The potential use of oil palm frond mulch treated with imazethapyr for weed control in Malaysian coconut plantation

Introduction of new weed management strategy for coconut plantation in Malaysia is essential since the current weed control methods are less effective and highly herbicide dependent, thus leading to development of herbicide resistance in weeds as well as environmental and human health concerns. Thus, the present study aimed to evaluate the phytotoxic effects of oil palm frond mulch treated with imazethapyr at a reduced rate on weed emergence and growth. The results of glasshouse experiments have shown that imazethapyr at 12 g a.i. ha-1 in combination with oil palm residues of leaflet (OPL), rachis (OPR) or frond (OPF) at rates of 1.4-1.8 t ha-1 inhibited Eleusine indica emergence and growth by 90-100%, implying that imazethapyr is compatible with oil palm residue mulches. In the field experiment, hand weeding followed by OPF at 3.4 t ha-1 treated with imazethapyr at 24 g a.i. ha-1 have demonstrated excellent control of Mikania micrantha, Asystasia gangetica, Phyllanthus amarus, Panicum sp. and Echinochloa colona by reducing their total dry weight up to 95% at three months after treatment. The present results suggested that the integration of chemical, physical and mechanical methods can provide effective weed control in the coconut plantation for months

The potential use of oil palm frond mulch treated with imazethapyr for weed control in Malaysian coconut plantation

Introduction of new weed management strategy for coconut plantation in Malaysia is essential since the current weed control methods are less effective and highly herbicide dependent, thus leading to development of herbicide resistance in weeds as well as environmental and human health concerns. Thus, the present study aimed to evaluate the phytotoxic effects of oil palm frond mulch treated with imazethapyr at a reduced rate on weed emergence and growth. The results of glasshouse experiments have shown that imazethapyr at 12 g a.i. ha-1 in combination with oil palm residues of leaflet (OPL), rachis (OPR) or frond (OPF) at rates of 1.4-1.8 t ha-1 inhibited Eleusine indica emergence and growth by 90-100%, implying that imazethapyr is compatible with oil palm residue mulches. In the field experiment, hand weeding followed by OPF at 3.4 t ha-1 treated with imazethapyr at 24 g a.i. ha-1 have demonstrated excellent control of Mikania micrantha, Asystasia gangetica, Phyllanthus amarus, Panicum sp. and Echinochloa colona by reducing their total dry weight up to 95% at three months after treatment. The present results suggested that the integration of chemical, physical and mechanical methods can provide effective weed control in the coconut plantation for months

Potential of oil palm frond residues in combination with S-metolachlor for the inhibition of selected herbicide-resistant biotypes of goosegrass emergence and seedling growth

Heavy reliance on herbicides for goosegrass (Eleusine indica Gaertn.) control has led to the development of paraquat, glufosinate, fluazifop and/or glyphosate resistance in goosegrass. This study aimed to evaluate the efficacy of preemergence herbicide, S-metolachlor-treated oil palm frond powder on inhibition of resistant biotypes of goosegrass under glasshouse and field conditions. The oil palm frond (OPF) powder was treated with S-metolachlor at its suboptimal rate and applied as mulch. The herbicide-resistant goosegrass plants were found to be more inhibited when treated with S-metolachlor-treated OPF mulch at the rate of 12 g ai ha–1 S-metolachlor + 1.5 t ha–1 OPF (with the exception of the glufosinate-resistant googegrass biotype in the sandy loam soil) compared to the growth of the resistant biotypes in silty loam soil under glasshouse conditions. Field experiments in an ambarella (Spondias dulcis L.) farm further showed that OPF -treated with S-metolachlor mulch at the rate of 32.0 g ai ha–1 S-metolachlor + 4.0 t ha–1 OPF provided great suppression of glyphosate-resistant biotypes of goosegrass with more than 85% reduction of weed density and biomass, respectively. These results suggested that the residue of OPF have the potential to reduce the application rate of S-metolachor without compromising on the excellent control obtained in combating these herbicide-resistant biotypes of goosegrass

Different imazethapyr placements and rainfall amounts affect phytotoxic activity of imazethapyr in combination with oil palm frond residue mulches against common weeds in landscapes

