فصلنامه گیاه پزشکی
سال چهل و چهارم شماره 2 (تابستان 1400)

The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is an important pest of tomato in Iran. Therefore, this study was done to investigate fluctuations in adult male population of this pest using sex pheromone traps in Sirvan County (Ilam Province, western Iran) during a growing season, which lasted before transplanting to the end of growing season.

For conducting this research, 4 tomato farms in Sirvan County were selected and the pest populations were sampled using pheromone traps. The Pearson's correlation coefficient was used to assess the relationship between adult moth density and temperature. For determining optimal sample size, the Green's method was used.

According to results of the present study, there were seven population peaks at intervals of approximately one month. Flight peak of this pest occurred on May 10, June 14, July 19, August 23, October 4, November 8 ,and  December 6, respectively. The highest population density was recorded on July 19 (397.75 moths) and population density of this pest was declined since late November. Studying the relationship between average number of male moths of T. absoluta captured by pheromone traps and average monthly temperature in a growing season showed that with the increase in temperature, population density of moths was also increased. Results of regression analysis indicated that peaks about abundance of male moth coincided with the previous monthly mean temperatures. Taylor's regression model showed a significant and high correlation between mean and variance regarding density of pest population. Statistically, the aggregation index of tomato leaf miner was equal to one. In this study, Green's method was used to estimate optimal sample size. The results showed that the required number of sampling units was decreased with the increase in average population density of the pest so that, when average population density of tomato leaf miner moth in each pheromone trap was one per week, the required number of samples with an accuracy level of 25 and 10% was equal to 1.86 and 11.65, respectively, and when average population density of this pest in each pheromone trap was 10 per week, the required number of samples with an accuracy level of 25 and 10% was equal to 0.37 and 2.32, respectively.

Our results demonstrated that pheromone traps can be used as a suitable sampling method for monitoring population of the tomato leaf miner. This study provided the data about sampling, population distribution, fluctuations in population of tomato leaf miner, and the relationship between population density of the pest and temperature. Our findings can greatly contribute to rational management of this pest in the region.

Macrocheles muscaedomesticae (Scopoli) is the most common mite found in cow and poultry manure worldwide. It feeds on manure-dwelling flies and spreads via flies. According to studies conducted in Khuzestan, Iran, and other countries, this is the dominant predator mite of immature the house flies, Musca domestica L. in domestic animal manures.  Control strategies for dipterous pest species continue to rely heavily on insecticides, even though these species have developed resistance to most insecticides currently available due to their widespread use. Increased public and farmer awareness have prompted scientists to investigate alternative methods for managing these filth flies. The purpose of this study was to determine the effect of two temperatures on M. muscaedomesticae'sfunctional response to varying egg densities of M. domestica.

In this study, the functional response of female predator mite M. muscaedomesticae was examined on the house fly eggs in an incubator at two constant temperatures of 27 ± 1°C and 33 ± 1°C, 65 ± 5% RH, 14:10 h (L: D). Densities of 1, 2, 4, 8, 12, 16, 25, 30, 40, and 80 house fly eggs were offered to mated adult female mites. Before the experiments, female predators were fed and mated for 48 hours and then starved for 24 hours. Each treatment was replicated ten times. After 24 hours of exposure, the number of preys killed by each predator was recorded.

By logistic regression, the functional response of M. muscaedomesticae to varying densities of the house fly eggs was classified as type III in 27°C and type II in 33°C. Rogers' equation was used to calculate the functional response parameters. At 27°C, the attack coefficient and handling time were 0.0204 h-1 and 0.6497 h, respectively, and 0.6493 h-1 and 0.4769 h at 33°C. At 33°C, the maximum attack rate (T/Th) was 50.32 eggs/day and 36.94 eggs/day at 27°C. R2 values for M. muscaedomesticae at two constant temperatures were estimated to be 0.935 and 0.996 at 27°C and 33°C, respectively. Only at 40 and 80 prey densities did the analysis of variance reveal a significant difference in adult females' daily prey consumption between two constant temperatures. Additionally, there were significant differences between all densities at 33°C and the majority of densities at 27°C.

