Reducing field infestation
1. Early planting. The emergence of adults coincides with the onset of the rainy season. As more adults emerge, there is a continuous increase in the number of females depositing their eggs. Early planting and the use of early maturing varieties reduce weevil infestation and damage.
2. Timely harvest. Delayed harvest extends tubers' exposure to weevils and increases infestation.
3. Handpicking of adults. Adult weevils in the potato field are active in the evening, climbing the foliage for feeding and mating. They can be captured easily by shaking the foliage over a container. Farmers have adopted this practice.
4. Avoidance of monocropping and destruction of volunteer plants. Weevil infestation is highest when potatoes are cultivated after potatoes. Crop rotation with any other crop or fallow period should be practiced. Larger distances between new and former potato fields also reduce the probability of weevil infestation because of a limited migration capability. Further, volunteer potato plants in rotations are significant sources of weevil infestation. It is therefore recommended to pull those plants.
Interrupting adult migration and larval movement for pupation
1. Barriers. Migratory weevils can be caught and controlled by insecticides applied in peripheral trenches around potato fields. Also, band spraying with pesticides within the first two meters of potato fields has been recommended. Early planting of field borders with other Andean crops as a vegetal barrier (tarwi, Lupinus mutabilis or mashua, Tropaeolum tuberosum) also disrupt the migration of weevils into fields.
2. Shelter traps. Weevils hide in the shade during the day. Straw bundles, pieces of jute (sisal), or plastic sheets and other materials can be used to provide shelter to weevils, facilitating their capture. An alternative is to treat potential shelters with insecticides (potato foliage collected from volunteer plants can be sprayed and placed under the shelter). These shelter traps are particularly effective prior to the emergence of potatoes.
3. Ground sheeting. At harvest, full-grown larvae leave the tubers to pupate in the soil. Larvae can be intercepted on their way to the soil by placing harvested tubers on plastic sheets or other materials. After, the collected larvae can then be fed to chickens or killed.
Reducing hibernating weevils
1. Winter plowing. Plowing fields two or three months after harvest can destroy large numbers of larvae and pupae. Chickens can also help destroy exposed larvae and pupae. Abandoned potato fields are a major source of weevil reproduction and migration. Plowing the soil during winter can also reduce the development of volunteer plants.
2. Control of hibernating weevils under former potato piles. If sheets are not used at harvest, large numbers of larvae dig into the soil. This also occurs during sorting potato prior to storage. Sites where potatoes have been piled should be marked, and two to three months after underground larvae and pupae should be destroyed to reduce sources of new infestation. Small-scale farmers have adopted the control of hibernating weevils under former potato piles because those are covering small areas near houses. There are good examples from Taracollo, Bolivia and Cusco, Peru.
Prospects for biological control
Ground beetles (Harpalus turmalinus and Hylitus spp. (both Carabidae) and Metius spp. (Tenebrionidae)) are predators of eggs and larvae. Further, ants (Iridomirmex spp., Formicidae) that predate on larvae have been described. Important entomopathogenic fungi are Beauveria brongniartii and Metharrizium anisopliae that infest larvae, pupae and adults of Andean potato weevils. Recently, a native entomopathogenic nematode (Heterorhabditis spp.) attacking larvae of Andean potato weevil has been reported from Peru.