A combination of oil palm frond (OPF) mulch and imazathapyr has been shown to provide great inhibition of weed but its phytotoxicity may be influenced by imazethapyr placement on the OPF mulch and rainfall amount. This study aimed to evaluate effects of herbicide placement and rainfall amount on the phytotoxic activity of imazethapyr in combination with OPF mulches against goosegrass, slender cyperus and coat buttons under glasshouse conditions. Imazethapyr was applied at 10.4 g a.i. ha-1 to under or above or as a pretreatment on the OPF mulch residue powder (< 2 mm) at 3.5 t ha-1. Imazethapyr placement did not influence its inhibitory effects against weed emergence. Both pretreated mulches and imazethapyr applied under the mulches had comparable inhibition of seedling growth for goosegrass and slender cyperus. However, the pretreated mulches gave better seedling growth inhibition of both bioassay species as compared to those of imazethapyr that applied above mulches. Coat button was highly inhibited regardless of any imazethapyr placements. An increase in rainfall amount from 150 to 450 mm could increase the seedling emergence of goosegrass and slender cyperus from 30 to 80% when subjected to pretreated mulches. However, different rainfall amounts had no significant effect on coat buttons seedling emergence. The pretreated mulches could reduce weed seedling growth by 75 to 80% without being affected by the rainfall amounts. The present results suggested that phytotoxic activity of imazethapyr in combination with OPF residue mulches is dependent on imazethapyr placement, rainfall amount and weed species

LIGHT-COLOR-INDUCED CHANGES IN FATTY ACID BIOSYNTHESIS IN Chlorella sp. STRAIN KS-MA2 IN EARLY STATIONARY GROWTH PHASE

Optimization of light supply remains a critical issue in microalgae biotechnology. The impacts of light color on fatty acid production and biosynthesis in microalgae are poorly understood. The aim of this study was to determine the effect of light color on growth and fatty acid content in Chlorella strain KS-MA2. Cells were cultured on F/2 medium and incubated under blue, green, red or white light. The cells’ growth, fatty acid composition and the expression levels of the ketoacyl synthase 1 (KAS-1), omega-6 desaturase (ω-6 FAD) and omega-3 desaturase (ω-3 FAD) genes were measured at the early stationary growth phase. Results of this study indicated that light color affected cell density and fatty acid profile produced by Chlorella sp. strain KS-MA2. Cells cultured under blue, red and white light had higher cell density than those cultured under green light. Palmitic acid (38.62 ± 3.29% of biomass dry weight) and linolenic acid (7.96 ± 0.88% of biomass dry weight) were highly accumulated under white light. Stearic acid was dominant under blue light (11.11 ± 0.14% of biomass dry weight), whereas oleic acid was dominant under red light (30.50 ± 0.14% of biomass dry weight). Linoleic acid was highly produced under green and blue light (28.63 ± 1.36% and 26.00 ± 0.81 % of biomass dry weight, respectively). KAS-1 and ω-6 FAD were highly expressed under blue light, whereas ω-3 FAD was highly expressed under green light. The production of particular fatty acids of interest from Chlorella could be achieved by shifting color of light used during the incubation of the cell cultures. Blue-light is the most suitable light color for producing biomass and stearic acid by Chlorellastrain KS-MA2.Â

Effects of 2,4-Di-tert-butylphenol and selected herbicides which induced lipid peroxidation on quantum yield and membrane integrity of weedy plants under dark and light conditions

2,4-Di-tert-butylphenol (2,4-DTBP) has herbicidal properties that cause lipid peroxidation on plant tissues. The present study aimed at examining the phytotoxic effects of 2,4-DTBP compared to that of selected herbicides which induced lipid peroxidation based on quantum yield (Φ) and membrane integrity of two bioassay weed species namely Oldenlandia verticillata and Leptochloa chinensis under light and dark conditions. Laboratory assays showed reduced Φ of 2,4-DTBP- and dinoterb-treated leaf discs within the first 3 h of the dark incubation period, with further decrease during the subsequent 15 h dark period and 6 h light period. Diuron drastically reduced the Φ of the bioassay species throughout the incubation period. The Φ of glufosinate-treated O. verticillata leaf discs was marginally reduced and decreased further upon light exposure; it had no effect on the Φ of L. chinensis. Fluridone, isoxaflutole, clomazone and oxyfluorfen also had negligible effect on Φ, whereas paraquat caused a rapid reduction in Φ upon light exposure for both bioassay species. 2,4-DTBP, paraquat and dinoterb induced electrolyte leakage during the dark incubation period; this was further increased in the presence of light for O. verticillata and L. chinensis. For both bioassay species, glufosinate caused a marked amount of electrolyte leakage, whereas diuron, fluridone, isoxaflutole, clomazone and oxyfluorfen had negligible effect on ion leakage. These results suggested that 2,4-DTBP has herbicidal activity comparable to that of dinoterb without dependence on light

Seed germination characteristics as affected by interaction of moisture stress and temperature in sethoxydim-resistant biotype of goosegrass (Eleusine indica (L.) Gaertn.) from Malaysia