The temperature affected the type of functional response, the handling time, and the maximum attack rate. The findings of this study may contribute to a better understanding of the mite M. muscae

Bacterial leaf streak of cereal was first reported from wheat and barley in the early twentieth century. This disease was observed in wheat and barley fields of Kerman province in 1987 and then isolated and identified from infected wheat and barley in different provinces of Iran, as Xanthomonas translucens pv. undulosa and X. t. pv. translucens respectively. In recent years, this disease became epidemic in Iran. For this reason, it was necessary to re-examine once again the different characteristics of the causal agents of this disease in different regions of Iran to determine if there is any possible genetic modification in these bacteria.

The phenotypic and genetic diversity of 12 bacterial strains isolated from wheat and barley (four isolates from wheat, six isolates from barley, one isolate from Phalaris sp. and one isolate from Lolium sp.) originated from Kerman, Kermanshah, and Fars provinces was studied. These isolates (selected from 67 isolates) were compared with three ancient Iranian standard strains (obtained from Unité de Phytopathologie, UCL, Louvain-la-Neuve, Belgium). The strains' pathogenicity test was performed on wheat and barley seedlings by spraying and injection methods. Then, the biochemical and physiological characteristics and SDS-PAGE profiles of the whole cell proteins of isolates were examined. Finally, using rep-PCR by BOX A1R, ERIC 1R, and ERIC 2 primers, the genetic diversity of isolates was performed.

All strains were Gram, oxidase, and urease negative, and catalase positive. All strains produced xanthomonadin pigment. The strains could produce hydrogen sulfide from cystine and peptone. Negative results were obtained for arginine dihydrolase, urease, starch hydrolysis, nitrate reduction, acetoin and indole production, and methyl red reaction. All isolates produced acid from cellobiose, fructose, galactose, di-mannose, arabinose, xylose, trehalose, arabitol, but not from salicin, mannitol, melibiose, rhamnose, dulcitol, sorbitol, and mesoinositol. They utilized acetate, citrate, and lactate but not d-tartrate and inulin. Only barley isolates could utilize lactose and hydrolyze lecithin and starch. There are no discriminating bands among PAGE profiles of wheat, barley, and standard strains. Genomic fingerprinting of isolates was performed, and the data were analyzed using NTSYS V 2.2 software and the UPGMA cluster analysis method. All isolates of wheat, Phalaris sp., Lolium sp. and one isolate from barley along with UPB922 standard strain were formed one group consists of three subgroups. Isolates of this group could infect wheat and barley plants. The rest of barley isolates, which were pathogenic only on barley, separated from the first group at a similarity coefficient of 84% and formed the second group, including the standard strain UPB922. Furthermore, this group had three subgroups. This grouping was completely related to the host range from the isolates. Based on biochemical, physiological, pathogenicity (host range) characteristics of strains and their genetic diversity compared to the standard strains, the first group, and the second group isolates were identified as X. t. pv. undulosa and X. t. pv. translucens, respectively.

It was found that the isolates are divided into two separate groups based on their host range. One group could contaminate wheat and barley plants, and another group infected only barley plants. Biochemical and physiological tests did not show much difference among the strains, but some tests were able to distinguish two pathovars, such as lactose utilization, the activity of lecithinase and lipase enzymes (hydrolysis of Tween 80), the tolerance of NaCl in the culture medium and the amount of slimes, produced on the nutrient agar medium containing glucose or sucrose. Rep-PCR tests could show the differences and variations within each pathovar. The grouping formed based on these tests showed a high correlation with the strain host range of pathovars. Using both BOX and ERIC primers showed that the genetic diversity of isolates was strongly related to the pathovars type and their host range. Since previous studies showed the same diversity in Iranian isolates, so it seems that there has not been a genetic change in the causal agent of this disease in Iran. The disease widespread occurred in recent years could be mainly due to environmental conditions and wheat and barley cultivars response to this disease.

