Effects of fumigation with 1,3-dichloropropene on soil enzyme activities and microbial communities in continuous-cropping soil.

The compound 1,3-D (1,3-dichloropropene) is a potential candidate soil fumigant due to the restrictions on methyl bromide (MB). To date, little is known about the soil microbial community changes induced by 1,3-D fumigation. Therefore, soil properties, related soil enzymes, genes encoding the key enzymes of ammonia oxidation in both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) and bacterial diversity were investigated to assess the effects of 1,3-D fumigation on the soil microbial community. The results exhibited that fumigation with 1,3-D caused accumulation of NH4+-N, but it led to decrease in the rate of NO3--N, and the concentration of NO3--N gradually recovered. At 12 weeks after transplant (WAT) of tomato seedlings, the concentration of NH4+-N and NO3--N were not statistically significant between the 1,3-D treatment groups and the untreated control group. A similar tendency was found for organic matter, soil pH, urease and protease activities. Moreover, quantitative real-time PCR (qPCR) showed that 1,3-D decreased total bacterial abundance, AOA-amoA and AOB-amoA genes. In addition, Illumina MiSeq sequencing analysis revealed that soil bacterial community diversities were significantly reduced at earlier sampling time points, and at later sampling time points, soil bacterial diversity gradually recovered, there was no significant difference compared to the control group. The present study provides useful information to evaluate the environmental safety of 1,3-D.

Single basal application of thiacloprid for the integrated management of Meloidogyne incognita and Bemisia tabaci in tomato crops.

Tomato growers commonly face heavy nematode (Meloidogyne incognita) and whitefly (B-biotype Bemisia tabaci) infestations, and previous studies demonstrated that thiacloprid could be used to control M. incognita and B. tabaci in cucumber. However, the efficacy of a single basal application of thiacloprid to control both pests and its effect on yield in tomato remains unknown. In this study, the potential of thiacloprid application to the soil for the integrated control of M. incognita and B. tabaci in tomato was evaluated in the laboratory and the field. Laboratory tests showed that thiacloprid was highly toxic to whitefly adults and eggs with an average lethal concentration 50 (LC50) of 14.7 and 62.2 mg ai L-1, respectively, and the LC50 of thiacloprid for nematode J2s and eggs averaged 36.2 and 70.4 mg ai L-1, respectively. In field trials, when thiacloprid was applied to the soil at 7.5, 15 and 30 kg ha-1 in two consecutive years, whitefly adults decreased by 37.8-75.4% within 60 days of treatment, and the root-galling index was reduced by 31.8-85.2%. Optimum tomato plant growth and maximum yields were observed in the 15 kg ha-1 treatment. The results indicated that a single basal application of thiacloprid could control M. incognita and B. tabaci and enhance tomato growth and yield.

Effect of Abamectin on the Cereal Cyst Nematode (CCN, Heterodera avenae) and Wheat Yield.

The cereal cyst nematode (CCN, Heterodera avenae) is a major pest in wheat and until now there is no pesticide registered to control this pest in China. Development of effective methods of controlling CCN is urgently needed. Abamectin is a biological pesticide that has a high nematicide activity. However, the efficacy of abamectin soil application to control CCN in wheat and its effect on yield in China remains unknown. Therefore, laboratory, greenhouse, and field tests were carried out to evaluate the potential of abamectin soil applications for CCN control and improvement of wheat yield. Laboratory tests showed that abamectin exhibited knockdown toxicity to CCN, with LC50 and LC90 values 9.8 and 59.4 mg liter-1. Greenhouse experiment and field trials showed that soil applications of abamectin provided significant CCN control and higher straw dry weights and wheat grain yields. There was an 8.5 to 19.3% yield increase from the various abamectin treatments compared with the control. The results of this study demonstrated that abamectin exhibited a high nematicidal activity to H. avenae and adequate performance to enhance wheat crop yields.