Isolation, Identification, And Pathogenicity Of The Entomogenous Fungi From Carposina Sasakii

Peach fruit moth, Carposina sasakii (Matsumura)(Lepidoptera: Carposinidae), is the pest which are damage seriously and widely distributed on fruit trees in northern China. At present, chemical pesticide is applied in controlling the peach fruit moth. Although chemical pesticides are quick in killing pests and low cost, but it caused a series of problems, such as the peach fruit moth being resistance, environmental pollutions, and pesticide residues. The development and promotion of biological control has become the general trend of arboriculture. The applying of entomopathogenic fungi is one of the important methods in biological control. In this study, a new strain was isolated and identification from the diseased larvae of the peach fruit moth which were collected from an orchard in Shanxi. These have great significance to control peach fruit moth. The main contents are as follows:(1) Isolation and identification of pathogenic fungi using optical microscopy, scanning electron microscopy, and molecular identification.(2) The fungi’ s biological characteristics and virulence to peach fruit moth.(3) The virulence of fungi to different developmental stages of peach fruit moth.(4) The ability of survival and insecticidal of pathogenic fungi in the orchard.The results are showed as followed:(1) A new strain No.TSL06was isolated from the diseased winter cocoon of the peach fruit moth from an orchard. The strain was identified based on morphological characteristics observed under the optical microscope and scanning electron microscope, and analysis of ITS sequence. The results showed that the strain belonged to the species of Metarhizium anisopliae (Metsch.) Sorokin. The colonies were round、 opaque and villous. The back of the colony was brown. Conidium was oblong, rounded at both ends. The mycelium was colorless and transparent. The conidiophores contained septum. Inoculation experiment showed that the strain was the pathogenic fungi of peach fruit moth. The morphological and molecular identification of strain was more scientific and accurate than single from morphological or molecular identification.(2) The colony diameter、 sporulation and spore germination rate of the TSL06strain showed that the optimum growth temperature was25℃. The growth rate was0.405cm/d-0.475cm/d, sporulation was4.120×108spores/cm2-4.440×10spores/cm2, and spore germination rate was50.67%±0.57%. In virulence test, five concentrations of conidial suspensions were used and the results showed that the maximal correction mortality rate of C. sasakii larvae reached86.08%in the infected section with concentration of1.2×109spores/mL. Peach fruit moth was infected with the spore suspension of different concentrations. The results showed that the virulence of five concentrations were very different, the maximal concentration rate of the infected C. sasakii larvae was2.3times to the lowest concentration rate.(3) TSL06strain’s spore suspension of1.2×108spores/mL infected Peach fruit moth eggs. The results showed the corrected mortality was only3.33±3.20%, and it was not significant difference with the control group, so eggshell played a better protective effect. The spore suspension of6.0×10’ spores/mL effected significantly cocoon and emergence rate of peach fruit moth with knotted summer cocoon. As the C. sasakii larvae infected by spore suspension, cocooning rate was only85.18±2.53%and the mortality was12.86%without cocooning corrected, while cocooning rate of the control group was98.04%. The C. sasakii began to appear feathering in the11th day of diapause. The emergence rate of experimental group was only46.51±1.73%, not emerged corrected mortality rate was44.31%, while the emergence rate of control group was83.52%, because a part of C. sasakii had infected by spore suspension before cocoon. It indicated that the spore suspension had great effect on C. sasakii with knotted summer cocoon. The spore suspension of6.0×107spores/mL infected peach fruit moth with knotted winter cocoon, the corrected mortality was50.65±5.95%. Three instars of C. sasakii which we fed after infected by spore suspension indoors. The results showed that the mortality rate was higher than C. sasakii of knotted summer cocoon and knotted winter cocoon. These provided a scientific basis for the prevention of peach fruit moth.(4) We detected the viability of the strain in the soil using plate culture and FISH. The results showed that the survival ability of TSL06strain decreased rapidly in the previous two months and the number of colonies can be maintained at a relative level in the3rd and4th months. The colony density was1.3×106spores/g in1st month, the colony density was4.4×105spores/g in2nd month, and the colony density was2.5×105spores/g in3rd and4th month. So the survival ability of TSL06strain was strong.We infected C. sasakii with the strain in the field. The average natural mortality rate of control group reached89.67±2.08%, while the average mortality rate of the experimental group was95.11±1.27%. The corrected mortality reached52.69±12.28%, and the pest density decreases by half. Not only the survival ability of TSL06strain was strong, but also the strain maintained good infection to target pests after a long period of existence.