Visual Phytotoxicity Research Articles

Enhanced Cd phytoextraction by rapeseed under future climate as a consequence of higher sensitivity of HMA genes and better photosynthetic performance

This study aimed to investigate the underlying physiological, biochemical, and molecular mechanisms responsible for Brassica napu's potential to remediate Cd-contaminated soil under current (CC) vs. future (FC) climate (400 vs. 800 ppm of CO2, 21/14 °C vs. 25/18 °C). B. napus exhibited good tolerance to low Cd treatments (Cd-1, Cd-10, i.e., 1, 10 mg kg−1) under both climates without visible phytotoxicity symptoms. TI sharply decreased by 47 % and 68 % (p < 0.05), respectively, in Cd-50 and Cd-100 treated shoots under CC, but to a lesser extent (−26 % and −53 %, p < 0.05) under FC. This agreed with increased photosynthetic apparatus performance under FC, primarily due to a significant decrease in the closure of active PSII RCs ((dV/dt)o, TRo/RC) and less dissipated excitation energy (DIo/RC, φDo). Calvin Benson cycle-related enzyme activity also improved under FC with 2.2-fold and 2.4-fold (p < 0.05) increases in Rubisco and TPI under Cd-50 and Cd-100, respectively. Consequentially, a 2.2-fold and 2.3-fold (p < 0.05) boosted Pr resulted in a 2.3-fold and 2.4-fold (p < 0.05) increase in the DW of Cd-50 and Cd-100 treated shoots, respectively. This also led to a decrease (26 %, p < 0.05) in shoot Cd concentration under both high Cd treatments with a slight reduction in BCF. Translocation factor (TF) decreased (on average 42 %, p < 0.05) by high Cd treatments under both climates. However, under Cd-100, FC increased TF by 1.7-fold (p < 0.05) compared to CC, which could be explained by significant increases in the expression of HMA genes, especially BnaHMA4a and BnaHMA4c. Finally, Cd TU increased under FC by 65 % and 76 % (p < 0.05) under Cd-50 and Cd-100. This led to a shorter hypothetical remediation time for reaching the Cd pollution limit by 35 (p > 0.05) and 61 (p < 0.05) years, respectively, compared to CC.

Propyrisulfuron plus cyhalofop butyl as one-shot herbicides provide high weed control efficiency and net economic performance in mechanically transplanted rice.

Propyrisulfuron is a novel pyrimidinylsulfonylurea herbicide with good activity for controlling annual weed in rice fields. To evaluate the economic performance of propyrisulfuron, a field study was conducted in 2021 and 2022 on a farm of the Jiangsu Academy of Agricultural Sciences, China. Eight different herbicide treatments were employed, including CB (cyhalofop butyl), Py (propyrisulfuron), CBPy (cyhalofop butyl plus propyrisulfuron), PrBe 3, PrBe 10, and PrBe 3+PrBe 10 (pretilachlor plus bensulfuron applied at different times [at 3 (PrBe 3) and 10 (PrBe 10) d] or sequentially, respectively), 2PrBe+PeCBBz (pretilachlor plus bensulfuron [applied sequentially] followed by penoxsulam plus cyhalofop butyl plus bentazone), 2PrBe+MeCBBz (pretilachlor plus bensulfuron [applied sequentially] followed by metamifop plus cyhalofop butyl plus bentazone), along with weed-free and nontreated weedy check treatments. Herbicide treatments did not cause visual phytotoxicity to rice, and bending and leaf rolling were not observed. Only the two propyrisulfuron treatments had temporary negative effects on rice height, but rice recovered quickly. Compared with the weed-free treatment, CBPy did not affect rice tiller number or dry matter accumulation. Compared with the nontreated weedy check, herbicide treatments reduced total weed density by 29.4% to 99.1% and dry biomass by 32.2% to 98.7%. The CBPy treatment provided the best weed control, reducing weed density and biomass by 96.7% and 95.9% in 2021 and 97.4% and 95.6% in 2022, respectively. Rice grain yield was not significantly different between CBPy and the weed-free treatment in either year. Economic analysis showed that CBPy provided the highest net profit, followed by that in 2PrBe+PeCBBz and 2PrBe+MeCBBz, with the lowest net profit in the nontreated weedy check. Thus, CBPy provides good weed control and could be promoted in mechanically transplanted rice fields in China.

