Visual Phytotoxicity Research Articles

Herbicide Selectivity In Eucalyptus Influenced By Spraying Nozzles

ABSTRACT The objective of this study was to verify the influence of spraying nozzles on the selectivity of herbicides in eucalyptus seedlings. XR 110.02 and TTI 110.02 spraying nozzles were used for the application of the herbicides: control treatment; oxyfluorfen (150 g ha–1) and saflufenacil (98 g ha–1). The experimental arrangement was a 2 × 3 factorial one (two spraying nozzles × 3 herbicides), using a randomized complete block design with four replications. The application was performed 15 days after transplanting the seedlings. Plant height (PH), stem diameter (SD), number of leaves (NL), total dry matter (DM), leaf area (LA), visual phytotoxicity (P), quantum efficiency of photosystem II - Fv/Fm, electron transport rate (ETR) and SPAD (S) index were evaluated. The XR 110.02 and TTI 110.02 nozzles did not change the selectivity of oxyfluorfen and saflufenacil.

Glyphosate as Growth Regulator for Bahiagrass and Broadleaf Carpetgrass

ABSTRACT: The objective of this work was to evaluate the effect of glyphosate herbicide as growth regulator on two turfgrasses bahiagrass and broadleaf carpetgrass. The experiments were conducted in a greenhouse, using a completely randomized design, with 10 glyphosate rates (0, 5.625, 11.25, 22.5, 45, 90, 180, 360, 720, and 1.440 g a.e. ha-1) and four replicates. Bahiagrass and broadleaf carpetgrass plants were transplanted to 2 liter pots filled with a clayey soil. Phytotoxicity and green cover index (GCI) were evaluated through digital analysis; plant height at 7, 14, 21, and 28 days after application (DAA); and dry biomass of cuttings at 28 DAA. The glyphosate rates of 5.625 to 22.5 g a.e. ha-1 (for bahiagrass) and up to 90 g a.e. ha-1 (for broadleaf carpetgrass) reduced the plant growth, without affecting the plant visual quality phytotoxicity, GCI, and dry biomass in the evaluated periods. Contrastingly, rates equal to and above 45 g a.e. ha-1 (for bahiagrass) and equal to and above 180 g a.e. ha-1 (for broadleaf carpetgrass) caused phytotoxic effects in all evaluated periods and affected negatively plant height, GCI, and dry biomass, denoting the sensitivity of these grass species to these glyphosate rates. The digital image analysis allowed the verification and quantification of the effects of the herbicides on turfgrasses.

Effect of irrigation and soil adjuvant on the efficacy and selectivity of pendimethalin and metazachlor in kohlrabi

Precipitation and irrigation strongly affect herbicide management of vegetables, especial fast- growing vegetables as a kohlrabi. The objective of this study was to compare the effects of irrigation and paraffin oil-based soil adjuvant on the efficacy and selectivity of pendimethalin and metazachlor herbicides and their tank-mix combination in kohlrabi. Small plot experiments were carried out in Prague, Czech Republic during 2015 and 2016. Herbicide efficacy on Chenopodium album, Mercurialis annua, and Solanum physalifolium was significantly affected by irrigation shortly after herbicide application, but the efficacy, visual phytotoxicity, as well as both aboveground and root kohlrabi biomass were not affected by the adjuvant. Pendimethalin caused significantly greater phytotoxicity than did metazachlor. Aboveground biomass of kohlrabi plants treated with pendimethalin was about 20–50% less compared to that of plants grown on hand-weeded plots, similar as a tuber yield (tuber weight was about 30% lower). Heavy irrigation shortly after the application of pendimethalin did not affect selectivity of this herbicide treatment. On the contrary, selectivity of metazachlor was strongly affected by irrigation and natural precipitation. Weight of tubers harvested on plots treated by pendimethalin was the same or lower compared to that from plots with competition of annual weeds. The lowest yield (50% compared to hand-weeded check) was on the plots treated by herbicide mixture pendimethalin + metazachlor and irrigated shortly after the application.

Decay of Quinclorac in Acidic Paddy Soil and Risk Evaluation to the Subsequent Crop, Tobacco (Nicotiana tabacum L.).

