The moth destroys potato tubers

Swedish Foundation for International Cooperation in Research and Higher Education

[BOGOTA] Spit from a major Latin American farming pest can produce bigger potato harvests, research has found.

The Guatemalan potato moth larva (Tecia solanivora) devastates crops in South and Central America. But when potato plants in the Colombian Andes are infested with low quantities of the pest they produce yields more than double those of undamaged plants.

Researchers had been looking for ways to demonstrate the extent of the harm done by the moth when they "surprisingly found this positive result", said Katja Poveda, a researcher at the University of Goettingen, Germany and the National University of Colombia, and lead author of the study.

They found that, when ten per cent of the tubers of the potato plant were infested, the overall yield of potato tubers was 2.5 times greater from than non-infested plants. When half the tubers were infested the plants ended up of equal yield to non-infested plants because of the increased size of the non-infested tubers.

The secret is in T. solanivora's saliva, which contains chemicals that stimulate potato tubers to grow, according to the research. But the effect only occurs in one variety — the Colombian Andes commercial potato plant, Solanum tuberosum CV Pastusa suprema , developed by the potato research group at the Agronomy Department of the National University of Colombia and released in 2002.

The mechanism is still unknown, Poveda told SciDev.Net. Researchers believe that compounds from the insect's saliva manage to increase the rate of the plant's photosynthesis to compensate for the tubers lost to the larval damage. As a result, the plant actually makes more starch which is stored in the undamaged tubers.

Scientists need to identify the substances in the saliva and understand the mechanism before there can be any practical application of the discovery, Poveda said.

Alejandro Chaparro — a professor at the Genetics Institute of the National University of Colombia, who has studied this potato variety — said that it is important to consider the genetic complexity of this hybrid.

"This is not only a new variety, but has parentals from three different species, one of which is wild," he told SciDev.Net.

Carlos Eduardo Ñustez, director of the potato research group and 'father' of this potato variety, told SciDev.Net that it is now the main variety cultivated in Colombia.

Link to abstract in Ecological Applications