JWSS - Journal of Water and Soil Science

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Elm leaf beetle were reared under controlled conditions (25± 2 ^oC, 70± 5%R.H. and 16L: 8D) to determine relationship between biological traits and the number of eggs per female on different hosts and to evaluate correlation between traits. U. carpinifolia, U .c. var. umbraculifera, U. glabra var. pendula and Celtis caucasica were examined as hosts. The biological traits consisted of 1^st, 2^nd and 3^rd larval developmental times first, second, and third larval percent mortality rates prepupal and pupal developmental times male and female longevity and pre-ovipositional period recorded during experiments. The relationships between traits and the number of eggs per female were determined by multiple regression (Foreward selection and stepwise). The correlation between traits was evaluated, too. The results showed that the number of eggs per female were mostly affected by certain special traits such as 2^nd and 3^rd larval developmental time, pre-ovipositional period and male longevity which are distinct in different hosts and seasons.

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Some bioecological aspects of grape leafhopper, Arboridia kermanshah Dlabola, including: the egg distribution under the leaf surface, eggs and nymphs spatial distribution on the vine arms, the adult distribution on three strata of the vine canopy, the adult diel activities and the geographical distribution of this species in Isfahan province were studied. Samplings were done in the 1997. The egg distribution under the leaf surface was determined by repeated sampling during the season and the egg density was estimated on three regions such as the main and secondary vein, the leaf surface margins and others. Eggs and nymphs spatial distribution along the vine arms were studied weekly for six weeks by sampling an arm of five vines during the second generation, the leafhopper population was the highest. The adult spatial distribution on the vine canopy was determined by sampling three strata of the vine canopy using the D-vac apparatus. Diel activities were studied by sweeping nets fifty times per vineyard at the two hour intervals from 8 a.m. to 20 p.m. Temperature and the relative humidity were also measured in the shade once per hour. The presence and the abundance of this species in 87 vineyards in the different climatic conditions were studied by a sweeping net. The leaf margin and around of the secondary vein were preferred for the oviposition of the leafhopper. Adults, nymphs and eggs were more abundant in the middle strata of the vine canopy than others. The mean pattern of the daily activity of the adult indicated one peak at 8 a.m. and the other one at 20 p.m. Maximum temperature thereshold for the adult activities was 28º C. The study of the grape leafhopper distribution in isfahan province indicated that this species was distributed in the most vineyards, but was highly abundant in more humid conditions.

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In 1997, in two vineyards of Isfahan university of technology and Zobeahan in Isfahan, the density fluctuations of Arboridia kermanshah Dlabola and their injury symptoms were studied. In each vineyard three leaves of each of ten randomly selected vines were sampled weekly. Nymphs in different instars were counted directly and rate of injury symptom (leaf discoloration) was determined with planimeter. Special cages were used to determine rate of injury symptom for each nymphal instar in comparison to each other. Rate of injury symptoms and nymphal density indicated two peaks through growing season until harvest. Tolerance threshold for A. kermanshah nymphs was determined 80 first instar nymphal days or presence of 11-12 first instar nymphs and feeding for seven days. With increase of nymph densities, damage symptom increased rapidly.

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Fecundity and sex ratio are the important factors in the quality control of parasitoid, Trichogramma. In this research, the effect of the host egg deprivation on these factors in Trichogramma brassicae Bezdenko was evaluated. The experiment was conducted with four treatments, each in five replications in a completely randomized design. Twenty mated females (24 h old) were transferred into the glass tubes (1.5×10 cm) separately and were fed by honey 20% daily. In one treatment, parasitoids were provided with the 150 host eggs (Sitotroga cerealella) in first day, but in other treatments the 150 host eggs were offered after 2, 4 and 6 days. In order to obtain fecundity, black eggs were counted after 3 or 4 days. After emergence, adult parasitoids were recognized as male and female by their antennae and sex ratio was obtained. Results indicated that as parasitoids, Trichogramma sp., were deprived from the host eggs longer, more decrease was observed in fecundity and female ratio. Therefore, parasitoid quality was decreased by the host egg deprivation.

