2017 ASHS Annual Conference

Chitosan is a cationic polymer derived from shellfish that has been reported to have antimicrobial properties and to enhance plant vigor and health. The objective was to evaluate the effects of chitosan on zucchini squash plant growth and fruit yield and root-knot nematode galling. The study was conducted on sandy loam soil (pH 6.5) at the Horticulture Farm, University of Georgia, Tifton, Georgia, during the fall season of 2015. Zucchini (‘Respect F1’) plants were transplanted in the field on 28 Aug. Plants were drip-irrigated and grown on raised beds (1.8 m) covered with white plastic mulch; fertilization was with chemical fertilizers. The experimental design was a randomized complete block with four replications and four treatments. Treatments were: a) Control (water); b) Chitosan (OII-YS, O2YS Corp.) applied before planting (2.34 L/ha); c) Chitosan applied before planting and foliarly (2.34 L/ha) three weeks after planting; d) Chitosan applied before planting, and foliarly three and six weeks after planting. Results showed that zucchini leaf net photosynthesis and fluorescence (measured as PSII efficiency) were reduced in plants treated with chitosan before planting + three and six weeks after planting. Stomatal conductance and water use efficiency were unaffected by chitosan treatments. Plant growth, marketable fruit number and weight, and root-knot nematode galling rate were unaffected by chitosan treatments. Individual fruit weight was reduced by chitosan treatments. Plants in all treatments showed low insect damage and low incidences of foliar and soil-borne diseases. Reduced leaf net photosynthesis and leaf fluorescence with chitosan applications, particularly when chitosan was applied before planting + three and six weeks after planting, suggest that chitosan had toxicity effects on zucchini plants.