Impact of Potential Organic Pesticides and Potential Fruit Crop Load Regulators on Photosynthesis and Growth of Apple

Project Overview

Project Type: Graduate Student
Funds awarded in 2004: $10,000.00
Projected End Date: 12/31/2005
Grant Recipient: University of Arkansas
Region: Southern
State: Arkansas
Graduate Student:
Major Professor:
Dr. Curt Rom
University of Arkansas

Annual Reports


  • Agronomic: rapeseed
  • Fruits: melons


  • Crop Production: cover crops
  • Pest Management: botanical pesticides, chemical control, mulching - plastic
  • Production Systems: agroecosystems
  • Soil Management: green manures

    Proposal abstract:

    The present increase in demand for organically grown food has increased the need for science-based technologies, which are certifiable organic alternatives to conventional methods and hand labors. A problem unique to tree fruit production is crop regulation and annual production. Fruit trees produce 10-15k flowers per tree but only need 200 fruits for a crop. Increases in fruit number both limit fruit size and quality, thus crop value, and inhibit flower formation for the succeeding crop. For a crop to be economically sustainable, annually flowers and young fruitlets must be removed (thinned) from the tree. Conventionally this is done with plant growth regulators. Based upon previous research, it is herein proposed that some certified organic spray materials may cause a transient suppression or inhibition of photosynthesis. The carbohydrate supply reduction caused by suppression would result in strong inter-fruit metabolite competition, whereby smaller, developmentally delayed fruit would not compete and abscise. A model-plant test of treatments on photosynthesis and vegetative growth under a controlled environment may indicate the usefulness of materials for fruit thinning. The objective of this project is to study effects of potential organic pesticides as thinning agents on gas exchange and growth of vegetative apple trees as a model system. Resulting data will determine what compounds may be effective and have use as crop-load regulating agents for certified fruit production. Greenhouse and field studies will be conducted to show effective concentrations of these compounds. This model system for screening compounds will be a basis for other researchers evaluating additonal compounds which may have the potential to be effective organically certifiable pesticides or used as fruit thinning agents.

    Project objectives from proposal:

    1) To evaluate the various concentrations of potential alternative pesticides and the effects on photosynthetic assimilation, dark respiration, evapotranspiration, and stomatal conductance of vegetative model apple trees grown in the greenhouse.
    2) To evaluate the various concentrations of potential alternative pesticides on the growth response of vegetative model apple trees.
    3) To evaluate the potential fruit thinning compounds on fruit abortion in the orchard during the post-bloom period.

    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.