the enhance of pest resistance to pesticides and the damage of local ecosystem,to solve this problem,this paper aimed to increase biodiversity and enhance the self-regulation ability of soybean field by plant a different crop adjacent to it,with the reference of major planting crops in northeast China,I also investigated and analyzed the insect population structure of the soybean fields adjacent to potato and maize fields and monoculture soybean field;made a compare of the population dynamics and dominant species of both natural enemies and pests,the community characteristic of the field's ecosystem stability,the main influence factors of the field ecosystem's population stability among three planting patterns;analyzed the relationship changes between pests and their natural enemies in soybean fields adjacent to potato and maize fields and provide a guidance for the design of planting pattern and reduce the use of pesticides in the practical production.The main results are as follows:During the investigation in 2014 and 2015 in Harbin,XiangYang farm,48 insect species which belong to 7 orders,24 families were recorded,among them,2 orders,8 families,12 species are piercing-sucking pests,3 orders,9 families and 14 species are leaf-eating pests,5 orders,6 families,8 species are natural enemies.The dominant piercing-sucking pests in soybean field are soybean aphid,soybean thrip,winged aphid and Acyrthosiphon solani,dominant natural enemies including minute pirate bug,spider,Harmonia axyridis,Propylaea japonica and Chinese green lacewing.Among them,minute pirate bug and spider occurred earlier and kept a large population in soybean field adjacent to potato field,main natural enemies showed a significant following effect and had a more notable influence on pests.In contrast to control field,pests of the two planting patterns had an obvious reduce on their population and a later peak with less quantity during this period,therefore,soybean planted adjacent to potato and maize modes show a hysteresis in the control of soybean aphid.During the whole growing season,in the soybean field adjacent to potato field,the quantity of soybean aphid cut down by 42%comparing with control group while the population ofAcyrthosiphon solani cut down by 38%;in the soybean field adjacent to maize field,the population of soybean aphid and Acyrthosiphon solani has a 59%and 30%cut down respectively,the maize-soybean mode can control soybean aphid more effectively,while the potato-soybean mode is better at the control of Acyrthosiphon solani.In 2014,the population of Chinese green lacewing in potato-soybean group increase by 45%comparing with control group while the population of minute pirate bug increase by 33%.In 2015,the population of Chinese green lacewing in maize-soybean group increase by 36%comparing with control group,the population of spider in potato-soybean group increase by 47%.Both potato-soybean mode and maize-soybean mode increased the population density of Chinese green lacewing effectively,potato-soybean mode also had a distinct effect on the increase of spider and minute pirate bug population,proved that different crops planted near soybean field could have different influences on pests and their natural enemies.Crop diversity can be beneficial to the occurrence of spider and minute pirate bug along with their population stability.A comparison has been made among soybean-potato group,soybean-maize group and the control about their structure of insect community.Overall,soybean-potato group and soybean-maize group have nearly the same evenness index,diversity index and dominant concentration index,the species abundance of potato-soybean group are 27 and 28 with a highest record,31,which are obviously higher than control group and prove that potato-soybean mode can increase the species abundance;As for diversity index,maize-soybean group(1.8462)>potato-soybean group(1.5392)>control group(1.0993);maize-soybean group has a maximum evenness index,0.5541,while potato-soybean group is 0.4781,control group is 0.3374.Plant soybean adjacent to maize and potato fields can increase diversity index and evenness index,change the main factors that influence the population structure stability,soybean-maize group become markedly higher than the other two groups on these indexes and have a better effect on pest control.By analyze the principal component,I found that in 2014,the factors influenced the community structure are diversity and species richness in potato-soybean group with abundance and species richness in maize-soybean group respectively,in 2015,the factors that influenced the community structure of potato-soybean group are abundance and species richness,while the factors of maize-soybean group are evenness and diversity index,which suggests different crops that planted adjacent to soybean has different influences to the soybean field' s community structure stability,this cropping pattern has an obvious effect to species diversity.By analyze the results of correlation degree,there are some conclusions can be made.In 2014,the natural enemies that have the maximum correlation degree with pests in control group are Chinese green lacewing(0.6525)and Harmonia axyridis(0.6521),in potato-soybean group the natural enemies that play the same role are Chinese green lacewing(0.8179)and spider(0.6899),while the maize-soybean group are Harmonia axyridis(0.6773)and Propylaea japonica(0.6826).Soybean planted adjacent to potato can increase the amount of spider,besides,soybean planted adjacent to maize can help Propylaea japonica keep a higher population,and different crops planted near soybean field could have different influences on pests and their natural enemies.In 2015,the natural enemies that have the maximum correlation degree with pests in control group,potato-soybean group and maize-soybean group are spider(0.8975)and Harmonia axyridis(0.8103);minute pirate bug(0.8768)and spider(0.8036);minute pirate bug(0.8493)and spider(0.8902)respectively,both the treatment groups increased the minute pirate bug's correlation degree with pests.On September 3,2014,the predator prey ratio of potato-soybean group reaches to 0.1030,the maize-soybean group reaches to 0.1153,on August 16,2015,predator prey ratio of both potato-soybean and maize-soybean group reached to the maximum value with 0.1257 and 0.2185 respectively,while control group only had a 0.0363.the predator prey ratio of two treatment groups have significant differences from control group and play an important part in the regulation of pest.As a result,plant soybean adjacent to different crop fields can increase the population of natural enemies effectively,be propitious for them to regulate pests and provide a basis for ecological regulation and reasonable usage of pesticides.