Quinclorac is a selective herbicide commonly used in China to control monocotyledonous weeds in paddy fields. A field experiment was conducted to quantify the environmental behavior of quinclorac in acidic paddy soil under rice (Oryza sativa L.) field conditions, and to evaluate the risk of its residues to the subsequent crop of tobacco (Nicotiana tabacum L.). Rice was sprayed once with quinclorac 50% WP at 562.5, 375.0, or 187.5g a.i. ha-1 at 7 days after transplanting the seedlings. Decay of quinclorac in paddy field soil followed first-order kinetics, with a half-life of 28.29-30.27days. At harvest time, 0.090, 0.074 and 0.034mg kg-1 of quinclorac were found in soils following the above-described treatments, respectively. Leaves of the subsequent crop, tobacco, sown the year after the quinclorac treatments, exhibited different dose-dependent degrees of visible phytotoxicity symptoms.

Copper supply and fruit yield of young Citrus trees: fertiliser sources and application methods

ABSTRACT This study aimed to evaluate the fertiliser sources and application methods of copper (Cu) in citrus trees during the first years of fruit production. Two experiments were set up in an orchard with 3-year-old sweet orange trees, which were applied with three sources of Cu (nitrate, sulfate or EDTA) either via fertigation (Experiment 1) or via foliar sprays (Experiment 2). Regardless of the fertiliser source, Cu application via fertigation was not efficacious to increase the micronutrient concentration in leaves and, consequently, did not affect fruit yield. Conversely, foliar application of Cu, either as nitrate or sulfate, increased this nutrient level in leaves but when applied as copper nitrate, visual phytotoxicity symptoms were verified in leaves due to salt accumulation in the plant canopy, which reduced the fruit yield. Considering the plant growth and intensified phytosanitary management of the orchard with the application of copperbased products after the third year of the experiment, the effects of Cu treatments on fruit yield are expected to be negligible as the trees age.

PHYTOTOXICITY AND EFFECTIVENESS OF SOME HERBICIDES IN WHEAT PLANTATIONS

Weeds are severely competition with wheat crop and it highly reduces crop yield. So, the present study was conducted on wheat cultivations during two seasons 2013/2014 and 2014/2015 to evaluated phytotoxicity effects of some herbicides on wheat (Triticum aestivum). Effectiveness of these herbicides on weed control in wheat crop and yield evaluation and quality of wheat was evaluated as well after treatment by herbicides. The field experiment was carried out in agricultural experimental station of Etay El-barod, El-Beheira Governorate, using randomized complete block design (RCBD) with four replicates for each treatment and unweeded check, having two rates of both herbicide recommended and double recommended rates (R, 2R). Treatments comprised of post-emergence application of pyroxsulam, flumetsulam+ florasulam, tribenuron-methyl, diclofop-methyl and tralkoxydim. The results indicated an increase in wheat plant height with all herbicides used compared to unweeded check. Tribenuron-methyl and flumetsulam + florasulam treatments did not cause any visible phytotoxicity, while pyroxsulam, diclofop-methyl and tralkoxydim treatments recorded a low indexes of phytotoxicity on wheat plants which disappeared completely after 8 weeks from post application, compared to unweeded check. Results also, indicated that all herbicide treatments decreased weed density. Herbicide treatments achieved the highest weed control expressed in lowest fresh weight after 56 days from application for broadleaved, grassy and total weeds. Herbicide treatments caused an excellent increase in yield attributes (spike length, biological and grain yield) and yield quality (weight of 1000 grains, total carbohydrates and crude protein) compared to unweeded check in both seasons. The maximum grain yield was recorded at two trials by pyroxsulam compared to unweeded check.

Alternative soilless media using olive-mill and paper waste for growing ornamental plants.

Peat-based growing media are not ecologically sustainable and peat extraction threatens sensitive peatland ecosystem. In this study, olive-stone waste (OSW) and paper waste (PW) were used in different ratios-as growing media-for ornamental crop production, as peat (P) substitutes. Marigold (Calendula officinalis L.), petunia (Petunia x hybrita L.) and matthiola (Matthiola incana L.) plants were grown in (1) P (100%), (2) P:OSW (90%:10%), (3) P:OSW (70%:30%), and (4) P:OSW:PW (60%:20%:20%). The physicochemical properties of these substrates and the effects on plant growth were determined. The addition of 10-30% OSW into the substrate increased marigold height compared to plants grown in 100% peat. No differences in plant size, plant biomass (leaves and flowers), and dry matter content were found. Adding PW, in combination with OSW, maintained marigold height and total number of flowers produced to similar levels as in plants grown in 100% peat. In matthiola, adding 30% OSW into the substrate reduced plant size and fresh weight, but not plant height. No differences were observed when plants grew in lower OSW (i.e., 10%) content. Petunia's height, its total number of flowers and flower earliness (flower opening) were increased in the presence of OSW compared to the plants grown in 100% peat. The addition of OSW did not affect petunia's size and fresh weight among treatments. The addition of PW suppressed several plant growth-related parameters for both matthiola and petunia. The insertion of OSW did not change leaf chlorophyll content whereas the presence of PW decreased chlorophylls for marigold, petunia, and matthiola. Both OSW and PW altered the content of total phenolics and antioxidant capacity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in leaves and flowers for marigold and petunia. Both 30% OSW and PW increased antioxidative enzyme metabolism due to the increased damage index and lipid peroxidation observed in plants. Leaf N and P content decreased in PW-based media, while matthiola displayed visual phytotoxicity symptoms when PW was added into the substrate. The present work indicates that up to 30% of OSW can replace peat for marigold and petunia growing and only up to 10% of OSW for matthiola, while the addition of PW on top of OSW is not recommended, so further research is needed.

