Control of Alternaria Spot Disease on Loquat (Eriobotrya japonica Lindl.) Using Detached Fruits and Leaf-disk Assay

Treatments with four types of new, slightly toxic and non-residual fungicides and two preparations of Trichoderma harzianum were applied against Alternaria alternata, causal organism of Alternaria leaf and fruit spot disease of loquat. Preventive and curative effects of the above-mentioned treatments were bioassessed by measuring lesion diameter of A. alternata and its sporulation density on detached loquat fruits and leaf discs. Results indicated that preventive and curative effects of the treatment with difenoconazole (Score®) and cyprodinil+flodioxonil (Switch®) applied at a rate of 0.35% (V/V) and 0.20% (W/V), respectively, significantly reduced the lesion diameter of A. alternata on treated fruits and leaf discs compared to the untreated control fruits and leaf discs. Also, application of the above-mentioned fungicides at the same rates completely inhibited the sporulation of A. alternata at preventive and curative treatment with Switch® and at curative treatment with Score® on treated leaf discs compared to the untreated control organs. Conidia of T. harzianum (strain Th2) formulated in invert emulsion and applied at a concentration of 1.3X108 conidia/ml of the preparation, significantly suppressed lesion diameter of A. alternata and its sporulation density on treated fruits compared to treatment with conidial suspension of T. harzianum in sterile distilled water, and the control (blank formulation of invert emulsion or sterile distilled water only). These results should be confirmed under field conditions before large scale application.