Page 189 - FRUTAS DEL TRÓPICO

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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