نشریه مهار زیستی در گیاه پزشکی
سال سوم شماره 1 (بهار و تابستان 1394)

The current project was done to investigate the role of microencapsulation and influence of different polymers on protection of Helicoverpa armigera nuclear polyhedrosis virus (HaNPV) virus against ultraviolet radiation. For this purpose Microencapsulated formulation of HaNPV is produced by emulsion technique using three natural polymers: sodium alginate, gelatin, and starch individually and in combined with each other. After exposed to UVA irradiation for 5 and 24 hours, the stability and viral activity of the obtained formulations were evaluated by bioassay test on H. armigera larvae. However the mortality value for the non-microencapsulated virus suspension, declined from 100% before UV radiation to 46.66% after 24 hours exposed to UVA radiation. Before UV radiation, each of the sodium alginate and starch microencapsulated formulations separately, not only could provide a proper coating for HaNPV virus, but also decreased the viral activity. Whereas the combination of these two polymers together had a synergistic effect and led to increased mortality. After 5 and 24 hours exposure to UVA, their combination was significantly different from the non-microencapsulated formulation (Duncan test, P<0.05, df = 7). After 5 and 24 hours exposure to UVA, the difference of gelatin and its combinations with the non-microencapsulated formulation was significant.

Habrobracon hebetor is one of the most important parasitoid wasps of larvae of many lepidopteran pests, particularly the family Noctuidae. In this study, the lethal and sub-lethal effects of four insecticides including azadirachtin, flonicamid, thiacloprid and thiocylcam were examined on adult parasitoid. Parasitoid larvae were reared on last instar of Mediterranean flour moth in a growth chamber at 27±2°C, relative humidity 70±5 and a photoperiod of 16 h light and 8 h dark. Bioassay tests on adults were conducted based on contact method and sub-lethal effect studies were done based on demographic tests. Estimated LC25 values for azadirachtin, flonicamid, thiacloprid and thiocylcam were 277, 269 and 44.1 mg ai per l, respectively. Estimated LC50 values for azadirachtin, flonicamid, thiacloprid and thiocylcam were 551, 467 and 15.3 mg ai per l, respectively. The LC25 and LC50 values for azadirachtin were not estimated because mortality was 19% at a rate, which was three times the field rate (6000 ppm). Thiocylcam was the most toxic component against females. The intrinsic rate of increase (rm) for control and azadirachtin, flonicamid, thiacloprid and thiocylcam were 0.26±0.005, 0.24±0.004, 0.23±0.005, 0.22±0.04 and 0.21±0.005 (day-1), respectively. Gross reproduction rate (GRR) for control and azadirachtin, flonicamid, thiacloprid and thiocylcam were 93.07±2.37, 82.99±1.77, 78.94±1.17, 69.84±0.85, and 62.01±1.01, (egg), respectively. Based on the results, azadirachtin and flonicamid were the least toxic compounds. If results were confirmed by field tests, the pesticides may be associated with the biological control agents in integrated pest management programs.

Tomato leafminer moth (Tuta absoluta) is a serious pest of tomato crops which could impose upto 100% yield loss. This study was designed to assess the pathogenicity of third stage juveniles (IJs) of Steinernema carpocapsae (Sc) and Heterorhabditis bacteriophora (Hb) on different instars of pest larvae in Petri dish and in a leaf bioassay. The most virulent nematode was selected for the following tests. The ability of different concentrations of the more efficient species in parasitizing the last instar larvae (L4) and pupae in Petri dish (50, 100 and 200 IJs/Petri dish) and pupae in soil (50, 100 and 200 IJs/cm2 soil) was determined. In greenhouse, the efficacy of the selected species against different larval stages of pest was examined and compared with chemical pesticide, indoxacarb. Hb was selected as the better species since its controlling ability was approximately 1.7 times more than Sc. 50 IJs of Hb per Petri dish parasitized 84% of pest’ L4. The highest mortality of pupae in Petri dishes (40%) and soil (28%) was achieved when IJs were respectively applied at a rate of 200 IJs/Petri dish and 200 IJs/cm2 soil. Increase in IJs’ concentrations resulted in higher mortality of pupae. In greenhouse, the most susceptible stage of pest to Hb was L4, while the chemical pesticide had a little effect on pest's larvae. According to the results, it seems that Hb could alleviate the damage and produce acceptable control level of the pest.

