Reduced rates of metribuzin and hilling time for weed management in potato -

Abstract

The current emphasis on reducing herbicide applications has led to an increase in alternative weed control measures. Field and greenhouse experiments were conducted in the spring and fall semesters of 2014-2015 to examine the effect of hilling-time and reduced- rates of metribuzin and their combinations on weed infestation in potato, and to determine their impact on potato yield. Metribuzin at 0.18, 0.35, 0.65, or 0.75kg ai-ha with or without hilling 6, 7, and 8 weeks after planting (WAP) were used. Weed count, weed control visual rating, weed dry weight, potato plant height, number of shoots and leaves, dry weight, phytotoxicity visual rating, and potato yield (number and weight of marketable and nonmarketable) were collected. Results of the field experiment showed that metribuzin, at all tested rates, with or without hilling significantly reduced weed infestation after 50, 70, and 110 days after planting (DAP) compared to the check. However, the effect of hilling alone on weed infestation was not significantly different from the check. All treatments (metribuzin or hilling) significantly reduced weed dry weight compared to the check. Best results considering long season weed management, selectivity, and marketable yield of potato were obtained by a combination of metribuzin at all tested rates with hilling 6, 7, and 8 WAP. Results of the greenhouse experiment showed that metribuzin at all tested rates significantly reduced all weeds early in the season, compared to the check. However, late in the season, only metribuzin at 0.56 and 0.75kg ai-ha were effective against weeds in comparison to the check. None of the metribuzin treatments was toxic to potato plants compared to the hand-weeded plots. The results suggest that long season weed control could be suppressed by metribuzin at 0.35kg ai-ha (53percent reduction in metribuzin) supplemented with hilling (6 and 8 WAP).