Poisoning Activity Of A New Strain Of Mucor Hiemalis To Bradysia Odoriphaga Yang Et Zhang

Brachysia odoriphaga Yang et Zhang commonly known as B.odoriphaga,is an important underground vegetable pest in my country,which seriously endangers the growth of leeks.At present,the main method to prevent and control the B.odoriphaga is the application of chemical insecticides,but excessive dependence on chemical agents is contrary to the great development of ecological agriculture.Compared with chemical control,biological control has the right.Compared with other insects,the biological control resources of B.odorata are less.In the early stage,the laboratory team isolated a pathogenic fungus with high pathogenic activity to B.odoriphaga,in order to develop and utilize it as a biocontrol resource.In this paper,the morphological characteristics and ITS homology of the strain were compared,classify and identify that strain,to explore the toxic effect of this strain on different insect States of B.odoriphaga,pot experiment was carried out to determine the field control effect of the strain,the effects of different temperatures on the growth and sporulation ability of the strain were studied,to provide available resources for the green prevention and control technology of B.odoriphaga.The main research results are as follows:The strain was inoculated on PDA medium and cultured at 23℃for 4 days,the colony diameter was 7.16-7.32 cm,the colony was round,and the hyphae were white and slender hairy,microscopic observation of hyphae as non-septal hyphae.According to the experiment,the temperature range for the growth of frozen soil Mucor is 11℃-32℃,when the temperature is higher than 32℃,the growth of frozen soil Mucor stops,and the most suitable temperature for the mycelium growth of frozen soil Mucor is23℃.According to the test,the most suitable temperature for permafrost Mucor to produce spores is 18℃.At 28℃,the sporulation of permafrost Mucor is the lowest.The sporulation of permafrost Mucor is:18℃>23℃>13℃>28℃.The mortality test of Mucor in frozen soil to the second and fourth instars of B.odoriphaga under different temperature conditions proved that,at 28℃,the pathogenicity of Mucor permafrost to the second and fourth instars of B.odoriphaga was inhibited.At 28℃,the mortality of the second instar larvae of B.odoriphaga was 29.67%,on the 4th day after treatment with Mucor permafrost with 10⁶spores/ml,and the mortality of B.odoriphaga after treatment with 10⁷spores/ml was 72.50%.At 23℃,the mortality rates of the second instar larvae of B.odoriphaga treated with 10⁶and 10⁷spores/ml Mucor in frozen soil were93.34%and 94.17%.23℃is the most suitable temperature condition for mycelia growth,sporulation and infection of Mucor.There are significant differences in pathogenicity of Mucor in frozen soil to different insect States of B.odoriphaga,the pathogenicity to the larvae of B.odoriphaga is obviously stronger than that of other insect States.On the 4th day after treatment,the LC₅₀of 1st-4th instar larvae were 2.9×10⁵,1.21×10⁵,0.7×10⁵and 1.89×10⁵,the LC₅₀of eggs and pupae are5.95×108 and 1.25×105,When the concentration of Mucor spore suspension in frozen soil was 10⁷spores/ml,the LT₅₀of the 1st-4th instar larvae of B.odoriphaga are 1.49,2.29,2.52and 2.69,and the LT50 of eggs and pupae are 1.37 and 2.10.After the larvae of B.odoriphaga are infected by the permafrost Mucor,the larvae are slow to move and eat less at the beginning of the disease,and there is a small amount of food in the digestive tract;In the middle stage,there is basically no movement,no feeding,the worm body is slightly transparent,and the fat body and digestive tract dissolve;In the later stage,the insect body is light yellow or yellowish brown,which softens and breaks with a brush,and the larvae have died;At the end,white hyphae grew from dead larvae with black spherical sporangia at the top.In the pot experiment,the corrected mortality of the 2nd instar larvae of B.odoriphaga with 10⁷spores/ml Mucor permafrost spore suspension was 48.64%on the 3rd day,69.44%on the 5th day,the corrected mortality of the second instar larvae of B.odoriphaga with 10⁹spores/ml Mucor permafrost spore suspension was 59.45%on the third day and 86.11%on the fifth day.The corrected mortality of the 4nd instar larvae of B.odoriphaga with 10⁷spores/ml Mucor permafrost spore suspension was 34.21%on the 3rd day,64.86%on the 5th day,the corrected mortality of the second instar larvae of B.odoriphaga with 10⁹spores/ml Mucor permafrost spore suspension was 47.36%on the third day and 78.37%on the fifth day.