Actividad de cletodim y haloxifop R-metil en el suelo y su efecto fitotóxico en el cultivo de maíz (Zea mays)

Los herbicidas haloxifop R-metil y cletodim pueden persistir activos en el suelo causando efectos fitotóxicos a cultivos de gramíneas cuando son aplicados próximos a la siembra. En este trabajo se realizaron experimentos de campo en cuatro ambientes y en macetas bajo invernáculo. El objetivo fue evaluar el efecto fitotóxico de distintas dosis de haloxifop R-metil y cletodim aplicados al suelo en el cultivo de maíz y estudiar los requerimientos de riego y tiempo entre aplicación y siembra, para evitar efectos fitotóxicos. En condiciones de campo, 62,5 y 120 g.i.a. ha-1 de haloxifop R-metil y cletodim respectivamente, produjeron fitotoxicidad visual menor a 14 %. Con dosis superiores, en dos de los cuatro ambientes se observaron mayores niveles de fitotoxicidad (32-78<br />%). Ambos herbicidas redujeron la biomasa de las plantas de maíz cuando no fueron incorporados al suelo mediante riego y la siembra se realizó 14 días después de su aplicación. Cuando se realizó riego tras la aplicación de los herbicidas, siete días resultaron suficientes para evitar fitotoxicidad con 62,5 y 125 g i.a. ha-1 de haloxifop R-metil y 120 g i.a. ha-1 de cletodim. Ninguno de los tratamientos evaluados redujo la biomasa de las plantas de maíz sembradas 14 días después del riego.

Evaluation of Municipal Solid Waste Compost and/or Fertigation as Peat Substituent for Pepper Seedlings Production

Pepper (Capsicum annuum L.) seed germination and seedling growth using municipal solid waste compost (MSWC) in various proportions was examined. MSWC extracts (10− 0 up to 10− 6 dilutions) were evaluated for seed priming/germination in Petri dishes. The MSWC extracts at 10− 1–10− 6 showed similar seedling germination, whereas extracts at 10− 1–10− 3 accelerated root radical length compared to the control treatment. However, pure extracts (at 10− 0) almost failed seed germination. Under nursery conditions, six substrates were prepared from commercial peat and MSWC and were further assessed in conjunction with the nutrient application as basic fertilizer (BF) or hydro fertilizer (HF). The addition of MSWC into peat inhibited seed emergence and increased the mean germination time, while fertigation accelerated seed emergence at 15% addition of MSWC. Addition of > 30% MSWC reduced seedling height, leaf number and fresh weight. BF and HF increased fresh weight in seedlings grown in 15% MSWC. Leaf chlorophyll and total carotenoids content decreased in > 60% MSWC into the peat. The greatest leaf photosynthetic rate was found with the application of HF, while higher leaf stomatal conductance and leaf internal CO2 concentration were found in plants grown without fertilizers for both 15 and 45% of MSWC addition. The K content decreased, Na content increased, while P content did not differ with MSWC addition. Fertigation improved seedlings’ nutritive status. No visual phytotoxicity was observed macroscopically. Low content (15–30%) of MSWC may act as alternative substitute to peat with more positive effects observed, if nutrients are provided through HF rather than BF.

Control of Lesion Nematodes, Pratylenchus spp., in Grapevine Nursery Material by Immersion in Fenamiphos Solutions and Hot Water

Control of Pratylenchus spp. in dormant grapevine nursery material was attempted using fenamiphos solutions and a hot-water treatment. Five months after treatment, the lesion nematodes were eradicated by all treatments. Although no visual phytotoxicity symptoms were recorded at any stage wiith any of the treatments tested, hot water significantly reduced plant growth of certain scion/rootstock combinations. Treatment with 0,1 % (a.i.) fenamiphos solution for 30 minutes at 25°C is recommended.

