In recent years phytosanitary situation in agrophytocenooses has worsened, and damage caused by diseases increased. In the conditions of field experiments in the vegetative seasons of 2015–2018 the dissemination of Fusarium and Alternaria spp., and composition of Fusarium species in Ukraine were studied. The selection of plant samples was carried out twice – at the beginning of vegetation and before entering into wintering. In autumn the samples of winter wheat with the symptoms of root rot from more than 150 fields from different oblasts of Ukraine were selected. Later these samples were analyzed using PCR method in real time to determine the species composition of Fusarium genus. In the analysis of grain material from different regions of Ukraine we determined high level of Fusarium infection. Fusariosis of grain were observed in several areas in more than 50% of samples from all regions of county. In all oblasts of Ukraine, the high level of Alternarìa infection were identified also. It is found out that the main sources of the root rot are F. tricinctum, F. graminearum, F. poae and F. avenaceum. The role of F. avenaceum, as the pathogen of root rot was at the level of F. graminearum and F. sporotrichioides in most regions of Ukraine. The studies reveiled that the dominant species in the grain material were F. tricinctum and F. graminearum, presence of which exceeded 20–25%. Quite often F. poae and F. sporotrichioides was observed, presence of which in grain equaled 15–20%. In the Central, Eastern and Southern regions, the dominant species was F. avenaceum with a level of identification 15–23%. F. culmorum, F. langsethiae were within 5–7%. The species composition of fusariosis in the grain and the species composition of pathogens that cause fusariosis root rot in general are similar. Fusariosis becomes one of the most common and harmful diseases of grain crops, and cause no less harm than smut diseases. The fact that their danger continues to grow is explained by adverse weather conditions (alternation of wet and arid periods) and reduction of general level of cultivation: distribution of corn fields, decrease of expenses on tillage, and low-quality pesticides, often generics. It should be noted that the best precursors for cereal crops, for example, soy bean, is also vulnerable to fusariosis. Therefore, performing protective measures at preparing of grain for sowing and in the period of vegetation of the crop will contribute to total reduction of the levels of infection of agrophytocenoses with Fusarium species and potential damage to the cultivated plants. The study revealed that species of fungi belonging to the Alternaria and Fusarium genera infect wheat grain in the yields of each year. The results of data analysis of the genera showed antagonistic interaction between them. Perhaps, particularly at such negative interaction in the vegetative season of 2018, during, practically continuous warm rains in the "grain belt" of Ukraine during the generative period of development of wheat, the grain was infected with Alternaria spp. at moderate presence of Fusarium species. These patterns in the interaction of Alternaria and Fusarium spp. are expedient to be taken into account during development of systems of control of fusariosis using fungicides. Absence of contamination of grains with mycotoxins of Fusarium species does not reduce the levels of danger for crops posed by probable increase in the levels of presence of Alternaria mycotoxins – alternariol, alternariol monomethyl ether, tenuazonic acid, etc. Certainly, the results of the vegetation season of 2018 year and the large-scale alternariosis infication require clarifications to the current normative documentation. The conducted researches are important for improvement of protection systems for crops in intensive technologies of cultivation.

