Applied Entomology and Phytopathology
Year:2005 | Volume:72 | Issue:2|Papers Count:17

Components such as population size, foraging behavior and spatial relationships are important in studying the termite populations. In order to estimate the colony density of subterranean termites in Dasht-e Ahmad (near Qum), two pistachio orchards (each of them 3.5 hectare) were selected and 700 traps installed. The traps were arranged in 7 columns and 50 rows. Each traps included a polica tube (40 cm length and 15 cm width) containing 6 pieces of wood (Length 25 cm, width 6 cm). The 350 traps (Orchard NO.2) surveyed monthly and the results recorded in related forms. In order to estimate the number of colony, the trend of termites attack to traps was used as a criterion. The first attack to traps was regarded as colony locus and marked using black color. The second, third, fourth and fifth were marked by blue, green, red and yellow colors. These observations indicated that there are continuous attacks, particularly from the loci, alongside the rows. According to the trend of attacks to traps, 60 complete colonies were estimated. As a result, there was a 583 m2 foraging area for each colony. Investigations also indicated that 3 termite species, Anacanthotermes vagans (Hagen), Microcerotermes ?gabrielis Weidner and Amitermes vilis (Hagen) are distributed in this region. In order to identify the prodominant species, percentages of attacks were compared. Therefore, Microcerotermes ?gabrielis with 66.60 % identified as predominant species.

In order to evaluate the rate of parasitism of alfalfa weevil Hypera postica (Gyllenhal) by its larval parasitoids, investigations were carried out in the experimental field of Agricultural Faculty of Tehran University (Karaj), during 1999-2002. Results showed that Bathyplectes curculionis (Thomson) was the most effective among the larval parasitoids for controlling its host population. The ability of producing two generations per year and such a high rate of activity that it could parasitize more than 36.3 percent of the host population at the time of pest outbreak are special advantages of this species. Although B. anurus (Thomson) parasitize in average 10% of its host population, due to univoltinity and low rate of parasitism, it is placed in the second order of importance. However the coincidence of its activity with the high level of the host population is a great advantage for this parasitoid. Oomyzus (=Tetrastichus) incertus (Ratzeburg) although parasitized up to 30% of pest population in some cases, but its low rate of parasitism at whole (less than 15%) and lack of coincidence with the high population of the pest, put it in the third rank of importance. However the ability of producing more than three generations a year was the advantage of the latter wasp.

Leaf rust is a potentially devastating disease of wheat that is basically controlled by use of resistant varieties. The fungus of wheat leaf rust Puccinia recondita Rob. ex Desm. f. sp. tritici Eriks. contains a variety of virulent races and errode resistant genes. To provide varieties resistant to leaf rust, it is essential to know which resistant genes will be effective against leaf rust pathotypes that occur where their varieties will be grown and then employ them in present wheat varieties. To identify pathotypes present in leaf rust population, twenty wheat leaf rust samples infected with Puccinia recondita f. sp. tritici were collected from different areas of Mazandaran and Golestan provinces and transfered to laboratory in 2003. After purification and spore multiplication, avirulence & virulence of cultures on 12 Thatcher near isogenic lines were determined by low & high infection types, respectively and eight different pathotypes were identified using system of designation of pathotypes of plant pathogens. Pathotype 5.5.0.7 collected from Sari- Mahdasht, carrying virulence on seven different Lr genes were found to be the most virulent pathotypes, while the pathotypes 5.0.0.5 and 4.1.4.4 collected from Ghaemshahr and Sari area with virulence on only four Lr genes were the weakest pathotype. Pathotype 4.1.4.5 carrying virulence on five different Lr genes and moderate virulence, with 40% of frequency were the most prevalent pathotype and was present in different areas of two provinces. In this study no virulence was found on Lr9, 24, 26 and Lr2a resistance genes but all isolates were virulent on Lr30 gene.

