Diversification of Andean crop systems at local and landscape scales: enhancing biological control of potato pests
Final Report Abstract
Simplification of agricultural landscapes is a major cause for the loss and fragmentation of habitats and thus a major factor contributing to the global loss in species diversity. Studies in temperate regions suggest that reduced biodiversity negatively affects ecosystem services such as pest control, pollination and production in agriculture, but evidence has been scarce. In the Colombian Andes we studied the effect of tropical biodiversity at a landscape and local scale on pest control and crop productivity. At the landscape scale we established potato plots along gradients of altitude and landscape complexity to assess their effects on herbivores, their natural enemies and potato production. Increased landscape biodiversity promoted arthropod diversity and abundance. Moreover, biodiversity at a landscape scale had a positive effect on crop productivity, which was mainly driven by a reduction in the incidence of the Guatemalan potato tuber moth, Tecia solanivora. The Guatemalan potato tuber moth is the most important pest affecting smallscale Andean potato farmers, who rely on potatoes as their main source of both food and cash income. Adult moths lay eggs either directly on potato tubers or at the base of the plant stems. Upon hatching, larvae burrow into the tubers, where they complete their life cycle. Infested tubers are not suitable for human consumption and the crop value is thereby greatly reduced. Even with multiple insecticide treatments, harvest losses of more than 50% are frequently reported in Central and South America. One of the most promising and also most sustainable pest control practices involves the integrated use of behavior-modifying stimuli to manipulate insect distribution and abundance in what is referred to as “push-pull” technology. This strategy is based on measures that make the protected plants unattractive for pests (push) while luring them toward another more attractive resource (pull) that is unsuitable for pest survival. We identified a potato variety which is higly attractive for oviposition and used it as a “pull” plant in the field and combined this treatment with the use of a “push” stimuli consisting of a mixture of garlic and pepper extracts which we sprayed on the potato plants. Our results show that this push-pull technology reduced potato damage and increased yield as effectively as the continous use of insecticides, but without its negative side-effect. Surprinsingly in our field surveys we discovered that the Guatemanal tuber moth not always has negative effects on crop productivity. We found that potato plants from a given variety attacked by low numbers of T. solanivora produce a 2.5 fold higher marketable potato yield than undamaged plants. Greenhouse experiments demonstrate that this effect is induced by larval regurgitant, rather than by mechanical tissue damage. This unexpected results catched the public’s attention and was reported in newspapers (for example Die Zeit, Die Welt, Abendblatt, among others) and webpages worldwide. Our long-term goal now is to combine the push-pull technology to reduce pest pressure by the Guatemalan tuber moth with the use of the overcompensating potato variety to successfully develop a sustainable management practice that can have a long-term impact on Colombian agriculture.
Publications
- (2008). Diversification practices: their effect on pest regulation and production. Revista Colombiana de Entomología 34 (2): 131-144
Poveda K., M.I. Gómez & E. Martinez
- (2009). Synergistic effects of repellents and attractants for potato tuber moth control. Basic and Applied Ecology. 10: 763–769
Gómez M. I. & K. Poveda
- (2010). The enemy as ally: herbivoreinduced increase in crop yield. Ecological Applications. 20: 1787-1793
Poveda K., A. Kessler, M.I. Gómez
- (2011). Herbivore-induced changes in fruit-frugivore interactions. Journal of Ecology. 99: 964–969
Whitehead S. & K. Poveda
- (2011). Predicting root resistance to herbivores during succession. Functional Ecology. 25: 368-379
Rasmann S., Bauerle T., Poveda K., and Vannette R.
