The grapevine (Vitis spp.) undoubtedly represents one of the woody crops most widely grown in temperate climates, and a highly valuable agricultural commodity. As most of the vegetatively propagated crops, grapevines are exposed to the attacks of a variety of pests and pathogens among which infectious intracellular agents (viruses, viroids, phloem‑ and xylem‑limited prokaryotes) play a major role, causing heavy losses, shortening the productive life of vineyars, and endangering the survival itself of affected vines. The importance of the grapevine industry and the magnitude of the problems caused by these pathogens has generated wide interest which, in turn, has fostered intensive research which has been especially active at the international scale from the late 1950’s onwards.

Directory of virus and virus-like diseases of the grapevine and their agents

Grapevine leafroll-associated virus 2 (GLRaV-2) was recognized in 1984, but its nomenclature was settled only in 1995. It is one of the five viruses involved in grapevine leafroll disease. It is also associated with graft incompatibility disorders. Because of peculiar genome structure and evolutionary history, GLRaV-2 belongs to the genus Closterovirus in the family Closteroviridae. The GLRaV-2 genome is a single-stranded, positive-sense RNA of ca. 16,500 nucleotides that is presumably capped at the 5′ terminus but lacks a poly(A) tail at the 3′ end. The nine ORFs encoded by GLRaV-2 comprise three functional modules, including the replication module, the quintuple gene block module, and the module for RNA silencing suppressors. The translation product of ORF1a lacks an AlkB domain, unlike all members of the genus Ampelovirus that infect the grapevine. The genetic diversity of GLRaV-2 is very high, with six lineages that are characterized by up to 25% nucleotide divergence and different biological behavior on plant hosts. All Vitis vinifera, rootstocks, and interspecific hybrids are susceptible to GLRaV-2. The identification of GLRaV-2 in wild Vitis spp. native to the American continent supports the hypothesis that the virus originated from North America. The virus is restricted to the phloem tissue, and infected cells are characterized by a massive presence of membranous vesicles that are typical of infection by members of the genus Closterovirus. No arthropod vector is known for GLRaV-2, but the virus is graft transmissible and mechanically transmissible to some herbaceous hosts, unlike other GLRaVs. Management of GLRaV-2 is through the use of virus-tested, clean propagation materials. The recent development of infectious GLRaV-2 clones sets the foundation for studies on gene function, virus replication, pathological properties, as well as virus-host interactions.

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Grapevine leafroll-associated virus 3

Grapevine leafroll disease (GLD) is caused by a complex of vector-borne virus species in the family Closteroviridae. GLD is present in all grape-growing regions of the world, primarily affecting wine grape varieties. The disease has emerged in the last two decades as one of the major factors affecting grape fruit quality, leading to research efforts aimed at reducing its economic impact. Most research has focused on the pathogens themselves, such as improved detection protocols, with limited work directed towards disease ecology and the development of management practices. Here we discuss the ecology and management of GLD, focusing primarily on Grapevine leafroll-associated virus 3, the most important virus species within the complex. We contextualize research done on this system within an ecological framework that forms the backbone of the discussion regarding current and potential GLD management strategies. To reach this goal, we introduce various aspects of GLD biology and ecology, followed by disease management case studies from four different countries and continents (South Africa, New Zealand, California-USA, and France). We review ongoing regional efforts that serve as models for improved strategies to control this economically important and worldwide disease, highlighting scientific gaps that must be filled for the development of knowledge-based sustainable GLD management practices.

/pdf/ecology-and-management-of-grapevine-leafroll-disease-1plsst6ur9.pdf

Ecology and management of grapevine leafroll disease.

Grapevine (Vitis spp.) is one of the most widely grown fruit crops in the world. It is a deciduous woody perennial vine for which the cultivation of domesticated species began approximatel...

https://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-08-13-0880-FE

Grapevine Leafroll: A Complex Viral Disease Affecting a High-Value Fruit Crop

Mealybugs are common sap feeding pests that infest a wide range of agricultural and horticultural crops. Besides weakening the plants, the honey dew secreted by mealybugs allow the growth of sooty mould, giving the plants a blackened appearance. Severe infestations can reduce plant vigour and lead to stunted growth and premature leaf fall. In India, different species of mealy bugs (viz. Planococcus citri, Planococcus lilacinus, Maconellicoccus hirsutus, Paracoccus marginatus, Phenacoccus solenopsis etc.) have become major pests on various crops. Recently, invasive species like Phenacoccus madeirensis and Pseudococcus jackbeardsleyi have been recorded as serious pests on several host plants. The cassava mealy bug Phenacoccus manihoti, one of the most serious pests of cassava worldwide, has recently reached Asia, BOOK REVIEW

Mealybugs and their Management in Agricultural and Horticultural crops

Economic losses resulting from vineyard mealybug infestations have increased dramatically during the past decade. In response, there has been a cosmopolitan effort to improve control strategies and better understand mealybug biology and ecology, as well as their role as vectors of plant pathogens. Mealybugs are named for the powdery secretions covering their bodies. The most important vineyard mealybugs belong to the subfamily Pseudococcinae (Hardy et al. 2008). Although numerous mealybug species are found in vineyards, this chapter will cover only those that have risen to the level of primary pest. These are the grape mealybug, Pseudococcus maritimus (Ehrhorn), obscure mealybug, Pseudococcus viburni (Signoret), long-tailed mealybug, Pseudococcus longispinus (Targioni Tozzetti), citrophilus mealybug, Pseudococcus calceolariae (Maskell), vine mealybug, Planococcus ficus (Signoret), citrus mealybug, Planococcus citri (Risso), pink hibiscus mealybug, Maconellicoccus hirsutus (Green), and the newly identified Gills mealybug, Ferrisia gilli Gullan. Meanwhile in Brazil and India, Dysmicoccus brevipes (Cockerell) and Xenococcus annandalei Silvestri respectively, feed on vine roots. Collectively, these species will be referred to as the vineyard mealybugs, although their host range is diverse and many are pests of other agricultural crops and ornamental plants (McKenzie 1967; Ben-Dov 1995).

M. Mani

Papers

Biology and Management of Mealybugs in Vineyards