“YOU can produce healthy potatoes without using expensive commercial chemical pesticides,” according to Rogelio Gualberto, an experienced vegetable farmer and former president of the Vegetable Industry Council of Southern Mindanao.

Gualberto said he tried planting potato in his farm in Kapatagan, Davao del Sur because of its relatively higher and more stable price, and longer shelf life.

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But he felt disappointed at first because he incurred yield losses of up to 50 percent due to bacterial wilt, the most serious soil-borne disease of potatoes and other solanaceous vegetables like eggplant, tomato, and bell pepper.

As he is a strong advocate of environmentally-friendly farming methods, he abhors using commercial chemical pesticides and opted to adopt the bio-fumigation technology introduced in his farm by the Australian Center for International Agricultural Research (Aciar) and the National Crop Protection Center (NCPC).

Gualberto averred that through the bio-fumigation technology, he was able to obtain a 50 percent increase in marketable yield of his potatoes and earned over P60,000 net income from his 2,000 sq. meter plot.

“Crucifers such as radish, Chinese mustard, cabbage, broccoli, cauliflower and pechay have significant quantities of natural gas called glucosinolates (GSL) in their tissues. These compounds are acted upon by myrosinase, an enzyme present in crucifers to release isothyocyanates or ITCs. The ITCs have biocidal activities like insectidal, nematocidal, fungicidal, antibiotic and phytotoxic effects. The ITCs suppress bacteria causing bacterial wilt by 40-80 percent,” Gualberto explained.

Gualberto said he chose radish as bio-fumigant for his potato plot, as it is relatively easier to grow.

“Prior to planting potato, I broadcast around one kilo or radish seed on a 2,000 sq. meter plot, waited for the radish plants to grow and mature and then plow the whole area in order to incorporate the radish plants into the soil. Then I watered the soil to hasten the release of the natural gas from the plant tissues, hence increasing efficiency of the bio-fumigation process,” he shared.

“After 14-21 days from soil incorporation the plant tissues by then have decomposed and therefore the plot is ready for planting potatoes,” he added. "Aside from bacterial wilt, bio-fumigation is also effective against root knot nematodes. It also improves soil condition due to added organic matter from decomposed plant tissues.”