Draining water after heavy rain to prevent papaya blight

It is currently the peak production season for papaya, guava, lemon and mango, but heavy rains in recent days have caused waterlogging or broken branches and leaves in some orchards across Taiwan. If no precautions are taken, the chances of diseases occurring after the rain may increase. The Kaohsiung Agricultural Improvement Station of the Council of Agriculture, Executive Yuan, reminds farmers that when the rain begins to ease and the weather clears up, they should drain the accumulated water as soon as possible, remove the dead branches and fallen fruits in the garden, reduce the density of pathogens, properly tidy up the branches to improve ventilation, and apply the correct pesticides for diseases such as blight and anthracnose to avoid the outbreak of fruit tree blight after the rain.

Papayas harvested after rain should be air-dried before being packed to avoid serious diseases during storage and transportation. (Photo provided by Council of Agriculture, Kaohsiung Agricultural Research and Development Center)

Papaya is prone to papaya blight and root rot after continuous heavy rain. The fruit will appear waterlogged and produce white mycelium and a large number of pathogens. Therefore, after the rain, the diseased fruit, fallen fruit and branches and leaves must be removed from the park as soon as possible to reduce the pathogen density of blight bacteria and anthracnose bacteria. In addition, the fruits harvested after the rain should be air-dried before packing to avoid serious diseases during the storage and transportation of the fruit.

The director of the Kaohsiung Farm said that in order to avoid papaya diseases caused by heavy rain, fruit farmers should drain the accumulated water as soon as possible after the rain, and those who have installed pumps in low-lying or water-prone areas can start pumping water immediately. When the weather clears up, orchards that are fully covered with plastic sheets should lift the plastic sheets on the surface of the ridges to allow excess moisture in the soil to evaporate as quickly as possible, shortening the time the roots are soaked in water and avoiding root rot. In addition, if a papaya tree with dense fruits has shown signs of weakness after the rain, you can remove or trim the appropriate fruits and drooping lower leaves to reduce nutrient loss and speed up the tree's recovery.

For the prevention of papaya blight, you can apply 1000 times of 23% iatromin aqueous suspension (safe harvesting period is 9 days), 3000 times of 50% damethoxazole wettable powder (safe harvesting period is 9 days) and other approved pesticides for prevention and control. However, the uniformity of the spray should be improved when applying the pesticide, and the finer the particles of the liquid, the better the effect.

In addition, when preventing guava, lemon and mango diseases, you should also first tidy up the branches, clean the garden, and then use appropriate pesticides to prevent diseases, scab and anthracnose to reduce the possible damage after rain. For guava blight, 800 times of 27.12% copper sulfate aqueous suspension (safe harvest period is 6 days) can be used; 2,000 times of 39.5% fujiamide aqueous suspension (safe harvest period is 6 days) or 1,000 times of 70% methyl dopoxetine wettable powder (safe harvest period is 6 days) can be used to prevent and control guava anthracnose and scab at the same time. However, it is reminded that if the mango orchard is close to the harvest period and it is not suitable to apply pesticides, you can choose pesticides with a shorter safe harvest period or apply lime-sulfur mixture.