The weed doctor is in

For most people, weeds are just a nuisance that grow in their backyard, mess up a picture-perfect park, or give them rashes when they sit on the ground. Weeds are often seen as merely pests, annoying and constantly popping up in all possible places.

This is why David Johnson, a senior weed scientist at the International Rice Research Institute, finds it hard sometimes to explain his work to people. “Unless people have worked in a field, trying to raise a crop, they often don’t appreciate how serious the losses to weeds can be and how much work can be involved in trying to keep them under control. Despite these efforts, we estimate that farmers lose 10–25% of their crop yield to weeds, depending on how the crop is grown,” says Dr. Johnson.

He first realized what a constraint weeds were to farmers when he worked with small farmers in Belize, Central America, in the 1980s. These farmers were involved in systems of shifting cultivation, and rice and maize were their two most important crops.

“Typically, a farmer might invest about 50 person-days to control weeds in a hectare of rice, which means if a husband and wife are working on the field, and they’ve got 1 hectare, they’ll spend more than 3 weeks working just to clear the weeds,” narrates Dr. Johnson. “When you put that together with the other work that they have to do for the crop—clearing, preparing the soil, and the harvest—weeds count for a very substantial portion of their effort.”

Since then, he has had 20 years of experience in agricultural research and development within national and international programs focused on smallholder cropping systems. His expertise on weed management and agronomy of food crops, especially rice, has led him to projects in India and Indonesia. Before IRRI, he worked at the West Africa Rice Development Association in Côte d’Ivoire, from 1992 to 2000, and in Ghana, Mali, and Tanzania from 1999 to 2003.

Working on rice in these different countries, it struck him that small farmers face similar problems such as labor shortage, lack of land tenure, few opportunities to diversify their production systems, and long distance from markets. “One of the most rewarding and memorable aspects of working in these countries is seeing how appreciative small farmers are of someone taking an interest in their crop, and in them,” says Dr. Johnson.

For 3½ years now, he has called the Philippines his home. But he doesn’t get to stay at his IRRI office for too long, since he’s always headed to one of the field sites of the Irrigated Rice Research Consortium’s (IRRC) Labor Productivity Work Group. He’s either in India or Bangladesh, where they have activities in direct seeding, or in Malaysia, working toward managing its serious weedy rice problem. Dr. Johnson and his team also make the rounds to Myanmar, Sri Lanka, Indonesia, Northern Lao PDR, and the Philippines to work with researchers involved in the management of weeds. In the future, they hope to be able to develop management options that can be widely applied across Southeast Asia.

We almost lost a brilliant weed scientist in David Johnson, who, in his early twenties, thought of taking up sailing professionally. He pursued agriculture at London University instead. Nowadays, he goes scuba-diving to quench his thirst for the seas. (Johnson personal archives)

If there’s one place though that Dr. Johnson doesn’t mind going often to, it’s the ocean. In fact, he would have gone off to sea, sailing professionally and going scuba-diving, were it not for weeds. “Being by the sea, scuba-diving, and relaxing with my wife, Liz, and sons, James, 14, Charles, 12, and Matthew, 9, are my favorite occupations,” says Dr. Johnson. He often dives in Anilao, Batangas, a famous diving site in the Philippines, with his son Charles, who, Dr. Johnson proudly reveals, has recently received his diver’s license. This April, they plan to explore Palawan and the Sulu Sea in the Philippines.

He says, however, that “with the challenges that farmers are facing now—shortages of irrigation water to suppress weeds, shortage of labor to control them, the emergence of new weed problems such as weedy rice and resistance to herbicides, and more serious weed problems brought about by farmers shifting from transplanting to direct seeding—we need to put more effort into anticipating the problems that farmers are going to face and providing solutions to at least some of them. When that job is done, that will be the chance to spend more time by the water.”

Trina Mendoza (t.mendoza@cgiar.org)

Our partners up close archive