نشریه آفات و بیماریهای گیاهی
سال هشتادم شماره 1 (پیاپی 94، شهریور 1391)

An experiment was carried out to evaluate the competitive effects of lambsquarters (Chenopodium album L.) on corn (Zea mays L.) grain yield, in Tabriz in 2008. Factorial experiment was established on randomized complete block design with three replications. Factors were five weed densities (1, 4, 8, 12 and 16 weeds m-1 of row) and four relative times of weed emergence (emerged with corn; 10, 20 and 30 days after corn emergence) including a weed free. Interaction of lambsquarters density and time of emergence on weed leaf area index at 75 days after corn emergence was significant. Leaf area index in weed ranged from in the highest to 0.19 at the lowest competitive condition. With increasing of weed density and delaying in emergence time its biomass reduced. Weed competition was caused a significant loss in grain yield and time of weed emergence is more effective than weed density. Yield loss of corn at different weed emergence times were 64%, 38%, 15%, 8%; and at different weed densities were zero, 23%, 35%, 46%, 53%, respectively, compared with control. Emergence of minimum four lambsquarters plants per meter of corn row before 20 days after crop emergence and competition until late growth season was the economical threshold of this weed.

Root knot nematodes (Meloidogyne spp.) are one of the important parasitic nematodes of tobacco in almost all tobacco-growing areas. Determination of damage of Meloidogyne incognita (Kofoid and White, 1919) Chitwood, 1949(race-2) on some of tobacco commercial cultivars, this study was carried out in factorial with two factors including: six inoculums levels namely, 1, 3, 5, 7, 9 eggs and second stage juveniles(J2) per gram of pot soil under artificial inoculations and some of tobacco commercial cultivars (Coker 347, Burely 21, K326) based on completely randomized design (CRD) with 18 treatments and four replication in Tirtash Research and Education Centre in 2009 year. After 4 times harvesting, nematodes were extracted from soil and root. The number of nematodes were counted in roots and soil. Gall index, reproduction factors (Rf), the growth factors, fresh and dry weight of leaves, height of plant, fresh and dry weight of roots, income and average Price per kilogram were measured. The givendata were analyzed with MSTAT-C program. The results showed that, there was a progressive decrease in plant growth as the inoculums levels of the nematode increased nine nematodes per gram soil, reduction maximum in growth parameters of all tested tobacco cultivars. Damage of root knot nematode (Meloidogyne incognita) on some of tobacco commercial cultivars was Determined 3 eggs and second stage juveniles (J2) per gram of pot soil. The maximum nematode reproduction factors (Rf) was 69/83 at an initial population density of 5 eggs and second stage juveniles (J2) per gram of pot soil. Maximum damage of 84%, 80% and 73% were obtained for Coker 347, Burley 21 and K326, respectively.

Root-knot nematodes (Meloidogyne spp.) cause major economic damage affecting the quantity and quality of the crop production. In recent years, using of medicinal plants has been considered to many scientists as effective methods for pests and diseases control. In this study effect of different products of clove (essential oils, aqueous extract and ethanol extract) were investigated on second stage juveniles(J2) and eggs of root-knot nematode, Meloidogyne javanica, also protective effect of essential oil of clove was evaluated in control of root-knot nematode in pot conditions. Ethanol extracts of clove (LC50=510ppm for egg & LC50=646ppm for second stage of juveniles) had the most toxic effect compared with other products of this plant. In other study, essential oils of clove have negative effect on mobility and movement of J2s and inhibited (37.1%) migration of J2s at 500ppm concentration. Results of pot experiment showed that plant treated with essential oil of clove (200 ppm) had noticeable reduction in infection levels compared with the control. Also, regarding to number of egg mass on root, there was significant difference among treatments (LSD test, P
0.05)

The interaction of the soybean cyst nematode, Heterodera glycines Hg Type 0 and Bradyrhizobium japonicum were studied on two resistant and susceptible soybean cultivars, DPX and JK respectively under sterilized soil and natural infested field soil. Data of plant growth parameters, number and weight of nodules, number of cyst, second stage juveniles and eggs and reproduction factor were recorded. The results showed in both experiments soybean cyst nematode was reproduced well on susceptible cultivar JK. B. japonicum was able to produce nodulation on both cultivars, the inoculated treatments with Rhzobium showed significant difference on growth parameters compared to non-inoculated treatments in both cultivars. H. glycines Hg Type 0 (race 3) caused significant decrease on bacterial growth parameters and plant growth factors, in all combinations of B. japonicum and SCN. In high population densities of soybean cyst nematode soybean plants not only are affected by the nematode but also the bacterial growth parameters are influenced by the nematode that enhances the nematode damage.

