عنوان مقاله [English]
Introduction: Pest and disease problem with the extension of fruit orchards, becomes a serious and restricted factor for orchard growers. Most of the scale insect of cold region fruit trees in Iran belongto family Diaspididae. One of the most important pests in the fruit orchards of Chaharmahal and Bakhtiari Province are scale insects. Hall scale, Mercetaspis halli (Green) (Hemiptera: Diaspididae) ), which is armoured scale, is known as a primarily pest of stone fruits. They are the most prevalent pests on trees mostly on Almond and Nectarine . In Iran, this pest is reported in the regions such as Khorasan, Marcazi, Semnan on Cherry, Almond and Apricot trees . Rajabi also reported the pest in Tehran, Esfahan, Yazd, Kermanshah, Fars and Kerman province on apricot, peach, cherry trees . Moghaddam in 2004 reported the pest distribution in Fars, Isfahan, Kerman, Sistan and Baluchestan on almond, peach and pistacia. Monthly abundance monitoring of M. halli, which was conducted by Berlinger et al in 1996 , indicated that adult population had three generations per year. From the ecological and biological aspects, no enough information is available in Iran about M. halli scale. Thus, the aim of this research was to investigate aspects of the biology and ecology and seasonal changes of M. halli on Almond and peach trees to clarify the effectiveness of nonchemical management strategy.
Materials and Methods: A field study carried out by weekly sampling of different growth stages of M. halli (egg, nymph, male and female) on twigs in two the Almond and the Peach orchards in Saman restrict in Chaharmahal and Bakhtiari Province. Different growth stages of armoured scales (egg, nymph, male and female) were counted and its population seasonal changes were studied. The population density was determined and compared on different twigs with different ages. The period for ovoviviparously and emergence of 1st and 2nd nymphal instars and matured insects were estimated. Based on Berlinger et al. (3), growth stages were collected and counted on branches especially in join sections of old and new branches and cracks of branches. The data were normalized by changing to ( ). Figure of population changes were drawn by Excel.
Results and Discussion: Berlinger et al. (3) studied the biology of M. halli and found that this armoured scale is a primarily pest of stone fruits especially on Peaches and Nectarines. These researchers reported 3 generations per year for the pest. In California, M. halli has one full and one partial generation per year and overwinters as adult females. The results of the present study was exactly in accordance to the results of Berlinger et al. (3) in that M. halli scales settle in all parts of the tree, but are more abundant beneath buds of current growth, or in bark crevices of the main branches, either in the lower tree center or on the trunk. Berlinger et al. (3) studies, showed that infestation and feeding of M. halli weakens fruit trees and reduces their growth and functionality. Feeding by hall scale weakens plants and may reduce the yield. However, the most important and direct economic damage is caused by nymphs settling on the fruit. Females settle in all parts of the tree and male were rare and emerged only in summer. In this survey, winged adult males didn’t emergeMeanwhile, the important economical damage is observed by settled nymphs on the fruits. Damage due to feeding of this insect appears as red depressions (2mm diameter) in the skin or as red spots which develop after the death of the scales and expand as the fruit grows. This case reduces the fruit market price. Berlinger et al. (3) and Gill (6) also reported that this pest overwinters as mated adult females. According to their results more than 90 percent of overwintering females had velum, which is an indication of mated female materials.
Conclusion: Infestation of the M. halli on the trees of Plum, Almond, Apricot and Peach in Saman region indicated that the pest is polyphagous and can damage to the different Rosaceae trees. Our results showed that this insect produced nymphs ovoviviparously. This stage lasted for a very long period. Since after the first generation being finished the next generations overlapped and in its population, all different growth stages were observed. This pest had two complete generations and the third incomplete generation in nymphal stages appeared when weather was getting cold. Males and females were seen simultaneously. Mated females overwintered on beneath buds or in bark crevices of the twigs and branches of host trees. Finally, all nymphs died. Thus only mated females overwintered on cracks of trunks and branches of Peach and Almond trees.