THE EFFICIENCY OF MODERN FUNGICIDES AGAINST YELLOW RUST (Puccinia striiformis West. f. sp. tritici Erikss. et Henn) ON WINTER WHEAT IN THE SOUTH OF STEPPE OF UKRAINE

Abstract

Relevance of the research. Grain production is an important branch of crop production In Ukraine. The first place covers winter wheat as the most valuable and high-yielding food crop.

One of the most harmful diseases of this crop is yellow rust Puccinia striiformis West. f. sp. tritici Erikss. et Henn. Rust fungi reduce photosynthesis, accelerate respiration and evaporation, what significantly affects the yield and grain quality. Even at the average degree of disease affection, crop losses are of 20 -50% [1]. With the emergence of the pathogen in the autumn, successful wintering and development in the growing season, 100% crop loss can be expected [3]. In recent years, outbreaks of yellow rust are increasingly observed in the South of Ukraine. The main factors contributing to the development of the disease are a mild winter, wet cool spring, development of the disease in the previous year, the availability of windfall, infestation of crops by grass weeds, and more importantly, growing varieties susceptible to yellow rust [2].

The most important element of the integrated protection of wheat from rust diseases is growing varieties resistant to these agents. To successfully manage patosystem "host-pathogen", one should support in agricultural ecosystems diversity for the resistance both in time and in space, taking into account the structure of the pathogen within a population [6] However, the most effective complex measure to prevent epiphytoties yellow rust is search and use of a highly efficient fungicides. At the first appearance of the disease, they must be applied to prevent mass distribution of the pathogen. Highly effective fungicides, increasing the gross grain yield, also improve its quality [6].

Development of yellow rust was observed on the crops of wheat in theOdessaregion in 2015. Epiphytoties of the disease (intensity of the lesion of 40-100%) were observed in susceptible varieties and lines Luzanovka, Zastava, Znakhidka Odeska, Selanka, Lytanivka, Hosponynya Odeska, Hoduvalnytsya Odeska, Sluzhnytsya Odeska, Epokha Odeska, Vatazhok, Zhuravka Odeska, Heine VII, Scarlett, Avocet.

Given all the foregoing, it is clear that a comprehensive study of yellow rust harmfulness and ways to it overcome it is very important. Therefore, the purpose of this research was to determine the effectiveness of modern fungicides against yellow rust in epiphytotic and non epiphytotic years.

Materials and methods. The effect of modern fungicides against yellow rust in Southern Steppes of Ukraine was studied during 2013-2015 in the field infectious nursery on a background of natural and artificial yellow rust infection in the rotation fallow- winter wheat. The experiment was carried out on a winter wheat variety Luzanivka (indicator of susceptibility to yellow rust pathogen). All the studied fungicides are included to the "List of drugs that are approved for use on the territory of Ukraine”. Seeding rate of seeds was 4.5 million pcs./ha. Experiment laid in triple repetition, on the plots of 10 m², in two options of treatment. The first : the studied fungicides were applied on the background of natural epiphytotic of yellow rust infection in the spring of 2013 - 2015, and after 4 days; after two days artificially inoculated plants by concentration of uredyniospores with talc (1: 100) [3]. Infection burden on 1m² of a crop totaled 30 mg of germinating spores. The second: the plants were artificially infected by concentration of yellow rust uredospores, after 4 days were of used different fungicides. The option without use of fungicides served as a control. The options for applying fungicides against yellow rust on winter wheat are shown in Table 1. In May 2013-2015, were performed assessments of efficient of studied drugs against yellow rust. The intensity of the lesion by winter wheat yellow rust of flag and under–flag leaves was evaluated according to a scale of Peterson [3]. In spring, to protect crops from weeds in a tillering phase, the herbicide Grodil Maxi (0.09 l / ha) was applied. In the phase of milky ripeness (phase BBCH83 (J. Zadoks), the plots were treated by the drug Connect ear (0.5 l / ha) against wheat bug and other pests. Artificial inoculation of winter wheat plants by yellow rust uredyniospores was conducted in the early phase of spire shooting, early morning by dusting the plants with a mixture of uredyniospores of the fungus P. striiformis with talc (1: 100). Uredyniospore material collected in the field infectious nursery last year was used for inoculation. Infection burden on 1m² of the crop was 30 mg of germinating spores. Inoculated plants were isolated by bags which were removed in the next morning. The second inoculation carried out in the shooting phase by aqueous suspension of uredyniospores (100 mg of spores per 100 mg of water) using a syringe with continuous working "Record SCH-19". After appearing uredyniospores, visual counts (three to five) of lesions plant intensity according to Cobb scale [4],  types of reaction to pathogens infection – according to a scale of Gassner and Straib [4], the degree of resistance and susceptibility - a scale developed by plant pathologists of  CMEA [4]. Mathematical processing of results was carried out by conventional methods of variation statistics according to P.F. Rokytsky [5]. The biological effectiveness was calculated by the formula Bef = ((Pk–Po) / Pk) x100% where Pc - the number of plants in the control option,Po - the number of plants in the experimental option.

