Journal of Research in Weed Science
Volume:4 Issue: 3, Sep 2021

Weeds are among the main phytosanitary problems and are responsible for numerous losses in agriculture. Integrated management has become increasingly important in weed control. Therefore, the present study aimed to investigate the allelopathic effect of 24 plants on morning glory (Ipomoea purpurea L.). The tests were performed in a completely randomized design, both in in vitro and in vivo experiments. The in vitro germination data were used to calculate the time and germination index, and in the in vivo experiment, the length and fresh weight of the aerial part and root of the seedlings were evaluated, with subsequent comparison of averages by ANOVA. The plant extracts used exerted allelopathy, delaying (negative) and advancing (positive) the germination of this species. The extracts of banana, black plum, carqueja, Mexican sunflower, rosemary, guaco, lavender, lemongrass and garden mint resulted in high germination delays of up to +5 days. Rosemary, garden mint, Mexican sunflower and guaco extracts also reduced the germination rate by up to -10.5%. None of the tested extracts reduced the length of the aerial part of morning glory. In all treatments, shorter root length was observed. The extracts of lemongrass, rosemary and guaco reduced the dry weight of the aerial part, and in all treatments a lower fresh weight of roots was observed, except for the treatment with guaco. It can be concluded that the germination or growth of some problematic weeds such as I. purpurea may be affected by allelochemical extracts from different plants such as bananas, black plum, boldo, Mexican sunflower, rosemary, guaco, lavender, lemongrass, and garden mint.

The search for cultivation practices that provide increased soybean yield has been recurrent. From this context, the objective of this study was to evaluate the agronomic performance of soybeans with the application of phytosanitary products, as well as the effect of 2,4-D amine subdoses on this crop. Two field experiments were conducted in a randomized block design (RCBD), in a factorial arrangement, with four replications. In the first experiment, one factor corresponded to the soybean post-emergence application of propiconazole, 2,4-D amine, lactofen, imazethapyr and Grainset®, while the other factor corresponded to the single or sequential application of these products. For the second experiment, one factor corresponded to the application of 2,4-D amine at two phenological stages of soybeans: V4 or V8 (4 and 8 fully expanded trifoliate leaves, respectively), while in the other factor the subdoses of this herbicide were evaluated: 4.03, 8.06, 12.09, 16.12, 20, 15 and 24.18 g a.i. ha-1. In both experiments, the additional treatment consisted of the control without application. 2,4-D amine applied in subdoses has potential for use in soybeans. The application of 2,4-D amine subdoses promotes changes in morphological parameters of this crop. Increase in the yield of this crop can be obtained with the application of 2,4-D amine in subdoses varying between 16.12 and 20.15 g a.i. ha-1.

Orobanche species, commonly known as broomrape, are root holo-parasite of the family Orobanchaceae.  In Nepal two species, Orobanche aegyptiaca and O. cernua are causing threat to wide range of important vegetables and crops of family Brassicaceae and Solanaceae. To evaluate non-host plants as potential trap crops, different crop plants were tested in two Orobanche infested tomato fields of Lalbandi, Sarlahi, South-Eastern part of Nepal in 2018 -19. Orobanche seed density in soil samples collected from plots before planting and after harvest of each crop species were recorded and compared for the seed bank. On the basis of Orobanche seed bank reduction in both the fields, the investigated crop species like Capsicum frutescens, Cicer arietinum, Lens culinaris and Vicia faba were classified as highly potential trap crops and reduced seed bank from 52 to 70%. Crops like Cuminum cyminum, Daucus carota, Foeniculum vulgare, Phaseolus vulgaris, Sessamum orientale and Trigonella foenum-graecum were classified as moderately potential trap crops and reduced Orobanche seed bank from 41 to 52 %. The other tested crops like Allium cepa, Allium sativum, Coriandrum sativum, Glycine max, Hordeum vulgare, Pisum sativum, Solanum tuberosum, Raphanus sativus are classified as non- potential trap crops. Among all the tested crops Capsicum frutescens, Cicer arietinum, Lens culinaris and Vicia faba were identified as the potential trap crop to reduce Orobanche seed bank in infested tomato fields.

Striga hermonthica (Del.) Benth is also known as witchweed, is a highly noxious parasite of cereal in Sub- Saharan Africa leading to enormous economic losses of above 7 billion US$ yearly. Some of the suggested control methods have been ineffective, therefore, the weed has continued to increase its host range and area under infestation. The objective of this study was to evaluate Alternaria brassicicola isolates against Striga hermonthica seeds' emergence on maize. A greenhouse experiment was performed at KALRO/CYMMTRY Kibos station, Kisumu, Kenya during April to August, 2019. The experiment included local maize landrace known as “Rachar”, Striga hermonthica seeds Kibos ecotype and four strains of Alternaria brassicicola. The treatments were; Soils (Treated) + two maize seed + S. hermonthica seeds + each isolate (LM017, LM013, LM019a and NY021) independently and soils (Treated) + three maize seeds + S. hermonthica seeds only (Control). A. brassicicola isolates LM019a, LM013 and LM017 inhibited Striga seeds emergence by 78.9%, 57.3% and 29.1% respectively. However, isolate NY021 enhanced Striga seeds emergence by 30.4% over the control. This study, established that some strains of A. brassicicola can inhibit the emergence of Striga weed. Therefore, the fungus could be used as a possible bio-agent in the production of mycoherbicide against Striga weed.

