Root-Knot in Durian... A Silent Threat Underground

Root-Knot in Durian... A Silent Threat Underground

Off-season durian prices have recently been quite high compared to in-season durian prices, which has led durian orchards to increasingly practice "forcing" — inducing the crop to bear fruit ahead of its normal season. To produce off-season durian, growers commonly use growth-inhibiting hormones such as Paclobutrazol, Uniconazole, or Daminozide. These hormones work by preventing the durian tree from producing the hormone Gibberellin. The most visible effect is that the new flush of young leaves produced after treatment is smaller than normal. In some cases, when orchards apply growth-inhibiting hormones in large amounts, the durian trees become so weakened that they eventually die.

When the topsoil around the canopy area of durian trees treated with growth-inhibiting hormones is dug up and examined, it becomes apparent that the roots have also had their growth stunted, just like the young leaves. As a result, the durian tree is unable to forage for or absorb nutrients from the soil into its vascular (food-conducting) system.

The solution is to spray Planet Gib — a liquid gibberellin product at 4% concentration — at a rate of 50 cc per 200 litres of water, combined with Magic Humic Plus Fulvic at a rate of 300 grams per 200 litres of water. Spray this mixture onto the canopy area over the root zone, as well as onto the foliage, applying it 2-3 times.