The cotton bollworm, Helicoverpa armigera is a serious pest of different agricultural crops in Iran and other parts of the world. The effect of different corn hybrids including SC700, SC704, SC500, DC370 and SC260 which incorporated into artificial diets on population growth parameters of H. armigera was studied at growth chamber conditions (25±1ºC, 65±5% RH and a photoperiod of 16:8 (L:D) hours). The intrinsic rate of increase (rm) on different hybrids varied from 0.1039 to 0.1394 (day -1), which was lowest on SC700 and highest on SC500. The highest net reproductive rate (R0) was on SC500 (203.90 females/female/generation) andthe lowest value of this parameter was on SC700 (68.30). The results showed that longest doubling time (DT) was on SC700 (6.59 days) and shortest one was on SC500 (4.96 days). Because of the higher coefficient of determination (r2) value in Gompertz model, data from different hybrids had a better fit to this model compared to Weibull model. The survival rate (lx) of individuals developed to adults from the initial cohort was 0.36, 0.44, 0.56, 0.46 and 0.48 on DC370, SC704, SC260, SC500 and SC700. The life expectancy (ex) of H. armigera was 13.55, 16.45, 13.53, 13.43 and 13.76 days, respectively at the first day of adult emergence. Our findings indicated that hybrid SC700 was unsuitable host and hybrid SC500 was suitable host for H. armigera.

Wettable powder formulation of L. muscarium blastospore was evaluated on second nymphal instars of A. gossypii (Glover) in six experiments. Treatments consisted of fresh blastospores and fresh formulated blastospores with six concentrations and distilled water as control, arranged in a completely randomized design with three replications. The experiments were separately repeated one and seven months later, with previous formulated blastospore stored in laboratory conditions (22±2ºC temperature) and in refrigerator (4±1ºC temperature) at similar conditions. Variance analysis of experiments demonstrated significant differences among treatments and concentrations (p<0.01). Comparing means showed that 1 month formulated blastospore stored in refrigerator with 56.19±7.28% and 7 months formulated blastospore stored on laboratory shelf with 15.15±1.83 % had the highest and the lowest mortality percent, respectively. Comparison of lower and upper confidence limits of LC50s showed significant differences only between 7 months formulated blastospore stored on laboratory condition and the other treatments. Comparison of lower and upper confidence limits of LT50s showed significant difference only between 108 spore/ml. of 1 month formulated blastospore stored in refrigerator and the others. Result of recent experiments illustrated that produced blastospores on potato extract, and prepared formulation was virulent on A. gossypii.

In order to identify Passalora species, nine samples with leaf spot symptoms from different localities in Ardebil, East Azarbaijan and Northern provinces of Iran were obtained and examined during spring of 2010-11. Furthermore all specimens belonging to the genus deposited in the fungus collection of the Ministry of Jihad-e-Agriculture in Iranian Research Institute of Plant Protection were re-examined and species identification key were provided for 14 species. As the result 8 species of Passalora on 9 host plants were identified including: Passalora chaetomium (from Euphorbia marschalliana), P. circumacissa (from Cerasus vulgaris, Prunus domestica), P. dubia (from Chenopodium album), P. graminis (from Agropyron sp., Poa annua, Stipa sp.), P. rosae (from Rosa persica), P. ziziphi (from Ziziphus spina-christi). Among these P. chaetomium and P. ziziphi are new records for Iran. Furthermore Agropyron sp., Poa annua, Stipa sp., Chenopodium album and Rosa persica are new hosts for Passalora graminis, P. dubia and P. rosae, respectively. Although other species have already been reported from Iran, but there is no enough information regarding their exact identification in Persian literature.

