نشریه کنترل بیولوژیک آفات و بیماری های گیاهی
سال یکم شماره 2 (پاییز و زمستان 1391)

The functional response is an important characteristic of predator–prey interactions that determinate which predator species or stage classes of predator is the most effective for pest control. Host plant morphological characteristics are the effective factors on predator’s functional response. The objective of this study was to determine whether differences in trichome density of wheat cultivars (Falat, Ghuds and Pishtaz) affect the functional response of Orius albidipennis to sipha maydis.Functional response of third nymphal stage and adult female of predatory bug to different densities (4, 6, 8, 12, 24 and 32) of barley aphid was evaluated under laboratory condition (24 ± 1ºC, 60 ± 10 RH and 16: 8 (L: D) photoperiod). Time of each experiment was 24 hours and all experiments were carried out in 10-14 replications. Based on logistic regression, functional response type II was determined for two life stages of predatory bug on tested wheat cultivars. Searching efficiency (a) and handling time (Th) for third nymphal stage on Falat, Pishtaz and Ghuds cultivars were estimated 0.019, 0.021, 0.036 h-1 and 1.17, 2.5, 5.09 h, respectively. In addition, searching efficiency and handling time for female adult were obtained 0.020, 0.018, 0.022 h-1 and 1.35, 1.41, 2.25 h on Falat, Pishtaz and Ghuds cultivars, respectively. Use of an equation with indicator variable revealed that there are significant differences among handling times of third nymphal stage of O. albidipennis on tested wheat cultivars.

Intraguild predation (IGP) occurs when one predator species consumes another predator species with whom it also competes for shared prey. We studied IGP between different stages of Hippodamia variegata and Aphidoletes aphidimyza in absence and presence of extraguild prey (Aphis gossypii) in Petri dish arena. In the absence of extraguild prey all stages of H. variegata (larva1, 2, 3, 4, female and male) consumed all stages of A. aphidimyza (egg, young larva and old larva). The most consumption of A. aphidimyza was recorded for old larva (48h) which reached to 100%. The minimum IGP recorded in combinations which contained eggs of A.aphidimyza. Interactions between H. variegata and A. aphidimyza in all combinations were asymmetric. In the presence of extraguild prey in density of 30, 60 and 120, There was no difference between observed and expected proportions of aphids eaten by both predators together but when the prey density reached at 240 aphids in each petri, IGP decreased.

The main purpose of this study was to determine factors influencing the adoption of biological control by paddy farmers. The population consisted of paddy farmers in SariCounty. Sampling of 260 farmers was selected by using proportional random sampling method. Data were collected by means of a questionnaire. Validity of questionnaire was confirmed by Agricultural Jihad experts of SariCounty and some faculty members at University of Tehran. Cronbach’s alpha was used to estimate the reliability. The reliability was found to be acceptable. The results revealed that the educational level, farming income, level knowledge of biological control, level of social participation, level influence of opinion Leadership, participation in extension-education courses, number of extension contacts have been positively and significantly correlated with level of adoption of biological control by paddy farmers. Also, the findings of correlation revealed that age, number of family work force, agricultural experience have been negatively and significantly correlated with level adoption of biological control among paddy farmers. Regression analysis indicated that about 44.8% of the variation in the extent of biological control application by paddy farmers, could be explained by variables consisting different levels of knowledge about the biological control and taking time of participation in extension-education courses.

