Pest problems in pistachio producing areas of the world and their current means of control
2014
Mehrnejad, M.R.
Pistachio trees are hosts to a relatively extensive arthropod fauna. Arthropod pests are the main problem for pistachio-growers and, for this reason, insects and mite infestations have received particular attention from pistachio-growers. The injurious species in the pistachio plantations of the Middle-East and Mediterranean region are the same, but are different from those found in pistachio orchards in California. In general, the hemipteran plant-sap-feeding insects, e.g. psyllids, plant bugs, mealybugs, stink bugs, scale insects and leafhoppers, are considered to be the major injurious agents worldwide. However, the twig borer moth and several beetle species also attack the fruit clusters, buds, twigs, stem, trunks and roots of trees, and these are found throughout the Middle-East and Mediterranean regions. Psyllids and hemipterous bugs, in both the nymphal and adult stages, cause direct yield loss, whereas leaf- and wood-boring groups weaken the tree and thus reduce yields indirectly. The navel-orange worm and the carob moth infest fruits either at pre-maturation or afterwards, and both play an important role in aflatoxin development in pistachios. Pistachio seed wasps and phytophagous mites are also present throughout the pistachio plantations of the world. The control of pistachio pests relies almost exclusively on pesticides. However, for most pistachio pests, sanitation procedures are the primary means of control. Cultural and mechanical control such as (i) clearing up leaf litter and such debris as pruned branches and twigs both inside and around the orchards, (ii) removal of unharvested nuts, (iii) destruction of any nuts left on the soil surface, and (iv) tilling and discing the orchard floor, particularly under the trees’ canopy, may help reduce overwintering populations of many pest species. Furthermore, appropriate and regular irrigation and fertilization regimes are considered efficient treatments against wood boring species. Pruning and removal of weak, damaged and dead pistachio twigs, branches and trunks are necessary to disrupt the egg laying sites for scolytid beetles. Although identification, evaluation and rearing methods of beneficial insects and mites against pistachio pests is being widely investigated, mass release of commercially produced parasitoids or predators is not being undertaken currently. At present, conservation is considered to be the best strategy to maintain and increase the efficiency of indigenous biological control agents, particularly in plantations in the Middle-East, due to the lack of IMP programmes. Further investigations are essential to develop IPM programmes, particularly to characterize the main factors responsible for changes in the population dynamics of both pests and biocontrol agents.
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