Fish extracts for integrated disease, insect and fertility management in organic blueberries

Project Overview

Project Type: Research and Education
Funds awarded in 2009: $119,000.00
Projected End Date: 12/31/2011
Region: Southern
State: Georgia
Principal Investigator:
Harald Scherm
University of Georgia

Annual Reports


  • Fruits: berries (blueberries)


  • Crop Production: foliar feeding, organic fertilizers, tissue analysis
  • Education and Training: demonstration, extension, on-farm/ranch research
  • Pest Management: biorational pesticides, botanical pesticides, integrated pest management
  • Production Systems: transitioning to organic


    This study sought to develop an integrated system for disease, insect, and nutrient management in organic blueberries centered around foliar applications of fish-derived products. Three on-farm trials (two in 2009 and one in 2010) were conducted on rabbiteye and southern highbush blueberries in southern Georgia. Four to six foliar sprays of four fish product formulations (Omega Grow, Organic Gem, Organocide, and SeaCide) were made during summer and early fall at each site and compared with an untreated check, an organic standard fungicide (Serenade Max), and one or two additional biofungicides. Two different foliar diseases, Septoria leaf spot and leaf rust, were suppressed successfully with fish products across the three trials. There was no clear "winner" among the four formulations, with Omega Grow, Organocide, and SeaCide being most effective in different trials. Effects on leaf beetle damage were inconsistent across trials, with one trial showing damage reduction by SeaCide and another showing no such effects. This inconsistency could be due to the higher amount of leaf damage already present at the onset of the latter trial. The effects of fish products on plant vigor and leaf retention also were variable, with Organocide and SeaCide improving both parameters at a low-vigor site (rabbiteye trial in 2009) but not a higher-vigor site (southern highbush trial in 2010). Thus, improvements in plant growth seem to be limited to conditions with weaker growth potential. None of the treatments translated into a higher flower bud set for the next growing season. Consistently across the three trials, application of Organic Gem resulted in considerably higher Na concentrations in leaf tissue of treated plants. Although these high Na levels did not appear to impact plant growth negatively, it would be advisable to apply this product only in rotations to preclude potential negative effects. In two of the three trials, increased concentrations of P were observed following application of some fish products, providing a potential nutritional benefit of these products. Overall, although fish products are no "silver bullets" for managing blueberries organically, they contribute consistently to leaf disease suppression and foliar nutrition.

    Project objectives:

    Overall aim: develop an integrated approach for disease, insect, and nutrient management in organic blueberries centered around foliar applications of fish byproducts.

    Specific objectives:
    (1) compare and demonstrate the efficacy of several fish products against foliar diseases of blueberry;
    (2) evaluate leaf beetle suppression in fish product-treated plots; and
    (3) determine the nutritional benefits of fish product applications by measuring foliar nutrient status as well as plant growth and yield parameters in treated plots.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.