English

Invasive plants, besides competing for space, also compete for water, light, and nutrients against the crop, what may cause drastic production cuts. Chemical control through herbicides is the most widely used method to control these plants. This study aimed to evaluate the persistence of the 2,4-D (dichlorophenoxyacetic acid) herbicide in soybean (Glycine max L.) crops in an Oxisol from the Brazilian Cerrado. The experiment was conducted in a greenhouse using a randomized block design, 5x3 factorial, five application periods (0, 3, 5, 7 and 10 days before sowing), and three herbicide doses (0, 750 and 1500 g e. a. ha-1), in four repetitions. Herbicides were sprayed with the assistance of knapsack sprayer at constant pressure (kept through CO2 compressed). Residual effect was assessed by emergence speed index (ESI), visual plant phytotoxicity, plant height, and shoots and root dry biomass. Persistence of 2,4-D herbicide was short in soybeans planted in an Oxisol. Periods from 0 to 3 days before sowing were the most harmful to soybeans, that is, the closer the spraying was from sowing, higher was its damage to the crop. The 1500 g e. a. ha-1 dose had a higher residual effect. Key words: Persistence, bioassay, Glycine max, dichlorophenoxyacetic acid.

Tolerance of newly sown cocksfoot-clover pastures to the herbicide imazethapyr

In New Zealand, subterranean clover is recommended as a companion legume in mixed swards, particularly in dryland cocksfoot-based pastures. However, establishment of cocksfoot is slower than perennial ryegrass and therefore weed ingress is more common. An experiment at Lincoln University, Canterbury showed imazethapyr applied when clover was at the 3-4 trifoliate leaf stage, and cocksfoot at the 2+ leaf stage, increased the subterranean clover content of the pastures by at least 1000 kg DM/ha, despite initial visual phytotoxicity responses. Balansa and white clover pasture yields were not different to their unsprayed unweeded controls. Imazethapyr application controlled broadleaf weeds from early in the season. The herbicide application reduced cocksfoot yields by 70% in early spring, but yields recovered and were not different to the unsprayed unweeded controls at 1350 ± 260 kg DM/ha after grazing. Imazethapyr application improved subterranean clover pastures through an increase in clover content by suppressing weeds and temporarily reducing the rate of cocksfoot growth. Keywords: subterranean clover, Spinnaker herbicide, seedling, white clover, balansa clover

Subdoses de glyphosate não reduzem a produtividade da cultura do milho

Na aplicação de herbicidas, utilizados como maturadores, deve ser levado em consideração as culturas cultivadas em áreas adjacentes, devido ao risco de ocorrência de deriva desses produtos. Partindo do pressuposto da sensibilidade da cultura do milho ao glyphosate, objetivou-se avaliar o efeito de subdoses de glyphosate na cultura do milho quando aplicadas em estádios de desenvolvimento V4 e V8. O experimento foi instalado em Jataí, GO, constituído de 10 tratamentos estabelecidos no delineamento com blocos casualizados em esquema fatorial 2 x 5, com quatro repetições. O primeiro fator correspondeu à aplicação do maturador nos estádios V4 e V8 de desenvolvimento da cultura do milho e o segundo fator às subdoses (0; 3; 6; 9 e 12% de 216,0 g ha-1 e.a.) de glyphosate. Cada parcela experimental continha 10 linhas do híbrido SYN 7G17 com 9 metros de comprimento. Efeitos de fitotoxicidade visual nas plantas não foram perceptíveis em ambos estádios de aplicação aos 7, 14, 21, 28 e 42 dias após aplicação. Componentes de crescimento e de produção não foram afetados por subdoses de até 12% (25,92 g ha-1 e.a.) de glyphosate.

