LOS BAÑOS, Philippines  The brown plant hopper, an insect no bigger than a gnat, is multiplying by the billions and chewing through rice paddies in East Asia, threatening the diets of many poor people.

The damage to rice crops, occurring at a time of scarcity and high prices, could have been prevented. Researchers at the International Rice Research Institute here say that they know how to create rice varieties resistant to the insects but that budget cuts have prevented them from doing so.

This is a stark example of the many problems that are coming to light in the world’s agricultural system. Experts say that during the food surpluses of recent decades, governments and development agencies lost focus on the importance of helping poor countries improve their agriculture.

The budgets of institutions that delivered the world from famine in the 1970s, including the rice institute, have stagnated or fallen, even as the problems they were trying to solve became harder.