The problem of weed resistance to herbicides has become very important in the last decade and threatens to dramatically reduce the productivity and profitability of modern crop production. Herbicides – ALS inhibitors dominate among current herbicides and are used annually on large areas of sunflower, wheat, corn, soybean, and rapeseed. Also, in recent years, Clearfield seeds of sunflower, corn, canola, soybean and wheat have been sown in large areas. In recent years, there has been a sharp decrease in Amaranthus retroflexus L. control levels by imidazolinone class herbicides. Thus, the effects of herbicides with different modes of action on the development of A. retroflexus on sunflower after imidazolinone application were investigated in field research. In the conditions of the Cherkasy region of Ukraine, the biotype A. retroflexus was identified, which is resistant to the post-emergence application of herbicides - acetolactate synthase (ALS) inhibitors of the imidazolinone class – imazapyr and imazamox. Weed plants treated with imidazolinone derivatives in the maximum doses registered in Ukraine did not differ from untreated control plants. Also, in the conditions of field experiments, cross resistance of the weed biotype to herbicides – ALS inhibitors of the sulfonylurea class – foramsulfuron and iodosulfuron-methyl-sodium, thifensulfuron-methyl, tribenuron-methyl, nicosulfuron was established; and also, to the triazolinone derivative – thiencarbazone-methyl; to triazolpyrimidine derivatives – florasulam and flumetsulam. Multiple resistance of the A. retroflexus biotype to herbicides of the classes of glycine derivatives – glyphosate, phenoxycarboxylates – 2,4-D, benzoic acid – dicamba has not been established; compositions of dicamba with triketone – topramesone; diphenyl ethers – aclonifen; pyridine carboxylates – clopyralid, picloram and aminopyralid. It was shown for the first time that herbicide compositions with selected nutrients (ammonium pool) can increase the level of effectiveness of controlling resistant weed biotypes. Thus, the addition of ammonium sulfate increases the effectiveness of controlling ALS-resistant A. retroflexus with herbicides – a derivative of benzoic acid (dianate) and a derivative of benzoic acid with a 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor (stellar – dicamba + topramesone). Thus, the A. retroflexus biotype resistant to ALS-herbicides of the imidazolinone class was identified for the first time in Ukraine, which is cross-resistant to other ALS-inhibitors of the sulfonylureas, triazolinones, and triazolpyrimidine classes. Multiple resistance of A. retroflexus to herbicides of the classes of glycine derivatives – glyphosate; phenoxycarboxylates – 2,4-D; benzoic acid – dicamba, triketones – topramesone; diphenyl ethers – aclonifen; pyridine carboxylates – clopyralid, picloram and aminopyralid has not been established. The identification of a highly harmful weed species resistant to widely used herbicides – ALS inhibitors in the central part of the "grain belt" of Ukraine requires a significant revision of the principles of crop rotation formation and ways of controlling weeds in the country in order to maintain high levels of profitability and productivity of agrophytocenoses.

В Україні ідентифіковано резистентні до дії гербіцидів — інгібіторів ацетолактатсинтази класу імі- дазолінонів — імазапіру та імазамоксу, біотипи злакового бур’яну плоскухи звичайної, дводольних видів щириці запрокинутої й лободи білої. Встановлено крос-резистентність бур’янів до дії гербіцидів: злаку до сульфонілсечовин (нікосульфурон) та триазолпіримідинів (пеноксулам), дводольних видів до сульфо- нілсечовин форамсульфурону та йодосульфурон-метил-натрію, тифенсульфурон-метилу, трибенурон- метилу; а також до похідного сульфоніламінокарбонілтриазолінонів — тієнкарбазон-метилу; до похідних триазолпіримідинів — флорасуламу та флуметсуламу. Не встановлено мультирезистентності плоскухи звичайної, щириці запрокинутої та лободи білої до гербіцидів класів похідних гліцину — гліфосату, злаку до піноксадену, а дводольних видів до похідних феноксикарбоксилатів — 2,4-Д, бензойної кислоти —дикамби; трикетонів — топрамезону; дифенілових етерів — аклоніфену; піридинкарбоксилатів. Вперше показано, що композиції гербіцидів під впливом пулу амонію можуть підвищувати рівень ефективності контролю- вання резистентних біотипів бур’янів. Ідентифікація високошкодочинних АЛС-резистентних плоскухи звичайної, щириці запрокинутої та лободи білої на півдні й у центральній частині “зернового поясу” України свідчить про обмеженість у ефективності контролювання бур’янів гербіцидами переважно з одним механізмом дії, що потребує істотного перегляду принципів формування сівозмін і шляхів контролювання бур’янів у державі для збереження високих рівнів рентабельності та продуктивності агрофітоценозів. Вирішення цих питань є нагальним щодо збереження потенціалу України, як одного з гарантів продовольчої безпеки світу.

