Weed Control and Cantaloupe Tolerance to Halosulfuron

1. Weed Control and Cantaloupe Tolerance to Halosulfuron W. C. Johnson, III Research Agronomist – Weed Science USDA-ARS Coastal Plain Experiment Station Tifton, GA

2. Halosulfuron Basics • Originally, a corn herbicide intended to be a replacement for atrazine • Reasonable broadleaf weed control spectrum • Good to excellent control of cocklebur, many pigweeds, ragweed, wild radish, and smallflower morningglory • Good to excellent control of yellow and purple nutsedge • No effect on grasses • Can be applied PRE or EPOST • Excellent results controlling nutsedge with either application

3. Halosulfuron Basics (cont.) • Little potential for carryover • 4 to 12 day half-life in sandy loam soil • In contrast, Cadre has 120 day half-life • Symptomology • PRE applications • Does not inhibit seed germination • Seedling growing point develops chlorosis and necrosis soon after seedling emergence • POST applications • Chlorosis: 3-7 days after application • Necrosis of growing point: 7-14 days after application • Complete death of plant: 14-21 days after application • Weed size often determines how fast symptoms develop

4. Research on Halosulfuron Since 1995 • Direct seeded cucumber and watermelon • Transplanted cantaloupe and watermelon on polyethylene covered beds • Times and methods of halosulfuron application on polyethylene covered beds • Residual benefits of halosulfuron applied to watermelon and sweet corn to future double-cropped crucifers

5. Weed Control Using Halosulfuron (2/3 oz./A) on Transplanted Cantaloupe

6. Visual Injury and Crop Yield Using Halosulfuron (2/3 oz./A) on Transplanted Cantaloupe

7. Weed Control with Halosulfuron (2/3 oz./A) in Transplanted Cantaloupe – Effects of Herbicide Placement

8. Crop Injury and Yield Response to Halosulfuron (2/3 oz./A) in Transplanted Cantaloupe – Effects of Herbicide Placement

9. Carroll Johnson’s Opinion on Halosulfuron • Best weed control spectrum of anything cucurbit growers would ever likely have registered • Significantly helps in the overall management of yellow and purple nutsedge • Controls several, but not all, broadleaf weed species • Application versatility (PRE or POST)

10. Carroll Johnson’s Opinion on Halosulfuron (cont.) • Acceptable crop tolerance among the cucurbit group • Most tolerant to least tolerant: Cucumber>cantaloupe=watermelon>squash • Safe application timings vary widely among cucurbit crops • My preference, based on considerable experience and research data is PRE to weeds but POST-Directed soon after transplanting • This is a simple application technique that does not require significant reconfiguration of sprayers

11. POST Transplanting – Directed Application for Herbicides

12. Carroll Johnson’s Opinion on Halosulfuron (cont.) • Cropping systems that routinely use herbicides such a halosulfuron will dramatically reduce populations of nutsedge since halosulfuron can control tubers. This may actually be the greatest benefit of halosulfuron in cropping systems that include vegetable crops. • Halosulfuron should not present a major carryover to other crops, either in single- or double-cropping systems.

13. Unanswered Questions • Refine the application timing by crop • Cultivar screening • Carryover to double- or rotation-crops • Sometimes seen, sometimes not seen – Why??? • Interactions among pH, soil type, tillage, and water events • We will soon have the qualified personnel in place to answer these questions

14. Dan Evarts – the technician who makes my off-the-wall ideas work.