Plant Protection
Year:2014 | Volume:37 | Issue:3|Papers Count:15

Endophytic bacteria are one of the most important potential agents for the control of plant pathogens and their destructive impacts. The aim of current study was to evaluate antagonistic activity of some recently isolated endophytic bacteria for control of Sclerotinia sclerotiorum, causing white mold disease in bean. In total, 103 bacterial isolates were collected from root, stem and leaves of healthy Fabaceae plants. The results showed that eight bacterial isolates had significant antagonistic effects on mycelia growth of S. sclerotiorum in dual culture on PDA medium. The eight isolates based on standard biochemical tests and 16S rRNA sequence analysis with 99% similarity were likely related to Streptomyces and Bacillus genus. All selected isolates showed significant inhibition in disease severity in greenhouse experiments. Biological traits, such as length, wet and dry weights of roots and stems in endophytic bacteria treatment showed no differences with healthy control. The results indicating that these endophytic bacteria could be successfully used for biological control of white mold disease of bean.

Environmental problems and threats to human health due to the use of synthetic pesticides have increased the demand for safe biological insecticides. DE is an effective alternative to chemical pesticides to control stored product pests. In this study, the insecticidal effect of Dryacide® (a commercial formulation of diatomaceous earth) was studied on second and third larval instars of the Mediterranean flour moth and Indian meal moth. Experiments were performed at 27±2ºc, 45±5% RH and continual darkness. Second and third larval instars were exposed to 40 g of wheat treated by various concentrations of diatomaceous earth. Larval mortality was assessed 7 and 14 days after exposure. The results indicated that the mortality was increased by increasing the concentration of Dryacide®. The LC50 values for second and third larval instars of the Mediterranean flour moth and Indian meal moth after 7 days were 116.3, 261.03, 43.58, 312.13 ppm and after 14 days were 20.06, 236.55, 13.82, 305.07 ppm, respectively. These results showed a promising potential for Dryacide® to control these stored product pests.

The genus Porphyrophora (Coccoidea: Margarodidae) is soil-inhabiting coccid, with spherical second inster and known as ground peaels. This paper describes morphological characters of Porphyrophora cynodontis (Archangelskaia), which is collected from western part of Iran and studied under both light microscopy (LM) and scanning electron microscopy (SEM) with photo equipment. The SME gives a very detailed description of some morphological characters and LM, based on preparasion slids, gives an overview of the important characters, such as multilocular disc-pores density and long hair-like setae distribution on the body and the number of thoracic spiracular disc pores inside of peritreme (atrium) and dorso-tarsal sensilla (campaniform pores) on prothoracic legs. The exprimental results show that SEM is valuable tool for examination of morphological structures because of great depth of field and identification of scale insects (P. cynodontis(.

According to the adverse effects of pesticides and their residues to the environment, and non-target organisms, it is necessary to utilize safe compounds with specific mode of action. Recently, studies on plant extracts especially phytoecdysteroids have been increased because of their performance in pest control. The purpose of this study was to identify phytoecdysterid compounds in a native plant Silene aucheriana Boiss and to investigate their efficacy on larval and pupal weight of Diamondback Moth, Plutella xylostella (L.). After concentrating of the crude extract, using HPLC-MS, three phytoecdysteroidal compounds, 20-Hydroxyecdysone (20E), Polypoin B (Pol B) and Integristerone A (Int A) were identified. Then leaves were exposed to concentrations of 2, 5, 10, 20, 40%. Third instar larvae were fed with treated leaves. Findings indicated that larval and pupal weight was decreased significantly as concentration increased. Therefore, it is necessary to establish comprehensive studies on phytoecdysteroidal extract of S. aucheriana for practical use in insect pest control of agricultural crops in the integrated pest management (IPM) program.

Causal agent of common scab and root knot nematodes are important pathogens of potato. Each of two pathogens alone are causing considerable damage to product. In order to study interaction of two pathogens, inoculation of potatoes (Agria cv.) by bacteria (S. scabies) and nematode (M. javanica) alone and combination both agents at different time were carried out in greenhouse in a completely randomized design with seven treatments and six replications. Bacterial inoculums were mixed with pot soil (2% w/w) and 10000 nematodes (egg and juvenile) added to each pot. Results of analyze variance and comparison of means were showed significant difference in the most pathogenisity indices and growth parameters between different treatments. Inoculation of plants by bacterium or nematode alone were reduced some of indices growth compare to control. Plants growth inoculated with both pathogens were also decreased than to control and bacteria-infected plants however, did not have significant difference with nematode-infected plants. Nematode population in soil and root of infected plants by both pathogens were low. In other word, the bacterium was caused reduction in pathogenisity of nematode. Wound in inoculated plants by two pathogens were increased than to inoculated plants by bacteria alone.

This research was carried out to investigate lethal and sublethal effects of commercial formulations of indoxacarb and lufenuron on survival, development and parasitism of Trichogramma brassicae Bezdenko under laboratory conditions (25±2oC, 60±5% RH, and 16:8 h L: D). Each insecticide was applied at four concenterations including 1000, 750, 500, and 250 ppm (i.e. at recommended field application rate and three lower concenterations) and their effects were studied through three exposure methods, including contaminating adult’s food (honey solution 10%) with insecticides, residual contact, and dipping parasitized host eggs (in pre-pupa stage of parasitoid) in insecticide solutions. The results showed that both insecticides significantly increased adults’ mortality and decreased their longevity, fecundity, and emergence rate in comparison to control, and these adverse effects, increased with increasing applied concenteration. The highest mortality (52.5±6 percent), shortest longevity (1.72±0.1 days), and lowest parasitism rate (14.7±0.97 percent) were observed in those parasitoids that fed on solution contaminated with indoxacarb 1000 ppm. Dipping parasitized host eggs in recommended field rates of indoxacarb and lufenuron adversely affected prepupa survival, and reduced adult emergence by 19.7 and 19.3%, respectively. According to the IOBC categories of toxicity, both insecticides were found to be "slightly harmful" when they ingested through contaminated honey solution, and "harmless" when adult parasitoids exposed to their residuals and prepupae dipped in their solutions. Therefore, these insecticides are recommended as nearly safe products in biological control programs of lepidopteran pests with T. brassicae.

