Weed management strategies for the coming season

Leslie Huffman, weed management specialist of horticultural crops, Ontario Ministry of Agriculture, suggested numerous strategies for vine crops in the integrated pest management (IPM) session at the latest Great Lakes Fruit and Vegetable Expo.

Huffman emphasized how weeds compete with the crop for moisture and nutrients. They can reduce yields, sometimes drastically; impede air circulation, which leads to greater disease pressure; and harbor and even attract pests, such as squash bugs and nematodes.

Herbicide options limited

With few herbicides labeled for cucurbits, rotating with a crop such as corn or soybeans should be considered. However, Huffman urged growers to be on the lookout for herbicide residues. They should also scout now for new perennial weed infestations. Perennial weeds typically demand a two to three-year management program.

Photo by Bob Ferguson.
Weed Management Specialist Leslie Huffman of the Ontario Ministry of Agriculture tells a crowd of growers that the alternative strategies of reduced tillage practices and plasticulture have been successful in weed reduction for cucurbit crops. Well-timed herbicides can be integrated into these alternatives, but need to be planned.

Regarding winter annuals, Huffman noted that the recent warm and lengthy fall seasons encouraged their establishment. Fortunately, they respond to herbicide sprays. Growers should also mow weed escapes before their seeds enter the soil.

Growers need to decide which fields to devote to particular cucurbit crops, and which production system to use next spring. Select fields with low weed pressure, then in the fall plant and fertilize a thick cover crop to smother weed seedlings. The next season’s tillage system should be planned.

Tillage system influences strategy

Huffman described how various levels of tillage can fit into weed management. She pointed out that our grandfathers, with no herbicides, used a technique of less tillage to minimize disturbance of the soil, termed a “stale seedbed” system.

With a no-till system, destroy the cover crop, by flaming or with an herbicide, as early in the spring as possible. Just before planting, do a second burndown, again with an herbicide or flaming. Fluted no-till coulters, added weights and narrower press wheels titlted inward will help cut through the crop debris when planting.

In a reduced tillage system, destroy the cover crop—again either with an herbicide or flaming—and till as soon as the soil can be worked. Weeds will emerge, but just before planting, do not till. Instead, kill the weed cover and plant directly with minimal disturbance to the soil.

Keep in mind that the type of weeds will change with lessening tillage. In the first year, shallow-germinating annual weeds will appear. If untilled, the field’s weeds will shift to winter annuals, then biennials and perennials. Proper weed management will differ with this change.

If tilling conventionally, kill the cover crop with an herbicide or flaming. Till as soon as the soil is fit. After the first weed flush emerges, kill it with a second tillage, and plant directly into the tilled soil.

Using plasticulture results in fewer weeds. Other advantages can include less disease because of reduced soil splash and faster growth with more rapid canopy development due to warmer soil. However, planter hole, edge and inter-row weeds still require control. There are costs associated with the drip and fertigation system, disposal and the mulch itself.

If choosing plasticulture, destroy the cover crop. Till and smooth the seedbed. Irrigate if dry before laying the plastic. Be sure the plastic contacts the soil tightly before planting.

Critical weed-free period

Regardless of the planting system, says Huffman, the first four weeks after planting is critical to be weed free. Weed researchers report no reduction in yields if weeds are controlled during this period. Consequently, following the principle of eliminating weeds as much as possible during the first four weeks can result in cost savings.

After this period, when the cucurbit vines run, flower and set fruit, herbicides can manage the grassy weeds fairly easily. On the other hand, except for cultivation and hoeing, there are few controls for broadleaf weeds. Huffman suggests spot sprays, wick weeders, shielded sprayers or spot flamers if labeled for the grower’s area. These strategies can be effective in both summer and fall.

More cucurbit IPM information available

The Great Lakes Vegetable Working Group has a limited number of DVDs on the IPM Workshop presentations available for a shipping and handling charge. Huffman’s weed management presentation includes a decision chart and herbicide recommendations for Canadian and U.S. growers. Other presentations on the DVD include the characteristics of various cover crops, as well as nutrient requirements and application rates for soil and nutrients, foliar diseases, fruit rots, pest thresholds, insecticide efficacy and resistance management. Contact Jim Jasinski at Ohio State University Extension, IPM Program at jasinski.4@osu.edu.

The author is a writer-researcher specializing in agriculture. She currently resides in central Pennsylvania.