Journal of Entomological Society of Iran
Year:2004 | Volume:23 | Issue:2|Papers Count:10

Mulberry thrips Pseudodendrothrips mori Niwa reduces the efficiency of silk production by feeding the leaf sap. In order to approach a non-chemical control measure for the pest, the effects of sprinkling irrigation and spring pruning were investigated separately in three mulberry varieties (Km, I & SI). For assessment of efficiency of sprinkler irrigation on reducing the thrips population, two half - ha. Plots were selected from each varieties and one of them was irrigated for 3 h and the other was kept as control. The number of thrips collected by random sampling was counted in each plot at four different intervals (before irrigation, 24, 48 & 72 h after irrigation). To determine the effects of spring pruning on thrips population, two plots from each variety were selected which one of them was taken under intensive pruning in mid- May. Population densities were recorded in ten different times in summer. The results indicated that the two methods as non-chemical measures don’t show any significant effects on mulberry thrips. The data determined that only 24 h after irrigation population of thrips lowered and the density of the insect after 48 h of irrigation didn’t show significant difference between two treatments. Also the average population of mulberry thrips in pruned treatments of SI, I and KM, were 0.28±0.170,.29±1.6 & 1.36±1.01 respectively. While this index in non-pruned treatments were 0.23±0.15, 0.15± 0.09 & 1.56±1.3 respectively, no significant difference was observed between two pruned treatments.

Creontiades pallidus Ramber is a major pest of cotton fields in some parts of Iran especially in Khorasan province. Two predators, Chrysoperla carnea (Steph.) and Nabis capsiformis Germ. as important natural enemies in cotton fields are able to reduce the population of C. pallidus. The main purpose of this study was to compare population growth statistics of both the predators and their prey to evaluate the efficacy of C. carnea and N. capsiformis on population change of C. pallidus. Both predators and the prey were originally collected from cotton plants and reared in laboratory. Insects rearing and all experiments were conducted in a growth chamber at 26±1°C, 65±5%RH and a photoperiod of 16:8 (L:D) h. Gross reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of natural increase (rm), finite rate of increase (e), mean generation time (T) and doubling time (DT) of C. pallidus were 68.48,20.37,0.068,1.071,29.37 and 10.12, respectively. However, the same parameters were estimated for C. carnea as 165.38, 133.57, 0.095, 1.10, 42.95 and 7.26, respectively, and for N. capsiformis as 95.10, 22.37, 0.037, 1.037, 48.35 and 18.63, respectively. The results indicated that the rate of population growth and reproduction parameters especially r m and R0 of C. carnea were greater than N. capsiformis and C. pallidus. Our findings suggest that C. carnea show greater efficacy on prey population than N. capsiformis and thus it may be a successful biological agent for reducing the population of C. pallidus.

Biology of Sphaerophoria scripta (Linnaeus) was studied in the following laboratory conditions: 22±2QC,70-75% R.H and 14:10 L. D. The adults were collected from Rostarn Abad of Guilan province and transferred to laboratory. The oviposition mean for each female was 195.2±56.08eggs in cage (60x60x100 cm). The maximum oviposition was in 4th and 5th days. The mean duration of development time (egg to adult) of S. scripta were 16.25±1.06 days while fed on Aphis craccivora in petri dishes (6 x 1.5 cm). The mean longevity of adult males and females were 3.5± 0.53and 3.6± 0.51days without feeding, 9.8±1.6 and 10.2±1.16 days feeding on rape seed flower, 14.62±1.06 and 14.87±1.12 feeding on sugar solution with water (4:1), respectively. The maximum longevity was related to those fed on sugar solution with water. Nutritional diet had no effects on male and female. Feeding capacity increased with age of larvae and mean total larval feeding was 284±21.69 aphids.

Biology and population parameters of chrysanthemum aphid, Macrosiphoniella sanborni (Gillette) were studied in three following conditions laboratory: (24±1°c& 35:1:5%;RH 28±1°c & 35± 5%;RH 28±1°C & 65± 5%RH) and in natural conditions (mean 25.91°C & mean 36.05% RH) on chrysanthemum flower var. Yellow Butten. A photoperiod of 16:8 (LD) h was used at all experiments in laboratory conditions. The nymphal period and longevity of aphid at 24°C was significantly higher compared to other conditions. The least nymphal period and longevity were observed at 28°C (with both humidities). Daily reproduction rate of aphid at 28°C was significantly higher than the other conditions but there was no significant difference between all conditions on aphid total reproduction rate. Intrinsic rate of increase under laboratory conditions of 24°C (35% RH), 28°C (35% RH), 28°C (65% RH) and natural conditions were 0.2239, 0.2965, 0.2961 and 0.2878, respectively. The maximum and minimum rates for the above parameter were obtained at 28°C and 24°C, respectively. Doubling time for the population of chrysanthemum aphid was more at 24°C (RH 35%) than other studied conditions.

