Emerging Phytoplasma Diseases in Forestry and the Role of Determining the Insect Vectors for the Management of the Diseases

Abstract

Pathosystem associated with phytoplasmas in forest plants is an emerging threat to forest productivity and biodiversity. Diseases caused by or associated with phytoplasmas occur in hundreds of commercial and native plants, causing minor to extensive damage. Phytoplasmas are wall-less, phloem-limited, insecttransmitted, plant pathogenic bacteria that are transmitted by phloem-sap feeding insects of the order Hemiptera under the families such as Cicadellidae, Delphacidae, Cixiidae, Derbidae, Psyllidae and rarely by Pentatomidae and Tingidae. Disease transmission occurs very quickly, often plants become infected before adopting any management strategies. The single most effective management practice of managing the vector in agricultural/horticultural crop is to cover plants with insect exclusion netting but this is not feasible and practical in the case of forest trees. Because of these limitations, researchers are shifting to manipulation genetics in host plants to affect vector populations and transmission of pathogen but big lacunae exists in our knowledge on the vectors of phytoplasma diseases in Indian forestry. We review the literature addressing the phytoplasma diseases in forest species, the lacunae existing in the insect vectors and the need for determining the vectors for possible management of phytoplasma diseases in forest trees.