Results of research. During the research, mass epiphytotic yellow rust was observed inUkraine on wheat crops. Especially this epiphytotic manifested in southernUkraine on winter wheat. The lesions intensity of varieties ofOdessa breeding ranged from 2 to 45%. In this regard, study of the effectiveness of modern fungicides in epiphytotic year was identified as the purpose of the study. Considering the intensity of yellow rust lesion in the first option on flag leaf for 2013 - 2014 we have noticed that the minimum intensity of lesion was observed in the options of Acanto Plus1.5 l / ha, Abakus0.3 l / ha, Rakurs0.7 l / ha and Spirit0.7 l / ha and was 0.5 - 0.7%. The highest lesion intensity was observed in the option cof Titul Duo1.0 l / ha (16.8%), optionMadison1.0 l / ha (11.5%) slightly inferior to him. The last options took an intermediate position on this indicator. In the control option, level of of yellow rust development was 38.0%. In the second option,  analyzing the intensity of yellow rust lesions of flag leafs of plants during 2014 - 2015, we have seen that the lack of yellow rust was observed in the option Acantho Plus1,5 l / ha (0%). The maximum value observed in the option with Titul Duo1.0 l / ha and made 16.3%. The last options took an intermediate position on this indicator. In the control option, development of yellow rust was 20%. Analyzing the intensity of winter wheat lesions by yellow rust in the first option on under–flag leaf during 2013 - 2014, we have noticed that the lack of yellow rust was observed in the options  Suprim 4001,125 l / ha and Vareon0.8 l / ha (0%), gave them something the option Acanto Plus1.5 l / ha (1%). The most lesions by yellow rust was observed in the options Evito0.7 l / ha andMadison1.0 l / ha (40.5%), they gave little option Abakus0.3 l / ha (35.0%). In the control,  yellow rust development was of 52%. Almost a similar situation was observed in the first option on under-flag leaf during 2014 - 2015. But in control option, the development of yellow rust was 60%.

Considering the intensity of the lesion by yellow rust in the second option on flag leaf during 2013 – 2014, we observed lack of yellow rust in the options Rakurs0.7 l/ ha and Spirit0,7 l/ ha (0%), the options  Aviator Chro0.9 l/ ha, Impact T0.8 l/ ha and Acanto Plus1.5 l/ ha (0.5%) were slightly inferior to them. The highest intensity of lesion observed in the options of Bumper Super1.0 l/ ha and Titul Duo1.0 l/ ha and constituted 16.5 and 12% respectively. In the control option, development of yellow rust was 40%. Almost a similar situation was observed in the second option on flag leaf for 2014 - 2015. In control herewith the development of infection was 30%. An analysis of yellow rust in the second option on under-flag leaf showed no infection in the options Rakurs 0.7 l / ha and Spirit 0,7 l / ha (0%), gave them something the option Aviator Chro 0.9 l / ha (0.5% ). Highest yellow rust was observed in the variant Bumper Super 1.0 l / ha (49%). The last options took an intermediate position on this indicator. In the control, yellow rust development was 55%. A close situation observed in the second option on under-flag leaf for 2014 - 2015. In the control development of infection was 60%.

Thus, analyzing the effectiveness of the drugs in the first and second options of treatment on flag and under-flsg leaves, we have found: the first and second options of the drug Acanto Plus 1.5 l / ha was highly efficient since lesion intensity appeared the least; in the second option, a similar effect showed the drug Rakurs 0.7 l / ha, as the yellow rust pustules were not observed at all. The drugs Aviator Chro 0.9 l / ha and T Impact 0.8 l / ha were some inferior to them. This is evidenced also the values of biological efficiency of the drugs.

Analyzing yield of winter wheat in the first option as average for two years, we have observed that the yield was the highest in the options Aviator Chro 0.9 l / ha and Impact 0.8 l / ha, it was 6.6 - 6.4 t / ha. The options Acanto Plus 1.5 l / ha and Starpro 0.6 l / ha were some inferior to them showing the yield of 6.3 / ha. In the control,  the yield was 5.2 t / ha. Analyzing yield of winter wheat in the second option, we have observed that the highest yield value was in a option Spirit 0.7 l / ha and made  6.7 t / ha, it some conceded the option Solihor 0.8 l / ha (6.29 t / ha). In the control yield was 5.23 t / ha.

Conclusion. analyzing the effectiveness of the studied drugs against yellow rust on winter wheat in two options of treatment, we have identified the following:

in non epiphytotic years for yellow rust, there should be used Acanto Plus 1.5 l / ha, Rakurs 0.7 l / ha, Spirit 0.7 l / ha, since the intensity of the destruction was minimal, and the yield was the highest.

In epiphytotic years for yellow rust, it should be used on winter wheat the drugs Spirit 0.7 l / ha, since in this option, urediniospores was absent on the plants of winter wheat and yield was maximum.