نشریه کنترل بیولوژیک آفات و بیماری های گیاهی
سال سوم شماره 2 (پاییز و زمستان 1393)

The codling moth, Cydia pomonella, is the most important pest insect in apple orchards. Efficacy of a native strain of the egg parasitoid wasp, Trichogramma embryophagum, was statistically compared with chemical control and check treatments in an apple orchard. The best times for releasing the parasitoid wasps were determined by using a forecasting model based on estimation of Growing Degree Hours (GDH). Codling moth biofix was determined by using pheromone traps, and environmental temperature in the apple orchard was recorded hourly for estimation of GDH. Based on the recorded temperatures and by using phenological forecasting model, the best times for releasing egg parasitoid wasps were determined. The wasps were released five times for two generations of the codling moth. The results of the efficacy test, showed that there was no statistically difference between chemical and biological control treatments using Tukey range test (P

Trichoderma is one of the important biocontrol agents for certain plant disease that control with different mechanisms. This fungus similar to other biocontrol agents is under the influence environmently factors. Medium is one of these factors. This study was investigated effect of the medium (Mol.C.B.M.) containing Sugar beet molasses, Corn steep liquor, Baker’s yeast and Malt extract as the liquid medium and two solid media including: Wheat bran (W.b.) and Wheat seed (W.s.) on sporulation, biocontrol efficacy of Trichoderma harzianum Tr6 against Phytophthora drechsleri and growth promotion of the plant. The media were inoculated with 1ml of suspension containing 108 spores of the antagonist and were maintained in an incubator a light intensity of 206 Lux and at 28°C for 10 days. The medium Mol.C.B.M. of biomass had the most effect on sporulation (1.83×1010 spore/gdw), disease control (62.5%), height, fresh and dry weight of shoots and roots of the plant. But percentage inhibition was lesser than solid media at laboratory surveys.Therefore, the medium Mol.C.B.M. was efficient to encompass the objectives of this study.

Pseudomonas fluorescens UTPF68, well-known biocontrol bacteria was used in this study. The volatile metabolites released from UTPF68 in NA, NAG, PDA media, could inhibit the growth of fungi P.drechsleri at the rate of 84.44, 83.55 and 67.33 percent, respectively. The results showed that antibiotics production in PDA and CMA media prevented the growth of P. drechsleri, 100% and 93%, respectively. The results showed that this strain is able to produce all three antibiotics DAPG, MAPG and the Plt. Also, the extracellular extracts of UTPF68 reduced the vegetative growth of P.drechsleri in extracts concentration. In addition, the bacterium effectiveness against the pathogen in greenhouse cucumber was studied. The bacterium under the in vitro and in vivo conditions was able to control the pathogen; So that, the application of bacterial concentration at 108 CFU/ml in to the soil, reduced the damage resulted from disease up to 60%. Also, the use of this bacterium, in the presence and absence of the pathogen as controls, increased the growth of cucumber. The bacterial colonization experiment showed that the population density of strain UTPF68 was increased on cucumber root system to 2.3×109 CFU.

Root-knot nematodes (Meloidogyne spp.) are among the most important groups of plant-parasitic nematodes, causing damage and yield losses to most cultivated plants. The bacterium Pseudomonas fluorescens CHA0 and the fungus Trichoderma harzianum BI were investigated for biological control capability and systemic induction of resistance against the nematode M. javanica under glasshouse conditions. Furthermore changes of peroxidase (POX) and polyphenol oxidase (PPO) activity in tomato were evaluated. In glasshouse tests, the results showed that tomato plants inoculated with both T. harzianum BI and P. fluorescens CHA0, nematode pathological indexes significantly decreased compared to P. fluorescens CHA0 inoculated as the sole biological agent and control (nematode), but there was no significant difference with T. harzianum BI inoculated plants. Results showed that the POX activity was started at the first day after nematode inoculation and reached to maximum level after the fourth day and then were decreased, There was no significantly different between T. harzianum BI and P. fluorescens CHA0 inoculated plant in comparison to P. fluorescens CHA0 inoculated plant alone. The polyphenol oxidase (PPO) activity reached to maximum level after five day in T. harzianum BI and P. fluorescens CHA0 inoculated plants. There was significant difference between treatments. So the both antagonists can induce plant defense mechanisms such as POX and PPO in tomato plant against nematode infection.