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The predatory beetle Cybocephalus fodori minor has recently been reported in Iran. Also few studies have been reported on life cycle of Cybocephalus beetles, especially on that of C. f. minor. Thus, the life cycle and feeding rate of this predatory beetle was studied on pistachio oyster shell scale, Lepidosaphes pistaciae under laboratory conditions (temperature: 25 ± 2 °c relative humidity: 65 ± 5% and photoperiod: 16:8 L: D/h). Life cycle of C. f. minor was completed at six stages including egg, three larval instars, pupa and adult. Duration of the development for one generation (not considering preoviposition period) was 43-46 days for males and 38- 42 days for females. The developmental time length for the egg, larval instars1-3, pupa, male and female adults longevity, preoviposition and postoviposition periods was 8.8 ± 0.1, 5.2 ± 0.1, 34 ± 0.1, 6.8 ± 0.1, 17.3 ± 0.3, 59.2 ± 2.2, 65.8 ± 3.1, 6.8 ± 1.6 and 3.5 ± 0.5, respectively. Average fecundidity (number of eggs laid by a female per her life time) was 64.7 ± 6.2. Sex ratio in the laboratory and in the field was 1:1. Daily feeding rate for the female and male adults, larval instars feeding on adult female scale was 7.1 ± 3.5, 6.9 ± 2.2, 1.8 ± 0.2, 3.7 ± 0.2 and 5.9 ± 0.3, respectively. These parameters were also determined when those stages were fed on the eggs and second nymphal stages of pistachio oyster shell scale. Adult beetles over 60 days exhibited the highest feeding on this scale.

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  Aphids are known as important pests of plants specially almond trees. Seasonal population fluctuation of two aphid species, Brachycaudus amygdalinus (Schout.) and Hyalopterus amygdali (Blanch.) were studied in 1999-2000 on almond trees in Najafabad area. Characteristics such as times of egg hatch, appearance, outbreak, spring migration to alternative hosts, migration from alternative hosts in fall, oviposition, number of eggs laid, damage degree, alternative, other primary hosts and some natural enemies were investigated. In early spring damage signs of B. amygdalinus were expressed on almond twigs as serious leaf curling followed by retarded growth of twigs and shortened internodes. Shortly after that H. amygdali colonized other leaves. For both species egg hatching was coincided in late winter however colonization and population increase of H. amygdalei were observed two weeks later than what was observed for B. amygdalinus. With the onset of warm season, both species moved from almonds to alternative hosts for aestivation. Gynoparae shortly followed by males appeared on alternative hosts in late summer and migrated to almonds. Oviparae produced by gynoparae mated with males and laid their eggs near the buds.

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In this study diflubenzuron as a chitin synthesis inhibitor with a dosage of 25 mg A.I/L, and Pyriproxyfen as a juvenile hormone analogue with a dosage of 0.4 mgA.I/L were incorporated in the wax diets of young and last instar larvae of greater wax moth and reared at different temperatures (25, 30, 35°C). Results showed that these compounds in comparison with control increased larval mortality. Diflubenzuron and pyriproxyfen caused 33.9% and 24.1% mortality respectively. The young larvae showed higher mortality with the mean of 57.8% in diflubenzuron and 31.5% in pyriproxyfen. In evaluation of pupation and emergence of adults, no significant differences were observed between diflubenzuron and control. Pyriproxyfen induced reduction in pupation about 48.4% and adult emergence about 44.8% and caused some abnormalities of pupae. Last larval instar was more sensitive to JHA in this respect. Maximum pupation disruption occurred at 25ºC and 30ºC in comparison with 35ºC which reduced abnormal pupae up to 19.7%. IGRs were effective in last larval instar at 35 ºC and increased abnormality of adult up to 49.4%. Reproductive potential (egg viability, hatchability) of adults reduced in F1 generation and was 70-90 percent. IGRs have unfavorable effects on biological aspects of larvae therefore, it is possible to use IGRs alone or in conjunction with other pesticides (Fumigants) in integrated control of these pests.