In this study, the effect of host diet on biological characteristics and life table parameters of Habrobracon hebetor Say (Hymenoptera: Braconidae) against the Mediterranean flour moth, Ephestia kuehniella (Zeller) was studied in the laboratory. The diets used were wheat, barley, rice, soybean+wheat, soybean and corn. The prasitoids were studied for three generations. The developmental periods of the female parasitoid in third generation were 11.24, 12.09, 11.60, 11.62, 11.17 and 12.44 days on above mentioned diets, respectively. Total preadult survivals of parasitoid on aforementioned diets in third generation were 0.71, 0.66, 0.74, 0.87, 0.78 and 0.71%, respectively. Sex ratio (% female) of parasitoid in the third generation on larvae fed by aforementioned diets were 35.86, 48.34, 20.5, 31.31, 36.55 and 35.04%, respectively. On above diets, and in third generation, female parasitoid longevity were 39.60, 34.03, 33.53, 28.96, 33.86 and 38.80 days, mean total eggs were 921.88, 708.68, 702.46, 548.77, 505.96 and 597.76 eggs, and intrinsic rate of increase were 0.267, 0.255, 0.216, 0.248, 0.257 and 0.228, respectively. In total wheat regime is recommended as the best regime of Mediterranean flour moth for development and reproduction of H. hebetor.

The sugar beet weevil, Lixus incanescens Boh., is an important pest of sugar beet in Razavi Khorasan province. In this research, population density of sugar beet weevil, diversity of its natural enemies, and percentage of larval parasitism were studied on six sugar beet cultivars including Ardabili, Aras, Persia, Flores, Laetitia and Rosirewere studied in an experimental field during 2012 and 2013. In two years, the lowest densities of sugar beet weevil eggs and larvae were observed on Persia. In this study, one larval parasitoid species Bracon intercessor Nees, and three egg predator species: Nabis punctatus A. Costa, Orius niger Wolf. and Chrysoperla carnea Steph. were collected and identified. Amongst the natural enemies of this weevil, B. intercessor had the highest relative abundance. The Shannon diversity index for the complex of natural enemies was greatest on Persia. The value of Morisita-Horn index for the complex of natural enemies between the six sugar beet cultivars were calculated 0.973 to 1. In two years, the highest percentage of larval parasitism was observed on Persia (62.2 and 73.5%, respectively). Furthermore, the percentage of parasitoid females emerged on the weevil-infested plants in Persia and Laetitia was significantly higher than on Ardabili, Aras and Flores. Therefore, it can be concluded that the cultivation of Persia cultivar integrated with using of larval parasitoid B. intercessorcould be useful in the integrated management programs of L. incanescens in sugar beet fields.

One of the most important problems of the hopbush plant is root and crown rot disease in Khuzestan province. The major important pathogen of this disease is Fusarium solani in this province. In greenhouse, the effects of various levels of soil pH ( 6 and 8 ), chelating agent EDDHA (0, 10 and 20 mmol/L) and calcium (0 and 12 meq/L) on disease severity caused by F.solani were determined through measurement of fresh and dry weight of aerial and underground parts of plants. Results indicated that there was a statistical significant difference in the effects of different levels of EDDHA in 2 used pH, but there was not any significant difference in characters which evaluated between 10 mmol/L and 20 mmol/L of chelating agent at both pH. Addition of EDDHA at 10 and 20 mmol/L concentrations reduced the disease severity 40% and 33.3% respectively at pH=6; and 13.3% and 6.7% at pH=8. On the other hand, there were significant differences in the effects of different levels (10 and 20 mmol/L) of EDDHA when compared with no using EDDHA. In other experiments the effects of calcium and EDDHA (10 and 20 mmol/L) on the same characters were studied. Results revealed that there were significant differences between the effect of Ca and EDDHA levels (10 and 20 mmol/L) and other treatments. Applied of Ca+EDDHA levels (10 and 20 mmol/L) led to disease severity reduced to 6.6%. Also results revealed no significant differences between the effects of applied levels of EDDHA and Ca (12 meq/L) in pH=6. Moreover, results indicated that there was significant differences between the effects of different levels of EDDHA (10 and 20 mmol/L) and Ca (12 meq/L) when compared with the results of applying no chelating agent and calcium.

In this research, the insecticidal efficacy of three commercial formulations of diatomaceous earth (DE), Insecto®, SilicoSec® and PyriSec® were investigated against Tribolium confusum Jacquelin du Val.adults on Behrang, Verinak and Chamran varieties of wheat. Experiments were carried out at 27±1oC and 55±5% R.H. in continuous darkness. Adult’s mortality was counted after 2, 5, 8, 11 and 15 days of exposure. The most effectiveness was observed in Behrang after 7 days of exposure to PyriSec®, Behrang to SilicoSec® and Verinak and Chamran exposed to PyriSec® with LD50 values of 231, 268, 280 and 330 mg/kg, respectively. Results indicated that PyriSec® followed by SilicoSec® have the most insecticidal effect against tested adults. However, Insecto® has less effect than the other two formulations to control T. confusum. In addition, the effects of DEs on Behrang were higher than two other varieties. The findings indicated good potential of DEs for the control of T. confusum, the red flour beetle.