Root-knot nematode is one of the most important nematodes world wide, due to its damage on different species of plant. With concern to human health and environmental hazards of chemical nematicides, research to introduce new methods for management of nematode population is important. The objective of this study was to evaluate the effect of different strains of P. fluorescens in control of root-knot nematode. In this study, inhibitory effects of 9 strains of this bacterium was evaluated in In vitro and under greenhouse conditions. Although the strains cause mortality in second stage juveniles in In vitro, the mortality levels were significantly different in treatments. On the other hand, the tested strains had different levels of nematicidal potential. In the greenhouse conditions, more strains reduced knots formation and nematode reproduction. The strains 2 and 16 which were isolated from rhizosphere soils in Boyerahmad region were more effective than P. fluorescens CHA0, which reduced reproduction rate of the nematode significantly. According to the results none of the bacterial strains could increase the plant growth factors of tomato as compared to the control. Root-knot nematode is one of the most important nematodes world wide, due to its damage on different species of plant. With concern to human health and environmental hazards of chemical nematicides, research to introduce new methods for management of nematode population is important. The objective of this study was to evaluate the effect of different strains of P. fluorescens in control of root-knot nematode. In this study, inhibitory effects of 9 strains of this bacterium was evaluated in In vitro and under greenhouse conditions. Although the strains cause mortality in second stage juveniles in In vitro, the mortality levels were significantly different in treatments. On the other hand, the tested strains had different levels of nematicidal potential. In the greenhouse conditions, more strains reduced knots formation and nematode reproduction. The strains 2 and 16 which were isolated from rhizosphere soils in Boyerahmad region were more effective than P. fluorescens CHA0, which reduced reproduction rate of the nematode significantly. According to the results none of the bacterial strains could increase the plant growth factors of tomato as compared to the control.

Phytophthora drechsleri is an important soilborne plant pathogen in Iran that causes root and crown rot disease in cucurbits. Recently, the biological suppression of this disease by the application of Plant Growth Promoting Rhizobacteria (PGPR) such as fluorescent pseudomonads as an alternative method for chemical fungicides has been regarded. In the present study, antagonistic effects of two DAPG-producing isolates of Pseudomonas fluorescens “F117 and F133” against the pathogenic fungal agent (P. drechsleri) in In vitro and greenhouse with different methods were investigated. The results showed that these isolates by employing several biocontrol mechanisms such as antibiosis, production of siderophore and hydrogen cyanide as well as secretion of protease, lipase and phosphates solubilization enzymes showed an effective control against the disease causal agent in the laboratory and the greenhouse conditions.

Sugar beet is one of the most important crops in Iran. Damping-off, root rot and leaf blight diseases caused by Rhizoctonia solani (Kuhn) rank first in sugar beet yield reduction. Since soilborne fungi chemical control have ecological consecutions, therefore in this study, six strains of Pythium oligandrum were isolated from sugar beet fields soil in Khorasan Razavi province to be used as biological control agents. These isolates have already shown 32.09-71.36inhibitory effect on R. solani under laboratory conditions. Selected isolates were evaluated using pasteurized and non-pasteurized soil under greenhouse conditions, by adding antagonistic fungi to the soil and seed coating with oospore (seed treatment) methods. This study was consisted of five separate experiments with five to six treatments each with four replicates.t. All experimrnts were conducted in a randomized complete block desgin. The results showed that among the antagonists Torbat-jam isolate had the most reducing effects on sugar beet damping-off disease. Adding P. oligandrum inoculum to the soil containing R. solani increased sugarbeet seed germination compared to the control and reduced the damping-off disease in both pasteurized and non-pasteurized soil by 66% and 36% respectively. Sugarbeet seed coating by oospores of P. oligandrum increased sugarbeet seed germination while reduced damping-off disease in both pasteurized and non-pasteurized soil by 64 and 43% respectively.

In order to investigate the antagonistic effects of the fungi associated with adult females and egg masses of Meloidogyne javanica in tomato and cucumber grown in greenhouses of Kermanshah province, research experiments were performed in 2009-2010. Among isolated fungi there were 49 isolates of Fusarium spp. from which F. chlamydosporum, F. oxysporum, F. proliferatum, F. solani, F. tricinctum and F. verticillioides were identified. For purification and propagation of the nematode, single egg masses of adult females were inoculated on the roots of cucumber seedlings in the growth chamber. After nematode propagation, pathogenicity experiments were carried out in transparent plastic trays with a completely randomized design. Antagonistic effects of these fungal species were investigated on M. javanica through parameters including parasitized eggs percent, hatching eggs percent and juvenile(J2) mortality. F. chlamydosporum, F. solani and F. oxysporum had the highest ability to parasitizing the eggs. F. solani for its effect on preventing egg hatching and all Fusariums isolates for their effects on juvenile mortality had significant difference. In conclusion, F. solani had the highest antagonistic effects over others and also had the most abundance.

