JOURNAL OF CROP PROTECTION
Year:2017 | Volume:6 | Issue:2 |Papers Count:10

Stem rot with the causal agent Sclerotium rolfsii is a major disease of peanut in Guilan province, Iran. The aim of this investigation was to determine the inhibitory effect of native isolates of peanut root nodulating symbiotic bacteria on this fungus based on in vitro and in vivo studies. Several bacterial strains were isolated and purified from peanut roots collected from different fields. Eight of them were detected as the main symbiotic nodulating strains. These eight isolates were identified as Bradyrhizobium based on 16S rDNA gene analysis and different biochemical tests. The inhibitory effect of these strains on the radial growth of S. rolfsii was studied in vitro using sealed plate and dual culture methods. Strains significantly inhibited radial growth of the fungus on the PDA medium. Br9, Br18 and Br16 were recognized as strong inhibitors and Br14 as weak strain in dual culture method and used in greenhouse experiments. Ability of the selected strains in controlling the stem rot disease, reducing the disease parameters and enhancing the peanut growth parameters was investigated in greenhouse conditions. The strains significantly decreased the white rot index and increased peanut dry matter (P ≤ 0. 01) in greenhouse.

The melon aphid, Aphis gossypii (Glover), is one of the major pests of cucurbits and an efficient vector of plant viruses such as Cucumber Mosaic Virus. Host-plant resistance is one of the management strategies that can be used to control this pest. In this study, choice test was conducted to identify antixenotic resistance against melon aphid in eight Cucumis genotypes, namely Hormozgan, Bushehr, Guilan, Girtap, Negeen, Sepehr, Pouya and Armenian cucumber. Choice tests were conducted at 25 ± 1 º C, 60 ± 5% RH and a photoperiod of 16: 8 (L: D) h. After introduction of apterous adult aphids to test arena, the number of aphids on each entry was counted at 2, 4, 6 and 24 hours of release. Total phenolic content, NPK essential elements, leaf thickness and leaf trichome density were also measured to discover any association between these factors and aphid host choice. The most antixenosis effect was observed on 'Bushehr'. Increase in antixenosis correlated with increase in leaf trichomes. Antixenosis can be important mode of resistance by reducing host selection and delaying aphid colonization. The identification of antixenotic resistance in several genotypes provides additional options for management of this pest. Moreover, the factors associated with this mode of resistance can be considered in plant breeding programs.

The functional response of the egg parasitoid, Trissolcus vassilievi (Nees) (Hym., Scelionidae), on eggs of the sunn pest, Eurygaster integriceps Put. (Hem., Scutelleridae) was investigated at six constant temperatures (12, 15, 20, 25, 28 and 32  C) for 8 hours. Using logistic regression, a type III functional response was determined for T. vassilievi at the two temperatures 15 and 32  C. Any functional response was not detected at other temperatures. The Hassells’ type III model was used for estimating searching efficiency (a) and handling time (Th). At 32  C the highest attack rate and the lowest handling time was recorded 0. 2029 per hour and 0. 1856 hour, respectively. Results show that the parasitoid can be used in the pest management programs at low and high temperatures.

A total of 78 rhizobacterial strains were isolated from 48 rhizospheric soil and root samples, collected from safflower Carthamus tinctorius L. fields located in different regions of Iran. The chitinolytic activity was measured in the presence of colloidal chitin as the sole carbon source. Eleven isolates were identified as chitinolytic bacteria, based on the formation of a clearly visible zone on the growth media. Four isolates including EM9, ES41, ES7 and ER13 exhibited the highest chitin degradation activity based on a clear zone diameter of more than 10 mm. According to a ribotyping analysis, EM9, ES41, and ES7 isolates were identified as Bacillus cereus and ER13 was found to be Pantoea agglomerans. In a dual-culture assay, morphogenic changes such as severely collapsed hyphae, decreased hyphal diameter with condensation and granulation of cytoplasm and highly rolled with formation of big clamydoconida in anomalous sporodochia-like structures were also observed using light microscope. Under greenhouse conditions, the application of selected chitinolytic isolates, i. e., EM9, ES41, ES7 and ER13, on safflower seeds significantly reduced seedling damping-off caused by Fusarium solani. In addition, the results revealed that root and shoot dry weight in infected plants that were treated with EM9 isolate suspension, increased by 14 and 22%, respectively.

Endophytic and epiphytic bacteria have been reported as agents of bio-control of diseases and plant growth promotors. Here, in vitro and greenhouse experiments were conducted to evaluate the action of two microbial strains; Aureobasidium pullulans and Pantoea agglomerans, on biocontrol of bacterial canker and growth promotion of tomato (Lycopersicon esculentum cv. Campbell 33). Two frequencies of treatment were used to assess their potential effect (15 and 30 days between two subsequent treatments). The two strains were able to inhibit, in vitro, the growth of Clavibacter michiganensis subsp. michiganensis the causative agent of tomato canker. Also, their antagonistic effects were confirmed in greenhouse conditions. Indeed, bacterial canker incidence in tomato plants treated with A. pullulans and P. agglomerans separately or in mixture was significantly less severe (16%) compared to the positive control (83%). The treatment frequency (intervals of 15 or 30 days) and the choice of strains to inoculate (separated or combined strains) appear to be essential for obtaining significant results. Consequently, both A. pullulans and P. agglomerans strains highly reduced incidence of bacterial canker particularly when tomato plants were treated at a frequency of fifteen days.

