Sorghum halepense (L.) Pers. is ranked among the worst and extensively disseminated weed species. It is emerging as a potential menace for agroecosystems in 53 different countries across the world. This weed is adapted to warmer regions and is native to Mediterranean areas of Africa, Asia, and Europe. In the mid-1900s, cultivation of this weed species as a potential forage crop resulted in its escape from crop fields and invasion of agricultural and natural areas, but in some European countries, it has been introduced deliberately (e.g., as contamination of seeds and soil). S. halepense interferes with economically important agronomic and horticultural crops and cause 57-88% yield losses. Herbicide tolerance, diverse propagation mechanisms, rapid development, and strong competitiveness are key attributes in its invasion. Conventional management approaches are limited in their scope to control this weed due to its rapid vegetative growth and increasing herbicidal tolerance. Integration of chemical methods with cultural or mechanical approaches is important for restricting its future spread to non-infested areas. This review provides insights into the invasion mechanisms of S. halepense, which will help in its
Avena fatua and Avena ludoviciana are closely related grass weed species infesting a large number of crops around the world. These species are widely distributed in diverse agro-ecosystems from temperate to sub-tropical regions due to their unique seed traits, successful germination ecology, high competitive ability, and allelopathic potential. A. fatua is more widespread, adaptable, and problematic than A. ludoviciana. Both these species infest major winter and spring crops, including wheat, oat, barley, canola, maize, alfalfa, and sunflower, causing up to 70% yield losses depending on crop species and weed density. Chemical control has been challenged by large-scale herbicide resistance evolution in these weed species. A. fatua is the most widespread herbicide-resistant weed in the world, infesting about 5 million hectares in 13 countries. The use of alternative herbicides with different modes of action has proved effective. Several cultural practices, including diverse crop rotations, cover crops, improved crop competition (using competitive cultivars, high seed rates, narrow row spacing, altered crop geometry), and allelopathic suppression, have shown promise for controlling A. fatua and A. ludoviciana. The integrated use of these cultural methods can reduce the herbicide dose required, and lower dependency on herbicides to control these grasses. Moreover, integrated management may successfully control herbicide-resistant populations of these weed species. The use of integrated approaches based on the knowledge of biology and ecology of A. fatua and A. ludoviciana may help to manage them sustainably in the future.
Three C 4 grass (Setaria incrassata, Astrebla squarrosa and Bothriochloa decipiens) and one C 3 legume (Clitoria ternatea) suppressive fodder species, were re-evaluated against the growth of the C 3 Parthenium hysterophorus under an ambient (390 lmol mol À1 ) and an elevated atmospheric CO 2 concentration (550 lmol mol À1 ). Under the elevated atmospheric CO 2 , shoot dry biomass and suppression index (SI) value of the C 4 S. incrassata were both reduced by 32% and 0.7 respectively, while those for A. squarrosa were reduced by 23% and 0.3. In contrast and under the same elevated atmospheric CO 2 concentration, the shoot dry biomass and SI of the C 4 B. decipiens were increased by 8% and 0.1 respectively, while those for the C 3 C. ternatea were increased by 38% and 0.8. Our results suggest that C 3 fodder plants along with certain C 4 species could be utilised for the effective management of P. hysterophorus under the future elevated atmospheric CO 2 conditions. However, this system needs more fodder species to be investigated. Our results suggest that rising CO 2 per se may alter the efficacy of suppressive fodder management of an invasive C 3 species, P. hysterophorus.
In Australia, soybean (Glycine max (L.) Merr.) is planted at a low density in wide rows, and weeds substantially reduce yield because of opportunities for their growth in the wide rows. Field studies were conducted over 2 years at the University of Queensland farm, Gatton, Australia, to assess the effect of row spacing and seeding rate on the competitiveness of soybeans with a model weed, Rhodes grass (Chloris gayana Kunth). The experiment was conducted in a split-split plot design, replicated three times. Main plots comprised two seeding rates (40 and 80 kg ha–1), subplots two row spacings (25 and 75 cm), and sub-subplots four Rhodes grass infestation periods (weedy from planting to maturity, weedy from 3 weeks after planting (WAP) to maturity, weedy from 6 WAP to maturity, and weed-free from planting to maturity). The results showed that seed rate did not influence Rhodes grass biomass or soybean yield. Soybean yield was greater and Rhodes grass biomass was less in the 25-cm rows than the 75-cm rows. For the 25-cm rows, Rhodes grass biomass in the plots infested beyond 3 WAP was 81–89% less than in the season-long weedy plots, whereas for the wider row crop, this reduction was only 60–75%. For the 25-cm rows, soybean yield in the plots infested with Rhodes grass beyond 3 WAP was 30–36% less than under weed-free condition. However, for the 75-cm rows, this reduction was 56–65%. The results suggest that planting soybean in wider rows caused greater reduction in yield and required an earlier weed management program than planting in narrow rows. The study also suggested that narrowing row spacing was more important than increasing seeding rates for improving weed control and soybean grain yield.
Parthenium weed (Parthenium hysterophorus L.) is an alien invasive species reducing pasture productivity and livestock production in Australia and other countries around the world. Three C 4 pasture grasses (Setaria incrassata, Astrebla squarrosa and Bothriochloa decipiens) and one C 3 pasture legume species (Clitoria ternatea), all previously known to be suppressive of the growth of parthenium weed under ambient CO 2 (390 µmolmol-1), were re-tested under an elevated atmospheric CO 2 (550 µmolmol-1) level in a controlled environment growth chamber. When grown alone and under elevated atmospheric CO 2 level, the root dry biomass of S. incrassata and A. squarrosa did not get affected significantly, whereas that of B. decipiens, C. ternatea and P. hysterophorus significantly increased by 10, 34 and 26 %, respectively. When S. incrassata and A. squarrosa were grown together with parthenium weed under the same conditions, their root dry biomass reduced by 20 and 16 %, while that of B. decipiens and C. ternatea was increased by 7 and 28 %, respectively. The root to shoot ratio of S. incrassata and A. squarrosa decreased significantly by 24 and 16 %, while that of B. decipiens, C. ternatea and parthenium weed increased by 6, 17 and 12 %, respectively, under the same conditions. These results have important implications for the management of parthenium weed in future climate scenarios involving elevated atmospheric CO 2 levels. Our results suggest that some pasture species with the potential to suppress the growth of parthenium weed under the present climate will remain an important tool in managing pastures invaded by parthenium weed in the future.
Certified citrus seed is one of vital component on the program of good agricultural practices for the development of healthy citrus plantation. Certified seed guarantee the free systemic disease and optimum vigor planting material, thus put an impact on maximum physiological response to the agriculture inputs that being applied. Production of healthy planting material is initially started from the acquisition of free diseases protocol of seeds from breeder seeds. However, there are still many issues regarding bud-stick in Indonesia which cause the spread of systemic diseases, one of which is CVPD/Huanglongbing (HLB). Therefore, this article presents a descriptive review of the important role of healthy citrus planting materials production that meets the requirements, so that it can become a reference for the citrus nurseries. There are several factors (limited availability of citrus planting materials, technology components to produce healthy seedlings that are not fully applied, as well as the partial application of certified citrus planting materials) that could inhibit the use of technology by the citrus nurseries. A number of recommendations from literatures to overcome these problems are the use of effective dissemination and extension methods, also the provision of understanding and supervision that is carried out on an ongoing basis.
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