Shizuoka Prefectural Research Institute of Agriculture and Forestry Iwata Japan

Shizuoka Prefectural, Japan

Shizuoka Prefectural Research Institute of Agriculture and Forestry Iwata Japan

Shizuoka Prefectural, Japan
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Handayani V.D.S.,University of Shizuoka | Tanno Y.,University of Shizuoka | Yamashita M.,University of Shizuoka | Tobina H.,University of Shizuoka | And 3 more authors.
Weed Biology and Management | Year: 2017

Italian ryegrass ( Lolium multiflorum Lam.) is a non-native annual winter grass that has seriously infested rice paddy levees and wheat fields in Japan. Recently, glyphosate-resistant Italian ryegrass was found on paddy levees in central Japan, thereby making control of the grass by using glyphosate less effective. In this study, physical control methods were tested that combined the timing and frequency of mowing in order to more effectively control glyphosate-resistant Italian ryegrass on rice paddy levees. A 3year field experiment was conducted from 2012 to 2014 in a western region of Shizuoka Prefecture, where glyphosate-resistant Italian ryegrass has become dominant. Five treatments were tested: (i) mowing once before the flowering of the grass (i.e. conventional mowing measure); (ii) mowing once during flowering; (iii) mowing twice during flowering; (iv) glyphosate application before flowering (i.e. one of the conventional mowing measures); and (v) no treatment. The above-ground biomass, seed production, soil seed bank and seedling occurrence of Italian ryegrass were measured to determine the effectiveness of these treatments. Mowing during the flowering period resulted in reduced above-ground biomass, seed production and soil seed bank when compared with the other treatments. Additionally, mowing twice during the flowering period resulted in a lower seedling density than mowing once. The results suggest that, in this region, physical control by mowing during the flowering period would be more effective than conventional measures for controlling glyphosate-resistant Italian ryegrass. © 2017 Weed Science Society of Japan.


Handayani V.D.S.,University of Shizuoka | Tanno Y.,University of Shizuoka | Yamashita M.,University of Shizuoka | Tobina H.,University of Shizuoka | And 3 more authors.
Weed Biology and Management | Year: 2017

Recently, glyphosate-resistant Italian ryegrass (Lolium multiflorum Lam.) was found on rice paddy levees in a western region of Shizuoka Prefecture, Japan. Naturalized populations of Italian ryegrass are frequently infected with fungal Epichloë endophytes. Endophytes often confer benefits to their host grasses. This study investigated the influence of five weed management treatments on glyphosate resistance and endophyte infection in Italian ryegrass that was growing on paddy levees where glyphosate-resistant individuals were dominant. The weed management treatments were: (i) mowing once before the grass flowered; (ii) mowing once during flowering; (iii) mowing twice during flowering; (iv) glyphosate application before flowering; and (v) no treatment. The seeds were collected from the treatment plots in 2013 and 2014. The seeds were examined for endophyte infection and the seedlings that had been grown from the seeds were tested for the frequency of glyphosate resistance. The seedlings that had been derived from the glyphosate treatment showed higher frequencies of glyphosate resistance than those seedlings that had been derived from all the other treatments. Endophytes were found in all populations of the seeds from the paddy levees, with higher infection rates in the seeds that had been derived from the glyphosate treatment and the twice-mowed treatment. There was a significant relationship between the endophyte infection frequency in the seeds and glyphosate resistance in the seedlings that had been grown from the same populations. The results indicate that where glyphosate herbicides are frequently used, selection for glyphosate-resistant Italian ryegrass occurs, and along with this, the frequency of endophyte infection also increases. © 2017 Weed Science Society of Japan.

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