Aphidiinae is one of the most important subfamilies of Braconidae, species of which play an important role in biological control of aphids (Hemiptera: Aphidoidea). In this study, the effects of humidity and temperature on the density and dispersal of different species of the subfamily Aphidiinae were investigated in three different ecological areas of Bardsir (Kerman province), located in southeast Iran. Specimens were collected by a hand net on field crops in three stations (Bardsir, Lalehzar and Negar) during March to November 2013. Altogether nine species belonging to five genera (Aphidius, Praon, Diaeretiella, Trioxys and Lysiphlebus) were recorded from these areas. The results revealed that the majority of species were found in the area with temperature between 18 to 20 ° C and/ or with humidity rate of 34 to 39%, 40. 1 and 50. 6 percent of specimens respectively. Most of the collected members of this subfamily were found in the average temperature of 18. 5 ± 1. 13 ° C. Trioxys complanatus Quilis, 1931 was the dominant species. According to biodiversity and ecological indices, species diversity and dispersal were different in the three stations. In conclusion, temperature and humidity have great impact on species diversity and distribution pattern of Aphidiinae.

Eight species of Paratylenchus were collected and identified from vineyards in Kermanshah province, western Iran. Description, measurements, line drawings and microscopic photographs are provided for two new records namely P. humilis and P. prunii. Paratylenchus humilis have a lip region truncate-conoid with distinct small submedian lobes in lateral view of female head, stylet shorter than 40 μ m, three lateral lines and distinct vulval flaps. Paratylenchus prunii have a lip region rounded (slightly truncate in some specimens), without distinct submedian lobes in lateral view of female head, stylet shorter than 40 μ m, four lateral lines and distinct vulval flaps. Male of P. straeleni is reported for the first time.

The Mediterranean flour moth, Ephestia kuehniella Zeller is one of the conventional hosts for rearing of natural enemies to be used in biological control programs. In this study, the effects of three cereal flours (wheat, corn and barley) on some biological parameters, nutritional responses, as well as proteolytic and amylolytic digestive activities of the fifth instar larvae of E. kuehniella were studied to determine suitability of the cereals for optimum growth and reproduction of E. kuehniella. The highest rate of larval survival (0. 88) and larval growth index (9. 77) were obtained in larvae which fed on corn flour. The relative growth rate (9. 17 ± 0. 33 mg/mg/day) and the efficiency of conversion of ingested food (12. 08 ± 1. 11%) were the highest rate for fifth instar larvae which fed on corn flour. The highest protein concentration in midgut of larvae (63. 77 ± 2. 31 mg/ml) and consequentially, proteolytic activity including tryptic (0. 0012 ± 0. 00 Umg-1) and chymotryptic (0. 543 ± 0. 001 Umg-1) were observed in larvae that fed on corn flour. According to the results obtained, corn (Var. 704) was the most suitable cereal for laboratory rearing of E. kuehniella, resulting in the highest rate of biological and physiological parameters.

Pieris brassicae L. is one of the most important pests of Brassicaceae. The insecticidal effect of two entomopathogenic nematodes (EPNs), Heterorhabditis bacteriophora and Steinernema feltiae, was determined through their interaction with Beauveria bassiana and Bacillus thuringiensis subsp. kurstaki (Btk) against P. brassicae. In the interaction tests, the EPNs were applied at LC50 level 0, 12 or 24h after treating the larvae with LC10 or LC25 of the B. bassiana or Btk. The interaction between the EPNs and B. bassiana was entirely different from the interaction of the EPNs and Btk. The interaction with B. bassiana was dependant on time intervals, while the interaction of the EPNs with Btk was almost additive or synergistic. An antagonistic effect was seen when the EPNs were applied immediately after the B. bassiana. However, the application of the EPNs 24h after their treatment with B. bassiana caused additive or synergistic effects. The results also showed the best mortality effect when the EPNs were used with Btk at 12 h and 24 h time intervals. Based on the results, a simultaneous use of the EPNs and B. bassiana is not recommended against P. brassica. However, the EPNs could be used simultaneously after Btk but it is better to allow a time interval to increase mortality.

An examination of the entire Schoenobinae material preserved in the Hayk Mirzayans Insect Museum (HMIM) of the Iranian Research Institute of Plant Protection (IRIPP) revealed the presence of 19 males and 18 females of Scirpophaga tongyaii Lewvanich collected in Kerman Province. This species is newly reported for the fauna of Iran. Brief description of the species as well as the figures of the adults and both male and female genitalia are presented.