Effect of growing media on growth and flowering of potted marigold (Tagetes erecta L.) irrigated with treated sewage water

The present study was undertaken with an objective to evaluate the effect of different soil-based and soilless growing media compositions supplemented with treated municipal sewage water and tap water in different ratios on growth and flowering of potted marigold. The experiment was conducted in a completely randomized block design comprising four media substrates (Soil, burnt rice husk [BRH], farmyard manure [FYM] and cocopeat [CP]) mixed in four different proportions (M1 to M4) and five irrigation levels (I1 to I5) of different combinations of tap water (TW) and treated sewage water (TSW). Results revealed that the media substrate composition (M4) comprising CP + BRH + FYM (25:25:50) was found to be suitable for sustaining the growth of potted marigold plants. The media had relatively higher percent N, P & K with acceptable pH and EC. The marigold plants raised in M4 media irrigated with TSW (100%) preformed significantly well for vegetative and floral characters, essential for a specimen display without any visual phytotoxicity symptoms. Number of flowers per plant and days to flowering duration were observed significantly higher in M4 compared to other media treatments. The analysis of TSW (100%) revealed higher N (0.91 ppm), P (1.67 ppm), K (24.13 ppm) with pH (7.73) and EC (2.10 ds m−1) in acceptable range.

Efficacy of calcium propionate against fungicide-resistant fungal plant pathogens and suppression of botrytis blight of ornamental flowers

Conventional fungicides are used in IPM programs to manage fungal plant pathogens, but there are concerns about resistance development in target organisms, environmental contamination, and human health risks. This study explored the potential of calcium propionate (CaP), a common food preservative generally recognized as safe (GRAS) to control fungicide-resistant plant pathogens, mainly Botrytis cinerea, and botrytis blight in ornamentals. In-vitro experiments using mycelium growth inhibition indicated a mean EC50 value for CaP (pH 6.0) of 527 mg/L for six isolates of Botrytis cinerea as well as 618, 1354, and 1310 mg/L for six isolates each of Monilinia fructicola, Alternaria alternata, and Colletotrichum acutatum. In vitro efficacy tests indicated CaP equally inhibited mycelium growth of fungal isolates sensitive and resistant to FRAC codes 1, 2, 3, 7, 9, 11, 12, and 17 fungicides. CaP at 0.1% (pH 6.0–6.5) reduced infection cushion (IC) formation in vitro, botrytis blight on petunia flowers, and botrytis blight of cut flower roses with little to no visible phytotoxicity. Although higher concentrations strongly inhibited infection cushion formation, they did not improve efficacy and exhibited phytotoxicity. We hypothesize that high concentrations may create tissue damage that facilitates direct fungal penetration without the need for infection cushion and subsequent appressoria formation. This study indicates the potential usefulness of CaP for blossom blight disease management in ornamentals if applied at concentrations low enough to avoid phytotoxicity.

Fungicidal activities of Cymbopogon winterianus against anthracnose of banana caused by Colletotrichum musae

The genus Cymbopogon (Poaceae) species have been widely cultivated throughout the world for a wide range of uses in the pharmaceutical and agricultural fields. The current work investigates the fungicidal activities of Cymbopogon winterianus extract (CWE) in controlling the C. musae that caused anthracnose disease in banana fruit. In vitro assay results showed that CWE at 1.5–2.5 gL−1 concentrations controlled the development of the test pathogen. Mycelial blast, cytoplasmic discharge, and spore edema were noticed when CWE was applied. The Minimum Effective Concentration (MEC) of CWE for the in vivo assay was 1.50 gL−1 and can be used as a postharvest treatment on banana fruit to deter anthracnose infection. Moreover, no visible phytotoxicity or changes in aroma were observed on banana fruit treated with CWE, even at the highest concentration of 2.5 gL−1. The GCMS analysis revealed 41 chemical components associated with CWE. The five main compounds were the following: Methyl oleyl ether (40.20%), γ-Sitosterol (15.80%), 6-Methylheptan-3-ol (7.13%), α-Terpineol (5.56%), and n-Pentadecanol (4.05%). The CWE possesses excellent fungicidal effects against C. musae; in the near future, it can be used as an alternative to commercially available traditional fungicides on the market.

