Evaluation Effect And Model Study Of Phosphine Fumigation Against Insect

Resistance caused by failure of phosphine fumigation is heavenly attributed to insufficient evaluation methods for insecticidal effects.Scientific evaluation and prediction of the effects of fumigation is more conducive to killing insects successfully and avoiding resistance.This project studied the lethal time at different temperatures for all life stages of two strains of Cryptolestes ferrugineus（Stephens）with respective resistance factors of 440and 1043 in order to determine the extent of delay of low temperature on insect death caused by phosphine fumigation.Studied the growth and development as well as population changes of survived Cryptolestes ferrugineus after phosphine fumigation in order to explore biological reasons for resistance formation.Studied the video of behavioral responses of Cryptolestes ferrugineus during the fumigation in order to predict insecticidal effects through monitoring the video image of the abnormal behaviors of adults,thereby provide new technological support to guarantee successful insect pest control with phosphine fumigation.The mortality and lethal time of the four insect states of Cryptolestes ferrugineus with1,043 and 440 times of resistance factor to phosphine were compared at temperatures of 18,23 and 28°C and phosphine concentrations with 200,300 and 400 m L/m³.The exposure time of full mortality of all life stages of R₄₄₀strain was 40,34 and 31 d,respectively,with the phosphine concentration of 200,300 and 400 m L/m³at 18°C,which was 4.8,7.8 and 6.7 d longer than that at 23°C,and 6.9,14.9 and 12.3 d longer than that at 28°C,respectively.The exposure time of full mortality of all life stages of R₁₀₄₃strain by phosphine concentration of200,300 and 400 m L/m³at 18°C was 52,38 and 37 d,respectively,which was 6.3,1.9 and3.1 d longer than that at 23°C,and 9.5,5.6 and 6.9 d longer than that at 28°C,respectively.The lethal time of all life stages of Cryptolestes ferrugineus strain significantly increased with temperature and phosphine concentration decreasing.The tolerance of the two strains of Cryptolestes ferrugineus with the different resistance to phosphine was pupae≈eggs>adults>>larvae.The relationship between complete lethal time（y）and phosphine concentration（x）was established at quasi-low temperature of 18℃and the most tolerable insect state:R₄₄₀y=1935.2x^-0.670,R₁₀₄₃y=5935.2x^-0.237.The population development of Cryptolestes ferrugineus with different survival rates after phosphine fumigation were observed under the conditions of temperature 30°C and relative humidity 70%.In the control group and the survival rate of 90%,80%,70%,60%of the rusty stag beetle,the developmental duration of each progeny stage of the progeny was significantly prolonged as the survival rate decreased,and the total developmental duration of60%survival rate was 6 d longer than that of the control group.Hatching rate,pupation rate,eclosion rate and survival rate all decreased significantly with the decrease of survival rate.With the decrease of survival rate,the F₀and F₁generation population trend index decreased from 37.05 and 35.45 in the control group to 5.7 and 19.78,respectively.Similarly,the adults lifespan and the number of eggs laid by a single female in F₀and F₁generations also had the same variation trend as the population trend index.In addition,with the increase of reproduction,the influence of phosphine on Cryptolestes ferrugineus decreased,and the spawning quantity,life span and population trend index of Cryptolestes ferrugineus in F₁generation increased significantly compared with that in F₀generation.The relationship model of survival rate（x）and development duration（y）was established,R₁₀₄₃:y=0.0105x²-2.075x+127.95、R₄₄₀:y=0.0011x²-0.3401x+47.742.The relationship model of population trend index（y）and survival rate（x）was established,R₁₀₄₃:y=0.0197x²-2.294x+65.945、R₄₄₀F₀:y=0.7844x-41.534,R₄₄₀F₁:y=-0.009x²+1.829x-57.339.At the temperature of 18,23 and 28°C,the behavior reaction for adults of Cryptolestes ferrugineus in the process of phosphine fumigation were monitored by video.Under different temperatures,the abnormal behavior of adults of Cryptolestes ferrugineus and the ratio of knockdown showed an obvious upward trend with the increase of fumigation time.The fumigation time to reach 100%of abnormal behavior ratio required 23.38,17.22 and 12.28 d at 18,23 and 28°C,respectively,which was 5.32,2.68 and 2.52 d different from the lethal time.The time to reach the 100%knockdown ratio was 22.01,16.88 and 13.69 d,which was5.21,4.32 and 2.11 d different from the lethal time.There were significant differences in the recovery rate at different temperatures after being fumigated for different periods of time.The longer of the fumigation time after knockdown,the lower the recovery rate of adults of Cryptolestes ferrugineus.After continued fumigation at 18°C and 23°C for 48 h,some adults were still able to wake up,and the recovery rate of Cryptolestes ferrugineus was only 2.4%after continued fumigation at 28°C for 24 h.The relationship model of death rate（y）and knockdown time（x）was established,18°C:y=-0.0455x²+4.1277x+0.3032、23°C:y=-0.0536x²+4.5083x+3.6129、28°C:y=-0.2146x²+9.3x-2.482.