BIOLOGICAL CONTROL OF PESTS AND PLANT DISEASES
Year:2020 | Volume:9 | Issue:1|Papers Count:8

Hoverflies can play an important role in aphid biological control. Adults are dependent on flower pollen and nectar to survive. The plants providing these sources for species of Eupoedes corollae, Episyrphus balteatus, Sphaerophoria scripta and Scaeva albomaculata in several agro-ecosystems including wheat, canola, apple and stone fruit trees in Kermanshah province were studied during 2015-16. Their visit numbers on the target plants in each square meter were recorded at each sampling time in 10 replications within 5 minutes. The experiments were carried out in a completely randomized, unbalanced design with respect to the canopy cover percentage of each plant from early spring until the plants were dried completely. The results showed that Geranium tuberosum, Capsella bursa-pastoris, Lamium amplexicaule, Senecio vernalis and Alyssum hirsutum were the most attractive plants for E. corollae respectively. For E. balteatus, the species, C. bursa-pastoris, Sinapis arvensis, Erodium cicutarium, G. tuberosum and Descurainia Sophia, were the best attractive plants respectively. For Sph. Scripta, the plants, C. bursa-pastoris, Brassica napus, S. arvensis, Rapistrum rugosum and G. tuberosum had the highest attraction respectively. Also for S. albomaculata, the species of Cardaria draba, Raphanus raphanistrum, Brassica napus, C. bursa-pastoris and G. tuberosum were the highest attractive respectively. In conclusion, G. tuberosum and C. bursa-pastoris were the most attractive plants for all studied syrphid species in all of the agro-ecosystems.

The western flower thrips, Frankliniella occidentalis is one of the strawberry pest which threats the health of strawberry consumers due to the widespread use of pesticides against it. The aim of this study was to evaluate the suitability of the host plant as a substrate for oviposition and growth of stable population of O. laevigatus and thus control of western flower thrips in strawberry greenhouse. O. laevigatus laid more eggs on marigold than strawberry and green bean in both choice and no-choice experiments. The number of eggs laid on the marigold was 19. 60 ± 1. 16 in choice and 42. 20 ± 2. 92 in no-choice test, respectively. In addition population density of immature stages and adults of both thrips and predator was measured throughout the growing season of green bean, marigold and strawberry. The results showed that the density of the thrips on green bean was significantly decreased whereas the density of the predator was significantly higher on marigold. Green bean showed a higher potential than marigold as a banker plant to support the population of O. laevigatus on strawberry to reduce the western flower thrips population.

The innate immune system of insects comprises both cellular and humoral mechanisms. The phenoloxidase activity and the production of antimicrobial peptides/ proteins (AMPs) are the most important parts of insect immune system. In this study, we investigated the humoral response of flour moth, Ephestia kuehniella challenged with two different entomopathogens, Bacillus thuringiensis (Bt) and Beauveria bassiana. The suspension of Bt and/or B. bassiana was injected to the fifth instar larvae of E. kuehniella. Afterwards, the phenoloxidase activity and the possible induction of AMPs in the haemolymph of treated larvae was assessed. Moreover, the antimicrobial activity of the collected haemolymph was examined against a Bt strain. As a result, the phenoloxidase activity of treated larvae was significantly reduced in comparison to non-treated larvae. Also, no band has been detected corresponding to insect AMPs in the haemolymph of immune-challenged larvae with both bacterial and fungal pathogens. Furthermore, the haemolymph did not show any antimicrobial activity in vitro against the tested Bt strain. Based on our findings, it can be concluded that the non-cellular immune system of flour moth did not respond to the cell walls of applied entomopathogens, thus further investigations are needed to determine the possible application of E. kuehniella as a model in the insect immune system studies against these two entomopathogens.

Storage at low temperature for host availability at different times is a valuable way to increase the mass production of natural enemies for biological control programs. Usually, host cold storage is done at temperatures below the optimum temperature and can affect the adaptations of natural enemies. Egg parasitoids, Trissolcus agriope and Psix saccharicola from Scelionidae family are as biological control agents against important pest of pistachio, greenstink bug, Acrosternum arabicum. In this study, effect of host egg storage at 4 ± 1 ° C on functional response of Trissolcus agriope and Psix saccharicola were evaluated at different densities (5, 10, 15, 20, 25, 30, 35, 50, 65, 80 and 95) under laboratory conditions. Logistic regression analysis revealed a functional response type III for T. agriope on both fresh and cold-stored eggs and type III and II for P. saccharicola on fresh eggs and cold-stored eggs, respectively. Although the type of treatment did not change the type of functional response in T. agriope but were reduced the type of response from III on fresh eggs to type II on cold-stored eggs in P. saccharicola. However handling time in both species were increased in cold-stored eggs treatment compared to fresh eggs treatment. Our results suggest that T. agriope can successfully parasitize cold-stored eggs of A. arabicum without considerable undesirable effects on its parasitism rates. However, this method may have negative effects on the performance of some other parasitoid wasp, including P. saccharicola.