Effect of different soil water managements on the selectivity of fomesafen in conventional and RR soybean

The study aimed to study the selectivity of the herbicide fomesafen, sprayed at different growth stages of the conventional and RR soybean cultivars, under different soil water managements. Two soybean cultivars were used: MG/BR 46 Conquista (conventional) and BRS Valiosa (RR), submitted to the spraying of fomesafen at two phenological stages (V2-first open trefoil; V4-third open trefoil), under three soil water conditions (-0.03, −0.07, and −0.5 MPa). Under water scarcity conditions, soybean plants have lower visual phytotoxicity when subjected to the spraying of the herbicide fomesafen. There were anatomical differences between the leaf blades of the conventional (MG/BR 46 Conquista) and transgenic (BRS Valiosa – RR) cultivars, and the water scarcity changed the anatomy of the soybean plants. The condition of moderate water shortage (-0.07 MPa) led the conventional cultivar to present a lower development than the transgenic cultivar. The transgenic cultivar had a greater ability to sustain the biological nitrogen fixation under moderate water shortage conditions (-0.07 MPa) than the conventional cultivar.

Desiccation of potato haulm with contact herbicides and the final quality of tubers

Desiccation of potato (Solanum tuberosum L.) haulms makes it possible to establish a physiological homogeneity of the haulms and anticipate the harvest of the tubers. This study aimed to evaluate the efficiency of different herbicides in the desiccation of potato haulms applied at the maturation phenological stages, and the effect of these treatments on the quality of tubers. An experiment was conducted in the field, in an area planted with Orchestra potatoes. This was a completely randomized experimental design with four repetitions. At the maturation phenological stages, the crop was applied with herbicides: diquat dibromide (400 g ha-1), paraquat dichloride (400 g ha-1), saflufenacil (70 g ha-1) and carfentrazone ethyl (60 g ha-1). Visual phytotoxicity assessments were performed at 3, 5, 10 and 15 days after application of treatments (DAT). At 15 DAT, tubers were harvested and evaluated for Brix (%), individual weight (g); diameter (cm); texture (kg/cm2) and starch. At 15 DAT, all herbicides resulted in desiccation close to 100%, however, saflufenacil showed the lowest speed of desiccation, since at 5 DAT the phytotoxicity was less than 86.25%. Texture, brix and diameter showed no statistical difference. The control and saflufenacil resulted in the lowest concentration of starch in the tubers and the highest concentration was obtained for carfentrazone-ethyl, paraquat and diquat. The treatments carfentrazone-ethyl, diquat dibromide and paraquat dichloride, were the most suitable for desiccation of potato haulms, providing fast desiccation speed and greater accumulation of starch in the tubers.

Using Advanced Optical Sensing to Quantify Phytotoxicity in Ornamental Plants

Ornamental crop production systems face low tolerance of aesthetic crop damage by consumers and during exports by quarantine inspection entities. Consequently, development and testing of pesticide applications on ornamental crops involve two equally important assessments: 1) demonstrate the ability of pesticides to suppress target pest populations significantly and 2) minimize risks of applied pesticides causing phytotoxicity of leaves, shoots, and flowers. To maximize the accuracy and repeatability of phytotoxicity assessments, it is paramount that methods of detection and diagnosis that are rapid, repeatable, and quantitative be developed and promoted. We performed visual phytotoxicity inspection of three ornamental plants [zinnia (Zinnia elegans), marigold (Tagetes patula), and gerbera (Gerbera sp.)] to a numbered compound applied at three doses. The same plants were also subjected to optical (remote) sensing and classified as having either no or low phytotoxicity response. Although results from visual inspections suggested very low levels of phytotoxicity, 32 of 40 plants (80%) were classified correctly based on optical sensing. Importantly, classified plants showed no significant morphometric differences. We provide proof-of-concept results that optical sensing may be used to detect accurately even highly subtle stress responses by ornamental plants to high doses of foliar pesticides.

