Application of citrus tree pruning residues in wood ear mushroom cultivation: Fate of pesticides and fruitbody safety

Abstract

Citrus pruning generates tens of millions of tons of biomass annually, representing an underutilized resource with potential for value-added production through mushroom cultivation. However, the extensive use of pesticides in citrus orchards, which involves the application of about 200 different pesticides, raises concerns about the potential transfer of pesticide from the pruning residues used as growth substrate to the mushroom fruit bodies. To assess the feasibility and safety of using this resource, wood ear mushroom (Auricularia polytricha) were cultivated on a medium composed of 85 % citrus pruning residues and 10 % sweet potato shochu lees. Mushroom fruitbody yield grown on this medium was comparable to that of the control medium of broadleaf tree sawdust and rice bran. Fruitbody composition showed slightly higher protein content and lower carbohydrate levels when grown on the pruning residue-based medium. After mycelial growth, six pesticides were detected in the mushroom medium, but only boscalid was found in the fruitbodies at trace levels of 0.003 ppm (fresh basis). These results demonstrate the potential of citrus pruning residues, in combination with sweet potato shochu lees, as a safe sustainable substrate for wood ear mushroom cultivation.