Leaf miner Liriomyza sativae has been widely distributed in the world in recent years and it is presently an important pest of vegetables and ornamentals. Because of its high potential for resistance to current insecticides, the use of resistant plant varieties seem to be an effective approach in developing IPM programs for the pest. Since bean is a preferred host for Liriomyza sativae, 19 varieties of bean were examined to study the antixenosis resistance mechanism to this insect and determining the damage rate in a growth chamber at 25± 1°C, 55± 5%RH and 16:8 (light dark) photoperiod. Bean varieties were evaluated in terms of indices such as number of feeding punctures, number of larval mines, proportion of mines to punctures and rate of damage. There was significant differences between varieties. Studied indices such as feeding punctures with larval mines (r=0.957) and larval mines with damage rating (r=0.869) showed high positive correlation among these varieties. Bean varieties were analyzed by cluster method based on all measured characters and were generally divided into three main groups including semi-resistant, moderately resistant and semi-susceptible. No variety was immune to the damage inflicted by L. sativae and Parastoo as a semi-resistant variety roughly sustained 31% damage. Meanwhile, Sayyad, a semi-susceptible variety, up to 61% damage was known as the most susceptible one among studied varieties.

Haemocytes of L. migratoria are categorized on the basis of morphological characteristics of spread cells in four groups, namely plasmatocytes, granulocytes, coagulocytes and prohaemocytes. In the current study the cell number fluctuation was studied during the progress of infection. The results showed that the total haemocyte count (THC) increased during the first three days of infection and decreased subsequently (significant at 99% confidence interval comparing controls). Regarding Differential Haemocyte count (DHC), the similar trend was observed, although the relative percent of coagulocytes increased compared to the other three cell categories. Furthermore, along with the spreading of disease the phagocytic potential of blood cells decreased and prior to insects death these cells were unable to spread their pseudopodia to engulf fungal elements. Although the blood cells were able to phagocytise the aerial conidia injected to insects’ haemocoel in the beginning of infection and blastospores produced in the course of fungal proliferation, these fungal elements were not killed and after germination or multiplication they destroyed the cells, in which they enclosed and colonized their host body. The other impact of the disease on insects cellular immune system was the production of granulomas that were sometimes without fungal elements and were produced under the effects of fungal metabolites.

Egg parasitoid wasp, Plateytelenomus hylas Nixon is a natural control agent of Sesamia species that is made great hope to biological control of these harmfull pests. This parasitoid was reported from many countries in Southern Africa, Middle East, Asia and Southern Europe. The rate of parasitism by this parasitoid varies in different condition and up to 94.2% was reported. In this study morphological and biological characteristics of this wasp in laboratory and field condition were studied.On the basis of result between 2001 and 2002, this parasitoid was able to parasitize up to 90% of Sesamia eggs in corn fields. Sex ratio in natural condition was (1 ♀: 1 ♂) while in lab. condition was (1.26 ♀:1 ♂ ). Parasitoid wasp can complete its life cycle in 11-14 days and it can produce several generations each year. The study on host acceptance range showed that only Sesamia eggs were parasitized by this parasitoid.

Seasonal parasitism and hyper parasitism of walnut aphid, Chromaphis juglandicola (Kaltenbach) were studied in Tehran. Five species including two primary parasitoids, Trioxys pallidus Haliday (Hym.: Braconidae: Aphidiinae) and Aphelinus asychis Walker (Hym.: Aphelinidae) as well as three hyperparasitoids, Alloxysta citripes Thompson (Hym.: Cynipidae), Pachyneuron aphidis (Bouche) (Hym.: Pteromalidae) and Syrphophagus aphidivorus (Mayr) (Hym.: Encyrtidae) were identified and the seasonal fluctuations in their population were accounted. Trioxyspallidus appeared to be fully synchronized and adapted to C. juglandicola, but A. asychis was recovered on occasion, and it seems poorly adapted to walnut aphid or its habitat. The population of T pallidus was observed to be fluctuated during the season. Population fluctuation of the parasitoid marked by a spring population peak, following changes in its host densities, and a summer disappearance, which was followed by a weak autumnal increase. Trioxys pallidus over winters as summer-winter or winter diapause mummies on the soil after leaf fall. The efficacy of T pallidus revealed to be restricted mainly by Alloxysta citripes which seemed to be a specialized hyperparasitoid of this wasp species. The two other hyper parasitoids, Pachyneuron aphidis and Syrphophagus aphidivorus were seemed to be more generalist.