Fitorremediation of contaminated soil with 2,4-D + picloram in Eastern Amazonia

The objective of this work was to evaluate the potential of Urochloa brizantha cv. Marandu and Panicum maximum cv. Mombasa in phytoremediation of soil treated with 2,4-D + picloram herbicide, using Raphanus sativus Crimson Gigante as a bioindicator plant. The experiment was carried out in a greenhouse, in a completely randomized design in two stages. In the first stage the treatments were: cultivation of U. brizantha and P. maximum treated with and without the herbicide dose, with five replications. In the second stage, the treatments consisted of cultivating R. sativus in soil: free of herbicide residue; and soil contaminated with cultivation: prior to U. brizantha; P. maximum; and without previous cultivation of grass, with five replications. The units were treated with the herbicide, individually in pre-emergence, after 15 days the grasses were sown. After 50 days, forages were harvested and segregated in aerial and root parts, analyzing fresh and dry biomass (g) and height (cm). After removing phytoremediation plants, R. sativus was transplanted, evaluating visual phytotoxicity at 5, 10, 15 and 20 days after emergence (DAE) and at 20 DAE, the accumulation of green and dry matter (g), height (cm). The evaluated grasses have phytoremediation characteristics for auxinic herbicides; R. sativus can be used as a bioindicator of the herbicide 2,4-D + picloram; the evaluated period was not enough to fully remove the effects of the herbicide.

Resposta de glyphosate em mucuna-preta desenvolvida em diferentes temperaturas

A mucuna-preta é uma leguminosa anual, que nos últimos anos assumiu posição de destaque como uma importante planta daninha em várias regiões. O controle químico constitui-se umas das principais ferramentas de manejo de plantas daninhas, contudo, diferentes condições climáticas podem influenciar consideravelmente a eficácia de muitas moléculas. O glyphosate é um dos herbicidas sistêmicos, de amplo espectro de controle, amplamente utilizado para o controle químico de plantas daninhas. Dessa forma, o objetivo desse trabalho foi avaliar as respostas de crescimento de plantas de mucuna-preta em diferentes temperaturas submetidas a doses de glyphosate. Foram realizados dois experimentos, em casa de vegetação, em delineamento inteiramente casualizado, com cinco repetições. Os tratamentos foram constituídos por nove doses de glyphosate (g ha-1 e.a.): 2,81; 5,62; 11,25; 22,5; 45,0; 90,0; 180,0; 360,0 e 720,0, além de um tratamento controle (sem aplicação de herbicida). Foram realizadas avaliações visuais de fitointoxicação aos 7, 14, 21 e 28 dias após a aplicação (DAA), e aos 28 DAA massa seca da parte aérea das plantas, além da extração e quantificação da cera epicuticular. Doses de glyphosate inferiores a 22,5 g ha-1 e.a. não ocasionaram nenhum efeito nas plantas e nas doses superiores a 360 g ha-1 e.a. proporcionou a morte da mucuna-preta em ambos os experimentos. A resposta da mucuna-preta nas doses intermediárias de glyphosate variou e associou-se as diferentes condições de temperatura que provocaram diferenças nas quantidades de ceras nos experimentos realizados. As plantas de mucuna-preta respondem de maneira diferente ao herbicida glyphosate em condições de temperatura diferente.

Divergence in response of japonica and hybrid rice to titanium dioxide nanoparticles

