Assessing the Weed-Suppressing Potential of Cotton Chromosome Substitution Lines Using the Stair-Step Assay

Palmer amaranth is a problematic common weed species, especially in cotton. With the wide use of chemical herbicide and herbicide-tolerant transgenic cotton lines, Palmer amaranth populations have developed tolerance to commonly used herbicides. It is imperative to develop alternative weed control methods to slow the evolution of herbicide-resistant weed populations and provide new strategies for weed management. Eleven chromosome substitution (CS) cotton lines (CS-B26lo, CS-T17, CS-B16-15, CS-B17-11, CS-B12, CS-T05sh, CS-T26lo, CS-T11sh, CS-M11sh, CS-B22sh, and CS-B22lo) were screened for weed-suppressing abilities in this study. The cotton lines were tested using the established stair-step assay. Height (cm) and chlorophyll concentration (cci) were measured for each plant in the system. The most significant variation in Palmer amaranth height reduction among the CS lines was observed 21 days after establishment. CS-B22sh (76.82%) and T26lo (68.32%) were most effective in reducing Palmer amaranth height. The cluster analysis revealed that CS-B22sh, and CS-T26lo were clustered in one group, suggesting similar genetic potential with reference to Palmer amaranth growth and development. CS-B22sh showed novel genetic potential to control the growth and development of Palmer amaranth, a problematic weed in cotton fields. Future experimentation should implement more parameters and chemical testing to explore allelopathic interactions among CS lines and Palmer amaranth.

Screening glyphosate-alternative weed control options in important perennial crops

The current study aimed to screen glyphosate-alternative weed control methods in three perennial crops in Greece. Field trials were conducted and repeated (2018 to 2019 and 2019 to 2020) in a citrus orchard (Citrus clementina Hort. ex Tan), an olive grove (Olea europaea L.), and a vineyard (Vitis vinifera L.) under the randomized complete block design (nine treatments, four blocks). Glyphosate was applied in the citrus orchard (720 g ae ha−1), the olive grove (720 g ae ha−1), and the vineyard (1,800 g ae ha−1). Pelargonic acid (1,088 g ha−1; two times), barley (Hordeum vulgare L.) residues and white mustard (Sinapis alba L.) residues were evaluated in all sites. Mowing was evaluated in the citrus orchard (one time) and the vineyard (two times). Flazasulfuron (50 g ha−1), oxyfluorfen (144 g ha−1), and flumioxazin (150 g ha−1) were applied in the citrus orchard and the olive grove. Penoxsulam + florasulam (15 + 7.5 g ha−1) was also applied in the olive grove. Cycloxydim (200 g ha−1), quizalofop-p-ethyl (150 g ha−1) and propaquizafop (150 g ha−1) were applied in the vineyard. An untreated control was included in all sites. Flazasulfuron, oxyfluorfen, and flumioxazin resulted in similar normalized difference vegetation index (NDVI) and weed biomass to glyphosate in the citrus orchard in both years and evaluations. Pelargonic acid (two times) and mowing (one time) were effective on broadleaf weeds. Flazasulfuron and penoxsulam + florasulam were the most promising glyphosate-alternative weed control methods against hairy fleabane [Conyza bonariensis (L.) Cronquist] in the olive grove. Cover crop residues showed their suppressive ability as in the citrus orchard. All selective herbicides resulted in similar NDVI and johnsongrass [Sorghum halepense (L.) Pers.] dry weight values in the vineyard in both years. Negative and strong correlations were observed in all sites and years between crop yield and weed dry weight (R2 = 0.543 to 0.924).

Respons pertumbuhan bibit kelapa sawit terhadap bioherbisida saliara di pembibitan awal

