Control Methods for Penicillium Mold and Green Mold in Pomelo
Symptom characteristics: mainly affects fruit after harvest during storage and transport. The symptoms of the two diseases are similar, mostly starting from the stem end or wounds, initially appearing as light brown water-soaked spots. The lesions expand rapidly, the fruit softens and rots, and a layer of white mold grows on the lesion surface; later the white mold patches turn into green mold patches (green mold) or blue-green mold patches (penicillium mold), with a ring of white mold around the outer edge of the mold patch, and water-soaked soft rot at the boundary between diseased and healthy tissue. Apart from having different pathogens (same genus, different species), the two diseases also differ in many symptom details, the most obvious differences being: penicillium mold patches are blue-green, the white mold band around the outer edge of the patch is narrower (1~2 mm), and the mold patch does not stick to the fruit wrapping paper; green mold patches are green, the white mold band around the outer edge is wider (8~15 mm), and the mold patch sticks to the fruit wrapping paper.
Pathogens and disease characteristics: The pathogens of both diseases are fungi of different species in the genus Penicillium, subphylum Deuteromycotina. The penicillium mold pathogen is called Penicillium italicum Weh.; the green mold pathogen is called Penicillium digitatum Sacc. Both fungi live saprophytically as mycelium on various organic matter. They produce large amounts of conidia, which spread through airflow and can also be transmitted through contact between diseased and healthy fruit, invading through wounds to cause disease. Generally, high temperature and high humidity favor the occurrence of both diseases, but penicillium mold occurs most at 18~26°C, while green mold develops rapidly at 25~27°C. If fruit is harvested after rain, in heavy fog, or before dew has dried, the peel has a high water content and is easily bruised and infected. If fruit sustains many wounds during harvesting, grading, packing, storage and transport, and if storage and transport conditions are warm (18~27°C) and humid (relative humidity 95%~98%), the disease is most severe.
Control methods
(1) Spray 50% Shibaogong wettable powder at 1500 times dilution + 2,4-D at 50~100 units once 7~15 days before harvest to reduce fruit rot during storage and transport.
(2) Harvest fruit on a sunny day after the dew has dried.
(3) During grading, packing, storage and transport, carefully prevent the fruit surface from being bumped, punctured or crushed.
(4) Carry out fruit preservation and anti-rot treatment on the day of harvest, or at the latest within 2~3 days (45% Tecto, or 25% ShibaoKe, or 45% Weixianan at 2500~3000 times dilution, each mixed with 2,4-D at 5000 times dilution, soak fruit for 1 minute).
(5) Disinfect the storage room well (ozone disinfection or sulfur fumigation for 24 hours (10 g/cubic meter), etc.).
(6) Control the temperature and humidity of the storage room (cellar) well (generally 5~9°C, relative humidity 85%~90%, but slightly different for different types), and pay attention to ventilation.
(7) Improve packaging (such as treating wrapping paper or film with “biphenyl”, etc.).