JWSS - Journal of Water and Soil Science

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In 1996 and 1997 pistachio orchards in Isfahan Province were surveyed to determine the presence and damage levels by Eurytoma plotnikovi Nikolskaya and Megastigmus pistacia Walker. In order to investigate seasonal population fluctuation of E. plotnikovi, larval, pupal and adult stages were monitored in three orchards. In each orchard, 200 nuts with more than 50% infestation to overwintering larvae were dissected and examined twice weekly. In 1997 in one orchard, at intervals of one week, 100 randomly selected fresh nuts were examined to determine oviposition trend and damage development. In this field, the biology of the pest was also compared to developmental stages of pistachio trees. In most orchards visited, E. plonikovi was present and was the dominant species in relation to M. pistacia and its damage varied between 0.8-75%. In 1997, start, peak, and end of pupal stage were observed on April 4th, May 7th and May 21st. Start, peak and end of adult emergence occurred on May 4th, May 18th and June 4th. In two other orchards, almost a similar trend was observed. Start, peak and end of oviposition were also observed on May 18th, May 28th and July 2nd. Development of pistachio tree was divided into nine stages and the above mentioned dates were compared to that.

E. plotnikovi had one generation every one or two years. Only one egg was found in each infested fruit and first stage larvae had a long prefeeding period. The use of the information obtained from this study in the management of these pests is discussed.

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In winter 1997 severely infested pistachio nuts were collected from orchards in Borkhar district of Isfahan to determine minimum threshold temperature and thermal constants. Minimum threshold temperatures were calculated according to rate of development or X-intercept method and the least coefficient of variation method. Thermal constants were calculated for different developmental stages in the laboratory and were initially compared to field information available.

Results showed that minimum threshold temperatures for covered larvae in nut to 50% pupation, bare larvae to 50% pupation and larvae within nut and 50% pupation to 50% adult emergence according to X-intercept method were 7.69°C, 7.78°C, 9.52°C and 11.14°C, respectively. In the case of least coefficient of variation method, the values were 7.92°C, 7.59°C, 9.81°C and 11.99°C. Thermal constant for occurrence of 50% adult emergence and 50% pupation from overwintering larvae and from 50% pupation to 50% adult emergence and 5% adult emergence to 50% adult emergence with minimum threshold temperatures of 9.5°C, 8°C, 11°C and 11°C under laboratory conditions were 783±17.03, 609±1.7, 215.3±19.05 and 107, respectively, which, except for the last case, they were far different from the thermal constant under field conditions. With regards to the nature of the available data for field conditions, possible reasons have been suggested for these differences.

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The pistachio twig borer moth, Kermania pistaciella Amsel (Lep.: Tineidae) is one of the most important pests of pistachio trees (Pistacia vera L.) in Iran. This study was carried out in two pistachio orchards of Rafsanjan area. Periods of pupal cocoon and adult emergence were recorded in two pistachio orchards for four years. Minimum threshold temperatures were calculated according to the least coefficient of variation method for different developmental stages. Cumulative effective temperatures were calculated for different percentages of pupal cocoon and adult emergence. Results showed that minimum threshold temperatures for overwintering larvae to pupal cocoon formation, Larvae to adult and pupal cocoon to adult were calculated 10ْ C, 11ْ C and 12ْ C, respectively. Cumulative effective temperatures for occurrence of 50% pupal cocoon from overwintering larvae with minimum threshold temperatures 10ْ C under field conditions were 73.6 degree-day. Cumulative effective temperatures for occurrence of 65% adult emergence from overwintering larvae with minimum threshold temperature of 11ْ C under field conditions were 213.8 degree-day. Cumulative effective temperature for occurrence of 65% adult emergence from 5% pupal cocoon, 50% pupal cocoon and 5% adult emergence with minimum threshold temperature of 12 ْ C were 145.3, 126.9 and 71.6 degree days, respectively.

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