Managing Glyphosate-Resistant Weeds in Glyphosate-Resistant Crops - PowerPoint PPT Presentation

Managing Glyphosate-Resistant Weeds in Glyphosate-Resistant Crops Dr. Bill McCloskey Extension Weed Specialist

* RR Flex cotton * RR alfalfa * RR Corn * Tree crops – lemons, pecans, pistachios, etc. * General farm weed control/sanitation * Over-reliance on glyphosate? * Problem of herbicide resistant weeds * 2 Desert Ag Conference – May 2012

* July 2012: field after 3 sprays of 44 oz/A (1.5 lb ae glyphosate/A). Difficulty controlling Palmer amaranth in 2011; cotton/wheat double crop 3

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Weeds too large when spray by grower *

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Robust annual – reproduces by seed Palmer amaranth seed production – 600,000 to 1.6 million seeds per large plant. An infestation of 1.6 plants/ft of crop row can produce 600 million seeds per acre. 12

Male Palmer amaranth - Male flowers with yellow anther sacs * Female Palmer amaranth flowers 13

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Male Palmer amaranth - Male flowers with yellow anther sacs Female Palmer amaranth flowers 16

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* Apply integrated weed management practices including sanitation, tillage and crop rotation. * Use multiple herbicide modes-of-action with overlapping weed spectrums in rotation, sequences, or mixtures. * Use the full recommended herbicide rate and proper application timing for the hardest to control weed species present in the field. * Scout fields after herbicide application to ensure control has been achieved. Avoid allowing weeds to reproduce by seed or to proliferate vegetatively. * Monitor site and clean equipment between sites. * 18

Herbicides Mechanical Cultural Multiple herbicides with different mechanisms of action Tillage Crop rotation Mixes Pre-plant Plant population Sequences In-crop cultivation Row spacing Across seasons In-row weeding Planting date Post-harvest Fertilizer placement Hand-rogueing before Cover crops seed set * 19