Applied Entomology and Phytopathology
Year:2003 | Volume:70 | Issue:2|Papers Count:12

Stage mortalities of Sunn pest Eurygaster integriceps Put. immatures was studied using age-specific life tables in four constant temperatures 22, 25, 21 and 30°C, 14 L.10 D photoperiod condition on Mahdavi wheat cultivar kernels, revealed that, 1.33, 34.00, 29.33 and 23.33% of initial cohort developed to adult stage in 4 above temperatures respectively. The highest mortality occurred in 22°C while the lowest was in 25 qc. Second instar nymphs experienced the most extent of mortality (21.42-69.89%) followed by the 3 rd. instar and egg, while the I st. instar had the lowest mortality by 1.59-12.26% followed by the 4 th. instar nymphs. It seems that two median temperatures (25 and 21°C) were more desirable than others. Survival curves were near to Slobodkins type IV. Lower developmental threshold was determined as 18.85 °C for the first time in Iran. An accumulative 215.26 degree-days found that is needed to complete whole preadult development.

The parameters of the predatory activity in densities I and 4, gut content and constant rate of gut emptying of the predatory bug, Orius niger Wolff on cucumber leaf disc containing of second onion thrips larvae, Thrips tabaci Lind. were studied under laboratory conditions (26 oC, 65±5% rh). hunting and attack behavior of the predator and prey reaction were also investigated. The mean parameters of predation rate were recorded 6.22± 1.18, 8.60±0.76preys killed per hour; encounter rate 0.525±0.08,0.724±0.029h-1"; success ratio 0.973±0.14, 0.852±0.041 and handling time 4.095±0.672, 3.006±0.520 larvae per minute in I and 4 densities respectively. Of these parameters, the encounter rate and success ratio were significantly higher in densities of 4 than I. Gut capacity and the rate constant of gut emptying were 0.059 mg, and 0.151 h-1,l. The effect of interference on predators behavior is discussed.

In order to determine the Economic Injury Level (ElL) of Sunn pest (Eurygaster integriceps) in the cereal fields, two groups of studies were carried out in three regions of Kermanshah province, namely: Droofaraman, Mahidasht and Dizgaran.During two consecutive years (1996-1998), 25 fields were selected in abovementioned regions. Investigation and sampling initiated as soon as the first migration of hibernating individuals to the cereal fields occurred, involving the determination and the evaluation of the injuries.Average density of hibernated adults has been found to be around 3.3 bugs per square meter. Each hibernated adult has proved to be able to destroy 61 central shoots along with 12.2 white heads, resulting in 126 kg yield reduction in one hectare. ElL for the hibermited adults has been estimated to be 1.30 and 1.65 individuals per square meter in two consecutive years. The density of the progenies including the various stages of nymphs and the new adults has been found to be 30 per square meter. Each individual from new generation was able to infest 0.5% of kernels at the time of physiological seed maturity and 0.7 % at the traditional harvesting time. ElL for the nymphs has been estimated to be 4 and 2.8 individuals per square meter at the physiological seed maturity and harvesting time respectively.

Cereal leaf miner Syringopis temperatella Led. (Lep. Elachistidae) is a major pest of wheat and barley in middle east, specially in South, south-west of Iran. This pest causes quantitative and qualitative damages through feeding of leaf tissue. Diapausing of leaf miner occurred at first instar larvae at a depth of 15-30cm.This stuty carried out in a split plot design for chemical and non-chemical controls with seven treatments (3 stages of ploughing with and without disking in July-September and a check treatment without post harvesting agronomic operations) as main plots at 3 phenological times (3-4 leaves, tillering and heading stages) as sub-plots with three replication during 1998.The second year treatments were almost the same without two plouphing which September replaced with chemical treatments (Diazinon E. M. 60% 1.5 Lit/ha at 3-4 leaves and tillering stages), in September.Sampling performed in 3 based on different times (No. of larvae/m2, No of larvae/wheat plant wheat, No. oflarvae/tiller. No. of larvae/leaf, No. of larval canals/m2,No. of larval canals per tiller, No. of larval canals/leaf and No. ofpupae/m2) Yield components (plant height, spike length, dry mass, grain yield weight and thousand grain weight) measured and analysed.The results showed that ploughing after harvesting in September on pest population reduction and the other ploghing treatments with disking were effective resulting in yield increase provided that the depth of ploughing with disk must not be less than 15cm. And it must be done up to late August. Chemical application in 3-4 leaves stages is comp lately effective, but it is not effective in tillering stage.

