Implementing and Extending Low Input Cranberry Production in the Northeast

Implementing and Extending Low Input Cranberry Production in the Northeast

Summary

This project introduced low input cranberry production on a demonstration basis in Massachusetts. It involves studies of weeds, diseases, insects, and fertilizer in cranberry bogs, with an aim of reducing pesticide and fertilizer use.

The project began in 1990 on LISA cranberry bogs at four sites. A fifth location, which had been managed as an organic production site in 1990 by Ocean Spray Cranberries was added for the 1991 season. In 1992, one of the bogs was replaced with a higher-yielding bog. In 1991 and 1992, two check locations were used for water quality and productivity comparisons to the LISA bogs.

Reductions in synthetic pesticide and fertilizer inputs were substantial in the 1992 season, with no significant increases in pest damage or inadequacy in soil fertility. Over the three years of our demonstration program, synthetic insecticide applications were reduced 60 percent and fungicide applications were reduced by 28 percent in comparison to previous years. Use of EDBC fungicides and chlorothalonil (known to be highly toxic to aquatic organisms and implicated elsewhere in groundwater contamination) were reduced 66 percent in favor of copper-based, mineral fungicides (which are accepted by organic growing standards). Broadcast herbicide dose was reduced 46 percent and fertilizer nitrogen reduced by 52 percent.

Owing to the heavy utilization of surface water in cranberry bog wetlands, studies of water quality, coming into and out of the bog system, were conducted. We found that if pesticides were applied, they generally could be detected in small quantities at the bog outlet. Lowered dose of a pesticide reduced these residues. Regarding fertilizer residues, little phosphorus was detected in bog water during the growing season. Although peaks of ammonium output were observed, these were not associated with applications of fertilizer. In a number of instances, nitrogen levels at the bog outlet were lower than at the inlet, suggesting that commercial cranberry bogs may filter nutrients from incoming swamp or pond waters.

Relative to more widely grown crops, knowledge of cranberry pests is exceedingly primitive. As a result, many of our ongoing projects may appear comparatively elementary. For example, regarding cranberry weed research, studies of the destructive weed pest, dodder are continuing with the focus on predicting weed seedling emergence for the maximization of timing of pre-emergence herbicides. In addition, promising post-emergence controls (preferred when available) were field tested. Investigation of long-term costs of perennial weeds were continued. The use of a summer flood for perennial weed control was investigated. Mycoherbicide studies for bramble and dodder were conducted with little success, but pointed to future avenues of endeavor.

Regarding Cranberry disease research: Research is directed towards an in-depth evaluation of existing cranberry varieties for their resistance to field rot and storage rot. Of 45 varieties evaluated in the field, over a dozen showed field and storage rot resistance. These varieties will be utilized as parents in future crosses performed by Dr. Nicholi Vorsa, cranberry breeder at the Rutgers (NJ) Blueberry & Cranberry Research Center. These same varieties will also be evaluated for their resistance to Phytophthora root rot and upright dieback, the two major dieback diseases in most of the cranberry-producing areas. In 1992, significant progress was made in the field establishment of variety evaluation plots.

Research directed towards a switch from the widely used chlorothalonil (a chemical which can be toxic to fish) to the more organically-acceptable copper-containing fungicides, was conclusive: The copper based fungicides cannot be the sole fungicide utilized under high rot pressure. Future rot control research will focus on the use of late water and resistant varieties, in addition to the more environmentally benign copper based fungicide. Results of the second year of spore trapping (as the first step in development of a model to forecast fruit rot) demonstrated correlations between spore release and precipitation. Spore identification and counting is ongoing with over 10,000 spores counted to date,

Regarding cranberry insect research: We have focused on biology and management of cranberry fruitworm, a pest that accounts for about 70 percent of all applications applied in IPM bogs. Cooperating pheromone chemists have made further progress in the difficult identification of the sex pheromone of cranberry fruitworm that likely will be essential as both a monitoring tool and in sex pheromone disruption of this moth. Following extensive studies to determine the egg distribution of cranberry fruitworm and subsequent development of a model to describe this distribution, a sampling plan for fruitworm has been completed that will allow confidence in the elimination of sprays based on egg counts. Studies showed that the cultural practice of holding late water is clearly an effective management tool for both cranberry fruitworm and southern red mite. Surveys completed show conclusively that indigenous natural enemies are diverse and abundant in wild bogs, but these predators and parasites are virtually eradicated under the current insecticide application regime in commercial bogs.

Regarding fertilizer research: A primary focus is to reduce movement of fertilizer out of the bog by identifying low-leaching materials. A leaching test in the laboratory showed that slow-release fertilizers, both organic and inorganic, had less leaching potential than the commonly used 12-24-12 granular soluble fertilizer. Three of the low-leaching fertilizers, composted chicken manure, fish fertilizer, and Osmocote were field tested on whole bogs with generally satisfactory results in terms of yield and fruit quality. A study to determine the suitability of low-leaching phosphorus forms for cranberry production was begun in 1992."