Ukraine is one of the world’s guarantors of food security and has the potential to further increase agricultural production. However, the vast majority of herbicides used on crops are acetolactate synthase (ALS) inhibitors, which poses a threat of herbicide-resistant weed species. The emergence and spread of herbicide-resistant weed biotypes can significantly increase the cost of growing crops to the point of loss of profitability. Herbicide resistance in barnyardgrass (Echinochloa crus-galli var. crus-galli) has been studied in long-term field and greenhouse experiments. Resistance of E. crus-galli to the ALS herbicide triazolopyrimidine derivative ‒ penoxsulam was identified. Expressed resistance was observed in weed plants grown from seeds collected under production conditions in Kherson region in 2015–2016 and 2020–2021. Cross resistance was observed for imidazolinone and sulfonylurea derivatives. It should be noted that the level of cross resistance to ALS herbicides was slightly higher for plants derived from weed seeds harvested in 2020–2021 compared to those harvested in 2015–2016. The introduction of a herbicidal composition of a herbicide mixture ‒ an inhibitor of 4-hydroxyphenylpyruvate dioxygenase (HPPD) (an enzyme in plants in the chain of carotenoid synthesis) ‒ mesotrione with an ALS-inhibitor (nicosulfuron) allowed effective control of the weed, which indicates the absence of multiple resistance to herbicides ‒ inhibitors of carotenoid synthesis. The high efficiency of E. crus-galli control was established by the application of herbicides ‒ inhibitors of fatty acid synthesis (graminicides). The highest level of efficiency in the experiments was observed with the application of fluazifop-butyl and somewhat less ‒ with pinoxaden. A tendency to reduce phytotoxicity to barnyardgrass from the south of Ukraine was observed with the introduction of tepraloxydim and quizalofop-ethyl. A lower level of phytotoxicity of fenoxaprop-p-ethyl on E. crus-galli should be noted compared to the effect of pinoxaden. No multiple resistance was observed with glyphosate (5-enolpyruvylshikimate-3-phosphate synthase inhibitor) and reglone (photosystem I inhibitor), allowing control of vegetative weeds at the beginning and end of the growing season. It has been established that monocot weed species have significantly increased their presence and harmfulness in agrophytocenoses in Ukraine and in the world since the 1950s with the widespread introduction of selective dicotyledonous species control with aryloxyphenoxyacetic, propionic and benzoic acid derivatives. This trend has been maintained until recently ‒ barnyardgrass is one of the dominant weed species in modern agrophytocenoses of Ukraine. Therefore, the identification of the ALS-resistant biotype of barnyardgrass complicates weed control in the following crops in rotations in the southern regions of the country: in maize crops with cross resistance to nicosulfuron, in sunflower ‒ to imidazolinones (imazamox, imazapyr), and also makes it impossible to use penoxsulam in rice production. Traditionally, the use of synthetic auxins, phenoxyacetic acid derivatives, etc. is used to control ALS-resistance. However, in Kherson region of Ukraine, already in the third year of application of rinskor (florpyrauxifen-benzyl), some weed plants were found on rice fields affected by ALS-resistant barnyardgrass, which recovered after the use of synthetic auxin. Therefore, the control of ALS-resistance (penoxsulam, etc.) in E. crus-galli with the application florpyrauxifen-benzyl in the Kherson region of Ukraine is already limited. An obvious and economically feasible preventive measure against the emergence of resistant weed biotypes is the implementation of GAP (Good Agricultural Practice, FAO) approaches: in particular, the use of high quality seeds without weed impurities, increasing the proportion of agrotechnical weed control measures, restoring and expanding crop rotations with mandatory rotation of herbicides with different modes of action, introducing dicotyledonous/leguminous crops into rotations, and using herbicides with different modes of action in crops separately or in mixtures. At the same time, agrotechnical measures and the preservation of biodiversity in agrophytocenoses should be the main factor in controlling resistance in weeds. The use of herbicides and their mixtures with different modes of action is of secondary importance. The identification of highly damaging ALS-resistant E. crus-galli in southern Ukraine indicates the insufficient effectiveness of weed control exclusively with herbicides with a single mechanism of action and requires a significant revision of the principles of crop rotation and ways of weed control in the country to maintain high levels of profitability and productivity of agrophytocenoses. Solving this problem is urgent for the preservation of Ukraine's potential as one of the guarantors of global food security.

