IPM/Weed Program - Research Highlights

Dr. Hilary Sandler

Economic Comparison of Initial Vine Density, Nitrogen Rate, and Weed Management Strategy in Commercial Cranberry
To remain economically competitive, MA growers are considering renovating existing beds to high-yielding varieties. Renovation is a very expensive activity ($10,000 to $25,000 per acre); obviously, growers need to minimize costs while maximizing quick and thorough establishment of the new vines. The purchase of vines can be a major portion of the initial costs for a new planting. No study had previously examined various vine densities and documented the progress of the cranberry plants.

An economic analysis was conducted on data collected from a 2-year field trial that examined the interaction of nitrogen rate, vine density, and weed management options for establishing new cranberry plantings. The study examined all combinations of the following: 4-rates of nitrogen (0,25,50,100 lb/acre), 4 planting densities (0, 0.8, 1.6, and 2.4 tons/acre) and three weed management options (preemergence herbicide [Devrinol], postemergence weed control [hand-weeding and grass herbicide] and untreated). Utilizing the vigorous hybrid, ‘Stevens’, the cost-efficiency of the treatment combinations was evaluated by combining cranberry and weed biomass data with various economic estimates. The most cost-effective production scheme for establishing new cranberry beds is to plant vines at a low density, use moderate rates of nitrogen, and apply an annual application of preemergence herbicide. This combination produced substantial vine coverage at very low cost, reduced weed biomass by 85% compared to untreated plots, and gave the best weed control per dollar spent. Growers may opt for other combinations that involve higher labor costs if they can produce their own cuttings (reducing initial costs) or if they are farming with the intent to reduce overall synthetic inputs.

Effects of Repeat Annual Applications of Dichlobenil on Weed Populations and Yield Components of Cranberry
Dichlobenil (Casoron or Norosac), a preemergence granular herbicide registered in 1964, has been used in the cranberry industry for decades to control annual and perennial grasses, sedges, and broadleaf weeds. Growers often have expressed concerns that annual repeat applications of Casoron caused direct vine injury or increased the susceptibity of the vines to environmental or pest stresses. Thus, to address grower concerns that repeated use of dichlobenil could negatively impact cranberry productivity, field studies were established at two commercial farms in either high-weed density of low-weed density areas. The objective of this study was to examine the effects of repeat annual applications of low (40 lb/acre) and maximum (100 lb/acre) rates of Casoron on yield components, upright characteristics, and weed species richness and diversity in commercial cranberry farms.

Data from 4 years of repeat annual applications of 0, 40, and 100 lb/acre Casoron indicated minimal negative impact on cranberry vines. Herbicide application did not adversely affect upright productivity, leaf biomass production, percentage fruit set, or other yield parameters; in addition, no improvements for these parameters were noted. Although the interaction of herbicide application with weed density on cranberry root length varied with sampling date, no consistent trend (adverse or positive) was seen. The presence of weeds, rather than herbicide application, was the important determinant of yield. Vines in low-weed density areas produced more marketable fruit and higher percentage fruit set than vines growing in high-weed density areas. Results suggest that repeat annual applications of dichlobenil to commercial cranberry beds may be considered as part of a viable integrated weed management program with no adverse affect in crop growth or yield.