Plant Protection
Year:2016 | Volume:39 | Issue:2|Papers Count:7

This study was conducted to evaluate the susceptibility of two stored product pests, Tribolium confusum (Col., Tenebrionidae) and Oryzaephilus surinamensis (Col., Silvanidae) treated with two Iranian fungal isolates of Metarhizium anisopliae Sorokin, Saravan (DMEI001) and Nour (DMEI002), based on two bioassay methods, suspension and dry conidia. After mass production of fungal isolates under laboratory conditions (16:8 photoperiods, 28± 1oC, 65±5% R.H) and preparing main suspension, five different conidial concentrations were prepared separately based on the logarithmic distances and then each insect were treated by immersing them in five milliliter of conidial suspensions for five second. In dry conidia bioassay method, to prepare the appropriate dosages, one gm dry conidia was blended with 10 milliliter Tween 80 and then the number of its conidia was calculated. Finally, five concentrations of each isolates were prepared, separately. All experiments were carried out in four replicates and for each replication 20 adult (7-10 days old) of each species were treated, separately. The results showed that in both bioassay methods, Saw-toothed grain beetle was more susceptible to both fungal isolates and Saravan isolate with LD50, 2.37×105 and 5.35×104 in suspension method and 9.5×109 and 8.2×108 conidia per milliliter in dry spore method on red flour beetle and sow-toothed grain beetle, respectively had higher pathogenicity than Nour isolate. In comparison of two bioassay methods, the suspension method had higher efficacy than dry conidia method for both fungal isolates.

Yellow rust or stripe rust is the most prevalent fungal disease in Iran and also different regions of the world. Therefore, it is necessary to study and identify the properties of different races of this fungal pathogen. For this purpose, 29 Pst isolates collected from different regions of Iran, were tested at the seedling stage using 44 differancial lines and the susceptible cultivar Bolani. The seedlings were inoculated with the pathogenic isolates. After 17 days, notes were taken using Johnson et al method, and the races were determined. According to the results, pathogenicity was detected for the plants carrying the gene YrA all isolates. No pathogenicity was recorded for the plants carrying the genes Yr5, Yr10, Y15, and YrSP in this study. The races 132E156A+,Yr27 of Ahvaz 3 and the race 2E2A+ of Mashhad were identified as the most and least agreesive races, respectively.

In this study, the reaction of 55 bread wheat genotypes to the dominant race of yellow rust was investigated under field condition in Kermanshah province. The genotypes were selected from four different climates including southern hot and dry, moderate, cold and hot and wet. Adult plant reaction of genotypes to yellow rust was evaluated following artificial inoculation by pathogen in booting stage and flowering stages. Disease severity, area under disease progress curve (AUDPC) and relative area under disease progress curve (rAUDPC) were also measured in wheat genotypes. Then, infection coefficients were calculated by combination of disease severity and infection type. Due to high significant correlation among infection coefficients and AUDPC, the cluster analysis of data was performed based on AUDPC. The wheat genotypes were partitioned to different groups according to 6E158A+ resistance. The results showed that 25% genotypes had the lowest AUDPC, 18% average level, 14% the highest level and 43% average or high level of AUDPC.

The leopard moth borer (LM), Zeuzera pyrina L., is a serious pest of walnut trees in semiarid regions of Iran. Chemigation, or irrigation in which an insecticide is incorporated into the irrigation water, is one strategy by which LM might be controlled. The experiment was carried out with five treatments in five replications in a completely randomized design in a 25 year-old walnut (variety Azarshahr at Kamalshahr) orchard in Karaj on 15 May, 2011. The treatments included imidacloprid SC350 at 20, 60, 100, 140 ml/tree and check (without spray). For sampling, 5 treated trees were randomly selected in each treatment. Ten annual branches were sampled in each tree and then the number of insect bore holes was counted in each 60 cm-branches individually. The mean numbers of bores per tree in imidacloprid treatments of 100 and 140 ml/tree were 14.25 and 8.25 bore holes, respectively, which were significantly fewer than the mean number of bores in the check (28). Lower imidacloprid treatments of 20 and 60 ml/tree had 32 and 38 bore holes per tree, respectively. Both of the last treatments could increase severity of LM infestation, whereas imidacloprid treatments of 100 and 140 ml/tree reduced LM infestation (50, 75%). The study showed that insectigation is a specialized method and should be carried out by a specialist knowledgeable about the physiochemical characters of the soil, tree physiology and pest biology; otherwise, this method can increase environmental pollution, LM infestation and the costs of pest control.

