INFLUENCE OF SOME COMPOUNDS USED FOR CONTROLLING POWDERY MILDEW DISEASE ON POLLEN VITALITY AND YIELD PRODUCTION OF MANGO

During two successive seasons 2017 and 2018 five fungicides viz., Microvit, Nimrod, Topsin M70, Amistar Top, and Bellis at the commercially recommended rate as well as one biofungicide AQ10 (Ampelomyces quisqualis) and lemon grass oil were used to control powdery mildew and improve yield productivity of five mango cultivars under field conditions. The trials were conducted by spraying with compounds at commercial recommended dose each alone, as well as in alternative order, at the four different inflorescence development stages i.e., red-colored, start opening, full-bloom and fruit set stage. The toxicity of those compounds on mango pollen grains germination was investigated in vitro as parameter potential factors limiting mango fruit set. All the tested compounds reduced powdery mildew disease and increased fruit yield of mango trees as compared with control treatment. Among the various treatments applied, Amistar Top and Bellis had minimum disease development and provided the highest values for the yield as kg /tree of the five cultivars during the two growing seasons. Although AQ10, Microvit and lemongrass oil gave the lowest mean of efficiency on controlling the disease during studies growing seasons, recorded the intermediate produced fruit yield and the highest values for germination of pollen grains in in vitro test. Nimrod was found effective in controlling powdery mildew recorded the lowest values for the yield as kg /tree and for germination of pollen grains in in vitro test. Spraying mango trees with alternation treatments was very effective in improving the efficiency of all treatments and fruit yield as kg/tree compared with spraying each alone. In this concern, the type of compound which sprayed at full bloom goes for the benefit of mango production. Data also cleared that inT1 (Bellis, Nimrod and Amistar Top) and T2 (Nimrod, Amistar Top and Bellis) which sprayed with the same fungicides in different alternative order where in T2 Amistar Top was sprayed in full bloom gave superior fruit yield more than inT1 which sprayed with Nimrod at full bloom in all cultivars in the two seasons. This is in agreement with in vitro test where Amistar Top was less effect on pollen grain germination than Nimrod. These results advise that any compound used for the control of powdery mildew in mango should be tested for their effect on pollen vitality and fruit yield.