Ho Van Chien, Southern Regional Plant Protection Center, Long Dinh, Vietnam, Nguyen Van Toan, Plant Protection Sub-Department, An Giang, Vietnam and K. L. Heong, International Rice Research Institute, Los Baños, Philippines
In Jin Hua China when insecticide use was reduced the frog populations increased markedly. Having a soft skin and being highly sensitive to their external environment, rice field frogs are very susceptible to pesticides in the water. Like canaries used in the coal mines as indicators of toxic gases, frogs can serve as indicators of polluted environmental conditions which can have severe health consequences. For more details see http://www.amphibianark.org/the-crisis/amphibians-as-indicators/ . In Australia frogs play significant roles as predators reported by Castellano et al 2007.
When we visited the area near dusk the sounds of frogs were impressive. However fields visited in mid day had hardly any insects or natural enemies giving an apparent lack of natural biological control services in the area. When we interviewed farmers they described the huge numbers of frogs the fields had but we were surprised that they did not think frog were important predators. Farmers seemed to associate spiders as natural enemies and yet frogs are far more ferocious predators than spiders. Some of the frog species are important protein source as well see report. Frog farms are also common in the Mekong.
Such areas where frogs are abundant have rich wetland habitats and deliberate efforts to grow nectar rich flowers to increase natural enemy biodiversity seem redundant and unnecessary. Since frogs are highly sensitive to insecticides, it might be more worthwhile for plant protection authorities to focus on preventing unnecessary insecticide through avoiding prophylactic spraying, spraying for leaf folders in the first 40 days after sowing and farmer training and support to appreciate the ecosystem services provided by conservation of frogs.