Scientists studying a major potato pest have found that the larvae feeding on tubers can actually increase crop yield. Greenhouse tests indicate that caterpillar saliva increases the marketable yield by up to 2.5 times from a potato plant when less than half the potatoes are infested.
The pest in question is the Guatemala moth (Tecia solanivora), which started moving out of its native habitat in Guatemala and destroying potato crops throughout much of South America in 1970. The Guatemala moth lays its eggs in the soil near flowering potato plants. When the eggs hatch, the larvae burrow through the soil to the tubers and begin feeding.
Increased Crop Yield
The scientists were trying to determine the amount of crop loss caused by the Guatemala moth. Instead, they found that when only 10% of the tubers were being munched on by the larvae, the yield of a commercial variety of potato grown in the Colombian Andes increased by 2.5 times the amount of uninfested plants – after the infested potatoes are removed. When 20% of the potatoes were infested, the plant still produced twice the amount of marketable potatoes as an uninfested potato plant. The potato plant compensates for the damage caused by the caterpillars and produces a bounty for farmers.
The most commonly used method for controlling the Guatemala moth is spraying pesticides every two weeks during the growing season. Genetically-engineered potatoes have also been developed using Bt to control the pest.
With proper breeding of commercial varieties of potatoes, this pest could become a boon to farmers.
Source: Katja Poveda, Maria Isabel Gomez Jimenez, André Kessler (2010) The enemy as ally: herbivore-induced increase in crop yield. Ecological Applications e-View. doi: 10.1890/09-1726