In this study the effect of different concentrations of silicon( 0, 2 , 4 and 6 mM, on expression of some genes involved in resistance and activity of several antioxidan enzymes was investigated: The plants was treated in flowering stage via soil solution. The treated plants were inoculated with 106 spore suspended in 1 mL by injection into the lower part of the spikelets and then were harvested at 0, 24, 72 and 120 h after inoculation for meausering enzymatic activity of gene expression analysis. The results showed that disease severity was reduced in treated plants compared to the control. Biochemical analysis showed that activity of peroxidase and polyphenol oxidase enzymes at all concentrations of silicon was increased significantly copared to the control . Gene expression analysis showed that expression level of beta-1, 3-glucanase and oxalate oxidase genes induced plants with silicon concentration of 6mmol/l were increased at 120h time point after inoculation. Overal, The results of this research indicate that silicon could increase plant resistance against pathogenic fungi by induction of induced systemic resistance.

In this study, the growth of two strains Pseudomonas fluorescens VUPf5 and P. fluorescens VUPf5-1 (mutant bacterium similar to mutants of regulatory GacS/GacA system) were evaluated in the organic media. This spontaneous mutation blocked biosynthesis of the antimicrobial compounds hydrogen cyanide, phenazine and exoprotease by biocontrol strain Pseudomonas fluorescens VUPf5. By using organic media amendments by zinc sulfate or without it considered to reduce the growth of mutants. With the aim of increasing VUPf5 population and decreasing VUPf5-1 population six carbon sources (sugar beet molasses, starch, potato, date, sugar and apple), three nitrogen sources (soybean, urea, ammonium sulfate) and one nitrogen-carbon source (wheat germ) were assessed. Medium 13B (molasses, wheat germ, soybean, sugar, apple, manganese sulfate) was more effective for growth of strain VUPf5 (5.56× 1010 cells per ml) compared other treatments and population difference was significant. Medium 1D (molasses, wheat germ, soybean, sugar, apple, zinc sulfate) greatly caused to reproduction reduction in strain VUPf5-1. The results could provide a reliable basis for optimized mass multiplication of biocontrol agent in fermentation processes.

The green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) is one of the important natural enemies of pest insects. Present study conducted to evaluate the side effects of some plant extracts, Calotropis procera (Willd.) R. Br. (Asclepiadaceae), Fumaria parviflora Lam. (Fumariaceae), Eucalyptus spp. (Myrtaceae) and pesticide amitraz on biological parameters of the second instar larvae of the green lacewingon. Experiments were conducted at controlled conditions (26 ±20 C, 60±5 RH and 16:8 h-L:D)feeding on common pistachio psylla, Agonoscena pistaciae Burckhardt and Lauterer using two methods of exposure, ingestion and topical application. Results showed that total developmental period (second instar larva to adult) when 2nd instar larvae was treated with C. procera extract and amitraz was longer than control (water). Results showed that maximum survival period for adult was observed in Eucalyptus spp. with 127 days and minimum with 110 and 113 days in amitraz, and C. procera treatment. There was no significant difference between, treatments with control. In topical application method, there was no significant difference between treatment effects on developmental period in immature stage. The developmental period for F. parviflora treatment with 22.76 was the highest and for C. procera treatment with 21.96 was the lowest. The results showed that predators feeding on infected Psylhay more local exposure to pesticides. Increase effect of treatments on developmental stages of predator with increase of life, Shows the effects of sub lethal effect of treatments.

Biological control plays a very important role in pest management. Bacillus thuringiensis Ber. has been widely used as a biological control agent in over 60% of microbial-based pesticides and moreover, its gene inducing pest resistance has been used in the production of a large number of transgenic plants (Bt-crops). The successful performance of some of these Bt-based bio-pesticides depends on the concentration of Delta endotoxin and spores in the final product. The medium composition and the conditions under which the bacteria are grown strongly influence these concentrations, Therefore, this study was set to optimize Bt growth conditions, i.e. pH, temperature and aeration rate. To reduce the number of experiments, Taguchi statistical method and Qualitek 4 were used. The results showed that the optimum conditions leading to the highest bacterial spores of 1.50 × 1012 were the temperature of 28 ° C, pH of 5.7, and oxygen saturation of 80%. Based on the results obtained, the highest and the lowest interactions among the process parameters were at 39.92% and 0.25% for temperature/aeration rate and temperature/pH, respectively.