Functional Response Of Neoseiulus Barkeri And Its Protection And Utilization

Neoseiulus barkeri is a polyphagous phytoseiid mite, which mainly preys onspider mites and thrips, and is widely used currently in the biological control in China.The efficiency of N. barkeri preyed on different stages of Tetranychus urticae (female,nymph and egg) and newly hatched nymphs of Frankliniella occidentalis werestudied in this thesis. Meanwhile, the selective toxicity of9kinds of acaricide to N.barkeri and T. urticae, and the control effect of releasing predatory mites on thedynamics population of T. urticae on ginseng fruit and eggplant in greenhouse weredetermined and discussed, respectively. The main results were as follows:1. Functional response of Neoseiulus barkeri on Tetranychus urticae and differentpredator prey ratio on the dynamics population of T. urticae.The functional response and interference response of N.barkeri to various stagesof T. urticae were discussed by using five temperature gradients in lab. The resultsshowed that curves of functional response of N.barkeri to various stages of T. urticaeare belonging to the type of Holling Ⅱ. Different temperature on predation functionalresponse has a certain impact. The rate of discovery of prey, predation capacity andthe theoretic maximum of the daily predation of N.barkeri to T. urticae increased withthe temperature increased. However, the ability of predation declined withtemperature increased while the treatment time were shortened, and the optimumtemperature was at28℃, The predation ability of N.barkeri to different stages of T.urticae were eggs> nymph> female adult mites when under the same temperature.The average predation number of N. barkeri decreased with the increasing of theirown population density when the T. urticae population density were constant, whichindicated that there was existed in competition or mutual interference among theirindividuals; With temperature increased, the interference effect between individualswere gradually increased. Different predator prey ratio had different impact on thepopulation density of T. urticae, and with the predator prey ratio increased, thepopulation of T. urticae declined significantly.2. Functional response of Neoseiulus barkeri to1st instar nymph of Frankliniella occidentalis.The functional response and interference response of N.barkeri to the1st instarnymph of F. occidentalis were studied from16℃to32℃in laboratory experiments.The results showed that predation functional response of N.barkeri to1st instarnymph of F. occidentalis was belonging to the type of HollingⅡ. The rate ofdiscovery of prey, predation capacity and the theoretic maximum of the dailypredation were increased with the temperature increased when the temperature from16℃to28℃, and the highest ability of predation was at28℃. But the predationability decreased when the temperature at32℃.The predation ability of N.barkeridecreased with its own population density increased when the1st instar nymph of F.occidentalis’s population density was always constant.3. Toxicity and selective toxicity of9kinds of acaricide to Neoseiulus barkeri andTetranychus urticaeIn order to coordinate chemical pesticides with protection and utilization ofpredatory mites, LC50and toxicity selective ratios (TSR) of9kinds of acaricide to N.barkeri and T. urticae were determined by using leaf-residue method. The resultsshowed that the order of toxicity selective ratios were chlorpyrifos＞spirodiclofen＞pyridaben＞propargite＞fenpyroximate＞avermectin＞azocyclotin＞fenpropathrin＞hexythiazox, of which the value of the chlorpyrifos and spirodiclofen was10.8641and9.3613respectively, which indicated that they had higher positive selectivity bothon N. barkeri and T. urticae, chlorpyrifos and spirodiclofen can be recommended touse preferentially in pest control to achieve predatory mites protection.4. Effect of releasing Neoseiulus barkeri on Tetranychus urticae populationdensity in greenhouse crops and its control effectThe inhibitory effect of N. barkeri on T. urticae was determined by releasingN.barkeri on ginseng fruit and eggplant, which had significant inhibitory effect on T.urticae, and the time of its persistence of controlling effect about150days. Thepopulation density of T. urticae was in wavy growth curve between two crops inbiocontrol areas. The population density of T. urticae on ginseng fruit was changedfrom5to15per leaf, the population density of T. urticae on eggplant was changed from15to25per leaf. The corrected mortality of T. urticae on ginseng fruit andeggplant in biocontrol areas had a regular pattern of increasing in initial stage, butdeclining and growing again in later stage. The highest corrected mortality was98.25%and96.95%respectively, and then remained constant for two months afterdeclined slightly. The population density of T. urticae on ginseng fruit and eggplantwere2per leaf and15per leaf in chemical control areas. The corrected mortality of T.urticae on ginseng fruit and eggplant in chemical control areas were slowly increased,thereafter remained stable. However, the population density of T. urticae was inS-Curve between two crops in control areas. The population density of T. urticae ontwo crops was in a regular pattern of growing in initial stage, but declining andgrowing slowly in later stage. The maximum and minimum population of T. urticaeon ginseng fruit was12.44and4.44per leaf, respectively. The maximum andminimum population of T. urticae on eggplant was15.67and5.79per leaf.