Many of biocontrol isolates of Trichoderma by increasing plant tolerance to environmental stress improves plant growth and yields. In order to evaluate salinity stress on 10 isolates from seven strains of Trichoderma, an experiment carried out as randomized design with three replications. The treatments included five levels of salinity (7, 9, 13, 30 and 60 dS/m) from NaCl, CaCl2, MgCl2 sources and 10 isolates of Trichoderma. Salt stress effect on isolates growth was done on PDA medium (1.4-Strenghth PDA) containing different concentration of salts to get desired salinity level. Also, the isolates were screened from temperature tolerance at 30, 35 and 40oC. The results demonstrated inhibitory effect of salinity on growth of isolates and showed significant difference among isolates. More tolerant and the most sensitive isolates against salinity (60dS/m) with respectively 12 and 100 percent growth inhibition were T. virens Ham 65 and T. capillare Isf-7. None of isolates are able to growth at 40oC and at 35oC and just 4 isolates could be grown. Temperature increase from 30 to 35oC causes to decrease growth of 3 isolates and increase growth of T. virens Ham 65. The results of zea mys inoculation with tolerant isolate to salinity and temperature (T. virens Ham 65) indicated significant effect of this fungus to increase wet and dry weight and height of root and shoot of plants grown under both saline and non-saline condition.

The cotton mealybug, Phenacoccus solenopsis Tinsley is one of the important pests of Malvaceae plants that has caused serious damage to China rose Hibiscus rosa-sinensis in Khuzestan province recently. Mean pre-imaginal duration of female P.solenopsis at 20, 25 and 35oC (65±5% R.H. and 14:10 L: D) were 19.02, 16.6 and 13.54 days, respectively. Mean pre-imaginal mortality were 26.94, 32.72 and 39.12% at above mentioned temperatures, respectively. One the same three temperatures, mean female longevities were 41.94, 33.8 and 24.6 days, mean daily nymph production were 13.9, 12.06 and 15.12 nymphs, mean total nymph production were 389.68, 318.23 and 214.45 nymphs, mean sex ratio were 70, 71 and 89% and intrinsic rate of increase were0.157, 0.181 and 0.207 most suitable temperature for developmental reproduction of P. solenopsis. mean total nymph production were 389.68, 318.23 and 214.45 nymphs, mean sex ratio were 70, 71 and 89% and intrinsic rate of increase were 0.157, 0.181 and 0.207 most suitable temperature for developmental reproduction of P. solenopsis.

Melon aphids, Aphis gossypii Glover (Hemiptera: Aphididae) is one of the most important pests causing damages in vegetables fields and greenhouses. In this regard, pesticide application is usually considered as the most common forms of pest control. Excessive use of chemical pesticides, leads to an increase in pesticide residue in vegetables, and affects on consumer health. In this study, the sensitivity of the different nymphal instars and adult melon aphids to field recommended dose and half-dose of the insecticides imidacloprid (35% SC) and primicarb (50% WP) was surveyed by leaf dipping. The bioassay was also carried on the third instar of melon aphid. Moreover, based on LC50, the sensitivity of third instar was compared at intervals of 24, 48 and 72 hours, in both insecticides. The results showed that the toxicity of both pesticides was significantly reduced in later stages. Based on the results obtained, LC50 and LC90 of imidacloprid were 71.648 and 365.548 and for primicarb were 212.62 and 457.49 ppm, respectively. The mortality for imidacloprid was 45, 48.89 and 49.45% and for primicarb 43.89, 47.78 and 50.56%, after 24, 48 and 72 hours, respectively. The results also revealed that in both insecticides, the highest mortality were occurred after 24 hours and the passage of time (48 and 72 hours) did not result in higher mortality. According to results, the pest is well controlled by low doses of both insecticides, the issue that can also reduce harmful side effects on consumer health and the environment.