نشریه پژوهش های کاربردی در گیاه پزشکی
سال نهم شماره 1 (بهار 1399)

Some species of Phytophthora genuse cause crown and root rot, and damping off of tomato seedlings. Fruits that contact with soil containing pathogen are affected by a type of decay called buckeye rot of tomato. In this research Pathogens were isolated from soil, tomato root and crown in North Khorasan province and identified as Phytophthora capsici and P.nicotianae . Pathogenicity of both species were demonstrated on tomato seedlings.The production Zoospores was investigated under different light and temperature conditions. The results showed that there was a significant differences between species in reaction to temperature condition. Temperature also had significant effect on the release of zoospore in both species. The highest release of zoospores occured in one of the P.capsici isolates at 20°C under dark conditions.In the case of P.nicotianae at 25°C and light conditions the highest zoospore were released. The largest wound length occurred in isolate Pc2 of P.capsici . It reached to 50 mm at 25°C and dark condition after 5 days. In the case of P.nicotianae the highest pathogenicity of zoospores occured at 27°C under light condition.

Codling moth, Cydiapomonella L. is the key pest of apple orchards in Iran. In order to succeed in chemical control of this pest and reduce the number of spraying, application of modern and accurate methods is very important. Nowadays, the total environmental efficient temperature based on Degree-Days is the most accurate forecasting method to forecast the development of different phenological stages of the pests. In this regard, this study was conducted to prepare a predictive model of Codling moth phenology based on the estimation of total efficient environmental temperature in two locations of Kamyaran and Saqez. In order to determine the start of recording environmental temperature and the calculation of efficient temperature, the biofix was determined based on the hunting of pheromone traps. From this date to the harvesting time, fluctuation of environment temperature was recorded in the garden hourly and the efficient temperature from the environment was calculated based on the hourly temperature indices of the growth and development of Codling moth. In the following to the apple harvesting, the population fluctuations of the different biological stages of the Codling moth were recorded in both regions weekly. Based on the results, in both of the studied areas, there were three flying peaks indicating two complete and one partial or incomplete generation of Codling moth in Kurdistan province. Considering that the best time to perform chemical control of Codling moth is at the peak of the larvae population of the first instar and before entering them into fruits, the results of two years of research in both Kamyaran and Saghez showed that the peak population of the first-generation larvae of the winter-generations is 6634±430 GDH, and in the summer generation is 23700± 846 GDH.

One of the applications of nanotechnology is the use of different nanoparticles in the management of plant diseases. Bacterial spot of tomato caused by Xanthomonas perforans is a devastating disease of tomato that can reduce the quality and quantity of crop. This study aimed to evaluate the antibacterial effects of silver nanoparticles (AgNPs) and silver-chitosan nanocomposite against X. perforans. The nanoparticles were synthesized with sumac extract and the antibacterial activity of different concentrations of biosynthesized nanoparticles was evaluated with minimum inhibitory concentration method. The structure and physical properties of nanoparticles were investigated by scanning electron microscope and X-ray diffraction. The results showed that the AgNPs and nanocomposite had quasi-spherical shape in a uniform distribution with the average size about 35 and 50 nm respectively. Minimum inhibitory concentrations of green biosynthesized AgNPs and silver-chitosan nanocomposite were at concentrations of 17 mg/L, and 3 mg/L AgNPs/6.94 mg/L chitosan respectively. Also, in greenhouse experiments, nanoparticles at 10, 50 and 100 mg/L concentrations reduced the disease severity of the bacterial spot on seedlings when compared to the control. The greatest decrease in the disease severity was caused using 100 mg/L concentration of AgNPs (91.11%). The results of this study showed that synthesized nanoparticles had effective antibacterial activity against the causal agent of tomato bacterial spot.