AbstrakKeberadaan gulma pada pembibitan kelapa sawit dapat menurunkan kualitas bibit. Pengendalian gulma di pembibitan awal harus dilakukan secara dengan tangan (hand weeding), karena bibit dapat mati akibat aplikasi herbisida. Aplikasi bioherbisida saliara (Lantana camara) pada bibit kelapa sawit (Elaeis guineensis Jacq.) dapat menjadi alternatif pengendalian gulma yang ramah lingkungan dan mengurangi tenaga kerja. Penelitian ini dilaksanakan di Kebun Percobaan 1 Politeknik CWE, pada November 2019 sampai Februari 2020. Percobaan disusun dalam Rancangan Acak Kelompok, dengan perlakuan: kontrol (tanpa aplikasi bioherbisida), Ekstrak Lantana camara 1%, 2%, dan 3%. Setiap perlakuan diulangi sebanyak tiga kali. Hasil penelitian menunjukkan bahwa Bioherbisida Lantana camara mengandung senyawa alelokimia yaitu Saponin (2,07%), Tanin (3,28%), dan Flavonoid (1,83%). Gulma Lantana camara dapat dijadikan bahan alternatif bioherbisida pra tumbuh karena berpengaruh nyata terhadap daya tumbuh gulma. Meskipun bioherbisida menurunkan tinggi bibit pada 3 bulan setelah tanam (BST) dan diameter batang bibit pada 1 BST, namun bioherbisida tidak mempengaruhi jumlah daun, kehijauan daun, dan biomassa bibit. Bioherbisida Lantana camara dengan konsentrasi 1% menunjukkan hasil terbaik dalam menekan laju pertumbuhan gulma.Kata Kunci: Bibit, Bioherbisida, Fisiologi, Gulma, Morfologi Abstract. The presence of weeds in oil palm nurseries can reduce the quality of the seedlings. Usually, mechanical weeding by hand is needed in pre-nursery because the use of chemical treatment caused the oil palm seeeling died. Bioherbicide application of Lantana camara to oil palm seedling (Elaeis guineensis Jacq.) can be alternative weed control that is environmental friendly and reduces labor. This research conducted at Teaching Farm Politeknik CWE, from November 2019 to Februari 2020. Experiment was arranged in Randomized Block Design, with treatments are Control (without bioherbicide application), Bioherbicide Lantana camara 1%, 2% and 3%. Every treatments was repeated three times. The results showed that Lantana camara bioherbicide contained allelochemical compounds, namely saponins (2.07%), tannins (3.28%), and flavonoids (1.83%). Lantana camara weed can be used as an alternative material for pre-growing herbicides because it has a significant effect on reduced weed population. Although bioherbicides decreased seedling height at 3 months after planting (MAP) and stem diameter at 1 MAP, bioherbicides did not affect leaf number, leaf greenness, and seedling biomass. Bioherbicide Lantana camara with concentration 1% showed the best treatment for controlling weeds in oil palm pre nursery.Keywords: Bioherbicide, Morphology, Physiology, Seedlings, Weed

Comparative Analysis of Microwave and Electric Arc as a New Method in Weed Control

The increase in the demand for organic production and the adverse effects of chemicals used in agriculture have brought non-chemical weed control methods to the fore. Among these methods, the most studied ones are microwave and electric arc methods. It has been determined in studies that microwaves and electric current, when applied at the correct power level and for sufficient time, biologically inactivate weeds, all kinds of unwanted plants and seeds. In this study, the mortality rates caused by microwave energy and electric current (arc) methods in some plants applied under laboratory conditions were compared. Studies have shown that the effectiveness of microwave and electric arc methods depends on the selected current, voltage, power level and exposure time. It is thought that the electric arc method is easier and more economical in terms of application in the field than the microwave method. Another purpose of this study is to remind agricultural policy makers and decision makers of the importance of alternative weed control methods and to ensure that they make policies in this direction.

Sustainable alternatives to chemicals for weed control in the orchard – a Review

This review is designed to address various alternative weed-control practices and their possibilities in the fruit orchard in terms of sustainability. Correct weed management and maintenance of adequate orchard biodiversity are crucial for sustainable orchard soil management. The key is to practice an alternative weed-management approach (single or integrated) rather than to use possibly harmful chemicals only. Integration of modern equipment with a shallow tillage system can provide effective weed control in tree rows, including optimised tree performance and soil biodiversity. Living mulch suppresses weeds and enhances orchard biodiversity, while selection of less competitive and less pest-attracting species is crucial. Plastic covers offer long-term weed control, but additional nutrient amendments are required to maintain the balanced fertility of the soil. Wood chip mulch is suggested where the materials are available on or near the farm, and where there is lower incidence of perennial weeds. High pressure water and robotic systems are still in their infancy for fruit orchards, and required more research to confirm their efficiency.

