Study On The Taxis To Light And Colors And Behavior Mechanism Of Bradysia Odoriphaga

Bradysia odoriphaga Yang et Zhang, one of the most important pests of Chinese chives, significantly affects its yield and quality. In recent years, the research of B. odoriphaga mainly focused on its occurrence regularity and control technique, especially on chemical control. Because of the “poison leek” cases caused by excessive pesticide residues and worsening environment pollution, more green, efficient and environmentally friendly methods of B. odoriphaga monitoring and controlling are needed in leek production. Therefore, we systematically compared and studied the taxis of B. odoriphaga to different light intensity and colors and its tropism mechanism, trying to provide scientific basis and reference for green and efficient monitoring and controlling technique based on light and colors. The main results are as follows: 1. The response behavior to different white light intensity of B. odoriphaga.Within the scope of certain light intensity(1og 0~1og4.5), each white light intensity could cause the phototaxis and photophobism behavior of B. odoriphaga. Phototaxis rates were the highest at log 2.5, 23.4% for females and 31.8% for males. Photophobism rates were the highest at log 0, 14.36% for females and 18.34% for males. Gender had significant effect on phototaxis behavior, but it had no significant effect on photophobism behavior. 2. The response behavior to different color substrates of B. odoriphaga.The color taxis of B. odoriphaga was experimented with ten color substrates, red(630 nm), orange(600 nm), brown(585 nm), lemon yellow(570 nm), olivine(545 nm), light green(535 nm), dark green(525 nm), light blue(505 nm), dark blue(475 nm) and black(0 nm), the results showed that: the taxis rates to different color substrates were not significantly different between females and males in the darkness. Both females and males had the highest trend rates(23.33% and 22.67%) to brown substrate(585 nm) and the lowest trend rates(5.00% and 4.00%) to orange substrate(600 nm) when exposed to light. Adding Chinese onion and Chinese chives as inducements could not obviously change their trend to different color substrates. Sex had no significant effect on their color taxis behavior. 3. The effects of oviposition surface colors on oviposition selectivity of B. odoriphaga.The oviposition selectivity of the adults(1~3 days) of B. odoriphaga was experimented throug setting five oviposition surface colors, white, orange(600 nm), brown(585 nm), green(525 nm), black(0 nm), and black, white backgroud, the results showed that: the surface colors of oviposition position had significant effects on the oviposition selectivity and fecundity of B. odoriphaga. Brown and black were their favorite colors to lay eggs, with oviposition selectivity rates of 37.25%(black background) and 27.44%(white background) on brown cards, 23.80% and 37.27% on black cards. Green had an avoidance effect on oviposition of B. odoriphaga, with oviposition selectivity rates of 7.64%(black background) and 6.67%(white background). The fecundity was the most on brown and black cards(493.4 and 315.9 in black background, 376.8 and 512.3 in white background), while was the least on green cards, 101.4 for black background and 91.6 for white background. Environment background colors had no significant effect on the oviposition selectivity and fecundity. Age also had no significant effect on the oviposition selectivity of B. odoriphaga. 4. The effects of environment colors on biological characteristics of B. odoriphaga.The effects of environment colors on biological characteristics of B. odoriphaga were investigated in this part, the colors used were red(630 nm), orange(600 nm), brown(585 nm), green(525 nm) and black(0 nm), the results revealed that: environment colors had significant effects on the biological characteristics of B. odoriphaga. The developmental duration was the longest on orange environment(26.15 d) and the shortest on black environment(22.35 d). The generation survival rate was the highest on black environment(43.88%) and lowest on orange environment(28.88%). There was no significant difference in sex ratio between different treatments. The adult longevity of both females and males was the longest on brown environment(2.06 d and 2.99 d) and shortest on orange environment(1.58 d and 2.57 d). The maximum number of eggs laid per female was 62.99 on brown environment and the least was 45.64 on orange environment. The indexes of population trend on different environment colors(from high to low) were: black(15.90) > brown(15.07) > contrast(12.93) > red(11.69) > green(11.67) > orange(8.50).To sum up, within the scope of the trial light intensity and colors, the adults of B. odoriphaga have certain light intensity taxis(phototaxis rates were higher in week light, photophobism rates were higher in medium light) and color trend(taxis rates were higher to color brown and black, lower to orange). The mechanism of the color taxis behavior of B. odoriphaga is that different colors have different effects on its biological characteristics, such as development and reproduction. Adults often tend to the colors which are beneficial to the development of their descendants and the reproduction of themselves.