The Trichogramma wasps have been successfully applied to control of several pests worldwide. In Iran the dominant Trichogramma species is T. brassicae. Age specific life tables of different ecotypes of the wasps which collected from different areas of Mazandaran province showed some differences among the population parameters in 25±1 ;C, 60±5% R.H. and 16 h light photoperiod condition. The intrinsic rate of increase (rm) was the lowest for Tazeh Abad Chalus (Ta) ecotype with 0.21 and the highest one for Ramsar(Ra) and Semeskandeh-Sari(Sd) ecotypes with 0.294. Doubling time (DT) were 3.3 days for Ta and 2.35 days for Ra and Sd ecotypes. The results showed that Ra and Sd ecotypes had better biological attributes than others and were superior ecotypes.

In 2003, some infected capitula were collected from Kashksara region in Marand (Province of Azarbaijan, Iran) and maintained in rearing boxes. Emerged adult insects were identified as Urophora terebrans (Loew, 1850). All 24 known species of genus Urophora in western Palearetic region live on Compositae weed. But only one species named U. mauritanica Macquart. 1843 collected trom Shirvan Chardavol city (Province of Ham, Iran) also lives on cultivated saffiower. Carthamus tinctorius L. The synonyms of the collected species are as follows: 1- Trypeta eriolepidis Loew, 1856 2- Euribia manni Hendel, 1927 There is a geographical and intraspecific variation among this species. Among their morphological chardcters, only shape of aculus (tip of ovipositor) has taxonomic value tor identification of the species. In this species aculus has two steps. The distance between the first and second steps is about 1.5 times of the distance between 2ndand the tip. This species has also been reported from warmer parts of the Palearctic region such as France, Spain. Hungary, Italy. Austria. Turkey, Azarbaijan and Annenia.

A few Lepidoptera pupae were observed during a survey on the infested boils collected from cotton cultivations in Chabahar-Uraki (Baluchestan) in December 27th 2003. The adult specimens were later identified as Earias insulana (Boisduval, 1833) and E. vittella (Fabricius, 1794). The latter species is one of the pests of cotton and other malvaceous genus such as Hibiscus. So that it's heavy infestations can destroy a whole crop. This species which is newly being recorded from Iran, is a widespread Old World tropical species which is common throughout sub-Saharan Africa, the Middle East and from India to Australia. It has also been reported from Afghanistan. Pakistan and Saudi Arabia (Hacker, 2001. Espcriana. Bd. 8: 18). This species is one of the well known and easily recognizable members of this genus, although some variations can be seen.Diagnosis: Wingspan 17-23 mm., Head, antennae, collar and patagium white, rest of the thorax green with longitudinal white median stripe., Metathorax with a prominent green tuft, Legs white, Forewings long and narrow cream with a green longitudinal median wedge, narrow at base, broader towards termen; Dorsum with a small green elongate blotch near base; Fringes white tinged green. Hindwings white, darker towards termen; Fringes and abdomen white. This species is more or less similar to E. lIuegeliana Gaede, but forewings have variable white and green stripes along their length and satin white hindwings have distinct brown margins.

In the course of bioecological study on spurge defoliator moth Simyra denlinosa Freyer (Lep.: Noctuidae) in the West Azarbaijan Province, Specimens of a Tachinid fly were collected from larvae of mentioned moth. Parasitized larvae of this moth collected in May and June 2002 from Nazlo region at 12 km west of Urmia. Parasitized larvae has been reared in weedy spurge Euphorbia bossieriana (Euphorbiles: Euphorbiaceae) as a host plant. In mid-June 2002, larvae of parasitic fly emerged from the host body and then pupated inside the soil. The adult flies emerged after 6-8 days. Specimens were sent to Dr. H. P. Tshorsnig in Staatliches Museum of Stuttgart (Germany) and were identified as Pales pavida (Meigen, 1824). This species belongs to Exoristinae subfamily and some of its basic characters are as follow: The 5th tergite 0.85-1.00 times the 41 hone length. Face in both sexes 1.08-1.25 times frontal length, 3rdantennal segment in males 3.5-4.6, in female 2.5-3.0 times as long as the 2nd one. Frons in males 0.72-0.84, in females 0.88-1.00 times ocular length. Body more weakly dusted. Body length 5-10 mm (rarely 11 mm). Males: bese of the surstyli (dorsal view) narrow, cerci (lateral view) bent a little upwards at the end. Tibia yellow or brown, this species distributed in Europe and Scandinavia and has 2-3 generations per year. It is a polyphagous parasitoid that has been reported as parasitoid on numerous Macrolepidoptra and some Microlepidoptera. Voucher specimens are maintained in the collection of the Department of Agricultural Entomology, Faculty of Agriculture, Tarbiat Modarres University, Tehran, Iran.