Bean yellow mosaic virus (BYMV) which belongs to Potyvirus genus, is able to infect wide range of plants because of its wide host range. This virus is transmitted by mechanical inoculation and aphid vectors in non-persistent manner. In this research the effects of six treatments including: synthesized silver nano particles of P. fluorescens CHA0, preparations of T. harizianum and P. fluorescens CHA0, olive (Olea europaea) and yarrow (Achillea millefolium) extracts and potassium phosphite on damage reduction in three common bean genotypes against a BYMV isolate was investigated. This experiment was carried out in a completely randomized factorial design. For this purpose, treatments were applied on plants immediately afterward first symptoms in mechanically inoculated plants were appeared. Virus concentration in treated plants was evaluated by DAS-ELISA test using BYMV polycolonal antibody. Evaluation of vegetative and reproductive parameters, measurement of peroxidase and polyphenol oxidase enzymes activity and virus accumulation indicated that potassium phosphite, silver nano particles of P. fluorescens CHA0 and yarrow extracts had highest influence on virus accumulation.

Fusarial yellowing and wilting caused by Fusarium oxysporum f. sp ciceris is one of the most important diseases of chickpea. The effects of separate and combined applications of Trichoderma harzianum T33, Pseudomonas putida RUP1 and Rhizophagus intraradices were evaluated on suppression of this disease and improving growth factors of chickpea in the presence of the pathogen. The experiments were conducted in greenhouse in a completely randomized design with four replications. Except for the triple treatment (consisting of three biocontrol agents), all treatments significantly reduced the yellowing symptoms of foliage and vascular necrosis caused by the pathogen and also increased the roots volume and dry weight and shoot dry weight. Also, in addition to the triple treatment and the combined treatment of R. intraradices and T. harzianum T33, other biocontrol treatments increased the fresh weight of roots and shoots. R. intraradices was able to colonize 60% and 74% of chickpea roots in the presence and absence of the pathogen, respectively. Despite their compatibility, the dual combination of biocontrol strains did not have a synergistic effect in improving biocontrol efficiency and chickpea growth promoting, and the triple combination of these factors did not have biocontrol capability or plant growth promoting. This study showed that the combination of biocontrol agents is not always synergistic or efficient.

Colonization and population of antagonistic bacteria on rhizosphere have a definite role on their antagonistic effect. In this study in order to determine optimal population density of antagonistic bacteria, in a way that they would be able to induce maximal defensive power in plant, and also in order to investigate effect of initial inoculated population and amount of plant defense enzymes, microelements uptake, chlorophyll and carotenoids; level of peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, total phenolic compounds, total protein, Zn, Fe, Mn, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids in population of 104, 106 and 108 of four antagonistic bacteria Pseudomonas fluorescens VUPF5, P. fluorescens T-17, Bacillus subtilis V1 and B. subtilis 96 in Sarakhs cultivar of pistachio was measured. Experiments were done in randomized complete block design with three replications per each treatment. Studies showed in the measured factors despite of diverse results in bacterial populational treatments, all populational treatments follow a constant pattern in a way that along with increasing in bacterial population, amount of measured enzymes, total phenol content, microelements, chlorophyll and carotenoids increases.

In current research Paenibacillus polymyxa strain N179 was selected based on its previous performance in greenhouse and field condition, and cheap by-products of food industry was used to introduce a best medium for its high quality and low-cost cultivation. The growth rate of this bacterium in various media was significantly different as the proliferation of it in medium M1 (with beet molasses and ammonium sulfate) was 17. 3 percent grater than the medium M5. addition, antagonistic activity of cells from various media either in-vitro or in greenhouse condition was significantly different. The cells from M4 (10 g date pomace, 4 g sesame press cake) and M10 (4 g sesame press cake, 5 g starch) have shown highest inhibition against Rhizoctonia solani fungus. The resistance of cells from media against formulation process and viability during preservation period was assessed and it was found that cells from LB, M9, M7, and M2 media were the most resistant ones during preservation period as the difference of population of formulation made from M7 medium was 26 percent greater than the one from medium M1 (worst performance). Moreover, efficacy of prepared formulations was assessed after three months in greenhouse condition and it was found that formulations made from M5 and LB were the most effective ones in controlling the disease and the disease index was 40 and 50 percent, respectively, lower than the infected control. However, considering all of the results from growth rate, shelf life, inhibitory effect, M9 was shown the best performance.