Cantaloupe Herbicide Weed Control Study

Kai Umeda, G. Gal, and B. Strickland

Abstract

Clomazone (Command®), bensulide (Prefar®), sulfentrazone, and halosulfuron treatments applied preemergence (PREE) provided very good control of prostrate pigweed (Amaranthus blitoides), lambsquarters (Chenopodium album), and common purslane (Portulaca oleracea) at better than 90% at 5 weeks after treatment (WAT). Halosulfuron was effective in controlling all weeds better than 90% at 7 WAT. Carfentrazone was not effective against most of the weeds present in the test but appeared to be safe on cantaloupe. Postemergence (POST) treatments alone did not provide acceptable control of pigweeds but controlled lambsquarters and common purslane at 2 WAT. Halosulfuron and bentazon (Basagran®) applied POST following PREE treatments controlled most of the weeds better than 90% through 7 WAT. Cantaloupe yields were highest with good weed control provided by PREE treatments followed by POST herbicide applications. Basagran at 0.50 lb/A injured cantaloupe after applications but yields were not affected compared to the untreated check. Command, sulfentrazone, and halosulfuron caused cantaloupe injury after PREE applications. Basagran caused substantial crop injury after POST applications

Introduction

Weed management in melon crops grown in the low desert regions of Arizona is difficult since very few effective herbicides are available. The spectrum of weeds in both spring and fall-planted melons differ depending on cultural growing practices. Some winter annual weeds may be a problem in spring plantings but small-seeded summer annual weeds such as pigweeds and purslane are problems in both fall plantings and in the spring plantings under plastic in the mid-bed trench. Prefar is widely used in most commercial acreages and ethafluralin (Curbit®) is applied in some growing areas. No POST herbicides are available for use against broadleaved weed species. The typical practice is to use Prefar or Curbit applied PREE and then cultivate several times during the season and hand-hoe escaping weeds. This field study was conducted to evaluate and determine the efficacy and safety of potential new herbicides for use in cantaloupes applied PREE and POST and evaluate potential use of these products in a systematic program to achieve successful stand establishment and season-long weed control.

Materials and Methods

A small plot field study was conducted at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ to evaluate and determine efficacy and safety of PREE and POST herbicide treatments on cantaloupe. Cantaloupe cv. Gold Eagle was planted on 40-inch beds in a single line on every other bed. Furrow irrigation was applied in a single furrow on one side of the bed during the season. Treatment plots measured 3.3 ft by 40 ft and were replicated four times in a randomized complete block design. PREE treatments were applied immediately after planting on 19 March 1997 and watered immediately after to completely wet across the beds. POST treatments were applied on 22 April when the air temperature was 88F and clear skies with an occasional slight breeze. Cantaloupe was at the 4-leaf stage of growth, Chenopodium album (lambsquarters) ranged from the 1- to 12-leaf stage, Amaranthus blitoides (prostrate pigweed) was at the 4- to 6-leaf stage, A. albus (tumble pigweed) was at the 3- to 4-leaf stage, and Portulaca oleracea (common purslane) was about 12-leaf stage. All treatments were applied using a hand-held boom equipped with two flat fan 8002 nozzle tips spaced 20 inches apart. A backpack CO2 sprayer pressurized to 40 psi delivered the herbicides in water at 25 gpa. POST treatments included nonionic surfactant Latron CS-7 at 0.25% v/v. Visual weed control and crop safety evaluations were made at intervals after herbicide applications and cantaloupes were harvested at the end of the season.

Results and Conclusions

Early weed control ratings on 22 Apr at 5 weeks after treatment (WAT), showed that PREE applications of Command and sulfentrazone were comparable to Prefar. All PREE herbicide treatments controlled prostrate pigweed, lambsquarters, and purslane while tumble pigweed control declined at 7 WAT. Command and sulfentrazone did not appear to improve weed control with higher rates of application. Halosulfuron applied PREE gave very good (>93%) weed control of all weeds at both rating dates. Halosulfuron caused marginally unacceptable cantaloupe injury, 16 and 23% at the two ratings dates. Sulfentrazone at 0.50 lb AI/A caused more injury than the 0.25 lb AI/A rate of application which caused marginally acceptable injury (15%). Similarly, Command at 0.25 lb AI/A caused less injury than the higher rate. Carfentrazone appeared to be safe on cantaloupes but control of the four weed species was not acceptable.

POST herbicide treatments applied alone controlled lambsquarters and purslane but pigweeds were not adequately controlled. Basagran caused a foliar burning injury after application but cantaloupe yields were similar to the untreated check. The higher rate of Basagran appeared to cause a reduction of yield compared to the lower rate. Sequential treatments of POST herbicides following PREE herbicides demonstrated acceptable season-long weed control (>85%). Prefar or Command followed by halosulfuron and Prefar followed by Basagran or Command plus Prefar followed by Basagran controlled prostrate pigweed, lambsquarters, and purslane. Tumble pigweed was also marginally controlled by these combinations of herbicides. Crop injury was minimal with the PREE applied herbicides and injury was more pronounced when Basagran followed POST. Higher yields were obtained following early Basagran injury on the cantaloupe. Yields appeared to be influenced to a greater extent more by degree of weed control than injury caused by herbicide application.

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This is a part ofpublication az1101: "1998 Vegetable Report," College of Agriculture, The University of Arizona, Tucson, Arizona, 85721.
This document located at http://ag.arizona.edu/pubs/crops/az1101/az1101_8.html
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