The migratory loucst, locst, Locustae migratoria Linnaeus (Acrididae: Orthoptera) is a major pest in sugarcane and rice fields in Khuzestan province. Effect of temprature, humiditiy and drought on developmental stages of the grasshopper was studied under laboratory and of Khuzestan field codition in 1998-1999.The capsuls and nymphs wer reared at different temperatures (ranging between 15-40oC) to study incubation period and survival of eggs and nymphs and the results were analysed by PMDS computer program. The results showed that, the model of Stinner was the best fit to the drvelopmental rates of eggs and nyumphs. The optimum temperature for survival and egg incubation period was 36.9oC under laboratory conditions which is usually occurred in July and August in Khuzestan. The highest rate of development and survival of eggs were recorded by 15% of soil humidity. There was a significant positive correlaion between drought period and incubation period (R2= 93.5) and a negative relation obserred between drought period and egg survival rate (R2= 90.5).

From a total of 49 isolates of Blumeria graminis f.sp. tritici collected from Sistan Province, races 66, 27, 11, 31, 50, 14, 28, 58, 21, 5, 19, 32,24,84,53.73 and 44 were identified and found to be new to Sistan province and Iran as well. Races 11, 53 and 71 constituted 40% of all isolates studeid and were dominant in Sistsan wheat fields.The Isolates showed differrent pathogenicity and virulence on respective wheat cultivars. Overall, maximum pathogenicity level of most races occurred on pm3 genotype and was 64.7%. The results showed the absence of virulence in isolates on pm4b genotype. Maximum virulence was associated with race 53 and was 85%. The results of the reactions of eight international wheat lines and 12 commerical cultivars from Iran and native to Sistan in greenhouse showed that line Carestem V. and cv. Sorkhtokhm exhibited a maximum level of 94% and 94.1% compatibility to the fungal isolates, respectively. In contrast, Weihenst. MI, Chul, Axminster, Haile 13471 and cvs. Hirmand, Pastor and Chamran were incompatible vis-a-viz most isolates, respectively, so as maximum incompatibility level againt the fungal isolate was associated with line Weihenst. MI and cv. Hirmand as well. The latters reactions to the race 53 in the greenhouse were also similar field experiment. ANOVA and mean comparison test in the field were significantly different at level and cv. Sorkhtokhm and Hirmand were the most susceptible and resistant cultivars againt race 53 and thus placed in A and L groups, respectively.

Two predatory mites species, Typhlodromus kettanehi Dosse and Euseius finlandicus (Oudemans), were found native to East Azarbaijan province of Iran. They often recorded with high population, especially on apple and walnut fruit trees. In order to comparison of their rearing methods, an experiment was carried out in the form of factorial with completely randomized design (CRD) in 5 replicates. Factors of the experiment were: factor A, rearing substrate (with two kinds of substrates, plastic substrate and bean leaf); factor B, kind of predatory mite species (with two above mentioned species) and factor C, rearing diet (with three kinds of foods, i. e. Tetranychus urticae Koch, almond pollen and combination of prey mite and pollen). Two kinds of rearing substrates with three kinds of diets formed six different rearing methods for each predator species. Experimental substrates sizes was 5x5 cm and 60 numbers of them were placed into 5 plastic pans. The initial numbers of the predatory mites per experimental substrate were 10 fertilized females. The number of predatory mite stages were counted for each experimental substrate after 15 days under 24± 2 oC, 60± 5% RH and 14L: 10D hours. The data obtained of predatory abundance were analyzied, which results indicated that, T. kettanehi on plastic substrate or bean leaf and almond pollen or combination of T. urticae with almond pollen, and rearing of E.finlandicus only on bean leaf and with these diets were found suitable methods, whereas, results was reversed when two predatory species reared on bean leaf and prey mite.

This study was carried out in two different localities of Hormozgan province, Minab and Syahoo, two important mango growing area of province. The results of this study are as follow.The overlapping generations are due to alternate infestation based on alternate bearing of new flashes.The results show that this pest completed its development in 46,594± 0.933days (egg 2.46± 0.244 days; larvae 35.984± 0.63 days ;pupa 8.15± 0.623 days) There are three generations of the pest in Syahoo and four generations in Minab during each year. The optimum activity of this insect occurs in the range of 10-26°c.The activity of this pest will decrease significantly out of this temperature range.The damage could be observed with the emerging of adult flies from infested leaves on the trees. It shows that the infested leaves are the source of starting new damage. The fluctuation of insect emerging from gall with damages, have two significant peaks in Syahoo and Minab in spring and automn respectively.