This survey-based research was conducted to assess the challenges and bottlenecks of biological control development against rice striped stem borer, as a key pest of rice, in Mazandaran province during 2006. By using classified random sampling method, 200 rice farmers were asked to fill the questioners. One hundred farmers used biological control method in their pest management program against this key pest, and the other 100 farmers applied insecticides against the stem borer. Data analysis was done based on the questioners filled by the farmers. An economic evaluation model, named ‘logit’, was used to analyze the data. Results showed that the main factors affecting acceptance or rejection of biological control method are as follows: avoidance of risk by farmers, yield value per hectare, number of rice plots, frequency of Trichogramma release, adoption of technology by neighboring farmers, area under cultivation, the experience of applying biological control, farmer age, and participation of farmers in extension training courses. There were positive relations between all factors (except farmer age and number of rice plots) and acceptance of the biological control method. There were negative relations between farmer age and number of rice plots, and acceptance of the biological control method.

Zearalenone is an estrogenic mycotoxin that causes vulvovaginitis and estrogenic responses and cancer which produces by Fusarium species specially Fusarium graminearum Schwabe. The antifungal effects of Thymus vulgaris, Satureja hortensis, Anethum grareolens, Mentha sativa and Capsicum annum essential oils were studied on the growth of Fusarium graminearum and zearalenone production. The essential oils were added to PDA medium at the concentrations of 25 to 250 with interval 25 μl/100 ml and at the concentrations of 10 to 80 with interval 10 and 100 to 200 with interval 25 μl/100 ml to PDB medium and one treatment as the control including Fusarium graminearum isolate without essential oil. The radial growth rate of the Fusarium graminearum isolate of each PDA medium treatment and the dried weight of its mycellial mass in each PDB medium were measured after incubation for seven days at 25°C. Zearalenone production of Fusarium graminearum isolate treated with Thymus vulgaris, Satureja hortensis, Anethum grareolens, Mentha sativa and Capsicum annum essential oils at the concentrations of 80,150,200,200 and 5000μl/100 ml PDB medium including the control treatment growing Fusarium graminearum without any essential oil were evaluated using HPLC. The experiments were done two times in three replicates. The most inhibitory effects of essential oils on the mycellial mass weights in PDB media were obtained at the concentrations 80, 150, 200, 200μl/100 ml of Thymus vulgaris, Satureja hortensis, Anethum grareolens and Mentha sativa treatments respectively which caused absolute mycelial growth inhibition of Fusarium graminearum in compare with the dried weight of mycelia mass of the control treatment (0.4g). Thymus vulgaris, Satureja hortensis, Anethum grareolens, Mentha sativa and Capsicum annum at the concentrations of 80, 150, 200 and 200μl/100 ml reduced zearalenone production 88%,87%,91%,89% and 93% respectively.

The cigarette beetle, Lasioderma serricorne, is a serious infesting pest of warehouses and retail stores thorough the world. Partial biochemical characterization of carbohydrases was performed in the larval digestive system of the pest. Midgut extracts from larvae showed an optimum activity for
-glucosidase, -glucosidase and
-amylase activity against, p-nitrophenyl-
-D glucopyranoside, p-nitrophenyl-- D-glucopyranoside and starch at pH 5, pH 6 and pH 7, respectively. Larval midgut
-glucosidase was more stable in acidic conditions (pH 4 to pH 6.0) than highly acidic and alkaline conditions. However, the enzyme showed to be more stable in slightly acidic condition (pH 5) when incubation time was increased. -Glucosidase was also stable in acidic conditions (pH 5 to pH 7) and its maximum stability occurred at pH 6. The range of stability for
-amylase was determined in slightly acidic to weakly alkaline conditions (pH 6 to pH 8). Maximum activity for
-glucosidase, -glucosidase and
-amylase incubated at different temperatures was observed at 35, 40 and 50°C, respectively. The KM and Vmax values for
-glucosidase and -glucosidase were 2.77 mM and 0.017 mmol min-1 mg-1 protein and 0.6961 mM and 0.0004 mmol min-1 mg-1 proteins, respectively. The KM and Vmax values for
-amylase were 3.2 mg ml-1 and 0.01 mmol min-1 mg-1 protein. Zymogram analysis revealed the presence of one band of
-amylase activity, one band for each
-glucosidase and  glucosidase activity in the larval midgut extract.