The carob moth, Ectomyelois ceratoniae Zeller (Lep.: Pyralidae), is a polyphagous and destructive pest that causes considerable damage to various crops worldwide both before and after harvest. Host plant resistance is a critical component of integrated pest management and can be beneficial when used in conjunction with biological and chemical pest control approaches. The host type has a substantial effect on the biological characteristics and population growth parameters of E. ceratoniae. The purpose of this contribution is to evaluate the impact of eleven hosts, including peanut, apple, date, fig, olive, orange, pistachio, pomegranate, quince, and walnut, on the life history and nutritional indices of this pest.

The carob moth larvae were reared on each plant host in a growth room set at 30 ± 1 °C, 60 ± 5 % RH, plus a 14:10 (L:D) hour photoperiod. Daily observations and records were made of the duration of each stage, developmental period, and survival rate. TWO SEX-MSChart was used to evaluate the raw data based on the age-stage two-sex life table. Additionally, hosts' phytochemical metabolites were measured using a spectrophotometer. Correlations between demographic factors and nutritional properties with biochemical features of various hosts were then estimated.

The results indicated that various hosts substantially affected E. ceratoniae's demographic characteristics and nutritional indices. On walnut and artificial diets, the immature development period was the longest and shortest, respectively. Additionally, the intrinsic rate of increase (r) of E. ceratoniae was lowest on quince, orange, apple, olive, and highest on an artificial diet. Compared to larvae fed on other hosts, larvae reared on an artificial diet had the highest efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD). Furthermore, larvae-fed pistachio had a greater relative growth rate (RGR) than other tested hosts. The cluster analysis findings revealed that pomegranate and artificial diet treatments were relatively vulnerable hosts, whereas quince, orange, apple, and olive were the least suitable (most resistant) hosts for E. ceratoniae feeding. Significant variations in biochemical metabolites were observed between the various hosts in this study. Moreover, significant positive or negative associations between life history variables and nutritional indices plus biochemical features of various hosts were found. A significant negative correlation was observed between total phenolic content and total anthocyanin content of different hosts and E. ceratoniae fecundity, net reproductive rate (R0), intrinsic rate of increase (r), the efficiency of conversion of ingested food (ECI), and relative growth rate (RGR).

The findings may provide essential information for a better understanding of plant-herbivore interactions, which may aid in the development of effective integrated pest management (IPM) strategies for E. ceratoniae control.

Bacterial leaf streak of wheat caused by Xanthomonas translucens and Asiatic citrus cankercaused by Xanthomonas citri subsp. citri are two important bacterial diseases that cause considerable damage in Iran. Copper compounds are usually applied to control these diseases. However, their phytotoxicity and development of copper-resistant bacterial strains have made to develop new antimicrobial compounds indispensable. On the other hand, because of awareness of the chemical pesticides' threats to the environment and human health, biopesticides were considered. Hence, this study aimed to identify plant extracts that effectively control these two bacteria.

Identifying bacterial isolates was accomplished based on phenotypic, molecular and pathogenicity tests. In the first step, the effect of aqueous extract of five medicinal plants was examined against X. translucens and X. citri subsp < em>. citri in vitro using the agar well diffusion method and minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were determined by serial dilution method. Then, according to the results of laboratory experiments, two extracts were chosen, and their effect was assessed on the control of wheat bacterial leaf streak under greenhouse conditions.

In the laboratory tests, measuring growth inhibitory zone diameter showed that the extracts of gol-e-arvaneh (Hymenocrater longiflorus Benth), yarrow (Achillea millefolium L.), garlic (Allium sativum L.) and Teucrium polium L. have different degrees of significant antibacterial effect on both examined bacteria. The extract of sage (Salvia officinalis L.) had no inhibitory effect on both bacteria. The extracts of gol-e-arvaneh and yarrow had the highest antibacterial activity against X. translucens with the inhibitory zone of 31 and 24 mm, respectively. In the case of X. citri, the extracts of T. polium and gol-e-arvaneh had the highest antibacterial activity with the inhibitory zone of 25 and 22 mm, respectively. In the greenhouse experiments, applying the extracts of yarrow and gol-e-arvaneh to control wheat leaf streak led to remarkable reduction of disease incidence and disease severity percent.