English

Weed infestations and the few post-emergent control alternatives available are some of the main problems in the management of ornamental and sports lawns. Given the exposed, the study aims to evaluate the selectivity of five herbicides to four grass varieties: Paspalum notatum (bahia grass), Cynodon dactylon (bahama grass- ITG6), Zoysia japonica (japanese lawn grass) and Zoysia japonica (imperial – ITG5), as well as the control efficiency of those upon nutsedge (Cyperus rotundus) and sudan grass (Urochloa decumbens). The following herbicides were applied in the recommended doses: sulfentrazone + diuron, isoxaflutole, triclopyr, 2,4-D and halosulfuron. Visual phytotoxicity symptoms in turfgrass and weed control were performed at 7, 14, 21, 28, 35 and 42 days after herbicide application and, at the end of the evaluations, was quantified the dry weight. The herbicides sulfentrazone + diuron and isoxaflutole were not selective to any turfgrass, although sulfentrazone + diuron controlled C. rotundus and U. decumbens species and isoxaflutole controlled only U. decumbens. However, halosulfuron and 2,4-D herbicides were selective to all of grasses and promoted weed species control. The herbicide triclopyr was selective to P. notatum, Z. japonica and Z. japonica– ITG5, and it can be used to control C. rotundus and U. decumbens. Key words: Urochloa decumbens, Cynodon dactylon–ITG6, Cyperus rotundus, Paspalum notatum, Zoysia japonica.

Chemical Control of Morning Glory Species in Sugarcane Harvested in the Dry and Semi-Wet Seasons1

ABSTRACT The control of morning glory (Ipomoea spp. and Merremia aegyptia) was evaluated in five commercial sugarcane-production fields receiving applications of the herbicides sulfentrazone (0.9 kg ha-1), amicarbazone (1.4 kg ha-1), imazapic (0.147 kg ha-1), and hexazinone + tebuthiuron (0.325 + 0.75 kg ha-1) applied pre-emergence in either the dry season (July and August) or in the semi-wet season (early October); mesotrione alone (0.192 kg ha-1) or in combination (0.12 kg ha-1) with atrazine (1.5 kg ha-1) or diuron + hexazinone (0.491 + 0.139 kg ha-1) applied post-emergence in the wet season (November), and the phytointoxication of the chemical treatments for sugarcane. Five species of morning glory (Ipomoea hederifolia, Ipomoea nil, Ipomoea quamoclit, Ipomoea triloba and Merremia aegyptia) were assessed in the experiments. The applications during the dry, semi-wet, and wet seasons resulted in similar levels of control of I. hederifolia, I. nil, I. quamoclit, and I. triloba. The herbicides imazapic and mesotrione alone resulted in lower levels of control of M. aegyptia. Imazapic and the combination of mesotrione + (diuron + hexazinone) caused greater visible phytotoxicity to sugarcane than other herbicides applied during the dry and semi-wet seasons. However, the greatest loss of production was attributed to amicarbazone.

Control of Colletotrichum fructicola on strawberry with a foliar spray of neutral electrolyzed water through an overhead irrigation system

Neutral electrolyzed water (NEW: pH 6.5–7.5) applied through an overhead irrigation system was evaluated for control of strawberry anthracnose caused by Colletotrichum fructicola. Conidia of the pathogen were completely killed by a 10-s exposure to 10.0 mg/L of available chlorine in the NEW. Disease suppression was significantly higher using the NEW treatment through overhead irrigation, either alone or combined with fungicides, than using conventional fungicides. Plants had no visible phytotoxicity after the NEW treatment, even when combined with fungicides. Thus, the NEW treatment was effective at controlling anthracnose caused by C. fructicola.

Seletividade de herbicidas sobre arroz irrigado em resposta à época de semeadura e redução da luminosidade em fases do desenvolvimento

RESUMO Diferentes fatores ambientais podem afetar a seletividade de herbicidas às culturas. O objetivo deste experimento foi avaliar os efeitos da época de semeadura e da redução artificial da luminosidade, em diferentes fases do desenvolvimento das plantas, sobre a seletividade de herbicidas e os componentes de produtividade do arroz irrigado. O experimento foi conduzido a campo, na safra 2012/2013, com o cultivar IRGA 424. Os fatores estudados foram: época de semeadura (18/outubro e 09/novembro); herbicidas (testemunha capinada, bispyribac-sodium e penoxsulam) e fases do desenvolvimento da cultura com luminosidade reduzida de 70% [testemunha, plântula (S0-V4), períodos vegetativo, reprodutivo e todo o ciclo]. Foi utilizado o delineamento inteiramente casualizado, em esquema fatorial, com quatro repetições, sendo que os fatores época de semeadura e redução de luminosidade foram dispostos em faixas, visando a viabilizar o experimento. Avaliaram-se: fitotoxicidade visual, colmos e panículas por área, espiguetas por panícula, esterilidade de espiguetas, peso de 1000 sementes e produtividade. Os dados foram submetidos à análise de variância pelo teste F (p≤0,05) e teste de médias de DMS de Fischer (p≤0,05). A época de semeadura influencia na seletividade de bispyribac-sodium, sendo que, quando realizada a semeadura perto do início do período recomendado, em 18/outubro, reduz-se a produtividade do cultivar estudado. A redução artificial de luz em diferentes fases do desenvolvimento não afeta a seletividade dos herbicidas bispyribac-sodium e penoxsulam sobre o arroz irrigado.