Effect of seven constant temperatures (17, 20, 23, 26, 29, 32, 35 oC) on development of immature stages of the predatory bug Orius niger Wolff, under 16L : 8D photoperiod and 70±5% RH, reared on Ephestia kuehneilla Zeller eggs, water and green bean pods were studied and their development rates modeled as a function of temperature. The mean development time of eggs, nymphs and egg to adult were 13.62, 51.4 and 65 days at 17 degree C and, 3.73, 9.5 and 13.42 days at 32 oC respectively. Egg hatch was fluctuated between 70 and 87 %. The relationship between growth rate of the immature stages of the predatory bug and temperature has been fitted with one linear and 4 non-linear model. If we consider temperature ranging (17 - 29o C), the linear model do accurately predict the developmental rate of O. niger adding more temperature ranging (17 - 32oC), the non-linear model Briere-2 explained best relationship between temperature and developmental rate. The lower, the optimum and the lethal temperatures were 13.99, 31 and 39.86 oC respectively. It was estimated that 238 degree-day, above a developmental zero of 13.82 oC were required to complete development from egg to adult.

Barnyard grass is one of the most important noxious weeds in tomato fields, which makes a huge damage on tomato fruit yield. In order to study the competition effects by using reciprocal yield model between tomato and barnyard grass, an experiment was conducted at the research center of Varamin in the year of 2000. The experimental design was randomized complete block with 15 treatments and 3 replications. The competition design was bivariate factorial. The treatments included the pure stands of tomato at three-plant densities 2, 4 and 6 plant/m2 and barnyard grass at 10, 60 and 110 plant/m2 and mixed stands of two crops at complete factorial densities. Results showed that the tomato plant was a stronger competitor compared to barnyard grass. The biologic and economic yields of tomato were mainly affected by intraspecific competition, while the interspecific competition was mostly responsible for the variation of these characteristics in the barnyard grass. Evaluation of competitive ability by using regression coefficient showed that the effect of each tomato plant on its economic and biologic yields was equivalent to 29 and 31 plant of barnyard grass, respectively. In other words, each 0.034 and 0.032 plants of tomato had an equivalent effect of one barnyard grass on reciprocal biologic and economic yields of the tomato crop.

To identify and determine density of weeds in canola fields, an investigation was carried out in four localities of Tehran province for two years (2001-2002). Weed densities were determined by quadratic method in W form once per month. Weeds were divided into 3 groups of Graminae, Brassicaceae and other dicot weeds (on the basis of different methods of control) and importance of Brassicaceae weeds. Results showed that the relative density of each groups of above-mentioned weeds was 22.61, 46.24, 31.24 % in South of Tehran, 4.12, 37.87, 42.01 % in Nazar-Abad, 15.34, 35.86, 48.96 % in Hashtgerd and 6.22, 20.46, 73.32 % in Varamin, respectively. The mean for the Tehran Province was 12.07, 35.11, 48.88 %. The relative density of Brassicaceae weeds in south of Tehran was higher than other localities. Sinapis arvensis only found in Varamin with 2.4 % relative density. Dicot weeds species were dominant compared to other groups. Dominant weeds included: Descurainia sophia, Cardaria draba, Rapistrum rugosum, Goldbachia laevigata, Erysimum rependum, Capsella bursa-pastories, Lamium amplexicaule, Malva neglecta, Veronica persica, Sonchus spp., Galium tricornutum, Vicia vilosa, Silene conoidea, Fumaria officinalis, Convolvulus aevensis, Avena ludoviciana, Bromus tectorum, Euphorbia helioscopia, Muscari neglectum.

