Tropentag, September 17 - 19, 2013 in Stuttgart-Hohenheim "Agricultural development within the rural-urban continuum"

Virus Diseases of Major Significance to Tropical Crop Production - From Diagnosis to Disease Management

Leibniz-Institute, German Collection of Microorganisms and Cell Cultures Gmbh, Plant Virus Department, Germany

Abstract

Viruses present a major constraint to plant cultivation in the tropics and those infecting food crops - tomato, cucurbits and leguminosae as well as cassava and banana - are most devastating. This significance is because of changing agricultural practices (intensification) and climatic conditions and is foremost a result of an increased abundance of insect vectors especially of Bemisia tabaci and Thrips sp. efficiently transmitting many viruses. In addition, changes of vector populations including invasion into new areas and, the indiscriminate use of infected planting material contribute significantly to virus dissemination and spread.
In tropical agricultures, begomoviruses cause major diseases with serious impact, yield reductions and losses. Whiteflies are very efficient in spreading viruses and diseases because these insects can reach enormous population densities. Once introduced by only few insects viruses spread rapidly and thus 100% infection can be reached in affected fields. Virus populations also change over time and this is because new viruses are introduced and can establish in their original host or other susceptible crops. Newly emerging viruses threaten virus resistance in crops and this highlights the necessity of continuous surveillance and monitoring of pests and diseases in crop management.
In protected production, crop management options directed at virus diseases generally are targeted to the exclusion of insect vectors and prevention of population growth and the use of virus-tolerant/ resistant cultivars. Disease management is feasible by a combination of measures that also include bio-control agents and the sensitive application of pesticides. In open field production, many of these control measures cannot be applied and here virus disease control is predominantly based on insecticide applications which reduce population densities but do not prevent virus spreading. Virus resistance in crops is a main element of disease management strategies but for many crops resistant, cultivars are not available. Disease management in open fields requires a combination of elements and well defined crop management strategies based on a thorough understanding of the epidemiological and ecological factors driving vector populations and virus dynamics.

Keywords: Bemisia tabaci, Begomovirus, disease management, insect-transmitted viruses, thrips, tospovirus

Contact Address: Stephan Winter, Leibniz-Institute, German Collection of Microorganisms and Cell Cultures Gmbh, Plant Virus Department, Messeweg 11/12, 38102 Braunschweig, Germany, e-mail: stephan.winterjki.bund.de