Durian trees are experiencing thermal shock, causing mass premature fruit drop. Photo: Cong Hoang.

Currently, the dry season is beginning, and the temperature difference between day and night in the Eastern and Central Highlands regions is very large. Daytime temperatures are quite hot, reaching 35-38˚C, but at night they drop to only 18-20˚C. This temperature difference can cause thermal shock to durian trees.

Symptoms of heat shock in durian

Durian trees suffer from heat shock , which typically occurs during hot weather, when water evaporation is rapid, the soil lacks sufficient moisture, and the tree is deprived of water. This leads to leaf burn during the dry season, burning in the middle of the leaf tissue, yellowing and shedding of leaves, and weakening of the root system. Insufficient and untimely water supply will cause mass shedding of flowers and young fruits.

For durian trees in the pollination stage, high temperatures can hinder pollination, leading to reduced fruit set and lower yields. When durian trees experience heat shock, their weakened state makes them susceptible to pests and diseases due to a loss of immunity, resulting in black spot and leaf spot infections on the leaves and fruits.

Measures to prevent and remedy heat shock in durian trees.

To properly care for durian  trees, it's essential to ensure they are healthy during these crucial stages (bud formation, flowering, fruit setting, etc.). Locals call this "making the tree vigorous," ensuring it has plenty of leaves and a strong root system, by: providing adequate and appropriate watering, and applying organic and mineral fertilizers to nourish the roots and leaves.

Increase plant resistance: By applying products containing micronutrients, especially fertilizers containing calcium and boron, it helps to reduce stem cracking and detachment of the stem.

Plants can be protected from heat shock by supplementing their fertilizers with components such as amino acids, proteins, and plant growth regulators.

During periods when durian trees are susceptible to heat shock, Saigon Plant Protection Joint Stock Company (SPC) recommends that farmers combine the plant growth regulator ANIMAT 40SL (active ingredient Mepiquat chloride) with biological foliar fertilizers, applying the spray alternately every 7 days using one of the following formulas:

- 20ml ANIMAT 40SL + 40ml SPC biological foliar fertilizer - Potassium Silicon,

- 20ml ANIMAT 40SL + 40ml SPC-NPK 5-5-15 biological foliar fertilizer

- 20ml ANIMAT 40SL + 50g NPK FERTIGONIA 18-18-18 + 3MgO + ME mixed foliar fertilizer

20ml ANIMAT 40SL + 35ml SPC AMINO CALCIUM-BO organic biological foliar fertilizer

Instructions for application : Mix the above mixture in a 25-liter sprayer and spray evenly on the trunk and branches where flowers bloom, on the fruit stalks, and on the underside of the leaves.

Note: Can be combined with pesticides to control pests and diseases.