The effects of the recommended dose (RD) and half of recommended dose (HRD) of four insecticides, abamectin, emamectin benzoate, acetamiprid and flubendiamide, were studied on different immature stages of Trichogramma evanescens, egg parasitoids of tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae). Parasitized eggs of the Angoumois grain moth, Sitotroga cereallela (Lepidoptera: Gelechiidae), were treated by the dipping method at the larval, prepupal, or pupal stages of the parasitoid. Cards containing 140 parasitized eggs of Sitotroga cerealella (Lepidoptera: Gelechiidae) were dipped into RD and HRD solutions of the insecticides for 10 seconds at each developmental stage of the parasitoid. Bioassay was performed only for immature stages of F0 generation. Reduction in emergence rate, parasitism rate and longevity of F0 generation as well as reduction in emergence rate and sex ratio of F1 generation were determined. Acetamiprid and flubendiamide were harmless at pupal stage, abamectin, emamectin benzoate and acetamiprid were slightly harmful but flubendiamide was harmless in regards of the emergence rate of the generation F1. Flubendiamide was the only insecticide with no significant difference on sex ratio compared to control. Both concentrations of abamectin and emamectin benzoate were slightly harmful and flubendiamide was harmless in terms of the rate of emergence and parasitism at the generation F0 in all developmental stages. In general, abamactin and flubendiamide in both generations were in slightly harmful and harmless groups, respectively.

 Choosing a suitable sampling method is a crucial step in insect population studies. A good sample must be precise, unbiased and consistent to population parameter and meanwhile shouldn't increase costs. Therefore comparison of different sampling methods in terms of relative net cost, and relative net precision (RNP) is the most important task of a scientific sampling. In this study, efficacy of different sampling methods of Italian locust, Calliptamus italicus L. (Orthoptera, Acrididae) was studied in pastures of Khodafarin region in 2010-2011. Quadrats of three sizes (0.64, 1.44 and 4 m2), a standard sweep net and mark-recapture methods were adopted for sampling. Costs were recorded as time consumed for sampling. Estimates by quadrats of different size were similar, while RNP was higher for 4m2 quadrat. Sweeping for a minute provided a rough insignificant estimate of population size per 2.36 m2. Sweep net was determined as a cost-effective, low precision method, which may be used only as a tool for quick decisions in IPM programs. Mark-recapture method is not consistent for population estimations of the Italian locust.

The cabbage aphid(CA), Brevicoryne brassicae L. (Hem.: Aphididae) is an important pest of brassicaceae family plants. In recent decades, biological control and use of entomopathogenic fungi (EPF) have been developed as an alternative or supplement of chemical pesticides to control aphids. Evaluation of the sublethal effects of pathogenic agents, such as EPF, is as important as mortality itself. Therefore, in this study, sublethal (LC25) effects of EPFs, Acremonium sclerotigenum, Lecanicillium muscarium, Beauveria bassiana, Paecilomyces variotii and Simplicillium sp., were studied on development, reproduction and life table parameters of the cabbage aphid under laboratory conditions. Among the tested isolates, the highest LC50 value was 2.57×103 conidia ml-1 in L. muscarium. The fungal treatment significantly (P<0. 05) reduced developmental rate, life span and fecundity of CA in comparison with control. The rm values in treatments of A. sclerotigenum, L. muscarium, B. bassiana, P. variotii  and Simplicillium sp., were 0.225±0.009, 0.219±0.011, 0.246±0.008, 0.254±0.004 and 0.215±0.008 day-1, respectively, which were significantly reduced in comparison with control (0.332±0.008 day-1). Results of peresent study showed that, A. sclerotigenum, L. muscarium and B. bassiana had greats effect on fertility, longevity, and life table parameters od CA and can be used as an effective microbial agent in integrated pest management of this pest if the results can be repeated in the field condition.

Bacillus thuringiensis generally applies for controlling of Spodoptera exigua larvae. Applying high doses for effective control increases the risk of resistance developing. Integration of different pest controlling tactics is a useful component of pest management by decreasing the applied doses. Here, the lethal and sublethal effects of Bacillus thuringiensis (Bt) in combination with ethanolic extract of Cupressus arizonica (CA) on mortality and some biological parameters of Spodoptera exigua were evaluated. For bioassays, different concentrations of both agents, incorporated into artificial diet of insects. The results revealed that, larval mortality and life spam, pupation and adult emergence were significantly affected. LC50 values of Bt was measured as 4.25 and 0.76 g/l in first and 7th days of experiments respectively. Efficiency of ingested food (ECI) decreased to 16.1 and 17.9% in combination treatments of Bt (2 g/l) with respectively 12.5 and 6.25 g/l of CA extract in comparison with controls as 38.99%. Significantly higher larval mortality and adverse effects on nutritional parameters of the pest in combination treatments confirm the suitability of this combination as a candidate for greenhouse and field studies to aim of reduce the Bt resistance phenomena frequency and sustainable control of pest population.