Improved herbicide selectivity in tomato by safening action of benoxacor and fenclorim

Safeners have been widely used to reduce phytotoxicity to crops, thus serving as an alternative weed control strategy. Benoxacor and fenclorim safeners have the potential to protect plants from herbicide phytotoxicity by increasing glutathione S-transferase (GST) activity within the plant. The study aimed to evaluate the safening effect of benoxacor and fenclorim on tomato against selected herbicides applied POST. The experiment was conducted in a greenhouse in a completely randomized designed with four replications in a 9 × 3 factorial scheme, where Factor A consisted of eight herbicides including a nontreated control, and Factor B consisted of two safeners including a nontreated control. The herbicide treatments were sulfentrazone (0.220 kg ai ha−1), fomesafen (0.280 kg ai ha−1), flumioxazin (0.070 kg ai ha−1), linuron (1.200 kg ai ha−1), metribuzin (0.840 kg ai ha−1), pyroxasulfone (0.220 kg ai ha−1), and bicyclopyrone (0.040 kg ai ha−1). Safener treatments consisted of benoxacor (0.67 g L−1) and fenclorim (10 µM). Tomato seeds were immersed in safener solution before sowing and herbicides were applied when tomato plants were at the 3-leaf stage, or 25 days after sowing. Visible injury was scored at 3, 7, 14, and 21 d after application (DAA), and shoot biomass was recorded 21 DAA. Seed treatment with fenclorim reduced injury caused by imazamox and bicyclopyrone by 5.5 and 1.3 times, respectively, whereas benoxacor reduced the injury from bicyclopyrone 1.3 times. In addition, tomato plants pretreated with fenclorim showed a lesser reduction in biomass after application of imazamox, fomesafen, and metribuzin, whereas plants pretreated with benoxacor showed lesser biomass reduction after metribuzin application. Thus, the use of safeners promotes greater crop selectivity, allowing the application of herbicides with different mechanisms of action on the crop.

Using energy requirements to compare the suitability of alternative methods for broadcast and site-specific weed control

The widespread use of herbicides in cropping systems has led to the evolution of resistance in major weeds. The resultant loss of herbicide efficacy is compounded by a lack of new herbicide sites of action, driving demand for alternative weed control technologies. While there are many alternative methods for control, identifying the most appropriate method to pursue for commercial development has been hampered by the inability to compare techniques in a fair and equitable manner. Given that all currently available and alternative weed control methods share an intrinsic energy consumption, the aim of this review was to compare methods based on energy consumption. Energy consumption was compared for chemical, mechanical, and thermal weed control technologies when applied as broadcast (whole-field) and site-specific treatments. Tillage systems, such as flex-tine harrow (4.2 to 5.5 MJ ha−1), sweep cultivator (13 to 14 MJ ha−1), and rotary hoe (12 to 17 MJ ha−1) consumed the least energy of broadcast weed control treatments. Thermal-based approaches, including flaming (1,008 to 4,334 MJ ha−1) and infrared (2,000 to 3,887 MJ ha−1), are more appropriate for use in conservation cropping systems; however, their energy requirements are 100- to 1,000-fold greater than those of tillage treatments. The site-specific application of weed control treatments to control 2-leaf-stage broadleaf weeds at a density of 5 plants m−2 reduced energy consumption of herbicidal, thermal, and mechanical treatments by 97%, 99%, and 97%, respectively. Significantly, this site-specific approach resulted in similar energy requirements for current and alternative technologies (e.g., electrocution [15 to 19 MJ ha−1], laser pyrolysis [15 to 249 MJ ha−1], hoeing [17 MJ ha−1], and herbicides [15 MJ ha−1]). Using similar energy sources, a standardized energy comparison provides an opportunity for estimation of weed control costs, suggesting site-specific weed management is critical in the economically realistic implementation of alternative technologies.

Development of High Levels of Metribuzin Tolerance in Lentil

Lentil (Lens culinarisMedik.) is an important and expanding crop in southern Australia and a significant crop in western Canada. Currently, production in both countries is limited by an inability to effectively control weeds, due in part to a lack of registered safe and effective herbicides. Metribuzin is a broad-spectrum herbicide providing an alternative weed control option to the imidazolinones, but it has low crop safety in lentil. Two methods, germplasm screening using a hydroponic sand assay and field screening of a large mutated population of the Australian cultivar ‘PBA Flash’ were initially used to identify lines with putative metribuzin tolerance over current cultivars. Dose–response experiments showed the germplasm line SP1333 had GR50(the rate required to reduce dry weight 50%) values up to four times higher than PBA Flash. However, the mutation selections M043 and M009 had GR50values more than 25 times higher than PBA Flash. A field study in Canada, under conditions of induced shade and no shade 72 h before POST application of metribuzin, confirmed the intermediate level of tolerance in SP1333 and the high level in the two mutant lines compared with 20 Canadian and Australian genotypes. This relative increase in metribuzin tolerance of the two mutant lines over the parent cultivar is higher than all previous reports in a range of crop species. The development of large mutant populations combined with large M2field screens was a successful method for developing high levels of metribuzin tolerance in lentil. The estimated mutation rate of the mutant lines was 9.4×10−8. All three lines are currently being used as parents in lentil breeding programs.