Development Of Sex Pheromone Microcapsules And Their Indoor Trapping Effects On The Diamondback Moth,Plutella Xylostella(L.)

The diamondback moth(DBM,Plutella xylostella L.)is the most destructive pest of cruciferous crops.Their incurred crop loss and global cost of management surpass $ 4-5 billion every year.Because of their high fecundity and rapidity of becoming resistant to any insecticide,new measures for their management are in great necessity.Adult controlling(AC)of pest insects is increasingly concerned because of its high efficiency,less dependence on pesticides and more safety to natural enemies.Sex pheromones are often-used chemicals in AC,but they should be developed into certain formulations prior to use for their high volatility and microcapsule formulation is preferred.In this study,the addition recoveries of sex pheromone components of DBM in water or blank microcapsules as well as their stability in water at different temperatures were firstly tested.Based on these,the qualities of sex pheromone microcapsules developed with different wall materials were compared,the technology of sex pheromone microcapsules prepared with gelatin and acacia as wall materials was optimized,the release dynamics of the sex pheromone components in the original chemicals and microcapsules were measured,and the effects of different sustained release agents on the release of sex pheromone components investigated.Finally,the indoor trapping ability of microcapsules made of 3 sex pheromone components and the mixture of microcapsules made of single-component of sex pheromone to newly emerged male adults of DBM was tested.The main results were as follows:The addition recoveries of sex pheromone components in DBM in water were higher than 96%and the coefficients of variation were 6.92%,7.06%and 6.76%,respectively.The addition recoveries of sex pheromone components in blank microcapsules were ranged from 97%to 100.5%,the coefficients of variation were from 0.91%to 2.69%.This indicated that the chosen extraction and concentration procedure for sex pheromone components had sound accuracy and precision.The recoveries of sex pheromone components of DBM decreased with water temperature increasing.At 35℃,40℃,45℃,50℃ and 55℃,the recoveries of Z11-16:Ald were 92.56%,91.61%,73.28%,68.67%and 60.37%,respectively,those of Z11-16:OH were 96.54%,98.41%,82.61%,82.68%and 74.26%,respectively and for Z11-16:Ac,those were 95.63%,96.73%,81.06%,81.43%and 73.59%,respectively.This suggested that temperature in the reaction system for developing sex pheromone microcapsules by means of complex coacervation method should not be over 40 ℃.According to the experimental results,the optimal reaction conditions for the development of sex pheromone microcapsules of DBM with gelatin and gum arabic as wall materials were:the concentration of wall materials was 3%(gelatin and gum arabic were mixed at 1:1),sex pheromone solution concentration was 10mg/mL and adding volume was 2 mL,the pH was 4.3,curing agent formaldehyde was 2 mL,and the dispersant(1%polyvinyl alcohol)was 10 mL.Following these,the embedding rates were 42.72%,46.87%,46.45%,respectively and the encapsulation efficiency were 60.86%、50.58%and 63.77%,respectively.Among all the wall material combinations,which were gelatin and gum arabic,gelatin and sodium carboxymethyl cellulose(CMC),chitosan and sodium alginate,gum arabic and chitosan,gelatin and sodium alginate and gelatin and chitosan,the embedding rates of the sex pheromone components of DBM were lowest in the microcapsules made with chitosan and sodium and the those in others were near the same.The components of sex pheromone of DBM disappeared fast in the original chemicals.At 35℃,the half retention time of Z11-16:Ald,Z11-16:OH and Z11-16:Ac were only 5.34 d,22.26 d,and 6.99 d,respectively.After being made into microcapsules with gelatin and gum arabic as wall materials,the half retention time were extended to 26.23 d,59.50 d and 51.88 d,respectively.Meanwhile,at 25℃,those were 28.91 d,66.08 d and 55.67 d,respectively.The half retention time of the 3 sex pheromone components in the microcapsules were changed after methyl oleate,dibutyl phthalate or n-dodecane being added.The extension effects of methyl oleate and n-dodecane on the retention time were comparatively low or even had the contrary effects,but dibutyl phthalate showed significant extension roles.The half retention time of the 3 sex pheromone components in the microcapsules were 28.91 d,66.08 d and 55.67 d respectively at 25℃.However,those were extended to 31.66 d,95.21 d and 49.42 d,respectively after adding 0.1 mL dibutyl phthalate and 56.96 d,131.18 d,78.23 d after adding 0.2 mL dibutyl phthalate.Similarly,at 35℃,those were 26.23 d,59.50 d and 51.88 d,respectively in the microcapsules and 33.14 d,68.65 d and 50.42 d,respectively after adding 0.1 mL dibutyl phthalate and 50.28 d,70.00 d and 66.20 d,respectively after adding 0.2 mL dibutyl phthalate.In the laboratory,the sex pheromone microcapsules showed a sound entrapping ability to the newly emerged male DBM adults.The trapping rate were 19.44%,66.67%,88.89%at the dosages of 0.1 g,0.2 g and 0.4 g microcapsules made from mixtures of 3 sex pheromone components within 3 h.Besides,the trapping rate of mixture microcapsules prepared by the single-component of the sex pheromone mixed at the ratio of Ald:Ac:OH =50:50:1 could also reached 55.56%,72.22%and 80.56%,respectively at 0.606 g,0.808 g and 1.212 g within 3 h.