Researcher: Dr. John O'Sullivan, Dept. of Plant Agriculture, University of Guelph, Simcoe

Objective:

The objective of this research project was to develop improved weed management programs for processing cucumbers, peppers, cole crops, squash, pumpkins and sweet corn by evaluating a range of herbicides for crop tolerance and weed control efficacy on these crops. Information on yield, crop sensitivity and control of problem weeds was developed. Improved weed management programs reduce the need for labor for hand hoeing and weeding, reduce the cost of production to the grower and enhance competitiveness of the processing vegetable industry.

Methodology:

Research trials were carried out at the Dept. of Plant Agriculture, University of Guelph, Simcoe during the summer of 2000. Treatments were replicated four times in each experiment. Plots were 30 feet long by 7.5 feet wide. Plants were thinned to a known stand appropriate for each crop. Crops were grown according to accepted commercial practices used in Ontario. Crop injury, weed counts, weed biomass, weed ratings and yield were recorded. All trials were harvested by hand at crop maturity. Data was statistically analyzed, tabulated and reported.

Results:

Cucumbers:

Two trials were conducted on cucumbers. In the first trial planted on June 5, a conventional tillage system was compared with reduced tillage systems (disk, zone-till and no-till). Roundup Fast Forward Preseed at 1.7 L/acre and Command ME at 0.5 L/acre (anticipated recommended rate for Command ME, depending on soil type), were applied preemergence. For both trials, 'Vlaspik M' cucumbers were seeded, in 30" rows to give a plant population of approximately 72,000 plants per acre. A John Deere vacuum seeder was utilized for precision seeding. Initial research indicates that reduced tillage will be a profitable option.

In a second trial planted June 26, stale-seedbed and conventional tillage systems were evaluated for potential use in cucumber production. Weeds were allowed to germinate and grow for 10, 20, 30, and 40 days before seeding. Weeds in the stale-seedbed were killed with either an application of Roundup Fast Forward Preseed at 1.7 L/acre alone or in combination with Command ME at 0.5 L/acre, following seeding. The predominant weeds present were curled doc, shepherds purse, common lamb's-quarters, crabgrass and foxtail. The stale-seedbed treatments resulted in improved weed control and better yields than the conventional system.

Peppers

Peppers were grown with conventional tillage and in a stale seedbed. A low application of Roundup (1 L/acre) was applied to the stale seedbed just prior to planting the peppers. Command and Dual Magnum were evaluated for weed control in both tillage systems. No product caused crop damage. Use of the stale seedbed improved weed control, especially the control of broadleaf weeds. Highest yields were obtained in the stale seedbed. Control with both Command and Dual Magnum were improved in the stale seedbed. A minor use application has been submitted for the use of Dual Magnum on peppers. Command ME has a very good potential for use on peppers due to excellent crop tolerance and broad spectrum weed control. Minor Use Registration is being pursued for this product on peppers.

Cole Crops

Several herbicides were tested for use on cabbage and cauliflower. Cabbage (Missouri) and cauliflower (Fremont) were planted on May 11. Dual Magnum preemergence, Devrinol preemergence and Devrinol plus Dual Magnum preemergence were applied. Lentagran, Lontrel and combinations of Lentagran plus Lontrel applied postemergence were also evaluated. Goal (550 ml/acre) applied preplanting caused injury in both cabbage and cauliflower. Post emergence applications of Lentagran also caused slight leaf injury but no yield reduction. A new formulation of Lentagran (EC) will be available for testing in 2001 and is reported to be less injurious to these crops. None of the herbicide treatments caused a significant yield reduction.

Pumpkins

Pumpkins were seeded into conventional tillage and stale seedbed plots. Roundup was applied at 1 L/acre shortly after seeding pumpkins. Weed control with Command and Command plus Devrinol was evaluated in both tillage systems. Pumpkin (Howden) was seeded on June 8. Highest yields were obtained in the stale seedbed system of production. An applicaion of Devrinol resulted in severe early season injury due to significant rainfall in early June. However this injury did not result in a significant yield reduction. Command did not result in any crop injury and gave yields comparable to the weeded check in both tillage systems.

Squash

Squash were grown in conventional tillage plots and in a stale seedbed system. Roundup at 1 L/acre was applied to the stale seedbed shortly after seeding. Weed control with Command and Devrinol was evaluated in both tillage systems. Waltham Butternut Squash was seeded on June 8. Command ME applied alone and in combination with Devrinol as a soil applied preemergence application on June 9. The application of Devrinol caused severe injury early on due to significant rainfall in early June. This injury however did not result in yield reduction. Command alone gave good weed control with no injury or yield reduction. Highest yields were obtained with the stale seedbed system of production.

Sweet Corn

Three separate trials were conducted to evaluate Accent, Liberty and ZA 1296 for variety tolerance in processing sweet corn. Accent and Liberty (on Bt corn varieties) are currently registered on field corn while ZA 1296 registrations are expected in 2002. Accent controls perennial grass weeds like proso millet and quackgrass plus annual grasses. Liberty and ZA 1296 control broadleaf and grass weeds. The objective of these trials was to evaluate varieties for tolerance to these herbicides since certain sweet corn varieties are extremely sensitive and require extensive testing to obtain registration.The effect of Accent at 1X and (13.5 g/acre) and 2X (27 g/acre) application rates was evaluated on nine sweet corn varieties. The 2X application rate in particular caused fairly significant damage to some varieties including Mystique and Fleet. There was however no yield reduction with this high application rate of Accent. Liberty herbicide was also evaluated for potential use for 6 Bt sweet corn varieties. No crop injury was observed on any sweet corn variety and yields were not reduced. Nine sweet corn varieties were evaluated for tolerance to a new field corn herbicide ZA1296. This herbicide represents a new mode of action and controls most annual grasses and broadleaf weeds that effect sweet corn. It is expected to be registered for use in field corn in the year 2002. Preemergence application of ZA1296 caused no injury to any sweet corn variety both in 1999 and 2000. However, postemergence application of this herbicide did cause injury to sweet corn, particularly to the variety Calico Belle and Delmonte 2038. Based on this information the registration for this product on sweet corn will be limited to preemergence applications only. Registration of ZA1296 for use in sweet corn will be a valuable herbicide for sweet corn growers.