The presence of phytoplasmas and their associated diseases is an emerging threat to vegetable production which leads to severe yield losses worldwide. Phytoplasmas are phloem-limited pleomorphic bacteria lacking the cell wall, mainly transmitted through leafhoppers but also by plant propagation materials and seeds. Phytoplasma diseases of vegetable crops are characterized by symptoms such as little leaves, phyllody, flower virescence, big buds, and witches’ brooms. Phytoplasmas enclosed in at least sixteen different ribosomal groups infecting vegetable crops have been reported thus far across the world. The aster yellows phytoplasma group (16SrI) is presently the prevalent, followed by the peanut witches’ broom (16SrII). Wide and overlapping crop and non-crop host ranges of phytoplasmas, polyphagous insect vectors, limited availability of resistance sources and unavailability of environmentally safe chemical control measures lead to an arduous effort in the management of these diseases. The most feasible control of vegetable phytoplasma diseases is a consequence of the development and implementation of integrated disease management programs. The availability of molecular tools for phytoplasma identification at the strain level greatly facilitated this kind of approach. It is moreover essential to understand the molecular basis of phytoplasma-vector interaction, epidemiology and other factors involved in disease development in order to reduce the disease outbreaks. Information on the knowledge about the most widespread phytoplasma diseases in vegetable crops is reviewed here in a comprehensive manner.

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Adulticidal, ovicidal and nymphicidal effects of different newer acaricides along with some conventional one were evaluated on the life stages of a susceptible laboratory strain of two-spotted spider mite (TSMM), Tetranychus urticae Koch (Acarina: Tetranychidae) using a spray method. Abamectin was found to be the most toxic to the adults (LC 50 = 0.39 ppm) followed by fenpyroximate (5.67 ppm), spiromesifen (12.53 ppm), chlorfenapyr (32.24 ppm), propargite (77.05 ppm) and dicofol (146.65 ppm). Hexythiazox was least toxic. There was no egg hatching when eggs were sprayed with one third of the recommended concentration of spiromesifen. This was statistically significantly different from all other treatments (fenpyroximate, chlorfenapyr, propargite, dicofol and hexythiazox) which were, however, at par with each other. Based on the 10 th day observations, the ovicidal activity of spiromesifen (100%) was followed by dicofol (7.78% egg mortality) and hexythiazox (6.67%). Almost no effect on hatching was observed in both abamectin and chlorfenapyr treatment (0.54%). In case of propargite, all the treated eggs hatched. Abamectin resulted in highest nymphal mortality (96.05%) followed by dicofol (94.51%), hexythiazox (90.24) propargite (90.00), chlorfenapyr (89.33) and fenpyroximate (86.84%) and all the treatments were at par with each other and statistically different from the control. The present study revealed that abamectin, spiromesifen, hexythiazox, fenpyroximate and chlorfenapyr acaricides can alternatively be used for effective management of the mites. ª 2015 Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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