Fish extracts for integrated disease, insect, and fertility management in organic blueberries in the Southeastern U.S.


Investigator: Harald Scherm, University of Georgia, Athens, GA
Project location: South Central Georgia

The purpose of this project is to develop a system for disease, insect, and nutrient management in organic blueberries centered around foliar applications of fish extracts, a renewable resource. Blueberry is the most important fruit crop in Georgia, and organic blueberry acreage is expanding rapidly in the state and in neighboring Florida. However, disease management options for organic blueberries are currently very limited. For example, sustainability of production is threatened by foliar diseases which cause premature defoliation in the summer, reduced flower bud set during the fall, and lower return yields the following year. In a recent field trial with a number of organic fungicides, two OMRI-approved fish extracts provided substantial control of Septoria leaf spot, the most important foliar disease on blueberry in Georgia. Based on these preliminary results, a primary goal is to compare and demonstrate the efficacy of several such products against the leaf diseases complex on organic blueberries.

Insect and nutrient management are also major challenges in organic blueberries. The blueberry leaf beetle can destroy the tender new vegetative growth produced after berry harvest during the summer. Furthermore, nutrient supply is often inadequate, leading to reduced shoot growth and flower bud formation, thereby providing a poor foundation for next year’s yield. In a systems context, the added value of fish extracts as foliar fertilizers and/or insecticides or insect repellents would provide a powerful incentive for their use as summer sprays in organic blueberries. Thus, additional objectives are to evaluate leaf beetle suppression, foliar status, and plant growth in organic blueberries treated with fish extracts.

Project objectives are:

  1. Compare and demonstrate the efficacy of several fish products against foliar diseases of blueberry in a certified organic setting
  2. Evaluate blueberry leaf beetle suppression in fish extract-treated plots
  3. Determine the nutritional benefits of fish extract applications by measuring foliar nutrient status, plant growth, and flower bud formation in treated plots.

A final report describing the results of this project will be posted upon completion.