JWSS - Journal of Water and Soil Science

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During years 2000 and 2001, biology and population changes of two- spotted spider mite (T. urticae) was studied on five bean cultivars of two species at 25±1ºC temp., 45±4% RH and 15: 9 (L:D) photoperiod, using leaf disks made from 2-, 6- leaf and flowering stages of the plants. The mite mass rearing was carried out on tomato plants under the same environmental conditions and the effects of feeding on 4 cultivars of phaseolus vulgaris namely Chiti Var. Zanjan, Picher, Sunray, Contender and Vigna unguiculata, Var. Kameran as host plants. Biological features as fertility, percentage of egg hatch, duration of embryonic and larval development, percentage were also Studied of lraval mortality, duration of nymphal stages, developmental period from lava to pre- oviposition stages, oviposition period, adult mite longevity, number of progenies, their percentage mortalities, and sex ratios were determined. The results indicated that the two cultivars Chiti Var: Zanjan, Contender, and species Vigna unguiculatat Var. Kameran at 2- leaf stage appeared to be suitable hosts causing higher egg production and hatches, lower embryonic and larval developmental time and lower rate of larval mortality, lower nymphal developmental period, lower duration from larval stage to preoviposition, extended oviposition period and higher adult longevity. In contrast, the cultivars, Sunray and Picker were shown to be unsuitable hosts. Regarding 6- leaf stage, the cultivar Contender and Vigna unguiculatat, were considered as suitable hosts in relation to embryonic developmental time, number of larvae, duration of larval stage, and rate of mortalities, nymphal developmental time and duration from larval stage to pre- oviposition, extended oviposition stage, sex ratio and adult longevity. But the cultivars Chiti, Picker and Sunray appeared to be unsuitable hosts. In relation to the number of eggs and percentage of egg hatch, number of larvae and nymphs, nymphal mortality rates and sex ratio, the cultivars, Picker and Sunray were considered as suitable hosts at their flowering stage but Vigna unguiculatat and Contender were identified as unsuitable ones.

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The cottony Cushion Scale, Icerya purchasi Mask., is a polyphagous, cosmopolitan and destructive pest that infests more than 200 plant species apart from citrus. Laboratory studies were carried out on the orange at three temperatures, 17±1, 27±1 and 40±1°C 65±5% RH and 14:10 (L:D). The duration of nymphal stages, female longevity and the life cycle at 17±1°C were 85.8±3.83, 74.9±3.53 and 173.6±7.63 days and at 27±1°C were 62.6±4.40, 72.6±4.59 and 144.1±9.26 days, respectively. The duration of pupal stage and the life cycle of male at 27±1°C were 16.1±0.78 and 59.4±1.30 days, respectively. Field studies on the pest were conducted from July 2003 to September 2004 at Sharafabad region of Dezful. At 10-days intervals, five randomly selected orange trees in a citrus orchards (3ha) were sampled by taking 75 twigs, 15cm in length, at random. Number of eggs, nymphal stages and adults were recorded. From these observations I. purchasi had three generations in a year that were recorded as spring, summer and autumn-winter generation for I. purchasi. The autumn-winter generation developed in 6 months. I. purchasi overwinters as different developmental stages on different host plants with the 2nd nymphal stage was more abundant. Apart from different citrus cultivars, altogether 41 species of 22 different families of plants were recorded as the host plants of this scale in Khuzestan province.

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Biological characteristics of Creontiades pallidus Ramber (an important pest of cotton in Khorasan province, Northeastern Iran) and its predator Nabis capsiformis Germar were determined and compared. The experiments were conducted in the laboratory conditions at 26±1؛C, 65±5% RH and a photoperiod of 16:8 (L:D) h. Statistical analysis of data showed that different developmental periods except the second instar nymph, oviposition, pre- and post-oviposition periods, adult longevity and life span in C. pallidus were significantly shorter than N. capsiformis. The egg incubation period, total nymphal period and total developmental period were 5.99±0.038, 10.83±0.11 and 16.86±0.11 days, respectively in C. pallidus and 7.23±0.50, 14.05±0.37 and 21.35±0.36 days, respectively in N. capsiformis. The oviposition period, female longevity and life span were 9.90±1.20, 14.45±1.30 and 28.76±1.10 days in C. pallidus and 18.40±2.40, 27.60±2.50 and 44.90±2.60 days in N. capsiformis, respectively. Each female of C. pallidus and N. capsiformis laid an average of 65.9±3.59 and 119.6±8.83 eggs, respectively in ovipositional period, which showed significantly high oviposition rate of the predator. In C. pallidus, 70.71% of eggs hatched and 23.93% of immatures developed to adult stage. The hatched eggs and developed immatures in N. capsiformis were 77.78% and 29.63%, respectively.

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