BIO CONTROL IN PLANT PROTECTION
Year:2018 | Volume:5 | Issue:2 (10) |Papers Count:7

The biological control of Heterodera schachtii, was investigated using Trichoderma harzianum, Talaromyces flauvs, Fusarium solani and Pochonia chlamydosporium antagonistic fungi isolated from sugar beet cyst nematode in Isfahan Province of Iran. Their effects were compared to those of two commercial bioproducts including Marigold (Amit Biotech Pvt. Ltd., India) and TRICHO-MIX H. V. (Fanavaran Hayat-e Sabz Co., Iran) in a completely randomized design greenhouse experiment with five replicates. Fungal isolates grown on sterile wheat seeds were added to the field soil and or pasteurized soil at the rate of 10 grams per pot along with Marigold and TRICHO-MIX H. V. at 0. 2 and 2 grams per pot respectively. Pots were kept in a greenhouse at 25± 2° C, with 70± 10% RH for 90 days. Analysis of the variance of the results was first performed and comparisons of the means were done using Duncan's multiple range test by SAS 9. 1 statistical software. The results showed that there were significant differences in final population density between treatments compared with nematode alone. T. harzianum128, Marigold, T. harzianum 93, TRICHO-MIX H. V., F. solani, T. flavus 94, T. flavus 134 and P. chlamydosporium reduced final population by 65. 08, 60. 72, 53. 08, 47. 99, 45. 81, 42. 17, 41. 45 and 20. 35%, respectively. Fresh and dry weight of the above and below ground and length of the stem and the root of sugar beet plants were significantly different in the pasteurized and field soil. Plants treated with Fusarium and Verticillium showed higher growth compared to the other treatments.

A biocontrol bacterium, Bacillus subtilis is well known for producing wide spectrum of antimicrobial compounds. Among these products, biosurfactant compounds such as surfactin have high importance. Biosurfactants that are produced by the microorganisms are applied in the various aspects of industry, medicine and agriculture because of their low toxicity and individual properties. However, these compounds are not produced in high quantity due to their low production yield and high purification cost. In the current study for investigating the production of surfactin in the isolate (UTB96), recognition of srf gene and determination of the amount of surfactin production, we used Drop collapse, PCR and HPLC methods. Molecular analysis with specific primer indicated that the isolate had srf gene. To optimize the fermentation process, influence of various inducers and physiochemical factors were studied on the biomass and surfactin production. The results indicated that maximum surfactin production occurred after amending the culture medium with glucose (1. 243 g/l) solution. After that influence of the combined inducer elements were studied in increasing the amount of surfactin production. Results revealed that maximum production (5. 055 g/l) was done in the presence of Fe2+, Mn2+ and Mg2+ mixture in the culture medium. The results also showed that the amount and the type of the food sources had remarkable impact on the surfactin production efficiency. The changes in the amount and composition of the food sources therefore, could be economically considered for the commercial production of this compound.

Host selection by parasitoids has vital effects on their fitness. Trissolcus vassilievi (Hym., Platygastridae) is a species with high biological potential in sunn pest control. Those parasitoids that develop in higher quality hosts are more vital and fecund than those develop in lower quality hosts. In this study, host preference and switching behavior of two populations of T. vassilievi (Tabriz and Varamin) was investigated on the same populations of the host at ratios of 5: 1, 4: 2, 3: 3, 2: 4 and 1: 5 clutches. Host measurements revealed that host eggs was significantly heavier in the Varamin bugs than the Tabriz ones. The Varamin wasps were also larger than the Tabriz wasps and the progeny of the crosses was closer to the maternal populations. Data analysis was done by Murdoch (1969) and Cock (1978) methods. Referring to the values of c1 (preference index for Tabriz sunn pest) and c2 (preference index for Varamin sunn pest), Varamin population of T. vassilievi presented negative tendency to Tabriz host and positive tendency although non-significant to Varamin host. Linear regression analysis also showed significant trend of the parameter "c" over the host ratio in both parasitoids which confirms presence of switching behavior. In general, we can say that difference between host populations is less considerable than what can affect host-preference by the wasp.

To evaluate the effects of Pseudomonas fluorescens on potato production in the presence of Rhizoctonia solani, a three replicated greenhouse experiment was conducted in a completely randomized factorial design containing three strains of Pseudomonas fluorescens including UTPF5 (P5), P. fluorescens UTPF68 (P68) and P. fluorescens UTPF74 (P74), Rhizoctonia solani AG3 and Agria and Sante cultivars of potato provided by the seed and plant certification and registration institute. Disease severity, root dry weight, stolon length and dry weight, tubers number, dry weight and fresh weight, Antioxidant activity (GPX,
-1, 3-glucanase), proline content, MDA and soluble sugar content were determined in different treatments. The results showed that Pseudomonas fluorescens treatment had a significant effect on all traits in the presence of fungus (pathogeninfected condition). The fungal virulence was also significantly decreased in this treatment compared to the control. P5 and Sante variety combined treatment showed highly significant effect on the measured traits than the other combined treatments, so that the highest amounts of dry weight of root, stolon length and dry weight, tubers dry and fresh weight and the number of stolon were observed in this treatment with 0. 62, 0. 86, 1. 40, 2. 31, 1. 37 and 0. 63 folds increase respectively compared to the control. Results also indicated that in P5 treatment Antioxidant enzyme activity, (GPX,
-1, 3-glucanase), proline and soluble sugar content were increased by 1. 32, 0. 61, 2 and 2. 6 and folds respectively and lipid peroxidation was decreased by 53% in comparison with the control.

