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                                                                diseases of impoRtant cRops in chiapas






           plantings should be situated as far as possible from affected plantations. Plantations can be
           surrounded by non-host crops or interplanted with other tree crops.  These measures help

           dilute the amount of virus inoculum reaching papaya, as aphids probe first on non-host species

           and lose their ability to transmit the virus in the process. Disease tolerance selections have

           provided contemporary advances in the management of this disease; progress has been made

           through either conventional breeding (crosses of Carica papaya with the resistant relatives C.

           cauliflora, C. quercifolia, C. pubscens and C. stipulata) or genetic transformation (coat protein

           or other genes of the pathogens).



                Pineapple (Anana commosus)

           Mealybug wilt. Mealybug wilt is a universal problem. The strong association of mealybugs with

           several species of ants makes control of mealybug wilt very difficult. When vegetative seed

           material (crowns and slips) is taken from affected plants, it can be a source of inoculum and

           eventually develop symptoms (Ploetz et al., 1994; Ploetz, 2003).

                The first symptoms are a reddening of the leaves, usually at the margins of fields. These
           symptoms are caused by a cessation of root growth and a collapse of the root system, but the

           same symptoms may also result from drought, nematode damage, and root rot. Leaf symp-

           toms are not diagnostic unless high levels of mealybugs are also present or they are associated

           with field edges.

                Ants,  mealybugs  and  at  least  three  viruses  are  present  in  affected  plants:  two  closte-

           roviruses, Pineapple mealybug wilt-associated virus-1, PMWaV-1, and Pineapple mealybug

           wilt-associated virus-2, PMWaV-2; and an unnamed badnavirus. Ants protect the mealybugs
           from parasites and predators, as well as remove honeydew that they produce (Ploetz et al.,












                                                                Universidad Autónoma de Chiapas
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