The present study aimed to compare the responses of two rice cultivars to titanium dioxide nanoparticles (nTiO2), in plant performance and root-associated soil microbes, and provide a reference for the selection of nanoparticle-responsive varieties. The field experiment was conducted to study the effects of nTiO2 (applied at 200 mg/kg) on typical Chinese rice cultivars, Wuyunjing23 (WYJ23) and Yongyou2640 (YY2640), for the whole life cycle. We evaluated agronomic and physiological parameters including chlorophyll content and antioxidant enzyme activities at the heading stage, and biomass, Ti, and nutrient elements uptake after harvest. Soil bacterial communities were also measured through 16S rRNA gene sequencing. Exposure to nTiO2 led to neither Ti accumulation nor changed biomass in either cultivar, but it increased root Fe uptake and reduced grain Cu content. Specifically, nTiO2 exposure decreased the chlorophyll content but increased the peroxidase activity in WYJ23; such altered physiology might affect root exudates and further modify bacterial communities. Although nTiO2 did not induce visible phytotoxicity in YY2640, it affected the abundance of bacteria genera associated with N turnover and plant-C-metabolizing (e.g., Geobacter and Gaiella), resulting in changed C and N cycling in the rhizosphere. This study revealed divergent responses of WYJ23 and YY2640 to nTiO2, both in plant physiology and rhizosphere system. nTiO2 induced greater physiological response but affected the rhizosphere little in WYJ23. By contrast, nTiO2 changed soil microbes and enzyme activities without affecting the physiology of YY2640, suggesting its superior adaptivity to nTiO2.

Control period and economic threshold level of glyphosate tolerant weeds in 2.4-D resistant soybean

Weed densities, species, costs of control, crop value and interference periods should be considered for weed management. With this regard, three experiments were carried out to evaluate weed control periods and weed density in a new soybean cultivar. In ths first trial, control efficacy was measured by visual phytotoxicity of four weed species I. hederifolia, E. heterophylla, Conyza spp. and R. brasiliensis using four different herbicides with two doses each: glyphosate (720 and 1,440 g ea ha-1), 2.4-D (670 and 1,340 g ea ha-1), glufosinate (400 and 600 g ea ha-1) and glyphosate + 2.4-D (410 + 390 and 820 + 780 g ea ha-1). Herbicides were sprayed in an entirely randomized 4x8+1 factorial scheme with six repetitions. In the second experiment, 2,4-D-resistant soybean growth was measured under increasing densities of the same weeds (21 plants m² vs 21, 42, 84, 168 and 336 plants m²). This experiment was conducted under entirely randomized design with 25 treatments with four repetitions. Critical level of damage and economic threshold level of each weed species in soybean were measured using non-linear regressions. In a third experiment, weed with soybean were submitted to increasing periods of control and coexistence (7, 14, 21, 28, 35, 49 and 70 days after soybean emergence, plus two control treatments). Glufosinate and glyphosate+2.4-D (820 + 780 g ea ha-1) showed greater weed control than glyphosate alone (720 g ea ha-1). The yield loss of 0.85, 2.12, 5.71 and 34.24% were found for each weed of E. heterophylla, I. hederifolia, R. brasiliensis and Conyza spp., coexisting with soybean. There was a soybean grain yield loss of 50% in the weedy treatment. Soybean weed management should occur between 18thand 48th days after its emergence. Economic threshold level on soybean yield suggested is below one plant of Conyza spp. and R. brasiliensis per m-². The use of glufosinate and glyphosate+2,4-D provides a greater flexibility of herbicide use for farmers

Production of Fenugreek (Trigonella foenum-graecum) as Influenced by Weed Management Practices and Vermicompost Application

Background: A field experiment was conducted at the Instructional Farm of Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur during Rabi 2016-17 and 2017-18 to study the weed flora, growth, yield and economics of fenugreek. The experiment was laid out in split plot design with three replications having Fenugreek variety RMT-305 (25 kg ha-1) and RDF of 40 kg N and 40 kg P2O5 ha-1 (basal dose through urea and DAP). Methods: Herbicide applied as pre-emergence (PE) at one day after sowing, while post-emergence (PoE) application at 2-4 leaf stage of weeds (21 DAS) with knapsack sprayer having flat fan nozzle using 500 liters of water ha-1. Result: The pooled results revealed that pre-emergence application of oxadiargyl 100 g/ha fb hoeing at 40 DAS recorded significantly higher weed control efficiency (82.3%), plant height (59.83 cm), number of branches (6.09), number of pods (44.86), number of seeds/pod (17.33), seed weight (9.05 g/plant) of fenugreek. Also, significantly maximum seed yield (2.82 t/ha), haulm yield (6.70 t/ha) and harvest index (29.7%) of fenugreek was recorded under oxadiargyl 100 g/ha PE fb hoeing at 40 DAS which was at par with weed free treatment. Significantly higher net returns (98158 `/ha) and B C ratio (2.63) was obtained with application of oxadiargyl 100 g/ha Pre-Emergence (PE) fb hoeing at 40 DAS. Residual effect of herbicides used in fenugreek did not showed any phytotoxic effect on succeeding summer fodder maize in terms of visual phytotoxicity rating at various growth stages of maize, weed flora, dry matter of weeds as well as crop at 30 DAS and green fodder yield of summer fodder maize.