As the mushroom dipterans flies are permanent pests of mushroom farms, the growers frequently use the chemical pesticides. Since the mushroom growers and the consumers are always at the risk of chemical pesticides contamination, introducing non-chemical and biological methods is therefore necessary. This research was conducted with two experiments in the mushroom farm conditions. In the first experiment, a commercial formulation (Bioflash® ) based on Bacillus thuringiensis subsp. israelensis was tested along with a number of common insecticides on composts. First experiment was carried out in a completely randomized design with seven treatments including Dimilin® 0. 75 & 1 g/l, Bioflash® 1 & 2 ml/l, Tracer® 0. 3 & 0. 6 g/l and the control (the usual method of controlling flies with oreganophosphate insecticides) each with 10 replications. Based on the results of the first assay, an experiment was conducted in the mushroom farm conditions in three stages including Bioflash® incorporated into compost simultaneously with spawn inoculation, Bioflash® spray in precasing and Bioflash® drench into casing in comparison with the control. The results of the first experiment showed that all test insecticides were effective in decreasing the pest population, so that the average efficiencies of Dimilin® (1g/l), Tracer® (0. 6 g/l) and Bioflash (2 ml/l) on 15 days after treatment were 67. 9%, 74. 2% and 79. 9%, respectively with no significant difference among them. Farm experiment results showed that the application of Bioflash® drench into casing at six days after casing had the highest efficiency with 79. 3% reduction in the population.

Cryptolaemus montrouzieri (Col.: Coccinellidae) is the most important predator of mealybugs in citrus and tea orchards in north of Iran. Cold storage is necessary in order to have a sufficient numbers of this ladybird and its release at desired times. This study was therefore carried out to assess the possibility of storing adult stage of this ladybird under refrigerator conditions (5± 1˚ C, 60± 10% RH and full darkness). Male and female adult ladybirds were stored at low temperature for different durations of 5, 7, 10, 14 and 30 days. After each storage period, the adults’ mortality was recorded in each treatment and was compared with the control. Survived ladybirds were then paired and transferred to the separate Petri dishes and kept in a growth chamber (26± 2 ° C, 60± 5% RH, and 16: 8 h L: D) and their fecundity data were recorded daily until the death of ladybirds. Results showed that cold storage significantly decreased their survival, longevity and fecundit. Mortality percent of males and females increased with storage duration from 29. 39± 5. 2 and 25. 78± 4. 8 percent in five days treatment to 100 percent in 30 days treatment, respectively. Female longevity ranged from 99. 8± 2. 2 days in control to 51. 5± 2. 3 days in 14-days treatment. Meanwhile, mean of oviposition in female ladybirds decreased from 4. 99± 0. 06 to 4. 51± 0. 07 eggs/day. In conclusion, the adult stage of this ladybird was more susceptible to low temperatures than other stages and their long-term cold storage (longer than seven days) is not recommended.

Two field experiments were conducted and executed during 2015 and 2016 to evaluate the effectiveness of six newly developed fungal bioformulations in controlling garlic white rot disease caused by Sclerotium cepivorum. The bioformulations were developed using three antagonistic fungi including Trichoderma harzianum, T. asperellum and Talaromyces flavus and rice bran as an organic carrier. They were selected based on their performance in the greenhouse conditions in a previous study, where they effectively controlled and reduced the garlic white rot disease. Field trials were conducted in a randomized complete blocks design with eight treatments (six bioformulations, an untreated control and a Carbendazim fungicide) each with four replicates. The garlic seeds (bulbs) were coated with each bioformulation and were sown in the field soil preinoculated with S. cepivorum. The incidence and the index of white rot disease severity were then determined in different treatments 90 days after sowing. Results showed that in the first year field experiment, most bioformulations were effective and reduced both disease factors significantly in comparison with the untreated control. The biofomulations R. B-T. h-1 and R. B-T. h-2, with 9. 11% and 13. 50% disease incidence, respectively, reduced the disease significantly and were as effective as the fungicide. However, in the second year due to the higher soil inoculum density, four out of the six applied bioformulations performed effectively in controlling the disease. The overall results of this study suggest that these newly developed bioformulations could replace harmful chemical fungicides in managing white rot disease in the garlic fields.