Explosive Outbreak of Dalbulus Sp. and Corn Stunt Disease Associated to Climatic Variations in the Cochabamba Inter-Andean Valley, Bolivia

Abstract

Corn (Zea mays L.) is a cereal that is traditionally grown in the inter-Andean valleys of Bolivia.Cochabamba inter-Andean Valley -2400 to 2700 meters above sea level -includes lower, central and high valleys, and diversity local varieties are grown for consumption such as "Choclo" and grain."Hualtaco" white corn is the most cultivated variety.Due the climate variations -temperature and rainfall-, water and intensive use of technology, winter corn -July to December -cultivation was promoted throughout the Cochabamba valley, generating an early planting different from the traditional summer planting -November to April.This led to a gradual proliferation of Dalbulus sp., as well as the emergence of the stunt or "Palmarado" disease corn.Stunt corn disease, presenting symptoms such as reddening of the leaves, short internodes, proliferation of ears and dwarfism, is Caused by Spiroplasma (CSS) and/ or phytoplasma (MBSP).According to technical reports, since the 1960s, Dalbulus sp. had a proliferation process and stunt disease began to be reported in the 1970s.Approximately, since the 1980s, in the lower and central valley, Hualtaco corn variety for "Choclo" stopped being cultivated due to the stunt disease corn.In the high valley, in a similar process, both Dalbulus sp and stunt disease corn were spread.In 2008, it was reported that Dalbulus and stunt disease corn were scattered throughout the valley.In 2018, was recorded severe damage to the "Choclo" production in communities in Toco municipality.In 2024, an outbreak was recorded with severe losses in the same communities in Toco and Punata municipalities, and other high valleys.In conclusion, Dalbulus sp and the stunt or "Palmarado" corn disease are widespread throughout the valley, due to the change in the cropping system and climatic variations causing severe losses in corn production.