The objective of this work was to evaluate the selectivity of herbicides applied in post-emergence of mulato II grass, in different stages of forage development, in areas with in-row and broadcast seeding. In order to understand the influence of the time of application of the herbicides on the selectivity of mulato II grass, two experiments were designed: the first with application of treatments 15 days after emergence (DAE) and the second to 45 DAE. The experiments were installed in two areas, one with broadcast seeding and the other with in-row seeding. For all experiments, 5 herbicides were applied in two doses, in the double control system: [aminopyralide+fluroxipyr] 1.0 and 1.5 L ha-1, [2,4D+picloran] 1.5 and 3.0 L ha-1, [aminopyralide+2,4-D] 1.0 and 2.0 L ha-1, [aminopyralide+metsulfuron] 0.075 and 0.150 kg ha-1 and [aminocyclopyrachlor+metsulfuron] 0.075 and 0.150 kg ha-1. For applications performed at 15 DAE only [aminocyclopyrachlor+metsulfuron] was not selective in both tested sowing systems. For applications performed at 45 DAE in-row seeding, the treatments [aminocyclopyrachlor+metsulfuron] in the two tested doses and [aminopyralide+metsulfuron] in the highest dose caused injuries to mulato II grass. For applications carried out at 45 DAE in a field sown by broadcast seeding, only [aminocyclopyrachlor+metsulfuron] caused injury to the culture. At all times of application, the herbicides [aminopyralide+fluroxipyr], [2,4-D+picloram] and [aminopyralide+2,4-D] in the two doses tested, proved to be selective for the fields sown by broadcast and in-row. In the second productive cycle, there was no negative effect of treatments in the four experiments.

Weeds have developed skills to compete with cultivated plants, making the former a major problem in agricultural areas. Morning glory (Ipomoea purpurea) is an important invasive plant that, in addition to competing for nutrients, makes harvesting difficult and presents seed dormancy mechanisms in soil banks. Some plants in this group have already been reported to be tolerant or resistant to herbicides. Therefore, it is necessary to seek alternative methods of management for these plants. The present study aimed to evaluate the influence of four extracts of lemon-scented gum (Corymbia citriodora) on the germination of morning glory seeds. Extracts were obtained from infusion, crushing, boiling and the alcoholic extract of the leaves. The experiment was carried out in gerboxes, containing three sheets of paper, with four repetitions of fifty seeds in each and in a completely randomized design. The germinated seeds were examined daily, until they all emitted the radicle. At the end of the experiment, it was understood that the alcoholic extract was the one that stood out the most, as it led to the delay and reduction in the germination rate of morning glory seeds by up to 2.22 days and 38.5% fewer seeds germinated, respectively. Extracts obtained by infusion and aqueous extracts also delayed germination with a significant difference. None of the extracts advanced germination. The results are promising in the sense that the allelopathy exerted by lemon-scented gum extracts can help to manage banks of morning glory seeds in the soil, delaying and reducing their germination.

The field survey focused on potential sorghum-producing east and west Hararghe zones in six districts comprising 18 villages in the 2019 cropping season. Overall, 720 growers were nominated for considering the socio-economic impact. The representative growers were purposively selected. Data collected were Striga counts per m2 and per plant, time of Striga introduction, awareness and impression of farmers, prevalence, management used, severity, and collective actions to manage Striga. Both genders were included. Data were collected from interviews and analyzed. Statistical software (SPSS) summarizes the information. Results showed two Striga species, Striga hermonthica and Striga asiatica were observed and recorded. Striga hermonthica is more distributed than Striga asiatica in all the study locations and its occurrence diverse between locations. The maximum levels of Striga occurrence was perceived at Kile-besidimo (92%), Edobaso (85%), Kufakas (82%), Kotora (80%), Homacho Riana(78%), Bal’ina arba (74%), Dire gudina (72%), Bishan babile,(66%), Qufa (65%), Oda Anesso (48%), Ijakechu (45%), Umer kulle (40%), Homacho Eba (38%) and Tofik (35%). In contradict less number of Striga prevalence was perceived at Bareda (29%), Haro Adii (27%), Jiru gemachu (25%), and Homacho dayo (23%) striga per m2 in assessed fields. The striga count per plant was also recorded from each site. Sorghum yield loss due to Striga across surveyed villages was estimated to range between 0% and 80%. The management practices focused on improving the shortages suggested for controlling Striga in the districts.