Journal of Applied Research in Plant Protection
Year:2014 | Volume:3 | Issue:2|Papers Count:8

Walnut tree is one of the most important orchard and jungle trees in Iran. It's world cultivation is growing up due to its plentiful uses. Meanwhile, some pests and diseases are known as the major reasons of restriction in walnut cultivation. Among walnut diseases, anthracnose is the most destructive in Iran. In this study, the main area of walnut cultivation in Zanjan were surveyed, walnut's infected organs (sprouts, leaves and fruits) were sampled and the disease agent was isolated and identified using ordinary plant pathological methods. The results showed that Ophiognomonia leptostyla (Fr.) Sogonov contribute to the walnut anthracnose disease, and it is permanently scattered in all Zanjan walnut orchards. It's damage varies between15% to 67% in different regions. Our study on Telemorph and Anamorph phases of the fungus showed that there are no significant differences between isolates collected from Zanjan and those from other provinces in vicinity. Meantime, the results showed that the majority of the collected isolates were Heterothal. Study on partial resistance of three Iranian local genotypes (Z53, Z63 and Z60) and six exotic cultivars (Sere, Lara, Franket, Pedro, RDM and B21) showed that local genotypes were more susceptible to walnut anthracnose in comparison to exotic varieties. Although none of the varieties and genotypes was totally resistant, in comparison to introduced interior superior genotypes, exotic varieties of Persian walnut were by far in better condition against anthracnose.

Nevertheless, Septoria leaf blotch disease management relies mainly on successful strategies of breeding for resistance which depends on primary data of pathotype of the pathogen population and their virulence in infected areas. In this research, 23 strains were individually inoculated on 19 differential wheat cultivars in seedling stage under greenhouse condition and pathotype determined. Results showed that differences due to cultivars and isolates were highly significant at 1% levels. The cultivar x isolate interaction component was relatively very small and not significant that showed isolates would thus not vary in aggressiveness and cultivars in race- nonspecific resistance. None of the isolates had virulence on cultivar TE 9111 carrying Stb6, Stb7 and Stb11. Since the virulence was observed on some cultivars carrying Stb6 and/or Stb7 by specific isolates, then the resistance of TE 9111 can be attributed to Stb11. Maximum and minimum frequency of virulence were observed on Boolani (general susceptible control), Taichung 29 (international control, susceptible to the standard isolate IPO323) by 69% and Estanzuela Federal (carrying Stb7) by 66%, and on TE9111 (carrying Stb4 and Stb6) by 4% and Oasis and Sulivan (carrying Stb1) by 9% and 11% respectively. Virulence frequency of isolates on other wheat cultivars carrying different Stb genes was varied between 16 to 59%. Three isolates proved to be one pathotype by showing the same virulence pattern on Stb genes, whereas other isolates showed different virulence patterns on wheat differential cultivars. This study identified 18 M. graminicola pathotypes which shows a high genetic diversity among the Iranian pathogen populations.

In order to optimize the fungicide application in almond orchards, the effects of eight different fungicides on the pollen germination, growth of pollen tubes of almond variety “Ferragness” were studied at in-vitro and in-vivo conditions. In addition, the effects of fungicides on fruit set in orchard condition were investigated. The effects of fungicide application on pollen germination and growth of pollen tubes were studied by using pollen grain culture at in-vitro condition. In order to determine fruit set percentage and treated flowers abortion after spray, two times counting of fruit set was carried out. Experiment was designed in complete randomized plan with 3 replications. Growth of pollen tubes in pistil after pollination was studied by using florescence microscope (UV). For this purpose, to check the status of pollen germination on the stigma and pollen tube penetration levels in different parts of the style, samples of flower were taken and fixed in FAA. Results showed that the fungicides affected pollen germination differently at in-vitro condition. The most pollen germination was observed in control and Sumi-eight (0.001), respectively. The least pollen germination was in Beam (0.002) and Dinocap (0.002). Results of the effects of fungicides on fruit set showed that the highest percentage of fruit set was in Sumi-eight treatment (0.001) with 44.18% and the least percentage of fruit set was in Dinocap treatment (0.002) with 27.97%. While percentage of fruit set in control was 51.72%. Results from pollen growth on the surface of stigma, 1.2 upper part of style and 1.2 lower part of style showed that, the number of germinated pollen grain on the surface of stigma with different fungicides was different, so that, in control, mean number of germinated pollen grain on the surface of stigma was 45%, at the 1.2 upper part of style was 37%, for the lower part of style was 7%, while in Sumi-eight treatment of 1 per thousand, mean number of germinated pollen grains on the surface of stigma was 37% and at the 1.2 upper part of style was 28% and lower part of style was 5%. This means that the fungicide has effect on the pollen germination in different parts of pistil.