Efficacy of different herbicides on weed dynamics and productivity of kharif maize (Zea mays) and their residual effect on succeeding wheat crop (Triticum aestivum)

Weeds are the major biotic constraints in maize crop due to its wider row spacing limiting its productivity. So, a field experiment was conducted during kharif and rabi seasons of 2015 and 2016, at RRS, Karnal, Haryana to study the effect of different weed control methods on weed flora, growth and yield of kharif planted maize, the residual effect of different herbicides applied in maize on succeeding wheat crop. Treatments included two pre-emergence (PRE) herbicides namely atrazine 750 or 1000 g/ha and alachlor 2000 g/ha along with three post-emergence herbicides (POST) atrazine 500 g/ha, 2,4-D 500 g/ha and tembotrione 120 or 140 g/ha +S (surfactant) at 35 days after sowing (DAS) were used. Hand weeding twice at 20 and 35 DAS, weedy check and weed free treatments were also included. Major weed species infesting the experimental field were Cyperus rotundus, Brachiaria reptans, Dactyloctenium aegyptium, Amaranthus viridis, Digera arvensis, Phyllanthus niruri and Portulaca oleracea. Among herbicide treatments at 50 DAS, alachlor 2000 g/ha as PRE fb tembotrione 120 g/ha provided the highest weed control efficiency (95.1 %). Maximum grain yield (6505 and 6903 kg/ha) and yield attributes of maize were obtained in weed free treatment which was statistically at par with alachlor 2000 g/ha fb tembotrione 120 g/ha +S at 35 DAS (T13) (6380 and 6816 kg/ha). No visual phyto-toxicity of any applied herbicide was observed on maize crop. All herbicide treatments employed in kharif maize, irrespective of their dose and application time did not show any residual carryover effect on succeeding wheat crop.

Phytotoxicity and leaf anatomy of young coffee plants subjected to herbicides exclusively and in associations

The lack of human resources and the damage that weeds can cause to coffee plants are the causes of the growing demand for selective herbicides to be used in coffee farming. Thus, the objective of this study was to evaluate the phytotoxicity symptoms and leaf anatomical characteristics of young coffee plants submitted to application isolated herbicides and also in associations. An experiment was conducted in a protected environment in randomized blocks: four replications with coffee seedlings (Coffea arabica L.) cultivar “Topazio MG-1190”, grown in pots with a capacity of 11 liters of substrate. The herbicides applied, in isolation, were: pyrazosulfuron-ethyl (15 g ha-1), saflufenacil (49 g ha-1), imazetaphyr (100 g ha-1), iodosulfuron-methyl (3.5 g ha-1), chlorimuron-ethyl (15 g ha-1) and sethoxydim (184 g ha-1). The latter was used in associations with the others. In addition, a control without herbicides was used. Phytotoxicity symptoms were evaluated up to 49 days after application (DAA) and anatomical characteristics at 65 DAA. Saflufenacil alone and in association with sethoxydim caused visual phytotoxicity symptoms in the leaves and negatively influence in the characteristics of the epidermis thickness of the adaxial face (EAD), thickness of the palisade parenchyma (EPP), thickness of the spongy parenchyma (EPE) and thickness of the mesophyll (MES). The other herbicides, isolated or in associations, didn’t cause phytotoxicity symptoms, but had a negative influence in the anatomical parameters of the leaf blade, however they did not interfere with the paradermic parameters and the vascular bundle. Key words: Coffea arabica; leaf; selectivity; symptoms.

