A new antimicrobial metabolite, named colletotric acid (1), was isolated from a liquid culture of Colletotrichum gloeosporioides, an endophytic fungus colonized inside the stem of Artemisia mongolica. The structure was determined using spectroscopic methods (EIMS and FABMS,(1)H and (13)C NMR, (1)H-(1)H COSY, HMBC, and HMQC). Compound 1 inhibited the growth of Bacillus subtilis, Staphylococcusaureus, and Sarcina lutea with minimal inhibitory concentrations (MICs) of 25, 50, and 50 microg/mL, respectively, and the crop pathogenic fungus Helminthosporium sativum (MIC: 50 microg/mL).
Botanical nematicides have recently received increasing interest because of the high risks of some traditional nematicides to human health and the environment. This study evaluated the nematicidal activity of a plant volatile, trans-2-hexenal, against Meloidogyne incognita. This compound exhibited higher activity in a fumigation experiment than in the aqueous phase in vitro. Both in pot tests and in field trials, trans-2-hexenal showed significant efficacy against M. incognita while maintaining excellent plant growth, especially at doses of 1000 and 500 L ha, which were superior to that of abamectin at 180 g ha via hole application treatment but not significantly different from fumigation with 400 kg ha of dazomet. Furthermore, plants treated with 500 L ha trans-2-hexenal had fruit yields 20.2 and 45% greater than the control group. On this basis, trans-2-hexenal may be a potential alternative fumigation agent for controlling M. incognita on tomato crops.
Gray mold is a common disease of many crops worldwide. Tetramycin is a broad-spectrum biopesticide that may control gray mold disease. In the present study, in vitro biological activity of tetramycin was measured in three development stages of Botrytis cinerea, and the baseline sensitivity of B. cinerea to tetramycin was characterized with a set of 165 isolates that were obtained from different geographical regions in Shandong Province, China. Tetramycin's protective and curative activity against the fungal pathogen was determined on strawberry fruit in laboratory trials, and the efficacy of tetramycin was also determined in field conditions. Spore germination was found to be the most sensitive growth stage that was inhibited by tetramycin, whereas the mycelial growth was the least sensitive growth stage. The baseline sensitivities showed that the frequency distributions of tetramycin were unimodal curves, with mean EC 50 values of 0.35 ± 0.20 and 0.020 ± 0.009 μg mL −1 for the inhibition of mycelial growth and spore germination, respectively. Tetramycin had no cross-resistance with other fungicides tested, including carbendazim, iprodione, diethofencarb, pyrimethanil, pyrisoxazole and boscalid. In field trials performed in Tai'an city, Shandong province in 2014 and 2015, tetramycin was used at a concentration of 60 g a.i. ha −1 , provided gray mold with an efficacy ranging from 70.73 % to 78.44 %, with no significant difference with other fungicide treatments. These results showed that tetramycin may serve as an alternative fungicide for the control of gray mold in strawberry fruits and cucumber.
Isopyrazam is a new broad-spectrum, foliar-absorbed and -translocated succinate dehydrogenase inhibitor fungicide. In this study, 159 Botrytis cinerea isolates collected from different geographical regions of Shandong Province of China were characterized for baseline sensitivity to isopyrazam. Furthermore, the protective and curative activity of isopyrazam on strawberry fruit and the control efficacy in the field were also determined. In contrast to its mycelial growth, the spore germination of B. cinerea was inhibited completely by lower concentrations of isopyrazam, about 1 μg ml−1 on yeast-peptone-acetate medium. Frequency distributions of isopyrazam 50% effective concentration (EC50) values were unimodal curves, with mean EC50 values of 0.07 ± 0.04 (standard deviation) and 0.68 ± 0.36 μg ml−1 for the inhibition of spore germination and mycelial growth, respectively. In addition, there was no positive multiple resistance between isopyrazam and other classes of botryticides such as diethofencarb, iprodione, pyrimethanil, or SYP-Z048. In field trials conducted during 2014 and 2015, isopyrazam used at a concentration of active ingredient at 150 and 200 g ha−1 provided a control efficacy ranging from 76.7 to 87.8% on leaves and from 81.5 to 90.7% on fruit. These results suggest that isopyrazam has the potential to play an important role in the management of gray mold.
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