Broomrape (Orobanche spp.) is one of the most serious weed pathogen on many dicotyledonous plants such as tomato, cucumber, melon, tobacco and others. This weed parasite caused serious problem in tomato cultivation fields, especially in North West Iran. Some isolates of Fusarium spp. and Pseudomonas fluorescens are known as effective biological agents in biocontrol of this weed. In order to find the pathogens from broomrape, infected bromrapes were sampled from different tomato cultivation areas of Alborz province including Karaj, Hashtgerd and Nazarabad during 2011. All isolated pathogens were cultured and identified according to key references. The effect of antagonists was evaluated against tomato broomrape in greenhouse condition and the best isolates were selected for subsequent experiments. Finally, 69 isolates of the fungus including 26 isolates of F. oxysporum, 43 isolates of F. solani and then 10 bacteria contain Pseudomonas spp. were isolated. Only five isolates of Fusarium spp. including Fso84, Fso106, Fox116, Fox135, Fso145 and 3 isolates of P. fluorescens including PfN2, PfN4 and PfX8 were experienced on tomato plant in greenhouse condition. Results showed these isolates inhibited the broomrape weed growth about 65 to 73%. The combinations of fungal and bacterial Isolates including Fox104-PfX7 and Fso68-PfX showed also a good percentage of inhibition on broomrape growth.

Greenhouse studies showed in the transplant of tomato that two weeks before infection with nematodes with two species of mycorrhizal G. mosseae and G. intraradices had been inoculated, were significantly offseted the reduction of growth that had been done by nematodes. It should be noted that the percentage of root colonization with two species 66.3% and 62.2% respectively and based on this study were set completely randomized design with five treatments and five replicates. Dry weight of shoots and roots of inoculated transplant with G. mosseae 44% and 45%, respectively, was higher compared with Nematodes alone (P ≤ 0.05). Dry weight of shoots and roots of inoculated transplant with G. intraradices was more than 40% and 37%. Number of nodes, the diameter of the root-knot nematode penetration in inoculated roots with G. mosseae wasdecreased 55%, 47%, and 55%respectively, compared with Nematodes alone (P ≤ 0.05). Number of nodes, the diameter of the root-knot nematode penetration in inoculated roots with G. intraradices was decreased 47%, 41% and 51% respectively. In treated plants with G1M and G2M, gall index was decreased the 1 unit compared with infection control (P ≤ 0.05). Nematode population in treated soil with each two species mycorrhizal fungus was decreased less than half compared with infection control with nematodes only (P ≤ 0.05).

Efficiency of Pleurotus ostreatus and P. sajor-caju as biocontrol agents of the root knot nematode, Meloidogyne javanica, was evaluated in vitro and in greenhouse experiments. Population of the nematode were prepared and nematicidal effects of culture filtrates of the fungal specieson second stage juveniles of M. javanica were tested. Substrates completely colonized by tested fungi as fungal inoculums in three weight levels and two levels of nematode populations were used to evaluate the effect of the fungi on severity of disease caused by the nematode in a greenhouse trial. Culture filtrates of the fungi were toxic to nematodes and filtrates of P. ostreatus showed greater nematicidal activity. Application of 100 and 150 gr. of completely colonized composts of the fungi improved the fresh root weight of the seedlings and reduced the galling index and nematode population as compared to the controls and application of P. ostreatus was more effective than P. sajor-caju

The biocontrol agents Candida membranifuciens (isolates A4 and A5), Pichia guilliermondi (A6) and Bacillus subtilis (B2 and B6) were tested both individually and in combination for biological control of the grey mold in fruit apple caused by Botrytis cinerea Pers.:Fr. Regarding the compatibility of the biocontrol agents, it showed that antagonists were compatible with each other according to in vitro antibiosis and cell-free metabolite by applying cellophane test. The interaction of the antagonists in liquid media showed that the growth of yeast isolates was not affected by the presence of B. subtilis isolates, and then the yeast population increased until the end of the experiment. Results of storage experiments of yeast, bacteria and their mixture indicated that the lesion diameters caused by the biocontrol agents combinations of B2 and B6 treated fruit were 5.23 and7.43mm, respectively, at 20 C° and 3.48 and 3.87 mm for 4 oC respectively, that provided better control than the antagonist alone. The combination of B2 caused an increase in peroxidase activity and phenolic accumulation showing a maximum level 2 day after pathogen inoculation. This combination decreased catalase activities 4 day after pathogen inoculation. These results indicated that by using antagonist mixtures, it is possible to further of induction of resistance in apple fruits and improving biological control.