A botanical fungicide from garden balsam or Impatiens balsamina, commonly known as ‘kamantigue,’ can effectively control durian diseases caused by Phytophthora palmivora, a study showed.

The study was conducted by a group of researchers led by Professor Belly T. Dionio of the University of Southeastern Philippines in Davao City.

In the Philippines, durian is an export winner and one of the priority crops in Southern Mindanao. Phytophthora palmivora Butler, on the other hand, is considered as one of the most economically important organisms causing diseases in durian. It infects all parts of the durian tree in all stages of its development causing patch or stem canker, root rot, leaf blight, die-back of seedlings and mature trees, and rot of mature and immature fruits.

Production loss due to Phytophthora disease was estimated at 20-25% in Thailand, Malaysia, Indonesia, and the Philippines.

Farmers currently rely on the use of synthetic fungicides and proper cultural practices to control the growth and spread of Phytophthora. However, synthetic fungicides are expensive and their indiscriminate use is hazardous to human health and the environment. In search for an alternative, Dionio’s team focused on using botanical fungicide from ‘kamantigue’ to control Phytophthora disease of durian. The use of ‘kamantigue’ as botanical fungicide could reduce production cost and lessen health and environmental hazards caused by synthetic pesticides.

In testing the toxicity of the aqueous extract of ‘kamantigue’ against P. palmivora, the team found that red and violet ‘kamantigue’ were as effective as fosetyl-al, a commercially available synthetic fungicide currently being used against P. palmivora. According to the researchers, aseptically prepared extracts retain their potency against P. palmivora even after 13 weeks of storage whether in an air conditioned room or at room temperature.

The researchers also evaluated the protective and eradicative properties of the extract based on the number of lesions and percentage of defoliation or leaf drop. In the experiment on six-month old durian seedlings, the number of lesions was reduced by 86% when these seedlings were sprayed with ‘kamantigue’ extract one hour before spray inoculation of P. palmivora. On the other hand, ‘kamantigue’ extract sprayed one hour after inoculation of P. palmivora resulted to 78% reduction in number of lesions. When ‘kamantigue’ extract was sprayed 24 hours before inoculation of P. palmivora, the number of lesions dropped by 60%. These results are comparable to fosetyl-al.

Compared to the untreated seedlings, percentage defoliation was significantly lower inseedlings sprayed with ‘kamantigue’ fruit extract regardless of when it was applied.

Scraped canker lesions dried up three weeks after application when sprayed with either 1:1 (wt/v) extract or the pure crude extract. All treated lesions dried up four weeks after extract application while the untreated lesions remained wet. In comparison, fosetyl-al-treated lesions dried up in only a week.

The extract from mature fruit/seed of red and violet ‘kamantigue’ can therefore be used as botanical fungicide against of Phytophthora leaf blight of durian. However, for patch canker treatment, it is best to scrape off the affected portion before applying the extract. (Angelito Carpio, S&T Media Service)