According to the laboratory experiments, the intensity of the inhibitory effect of extracts varied based on the bacterial species. Therefore, to produce a plant extract as an antimicrobial agent against a bacterial pathogen, the performance of screening tests is unavoidable. The affectivity of the extracts of yarrow and gol-e-arvaneh for controlling X. translucens in laboratory and greenhouse conditions showed that these two extracts are suitable candidates for further investigation, to synthesis safe antibacterial compounds for the management of wheat bacterial leaf streak.

A field experiment was conducted during spring 2017 to determine the effect of honeybee(Apis mellifera L.) pollination and four concentrations (0, 1, 1.5, and 2 ml/L) of the protic-carbon nanocomposite on vegetative (plant height and plant leaf area) and reproductive (number of seeds per head) characteristics of 6 cultivars of sunflower (Helianthus annuus L.). For this purpose, a plot of land (420 mm2) was selected and 6 cultivars (French E5g12, Argentine A4g13, American F13g4, Turkish C13s4, Iraqi G14s, and Iraqi Q5g14) were individually planted in 6 replicates. For non-pollination treatment, the plants were covered with muslin cloth (40 Mesh), while in pollination treatment; plants were uncovered so that, honeybees and other pollinators could easily pollinate the sunflowers. Nine honeybee hives were located nearby the field. Data were analyzed using a two-way analysis of variance to investigate the effects of insect pollination and different concentrations of nanocomposite, or the effects of insect pollination and different cultivars of sunflower. The results revealed that occurrence of pollination and increasing concentration of nanocomposite significantly influenced vegetative and reproductive characteristics of all cultivars. Moreover, unlike vegetative characteristics, in which there were no interactions between pollination and cultivar type, reproductive characteristics were influenced by the interaction of these two variables, and in most treatments, vegetative and reproductive characteristics were significantly higher in the plant treated by insect pollination than non-pollinated plants. Our results confirmed the previous findings regarding higher vegetative characteristics and production of seeds in sunflowers as a result of introduction of honeybee colonies in culture.

The sugarcane stem borers, Sesamia cretica Lederer and S. nonagrioides Lefever are the most important pests of sugarcane in Iran causing heavy losses in cane and considerable reduction in sugar yield. The egg parasitoid wasp, Telenomus busseolae Gahan is the most remarkable natural enemy of Sesamia spp. in Khuzestan province, Iran that plays an important role in regulating the populations of sugarcane stem borers. Temperature is an effective abiotic factor that influences the development of natural enemies. The present study aimed to investigate the temperature-dependent development of T. busseolae on S. cretica.

The development rates and thermal constant of the immature stages of T. busseolae on S. cretica eggs were studied at seven constant temperatures (15, 18, 20, 25, 30, 35, and 37ºC), a photoperiod of 16L:8L, and 65%±5% RH. Fresh egg masses of S. cretica were exposed to the newly mated female of T. busseolae for 6 h. Afterwards, the parasitized eggs were kept at different temperatures. The parasitized eggs were checked daily until adult emergence. Development rate was modeled as a function of temperature using two mathematical models, including common and Ikemoto and Takai linear models. The linear models were analyzed using the SAS software.

The results of regression analysis showed that the immature developmental period of T. busseolae decreased with elevating temperature from 18ºC to 35ºC. In 15ºC and 37ºC, no development rate was found for T. busseolae. Immature development time declined from 45 to 11 days and 46 to 12 days in male and female parasitoids, respectively. The percent of adult emergence was not affected by temperature. However, two linear models provided a satisfactory relationship between immature development rate and temperature. Based on statistical criteria, Ikemoto and Takai linear model estimated thermal constant and temperature threshold more precisely. For male and female parasitoids, the thermal constant was 250 and 255 degree-days and the low-temperature threshold was 12.44ºC and 12.5ºC on S. cretica eggs, respectively.

In the current study, the thermal requirement of T. busseolae on S, cretica was estimated for the first one. Information regarding the thermal requirement of T. busseolae can be useful for the rearing and application of this parasitoid in the biological control of sugarcane stem borers. This finding could be used to predict the number of T. busseolae generations and the best time for parasitoid release in sugarcane fields.