Gummosis causes heavy economic loss to orange growers

Gummosis locally called ‘dinkya’ has appeared on the citrus trees in all the orange mosambi growing areas after retreat of monsoon all over the Vidarbha, said well-known entomologist and and retired subject matter specialist at ICAR-Central Citrus Research Institute in Nagpur, D O Garg here.

The gummosis should not be ignored as about 2 to 3 lakh trees die each year in Vidarbha due to ‘dinkya’ due to ignorance and bad cultural and mechanical processes on the farm- causing heavy financia loss to farmers.

Early sign of gummosis is sap oozing from small cracks in the infected bark as if the trees are bleeding. Many times if no control measures are taken at an early stage then the gummosis symptoms appear on citrus fruits, he added. Named locally by the citrus growers of Vidarbha as dinkya, it occurs due to the sticky gum like liquid emerging from the cracks on the bark of the tree trunk.

Farmers notice the disease after rains have stopped, but, the disease sets inside the trees during the rainy season itself. However, the oozing gum from the bark crack is washed off during heavy rains, but, this bark stays firm, dries and eventually cracks, informs D O Garg

Decline may occur rapidly within a year, especially under favorable disease development condition.

According to him, a gram of soil contains 40,000 motile zoospores of the fungus Phytopthora. This fungus during water stagnation in the orchard touches bark of the tree.

The disease causes collapse of the tree system and many farmers term it as cancer of the tree as the entire tree dries up and the fruits drop down prematurely on the ground.

Heavy black cotton soil with poor drainages, excessive irrigation and prolonged contact of water with tree accelerates the disease even after the monsoon.

For prevention of the disease, resistant rootstock like Jambheri or Rangpur lime or Alemow for budding should be used. Flood irrigation method and flat bed system should be avoided.

Instead tree should be planted on the raised bed from the soil level. Construction of drainage channels in between the two rows of the trees for drainage of rain water from the orchard. Provision of double ring methods of irrigation for keeping irrigation water away from the trunk should be done.

Similarly, pre and post monsoon application of bordeaux paste by mixing 1 kg copper sulphate and 1 kg lime in 10 litre of water in tree trunk upto a height of 90 cms by paint brush should be done.

Soil drenching and foliar spraying of Mefenoxam MZ 68 (0.25 per cent ) 8 to 10 litre per tree or foliar spraying of Fosetyl twice during August to October at 40 days interval will kill all the fungi in the soil.

Application of trichoderma 1 kg per tree in the soil below the tree before onset of monsoon will eat away the fungus. Similarly, sprying the Phytophthora diseased trees with Redomil Gold MZ 68 at 2.5 grams per litre of water will not let the disease spread to the aerial parts of the trees as well as the fruits. After monsoon or as soon as oozing of gum is observed, the area of the tree bark should be scrapped with sharp knife and application of Mefenoxam MZ 68 paste should be done.

The gummosis should not be ignored. About 2 to 3 lakh trees die each year in Vidarbha due to ‘dinkya’ due to ignorance and bad cultural and mechanical processes on the farm.