Nematicidal Properties of Three Adjuvants for Management of Southern Root-Knot nematode, Meloidogyne incognita in vitro and under Greenhouse Conditions

Lettuce and French bean production are severely infected by root-knot nematode, Meloidogyne incognita which causes critical damage to economic plants. Therefore, the farmers have to use chemical nematicides with or without adding adjuvants to enhance the active ingredient delivery to the target nematode. A current study was conducted to assess the direct effect of three adjuvants namely Silwet L-77, Sylgard 309 and Agrimax 3H comparing with three formulations of oxamyl, fosthiazate and fenamiphos on root-knot nematode Meloidogyne incognita. In vitro experiments, ovicidal effect of Silwet L-77, Sylgard 309 and Agrimax 3H on eggs hatching of root-knot nematode was close to the lowest efficient nematicide fenamiphos when the adjuvants were applied at double recommended rate but their effect does not rise to the level of oxamyl or fosthiazate. On the other hand, mortality percentages of second-stage juveniles resulted from Silwet L-77, Sylgard 309 and Agrimax 3H at the recommended rate were 37.33, 50.00 and 42.19 %, respectively. Whereas, double recommended rate of such materials induced mortality percentages reached 46.66, 47.83 and 48.66 %, respectively comparing with 90.83,74.33 and 45.83% resulted from the tested nematicides oxamyl, fosthiazate and fenamiphos, respectively. On the other hand, controlling the root-knot nematode infecting lettuce and French bean plants under greenhouse conditions revealed that adjuvants have weak or limited nematicidal effect with minor potency in reduction nematode development incomparable with the tested standard nematicides, and does not rise to the lowest effect of a tested nematicide fenamiphos. However, both tested plants showed no visual phytotoxicity symptoms.

Investigation into interactions of environmental and application time effects on 2,4-D and dicamba-induced phytotoxicity and hydrogen peroxide formation

AbstractApplication timing and environmental factors reportedly influence the efficacy of auxinic herbicides. In resistance-prone weed species such as Palmer amaranth (Amaranthus palmeri S. Watson), efficacy of auxinic herbicides recently adopted for use in resistant crops is of utmost importance to reduce selection pressure for herbicide-resistance traits. Growth chamber experiments were conducted comparing the interaction of different environmental effects with application time to determine the influence of these factors on visible phytotoxicity and hydrogen peroxide (H2O2) formation in A. palmeri. Temperature displayed a high degree of influence on 2,4-D and dicamba efficacy in general, with applications at the low-temperature treatment (31/20 C day/night) resulting in an increase in phytotoxicity compared with high-temperature treatments (41/30 C day/night). Application time across temperature treatments significantly affected 2,4-D–induced phytotoxicity, resulting in a ≥30% increase across rates with treatments at 4:00 PM compared with 8:00 AM. Temperature differential had a significant influence on dicamba efficacy based on visible phytotoxicity data, with a ≥46% increase with a high (37/20 C day/night) compared with a low differential (41/30 C day/night). Concentration of H2O2 in herbicide-treated plants was 34% higher under a high temperature differential compared with the low differential. Humidity treatments and application time interactions displayed undetected or inconsistent effects on visible phytotoxicity and H2O2 production. Overall, temperature-related influences seem to have the largest environmental effect on auxinic herbicides within conditions evaluated in this study. Leaf concentration of H2O2 appears to be generally correlated with phytotoxicity, providing a potentially useful tool in determining efficacy of auxinic herbicides in field settings.