The functional response of the lady beetle, Exochomus nigromaculatus, was examined at different densities of Aphis nerii and Aphis craccivora under laboratory conditions (30 ±1 oC and 65±5 %RH, with a 14:10 L:D photoperiod). For each experiments, a piece of host plant and a given density of prey and one predator were placed in a Petri dish. After 24 hours, the total number of prey attacked was counted and experiments conducted in 5 replicates. The results revealed that, 4th instar larvae and adult of E. nigromaculatus exhibited a type II functional response to density levels of 4, 8, 16, 32, 64, 96, and 128 aphid preys. A non-linear regression analysis (Least squars procedure) was used to estimate searching efficiency and handling time of predator. Searching efficiency and handling time of 4th instar larvae of the predator reared on A. nerii were 1.24 and 0.006, and for those reared on A. craccivora were 1.17 and 0.009, respectively. Searching efficiency and handling time of Adult predators reared on A. nerii were 1.12 and 0.007, and for those reared on A. craccivora were 1.01 and 0.008, respectively. The difference in prey species seems to have a contributing factor in determining the rate of predation, whereas searching efficiency in both stages of predator with prey of A. nerii was higher than A. craccivora.

In order to study the competitiveness of six canola cultivars (three resistant and three susceptible canola cultivars to herbicide) against two wild oat populations (UM5 and Organic), an experiment was conducted under controlled environment conditions at Saskatoon Research Center during 2000. The competition pattern was replacement series at five canola: wild oat ratios (100:0, 75:25, 50:50, 25:75, 0:100) and two total high densities (20 p m-2) and low densities (12 p m-2). Results through analysis of replacement series and derivation of relative crowding coefficient, based on shoot dry weight and leaf area, indicated that both resistant and susceptible canola cultivars to herbicides were stronger competitors compared to wild oat. Results showed that resistant canola cultivars to herbicides at low density in both of wild oat populations had higher competitive ability compared to susceptible canola cultivars. Susceptible canola cultivars showed higher competitive ability compared to resistant canola cultivars at high density in both of wild oat populations. Comparison of resistant and susceptible canola cultivars indicated that the wild oat population of UM5 is strong competitor compared to wild oat population of Organic.

Trichoderma harzianum T39, T. harzianum M, T. virens DAR 74290, T. viride and Trichoderma sp. 96 were evaluated for biological control root of and stem rot of cucurbit caused by Phytophthora drechsleri in vitro and in galsshouse. Dual culture, cellophane overlays technique and volatile metabolites were used in vitro assay. Greenhouse experiments were carried out to test Trichoderma isolates against P. drechsleri by seed and soil treatments. Results of in vitro assay indicated that, all tested isolates of Trichoderma inhibited the growth of P. drechsleri. Mycelial inhibition varied between isolates of Trichoderma and ranged from 17.82 to 82.65 in dual culture and from 15.96 to 100% using the cellophane overlay methods. Cell-free metabolites of T. virens DAR74290 completely inhibited the growth of P. drechsleri in vitro and appeared having fungicidal properties. Mycelial growth of P. drechsleri was reduced 11-50% by volalite metabolite of Trichoderma isolates throughout 120 hours inoculation. Survival of seedling in pots treated with Trichoderma only or Trichoderma + pathogen was significantly (P≤ 0.001) greater than inoculated plant with the pathogen only. Population of antagonists and pathogen were estimated (cfu/g) in potting mix 10 and 40 days after planting. The population (cfu/g) of pathogen and antagonist were fixed during experiments.