Two-year study on the efficacy of Pix~(TM) when foliar application is followed by precipitation

摘要

Rainfall is a frequent event where Mepiquat Chloride (Pix~(TM)) is used in the Mid-South. However, uncertainty exists about the minimum time needed after foliar Pix application for effective absorption of Pix. Field studies were conducted in 1998 and 1999 to determine the efficacy of Pix in controlling plant growth after simulated rain had washed Pix off the plants at different time intervals after spraying. A rain simulator was used to wash off the Pix at select intervals after foliar application. In 1998 the six treatments consisted of an untreated control, Pix not washed off, and Pix washed off 1, 2, 4 and 8 h after spraying. In 1999 the five treatments, repeated under well-watered(WW) and water deficit stressed (WS) conditions, consisted of an untreated control, Pix not washed off, and Pix washed off starting 8, 12 and 24 h after spraying. In all cases Pix was applied with a backpack sprayer at 6 oz/acre in 10 gallons of water. In 1998, rain within 8 hours significantly reduced the efficacy of Pix for controlling vegetative growth, indicating that more than 8 hours were needed for adequate Pix absorption, in 1999, foliar application of Pix significantly controlled plant height and leaf growth. Simulated rain washing eight hours after Pix application significantly reduced the efficacy of Pix, whereas 12 and 24 hours allowed adequate time for Pix absorption and control of vegetative growth. The minimum critical time period between foliar application of Pix and rain was 12 hours after which respraying Pix would not be necessary. Water deficit stress during the vegetative phase did not affect the time needed for leaf absorption of Pix in this study.