| Tomato (Solanum lycopersicum L.) is one of the major vegetable crops throughout the world. In recent years, tomato production has been severely impacted by root-knot nematode (Meloidogyne incognita) and whitefly(Bemisia tabaci). For the last20years, soil fumigation with methyl bromide (MeBr) has been the primary way to control nematode in China. As a result of the Montreal Protocol, the use of MeBr for fumigation will eventually be eliminated. In this context, alternative control strategies are urgently needed. Control of Bemisia tabaci in the greenhouse has been heavily dependent on the repeated spraying of insecticides, such as imidacloprid. However, the spraying of pesticides increases the humidity and causes heavier viral diseases. Here, we consider choosing some systemic pesticides, which can be applied directly to the soil and absorbed by plants for the control of nematode and whitefly. Thiacloprid is the second neonicotinoid pesticide. At present, thiacloprid is only registered as controlling aphids in cucumber and cabbage, planthoppers and thrips in rice and longicorn in China. Therefore, in this study, a series of laboratory test, greenhouse pot experiment and field trials were conducted to determine the potential of thiacloprid to control M. incognita and B. tabaci B biotype after soil application in tomato production, as well as the effects on tomato growth. Meanwhile, evaluate the influence of thiacloprid on soil enzyme activities under various doses. The results of this study will evaluate the bioactivities and ecological safety of thiacloprid, offering a theoretical foundation to the use of thiacloprid on greenhouse vegetable industry. The results were as follows:1. Laboratory tests showed that thiacloprid had a certain effect to M. incognita J2and the eggs, with LC50averaged36.2and70.4mg ai L"1, respectively. Thiacloprid also exhibited high toxicity to B. tabaci B biotype adults and eggs with LC50averaged14.7and62.2mg ai L-1, respectively, which were superior to imidacloprid.2. Greenhouse pot experiments showed that:(1) Thiacloprid was present in the tomato leaves until day25, and all application rates of thiacloprid effectively suppressed the B. tabaci B biotype population until20days after soil application. Thiacloprid in soil had half-lives of11.8and12.5days for the normal treatment and the double treatment respectively. Thiacloprid at the dose of6and12mg ai kg-1soil also provided significant M. incognita control effect similar to cadusafos while maintaining excellent plant growth.(2) The results also showed that thiacloprid at1.0-2.5a.i. mg/plant could increase the leave numbers, plant height, root length, shoot fresh weight and root fresh weight. The activities of SOD, POD, CAT, PAL, PPO and root vigor were increased for all the thiacloprid treatments. 3. Field trials in tomato were conducted determine the efficacy of thiacloprid (7.5,15and30kg/hm2) for its potential to control nematode and whitefly. The results revealed that thiacloprid exhibited excellent control effects to M. incognita and B. tabaci B biotype. In both trials, thiacloprid increased the plant height, vigor, tomato yield and maintained excellent nematode control efficiency.4. The effects of thiacloprid after soil application on the activities of dehydrogenase, phosphomonoesterase, catalase, urease and invertase were measured. The results showed that, for all the treatments, the activities of five soil enzymes generally recovered to the control level on the80th day. There were no adverse effects on the soil ecosystem. |
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