SELECTIVITY OF FLUAZIFOP-P-BUTYL IN YOUNG COFFEE PLANTS

Weed control is fundamental in coffee cultivation due to their big interference, competing with the crop for water, light and nutrients. Among the control methods used, chemical control is highlighted, as a function of its high efficiency and low cost. However, due to application failures, herbicide drift phytotoxicity is common. Aiming at the search for selective active ingredients in coffee plants, the objective of this study was to evaluate the selectivity of the active ingredient Fluazifop-p-butyl in young coffee plants, and its effects on plant morphology, anatomy and physiology. The experiment was carried out in a greenhouse, with ‘Topázio MG 1190’ coffee plants (&lt;em&gt;Coffea arabica&lt;/em&gt; L.), cultivated in pots with a capacity of 11 L substrate. The statistical design was randomized block design (RBD), with four replications and four doses of the herbicide, making up 16 experimental plots. Each plot consisted of three plants. The treatments were: 0%; 50%; 100% and 200% of the recommended commercial dose of the herbicide Fluazifop-p-butyl. The evaluations were performed at 120 days after application of the treatments. Morphological, physiological and anatomical characteristics were evaluated. Regardless of the evaluated characteristic, there was no difference between the doses of the herbicide. There were no visual phytotoxicity symptoms in the young coffee plants that received the herbicide Fluazifop-p-butyl. The growth of the coffee plants, as well as the physiological and anatomical characteristics, were not altered due to the application of the herbicide Fluazifop-p-butyl.

Genetic variations for post emergence herbicide tolerance in field pea (Pisum sativum)

Weeds are highly competitive to the crops for nutrient and water from soil, sunlight, space and also harbour many insect-pest and diseases, consequently lead to drastic yield reduction. Pisum sativum is sensitive to the most of the potential post emergence herbicides and thus, effective weed management is a difficult assignment particularly the later flush of weed emergence. The identification of herbicide resistant genotypes is the potential way to develop herbicide tolerant varieties as well as to control weeds and minimise yield losses. So far no report is available for herbicide tolerant genotypes in field pea. Therefore, an attempt has been made to identify the genotypes as a source of resistance to the post-emergence herbicide metribuzin. Total 822 genotypes were examined for their sensitivity under preliminary screening against metribuzin at 0.5 kg ai/ha during the winter season of 2015-16. Of the tested genotypes, a set of 85 promising genotypes were re-evaluated with same dose during the winter season of 2016-17 with visual phyto-toxicity score. The results of experiment revealed that there was a huge amount of genetic variation for tolerance against metribuzin in field pea. The frequency distribution grouped the genotypes as tolerant (1), moderately tolerant (5), susceptible (18), and highly susceptible (61) categories. None of the genotypes showed highly tolerant reaction. Notably, accession P-637 witnessed tolerance and other five accessions, viz. P-729, P-647, P-1075, P-2016, and P-1448-2 registered moderately tolerance reaction against metribuzin. Hence, aforesaid promising genotypes may be utilized as donor to speed up breeding for development of herbicide tolerant varieties in field pea and in other genetical studies too.

Quantifying the Effects of Chelated Calcium and Salicylic Acid on the Postharvest Quality of Poinsettia Cuttings

Vegetatively propagated unrooted cuttings typically are grown in equatorial locations and shipped via airfreight to propagators located in temperate climates. Cutting quality, defined as the resistance to external forces, such as physical damage and pathogen infection, impacts postharvest durability during shipping and propagation. During our previous studies, foliar application of calcium (Ca) in the form of Ca chloride was effective at increasing leaf mechanical strength of poinsettia (Euphorbia pulcherrima) and zonal geranium (Pelargonium ×hortorum). Calcium chloride applied at ≥800 mg·L−1 Ca caused phytotoxicity symptoms in poinsettia; therefore, in the current work, we investigated the use of chelated Ca by providing Ca at 40, 80, or 160 mg·L−1 and salicylic acid (SA) at 150 or 300 mg·L−1 to increase the mechanical strength of poinsettia leaves. Mechanical strength of leaves was assessed using a force-displacement graph generated from a texture analyzer using a ball probe to penetrate a unit area of a clamped leaf. The peak force to fracture the leaf and work-of-penetration, defined as the area under the force-displacement curve, were used as indicators of mechanical strength. Calcium concentration in the leaves increased by 27% with increased application of Ca from 0 to 160 mg·L−1. Peak force was 26% greater in treatments with Ca at 80 or 160 mg·L−1 compared with the untreated control. Work-of-penetration was 24% and 29% greater for treatments with Ca at 80 and 160 mg·L−1, respectively, compared with the control. Foliar application of SA did not affect leaf mechanical strength. Chelated Ca applied at 160 mg·L−1 Ca caused visual phytotoxicity symptoms; thus, applications of 80 mg·L−1 Ca are recommended to improve resistance to physical damage for poinsettia leaves.