English

The state of Mato Grosso is the main grain producer in Brazil, and weeds occurrence remains the major obstacle in the production of these grains, also increasing herbicide consumption. The aim of this study was to assess 2, 4-dichlorophenoxyacetic acid and Glyphosate (N-phosphonomethyl-glycine) herbicides mixture persistence in soybeans of Ultisol in the Brazilian Cerrado. The study was conducted in a greenhouse with randomized blocks experimental design consisting of 6x5 factorial, six application periods (0, 3, 5, 7, 10 and 14 days before sowing), five herbicide doses (0, 750 , 1500, 2250 and 3000 g ia. ha-1) and four repetitions. Herbicides were sprayed with a knapsack sprayer. Residual effect was assessed through emergence speed index (ESI), plant height, visual phytotoxicity and dry biomass of shoot and root. Results showed that, according to the decrease in the interval between herbicide application and soybean seeding, the residual effect of products was higher. As the dose increased, higher was the plant phytointoxication, influencing in the reduction of emergence speed, shoot dry matter, root dry matter and plant height, and negatively acting on crop development.   Key words: Pesticides, residual effect, sowing, soybean.

Changes in Photosynthesis and Oxidative Stress in Wheat Plants Submmited to Herbicides Application

The use of herbicides, even in tolerant crops, can cause stress evidenced by increase phytotoxicity affecting growth and development. The objectives of this study were to evaluate herbicides effect from different mechanisms of action in photosynthetic and oxidative stress parameters, as well visual phytotoxicity and wild radish control in wheat crop, cultivar Quartzo. Two trials were conducted where the first one evaluated the photosynthetic parameters on wheat plants in two seasons collection, following the application of herbicides bentazon, clodinafop, iodosulfuron, metribuzin, metsulfuron and 2,4-D; and the second one evaluated wild radish (Raphanus sativus) control, wheat phytotoxicity and yield due to bentazon, iodosulfuron, metribuzin, metsulfuron and 2,4-D herbicides application. Photosynthetic rate, stomatal conductance and transpiration were negatively affected by metribuzin, metsulfuron and 2,4-D herbicides at 24 and 120 HAS (hours after spraying) compared to control. Oxidative stress was similar or lower to control, when herbicide was applied and, in general, there was no difference between application times. Lipid peroxidation, catalase activity and phenols were higher in the first collection time. The application of herbicides iodosulfuron and 2,4-D reduces chlorophylls and carotenoids in wheat. Herbicides bentazon, iodosulfuron, metribuzin, metsulfuron and 2,4-D are selective to wheat, cultivar Quartzo and do not affect wheat yield. 2,4-D, metribuzin and iodosulfuron are more efficient for wild radish control.

Fruit set and quality of self-fertile sweet cherries as affected by chemical flower thinning

Milic B., Keserovic Z., Doric M., Ognjanov V., Magazin N. (2015): Fruit set and quality of self-fertile sweet cherries as affected by chemical flower thinning . Hort. Sci., 42: 119–124. Self-fertile cherry cultivars can produce an excessive crop of small fruits with low sugar content. In order to prevent overcropping and provide high quality fruits, chemical thinning of flowers is required. Ammonium thiosulfate (ATS), surfactants and plant oils are used to thin flowers, mostly in apple and peach. The purpose of this research was to com pare the effectiveness of the blossom thinners ATS, surfactant Silwet and rapeseed oil (Ogriol) in reducing fruit set of the self-fertile sweet cherry cultivars Alex and Sunburst and their potential to improve fruit quality. At lower rates (1 and 2%) ATS did not consistently reduce fruit set, while at higher rate (3%) it produced visible phytotoxicity on the leaves. ATS treatments did not increase the average weight and diameter of fruits. 10 and 30 ml/l Ogriol application did not reduce fruit set significantly or improve fruit quality of self-fertile sweet cherries. The surfactant Silwet applied at the rates of 1 or 3 ml/l was found to consistently thin self-fertile sweet cherry cultivars, leading to better fruit quality.