ISHS Acta Horticulturae 591: III International Symposium on Pistachios and Almonds
THE NATURAL PARASITISM RATIO OF THE PISTACHIO TWIG BORER MOTH, KERMANIA PISTACIELLA, IN IRAN |
| Author: | M.R. Mehrnejad |
| Keywords: | parasitoid, biological control, pistachio, Pistacia vera, Chelonus, Dibrachys boarmiae, Gelis exareolatus, Gelis liparae, Pteromalus |
| Abstract:
The pistachio twig borer is widely distributed in the pistachio plantation areas of Iran, and is known as an important pistachio pest. Several parasitoid wasps attack the eggs, larvae and pupae of this insect and the wasp progenies emerge from host cocoons. The natural parasitism ratio of this pest was studied in five different pistachio growing areas of Rafsanjan in three years. Sampling was carried out from 10 March to 20 April once a week, and the moth cocoons were collected from pistachio twigs. The cocoons were kept separately in small vials (10 ml), then the emerged insects, either moths or wasps, were recorded. This study was conducted in 1995, 1999 and 2000, when the number of cocoons studied was 3452, 3722 and 6191 and the natural parasitism was 42.6%, 46.2% and 47.7%, respectively. This study showed an 8% (mean) mortality among the moth cocoons which means no wasp or moth emerged. Therefore, only about 46% (mean) of moth progenies developed to adult. Furthermore, it was found that ants and spiders also attack moth cocoons and feed upon the moth larvae and pupae. However, these biocontrol agents are active in the pistachio orchards only where they are not subjected to heavy spray application. The available information shows that this insect was considered a minor pest before 1970. Chemicals (e.g. insecticides) were heavily applied in the pistachio orchards especially in late winter and early spring during the 1970s and 1980s, and subsequently this insect has become a major pest. It is proposed that under a pest management programme, spraying applications should be phased out in the pistachio orchards, allowing parasitoid populations to rise and resulting in effective improvement in control by the parasitoids. | |
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