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Litura Host Fitness By Nature And The Role Of The Sex Pheromone Lure Measurement And Other Monitoring Technologies To Assess

Posted on:2009-07-30Degree:MasterType:Thesis
Country:ChinaCandidate:X J ShiFull Text:PDF
GTID:2193360242493629Subject:Agricultural Entomology and Pest Control
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Spodoptera litura (Fabricius) is a kind of polyphagous insect pest which could cause crop calamity and distributed in the worldwide. In the recent years it has endangered many kinds of vegetables and industrial crops in China. Now It has become into a kind of standing and easy break out insect pest from intermittent, abiogenetic and secondary pest. So improvement of its predicting and controlling techniques are demanded urgently. The authors have done a series of experiments in the lab and much more investigation in the fields in order to explore the relationship between Spodoptera litura and host crops, solve the existed gaps on its forecasting and controlling technique. We want to explain the influence of different host crops on the growth and reproduction of Spodoptera litura. The effects of predicting and controlling with sex pheromone were studied. The toxicity and controlling effect of different single insecticide along with their admixture to Spodoptera litura had been tested. The main results were as follows:1. There were the selective taxis difference of laying eggs and larva feed of the Spodoptera litura among different host crops. The order of taxis of laying eggs among different host species was: Chinese cabbage, cabbage, radish, cotton, greengrocery, kidney bean, cowpea, capsicum, tomato, cucumber. The amount of laying eggs in Chinese cabbage is the most, had occupied 17% of the total amount at the hosts. The amount of laying eggs in cucumber is the least, had only occupied 2% of the total amount at the hosts. The order of taxis which the larva likes to feed among different host species was: lettuce, greengrocery, cucumber, tomato, Chinese cabbage, kidney bean, aubergine, capsicum, cabbage. The larva liked lettuce and greengrocery occupied 30% and 19% respectively. The amount of larva liking cabbage was very small and only occupied 1%.2. The larva of Spodoptera litura feed on different hosts result in the difference of the insect growth, development, reproduction and population's quality. For example, the larva period and pupa period in cabbage were 22.45 days and 12.23 days respectively, which were significantly longer than the ones in the other host crops. The larva period in aubergine is the shortest, only 10.41 days. The pupa period in greengrocery is the shortest, only 6 days. The larva survival rate, pupation rate and emergence rate in kidney bean, cowpea and aubergine was much higher than the ones in cabbage and Chinese cabbage. There were significant difference on their average pupa weight and the average amount of eggs-lying by female, too. The average pupa weight in Chinese cabbage was 313.8mg, but the average pupa weight in cabbage was only 55.33mg. The amount of single female's eggs in cowpea was the highest which reached 497.47, but in greengrocery it was the lowest which only reached 192.47. According to the experiment results comprehensively, we found cowpea, kidney bean, cotton (Sumian 9) and aubergine were the more suitable host crops, whereas cabbage and Chinese cabbage weren't the suitable host crops. The larva survival rate, pupation rate, pupa weight and emergence rate of the former were all significantly higher than the ones of the latter.3. The toxicity of 12 kinds of insecticide to Spodoptera litura had been determined in the lab. The results showed that 0.3%Aihe EC (ingredient:azadirachtin), 2% Haoshangjia EC (ingredient : Abamectin),10% Chujin flowable formulation (ingredient :chlorfenapyr), 40% chlorpyrifos EC and 24% Caiman flowable formulation (ingredient:Tebufenozide ) to 2 instar larva were high and their LC50 was 1.7527 mg/L ,2.79 mg/L, 6.87 mg/L, 8.0942 mg/L and 8.2029mg/L, respectively. The toxicity of Fenpropathrin to 2 instar larva was the lowest and its LC50 reached 182.16 mg/L.4. The common-toxicity coefficient (CTC) of different insecticides admixture to Spodoptera litura had been determined in the lab, too. There was significant difference on the combined action of the admixture among them. The CTC of Alphamethrin–azadirachtin reached 843.23, their enhance-effect role to toxicity was signifcant. The CTC of Alphamethrin–abamectin and Chlorpyrifos–azadirachtin were 252.22 and 178.49 respectively, their enhance-effect role to toxicity was very high, also. But the CTC of Abamectin-deltamethrin , Abamectin-chlorpyrifos, Chlorfenapyr–Alphamethrin and Chlorfenapyr–azadirachtin was litter. The results above tell us a good admixture insecticide should be admixture reasonablely and could significantly increase its control effect to target insect pests, decrease the spray cost and delay the occurrence of insect resistancd to the insecticide.5. The field experiment results showed there was the good technique effect and application value of sex pheromone in monitoring and controlling Spodoptera liturac. The monitoring result of sex pheromone indicated that the quantity of trapped emergence male moths reached 33120 from May 10 to Oct 31, 2007 and reached 27512 from July 18 to Sep 25, 2007. But the amount of emergence male moths captured was only 163 from July 18 to Sep 25, 2006. It was clear that the Spodoptera litura broke out in Nanjing in 2007, the quantity of trapped moths in 2007 was about 100 times more than the ones in 2006. The factors which affected quantity fluctuate of the moths in the sex pheromone traps include air temperature, wind, rainfall, crop species and the imaginal emergence process. From the monitoring results of the sex pheromone traps in 2006-2007, we found the moths could be captured with the traits of sensitivity, stability and a great quantity. It had dual effect of trapping male moth and disturbing mating. The using of sex pheromone could reduce the application of pesticide and was safe to both ecological environment and natural enemy. Based on this point, our suggestion is controlling with sex pheromone, as an monitoring and integrated Spodoptera litura management measure, could be popularized and applied.
Keywords/Search Tags:Spodoptera litura, host fitness, sex pheromone, pesticide, pesticide admixture, synergistic effect
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