Understanding temperature and moisture stress that influence sethoxydim-resistant (R) goosegrass (Eleusine indica) germination is crucial for effective weed control, but little research has been done on the impact of these environmental factors on germination of the R goosegrass biotype. This research aims to confirm sethoxydim resistance in goosegrass and to examine interaction effects of different temperatures and water potentials on germination of the R goosegrass biotype. Dose–response tests showed that the R goosegrass biotype exhibited high resistance level to sethoxydim with 17-fold. In laboratory bioassays, the R goosegrass biotype germinated by 88-100% at 35 °C with water potentials ranging from 0 to -0.80 MPa, but no seed germination occurred at 10 °C and 40 °C under all water potential treatments. With rising water potentials from 0 to -0.80 MPa, seed germination at 15 to 30 °C decreased markedly. The time it took to achieve 50% seed germination (T50) increased drastically when decreasing temperature from 35 to 15 °C. The T50 at 20 to 30 °C also increased as the water potential increased from -0.20 to -0.80 MPa. At 35 °C, however, the water potential level had no impact on T50, implying that the R goosegrass biotype seed is water stress tolerant at 35 °C. The base temperature and base water potentials estimated were 10.6 °C and -1.28 MPa, respectively. These findings can help in determining the optimal time to apply pre-emergent and early post-emergent controls when a large proportion of R goosegrass biotype have already germinated or emerged

Inhibition of pre-emergent herbicide on weedy rice under flooded and saturated soil conditions in rice

Weedy rice poses a formidable challenge in rice cultivation due to its genetic similarity to cultivated rice, making selective herbicides less effective in controlling it without causing harm to the cultivated rice. The potential use of pre-emergent herbicides before rice sowing to inhibit emergence and growth of weedy rice seedlings in the soil remain unknown. Thus, this study aimed to evaluate the responses of weedy rice towards selected pre-emergent herbicides under different soil water conditions and to identify the optimal timing for rice seed sowing following the application of preemergent herbicide to the soil under glasshouse conditions. The results showed that oxadiazon and pretilachlor at 500 g ai ha-1 exhibited higher reductions in weedy rice density and dry weight compared to those given by pendimethalin. Under saturated soil conditions, oxadiazon demonstrated 79 and 80% reductions whereas pretilachlor gave 50 and 59% reductions in weedy rice density and dry weight, respectively. By contrast, under flooded soil conditions both oxadiazon and pretilachlor resulted in complete inhibition of weedy rice. The study showed that delaying rice seed sowing for at least six days after application of pretilachlor or oxadiazon effectively minimized phytotoxic effects on rice. These findings provide valuable insights on the impact of soil water conditions when applying pretilachlor and oxadiazon for effective weedy rice control in direct-seeded rice systems

Biowastes as sustainable source for nanoparticle synthesis and their pesticide properties: A review

Over the last decade, nanoparticles derived from biowaste have been widely investigated as one of the greener approaches to preparing pesticides as its application offer the usage of environmentally friendly and earth-abundance resources, cost effectiveness due to low energy consumption, biocompatibility, as well as flexibility in preparation of biomolecules as a medium or bio-reducing agents for pesticide production. Integrating biowastes in nanomaterials-based pesticide preparation marks a new age of innovation in nanomaterial technology to overcome the contemporary problems currently plaguing the agriculture sector with the possibility of mitigating environmental pollution. In this review, the synthesis of nanomaterials derived from biowastes as agrochemicals and their advantages are presented. It is expected that this review would serve as a guide for selected industry and scientific communities working with nanomaterials in the form of agrochemicals to enhance crop protection. It is anticipated that the next generation agrochemicals will mark the use of ecofriendly sustainable materials to which nanomaterials-based pesticides derived from the biowastes will play a major part ensuring food security thus achieving the Zero Hunger goal in the Sustainable Development Goals

Herbicidal activity of pre and post emergent herbicide on control eleusine indica in aerobic rice system

Aerobic rice system can be an alternate way to cultivate rice in less water conditions. However, weeds are a major constrain in aerobic rice field which decline its success. Weeds are being controlled by herbicides in aerobic rice but not all herbicides are effective in controlling various types of weeds. In this study, two pre-emergent (pretilachor and pendimethalin) and two post-emergent (cyhalofop-butyl and bispyribac-sodium) herbicides were evaluated for effective control of the bioassay species, Eleusine indica. It was found that pendimethalin at a higher application rate of 1.0 kg ai ha⁻¹ strongly inhibit the emergence and shoot growth of E. indica by >75% with negligible effect on the rice growth with stimulation on the leaf greenness. Conversely, pretilachor, cyhalofop-butyl and bispyribac-sodium gave moderate inhibition (55-60% inhibition) on weed emergence and shoot growth at higher application rates of 0.44, 0.1 and 0.035 kg ai ha⁻¹, respectively. Significant inhibitory effects on rice root growth were noticed at highest application rates of pretilachor, cyhalofop-butyl and bispyribac-sodium (40-50% inhibition) across the growth stage of rice seedlings. Great reduction in shoot height, shoot fresh weight, and greenness of rice plant also was evident at 0 DAS across herbicides rates. However, with increasing growth stages, the rice plant became less susceptible to the applied treatments. The finding suggested that pendimethalin at 1.0 kg ai ha⁻¹ was the most suitable application rate for inhibiting E. indica without injuring the rice seedlings