In order to provide a phenological forecasting model, estimation of lower temperature threshold and thermal requirements are necessary. Therefore, current study was carried out to estimate lower temperature threshold and thermal requirements of Sesamia cretica Led., using Degree-days and Ikemoto and Takai linear models. Developmental times of the corn stem borer immature stages were determined at five constant temperatures, 18, 20.5, 24, 27, and 30 (±0.5)oC, a photoperiod of 16L: 8D h and 50±10% relative humidity. Cut corn stems were used for feeding of the larvae. Between examined linear models, Ikemoto and Takai model was estimated thermal constant and lower temperature threshold for development of S.cretica more precisely than Degreedays model. Based on the estimations of Ikemoto and Takai linear model, lower temperature threshold of egg, larva, pupa and overall immature stages of S. cretica were 13.97, 13.45, 12.57 and 13.27oC respectively, and thermal requirements were 68.44, 328.73, 140.16 and 537.43 degreedays for above mentioned immature stages, respectively.

In order to evaluate the role of infected host parts, cankers, etc. in dispersion and survival of fire blight of pome fruits, thirteen fruit gardens throughout Semnan province were inspected during 2007-2008. Infected plant parts were collected from different localities and the causal agent was isolated from different samples using SNA (sucrose nutrient agar) medium following standard methods. Results indicated that epiphytic population of bacteria at a range of 3´103-106 cfu/flower in pear and 3´106 - 1.7 ´107 cfu/flower in quince caused blossom blight during rainy days with moderate temperature. It was found that except apple trees of Tash region, pome fruits of remaining regions were infected with the disease. Higher disease incidence occurred in quince (88%), pear (55%) and apple (24%) respectively. It was also found that the role of different plant parts in maintenance of fire blight was directed by weather in such a way that total plant parts of quince and specially their cankers caused highest disease incidence. It was found that the disease can be transmitted to the next year by different infected plant parts of pome fruit trees while one year old cankers of trunks and main branches had the most important role in this connection.

The functional response is an essential factor in selecting natural enemies for biological control programs. Orius albidipennis (Reuter), the abundant anthocorid species is an important predator of immature stages of thrips, aphids, whiteflies and spider mites. In this research, type and parameters of functional response of this predator were assessed against two prey species, Tetranychus urticae Koch and Aphis gossypii Glover. Different prey densities of 5, 10, 20, 30, 40 and 50 two-day old nymphs were presented as prey and the experiments replicated 10 times. After 24 h, the numbers of survived preys were counted. The results of logistic regression indicated that the O. albidipennis exhibited type III functional response to both preys. Values of b constant that relates attack rate to initial prey density (a=bN0) using Rogers' model for T. urticae and A. gossypii nymphs were 0.0065±0.00096 and 0.0046±0.0004 h-1, respectively, which were differed significantly. Additionally, handling time for T. urticae and A. gossypii were estimated to be 0.646±0.029 and 0.625±0.022 h, respectively. Our study, as a part of evaluation of O. albidipennis as a biocontrol agent, suggests that this predator has good potential for using against two spotted spider mite and cotton aphid.

Iran is one of the biggest producer and exporter of pistachio nut around the world as well as the area under cultivation. Aflatoxin contamination is a major issue in food safety affecting the whole chain pistachio production. As pistachio nut infection occurs during the maturation period before harvest, the population density of Aspergillus sections Flavi (aflatoxin producers) and Aspergillus section Nigri (dominant saprophytic) were determined in cracked, fall to the ground, in contact with the ground, located at a height of more than one meter and four cardinal directions pistachios, during the second half of June to early September 2011-2012. To determine the density of fungal species, Blotter test and serial dilution method by AFPA and CZ media were used. Overall, the density of the fungal species in different assessed pistachios decreased in the order of cracked, fall to the ground, in contact with the ground, the four cardinal directions, and more than one meter in height, respectively. The frequency of Nigri section significantly was higher than Flavi ones. There were also significant differences between sampling times, and density of fungal species was at the highest level closer to harvest time. The results could show the critical points to manage aflatoxin contamination in pistachio nuts using different approaches.

Inappropriate application of pesticides and their subsequent residuals in agricultural products have increased concerns about their health hazards. In order to measure the residue of the most common pesticides applied on cucurbit, tomato, cherry, grape and apple, this study was conducted in Khorassan Razavi province. Samples were collected from the major cultivation regions of above mentioned crops. According to the type of the products, extraction was performed by QuEChERS method. The extracted substances were injected to gas chromatography-mass spectrometer (GC-MS) to detect various pesticides. The results were evaluated according to the national standard. Pesticides residue from cucurbit were: malathion, oxydemethon methyl, diazinon, dichlrovos, metalaxyl, fenpropathrin, and propargite with the average rate of 5.09, 3.33, 0.18, 0.43, 2.38, 0.41, and 6.32 mg kg-1; tomato: fanpropatrin, azinphos methyl, diazinon, phosalone, with the average rate of 7.65, 0.16 and 0.235, 0.1 mg kg-1; from cherry: diazinon, malation, fenitrothion, with the average rate of 11.2, 0.79 and 1.57, mg kg-1; from Grape: ethion, malathion, and diazinon, with the average rate of 2.4, 12.46 and 0.48, mg kg-1 ; and apple: ethion and fenitrothion with the average rate of 1.59 and 0.06 mg kg-1, respectively.