Chlorine is an essential nutrient, a deficiency of which reduces plant productivity. Chlorine-containing substances have been known and used for a long time. The most common chlorine compound, sodium chloride (table salt), has been in use since ancient times. It was used as early as 3000 BC and brine as early as 6000 BC. Cl substances are mentioned in ancient texts from different cultures. The discovery of chlorine was in 1774 by Carl Wilhelm Scheele. He obtained it by reacting pyrolusite (manganese dioxide, MnO 2 ) with hydrochloric acid (HCl, then known as muriatic acid). Scheele thought that the gas produced contained oxygen. It was Sir Humphry Davy's proposal and confirmation in 1810 that chlorine was an element, and he also named the element. Chlorine has been considered a biologically importa nt element almost since its discovery. Research into the effects of chloride fertilisers was carried out in the second half of the last century. In 1949, Warburg argued that chloride was an important trace element for plant growth and showed that it was necessary for the water distribution system at the site of photosystem II oxidation. In the 1954 Broyer et al. finally demonstrated the biological importance of chlorine for plants. Chloride is the most abundant inorganic anion in plant cells, an element available in most agrophytocenoses. The average Cl - content in plants ranges from 2.0 – 20.0 mg / g DM, but for Cl-sensitive and Cl-tolerant glycophyte species, the critical (often toxic) Cl-content in tissues can be around 4 – 7 and 15 – 35 mg / g DM, respectively. Chlorine deficiency in plants has characteristic symptoms: wilting, numerous spots, and reduced productivity. Chloride performs a wide range of functions in plants, primarily forming turgor and osmoregulation, respectively, affecting transport processes on membranes (plasmalemma, tonoplast, etc.), water & nitrogen use efficiency (WUE & NUE), and affects the functioning of photosystem II, and is therefore an important part of agricultural plant productivity. Chloride stimulates the structural and functional role of the plasma membrane, sugar transport, as well as nitrogen fixation and assimilation in the plant. Nitrogen assimilation , and photorespiration become more efficient when fed with chloride. Recent studies have discussed the role of chlorine in nitrogen assimilation and photorespiration. It has been shown that Cl plays an important role in the oxygen-evolving complex by adjusting the affinity of different amino acid residues for manganese (Mn). Chlorine acts as a counterion, balancing the positive charges of potassium (K⁺) and other cations in plant cells, which is essential for maintaining electrical neutrality and proper ionic balance in cells. Chlorine plays a significant role in soil salinity. Sources of chlorine in soil include mineral weathering, chlorine from marine species and anthropogenic pollution. Fertilisers such as potassium chloride help to increase the chloride content of the soil. Planting salt-tolerant crops can help maintain agricultural productivity on saline soils. The sensitivity of crops to chlorine varies according to the type of crop. Some crops can tolerate higher levels of chloride without adverse effects, while others are more sensitive and may show symptoms of toxicity or growth retardation when exposed to higher chloride concentrations. Understanding the response of specific crops to chloride is important for the development of nutrient systems and irrigation practices. Chloride increases plant resistance to diseases that require relatively large amounts of Cl - . These doses are much higher than those required for its use as a trace element, but much lower than those required to induce salinity control effects. Most of the research on chlorine nutrition has been devoted to studying the effect of the element on the incidence of physiological leaf spot (PLS) in cereals. PLS form on the leaves of cereal crops when there is a lack of chlorine in the nutritional systems. The necrosis that develops in Cl-deficient plants is thought to be associated with the accumulation of H 2 O 2 during the release of Cl from the Mn cluster of the oxygen-evolving complex. Physiological spotting in the form of completely/partially transparent dots/spots on the leaf was observed, which may indicate inhibition of chlorophyll synthesis rather than degradation. Given that chlorine at micromolar concentrations affects transport processes on membranes and that the element is easily leached through the soil profile, its deficiency occurs in the second half of the growing season, during the period of generative development, which may be the initial mechanism for the formation of PLS in the form of transparent/translucent leaf spots. The development of these spots in the generative period of development, during grain filling, can be significantly accelerated by high levels of actinic light and, accordingly, significantly limit the productivity of cereal crops and their quality. A possible component of chlorine deficiency and leaf damage in wheat and other cereals by PLS may be the application of phosphate fertilizers with high fluoride content, such as phosphate rock, etc. Therefore, in high productivity technologies, it is advisable to use phosphate fertilizers with a low fluoride content, such as potassium monophosphate. Therefore, the use of chlorine fertilisers, mainly potassium chloride in the basic application, ammonium chloride, calcium chloride, etc. in the foliar application, is important to provide plants with chlorine during the growing season to increase WUE & NUE, increase plant resi s tance to pathogens, control PLS, and increase productivity of cereals and other agricultural crops. Chlorine's role in increasing WUE & NUE is particularly important for the country's profitable crop production in the face of resource shortages.

The key to high productivity of plants, especially cereals, is to control lodging of cereals. Among the derivatives of acylcyclohexadiones (ACHD), highly effective retardants have been invented, which are widely used in modern crop production to control the lodging of cereals, mainly winter wheat, spring and winter wheat, winter, spring and hybrids of barley. The mechanisms of influence of ACHD derivatives – trinexapac-ethyl and prohexadione-Ca on plants and features of their application in technologies of cultivation of cultivated plants are considered. By using a composition of ACHD derivatives with a number of agrochemicals, enhancement of retardant activity is achieved. Given the identified varietal variability of the effectiveness of the use of ACHD derivatives in cereals, it is advisable to conduct registration and post-registration studies primarily on varieties that occupy the largest sown areas in the country. The peculiarities of ACHD derivatives’ influence on stem components as the main one, along with the flag leaf, carbon pool for grain filling in the ear and possible reasons for the lack of productivity increase of grain crops due to ACHD derivatives are also considered. This class of substances continues to be widely studied in the world and remains among the most promising for the development of new agrochemicals and drugs.