Egg parasitoids are the most important natural enemies of sunn pest, Eurygaster integriceps (Hem.: Scutelleridae). Knowledge on ecological requirements of natural enemies has essential role in success of applied biological control programs. One issue in this context is the effect of host embryogenesis upon performance of those wasps that developed within host eggs. This issue was studied by exposing new laid eggs (control), as well as one, two, three, four and five day old eggs to Trissolcus vassilievi. Two parasitoid populations were used in this study obtained from Tabriz and Varamin. Five day old eggs were rejected by the parasitoid except in six cases, all of which were allocated to male progeny. No significant difference was observed in the number of parasitized eggs between the two populations, but difference among host ages was significant. There was no significant difference in parasitism rate of wasps in ≤ 2 day old eggs, nevertheless significant decrease was observed in three and four day old eggs. Adult emergence rate, sex ratio (female%) and fecundity were influenced by host age. Fecundity significantly decreased by increasing host age over one day and a maximum 50% difference was recorded between control and four day old eggs. Those wasps that were developed in developed stages of host eggs were capable to partially compensate their initial lag in first week of the reproductive life. As a conclusion, host embryogenesis has little impact on the parasitoid fitness before two days, while more effects were observed in older eggs.

Oenopia conglobata contaminata (Menetries) is an insect predator that has been observed and collected from ornamental trees and Spanner and useful trees in most regions of the world and Iran. Both larvae and adults of this ladybird feed on aphids, scales, psylla and eggs of some insect pests and play important role in control of these insect pests. Identification of biological characteristic of O. conglobata is essential for its use in the field aphids, medicinal plants and in city green space. In this research study, Rhopalosiphum padi (L.), Macrosiphum rosae (A)and Chaitophorous populi (Panzer) were reared on Wheat, Rosa sp. and Populus sp. respectively, as hosts in the greenhouse. According to the results, mean of daily and total feeding rate on R. padi were more than other aphids in both larvae and adults. Longevity immature stages of beetles were shorter since they feed on R. padi and was 2.5±0.2, 2, 2.5±0.1 and 2.5±0.1 for the first, second, third and fourth instar, respectively. Voracity rate of different instar larvaewas direct correlated with instar of larvae. Male and female of coccinellid consumed higher number of aphids (3316±43 and 3390±21 respectively) in comparision with the larvae. Fecundity and oviposition rate of female beetles was more by feeding on R. padi (415±11 eggs)in comparison with the other aphids. Fecundity of coccinellid was placed in next order by feeding on M. rosae and C. populi, respectively. Overall result showed that R. padi regarding to high nutritional quality effect on biological characteristic of O. conglobata.

Outbreak of sugarcane whitefly, Neomaskellia andropogonis Corbett has occurred in the fields of sugarcane in Khuzestan province in recent years. The pest activity starts from early August and continues until late November. The aim of this study was to identify natural enemies and parasitism rate of the dominant species on the sugarcane whitefly in the south of Khuzestan. Adult wasps were collected directly by an aspirator from undersides of leaves. Pupae of the pest were also collected from field and then twere reared in the laboratory conditions (27◦C) until emerging of adult wasps. Number of parasitized nymphs were then counted and calculated for parasitism rate. Two collected parasitoid wasps on nymphs were identified as known Encarsia inaron (Walker) and Eretmocerus sp. (Hym., Aphelinidae). A true bug was also observed on the colony of nymphs. It appears that ants feed on eggs of the whitefly. During 2006, Results showed that the parasitism rate of the nymphs was over 30 percent in October and parasitism increased gradually to 85 percent to the late November. The parasitoids wasps have high potential to control nymphs of the sugarcane whitefly in this region.

During the research study on natural enemies of agromyzid leaf miners in Urmia region, infested leaves of Nonea lutea (Desr.) (Boraginaceae) were collected and transferred to the laboratory for rearing of adults. Coincide with adult emergence of Chromatomyia horticola (Goureau, 1985) samples of Eulophid wasp were obtained. The parasitoid species was identified as Diglyphus sensilis (Yefremova, 2011). Based on the present literature, this is the first report of D. sesilis from Iran and its association with C. horticola is new.