Incidence of
Abstract
This chapter highlights a survey of vegetable-producing areas to determine the occurrence, distribution and importance of Parthenium hysterophorus in Trinidad. The weed can significantly reduce crop yields and quality due to its aggressive growth habit, competitiveness and allelopathic interference. Due to its invasive capacity and allelopathic properties, Parthenium hysterophorus has the potential to disrupt the natural ecosystem and threaten the biodiversity. It is a difficult weed to manage, and a wide variety of methods, starting with prevention and containment, is necessary to reduce the incidence and spread of this weed. An integrated approach using cultural, physical, chemical and biological techniques is necessary to be successful. Focus is made on specific herbicides currently being used to manage this weed in vegetables. Despite the negative impact of this weed on the biodiversity, this chapter also explores the potential of the beneficial properties of Parthenium hysterophorous as a mechanism of management.
Keywords
- Vegetable production
- Parthenium hysterophorus
- herbicide use
- integrated approach
1. Introduction
The weed displays characteristics of profuse seeding ability, photo and thermal insensitivity, non-dormancy, high germination and growth rate and low photorespiratory rate, enormous seed bank, rapid spread and colonization and extreme adaptability in a range of habitats [4] and has spread within the last two decades to all Commonwealth Caribbean countries [2]. It is among the top ten worst weeds of the world and has been listed in the global invasive species [5]. It is now considered one of the worst weeds because of its invasiveness, potential for rapid spread, economic and environmental impacts, its high adaptability to almost any type of environmental conditions and high losses in crop yield and its direct contact with plant or plant parts [5]. As a C3 weed,
The weed is predominant in the major vegetable-growing areas of Trinidad and has been shown to be effectively controlled by dinitroanilines, e.g. butralin (4- (1, 1-Dimethylethyl)-N-(1-methylpropyl)-2, 6-dinitro-benzenamine) in eggplant (
In the major vegetable production areas of Trinidad and Tobago, the weed was identified as early as 1956. However, it was not of any significance until the 1960s when the use of paraquat (1, 1’-dimethyl-4-4’-bipyridinium ion) and diquat (6, 7-dihydrodipyrido (1, 2- a: 2, 1-c) pyrazinedium ion) became widespread.
2. Biology and ecology
The genus
Flower heads are creamy white, about 4 mm across, arising from the leaf fork and forming a capitula. Flowering usually occurs one month after germination with each flower containing five seeds, which are small (2 mm), wedge-shaped, brown to black in colour and bear two thin white scales. Pollen grains are produced in clusters and are pollinated by wind. A single plant can produce around 15,000 seeds or even up to 100,000 seeds. Seeds are mainly dispersed through water currents, animals and the movement of vehicles, machinery, livestock and stock feed, and to a lesser extent by wind. Seeds can remain viable for long periods and are capable of germinating as long as moisture is available [10].
The ideal conditions for growth are high moisture content, high humidity and a temperature of around 25°C. However, it can grow under a wide range of environmental conditions with soil moisture being the only limiting factor for germination and growth. It can grow under a wide range of soil pH (2.5 to 10.0) [15]. Additionally, it grows well in areas where annual rainfall is higher than 500 mm. In Trinidad, this weed grows on abandoned lands, along highways and roadsides, in drains, gardens, plantations and vegetable crop plots. It colonizes disturbed sites very aggressively, possesses allelopathic properties and has no documented natural enemies like insects or diseases.
3. Phytochemical analysis of P. hysterophorus
Phytochemical analysis of
4. Incidence of P. hysterophorus in vegetable crops
Weed surveys in the main vegetable production areas were conducted in both dry and wet season using seven quantitative measures [21–24]
The IVI allowed for comparisons between seasons and years and among crops. However, it does not necessarily represent losses in crop production caused by the weed as crops vary in their competitive ability. The level of losses due to the presence of the weed in various vegetable crops was assessed and the economic importance of the weed determined. Irrespective of the visual estimate (VE) of
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Cauliflower1 | 50 | 90 | 417.1 |
Cauliflower2 | 10 | 70 | 262.5 |
Tomato3 | 25 | 100 | 274.1 |
Tomato4 | 50 | 90 | 430.0 |
Tomato5 | 75 | 100 | 562.5 |
Cabbage6 | 40 | 100 | 379.9 |
Cabbage7 | 50 | 100 | 974.7 |
Patchoi | 40 | 100 | 382.2 |
Sweet Pepper | 25 | 50 | 265.4 |
Hot Pepper | 25 | 50 | 273.5 |
Spinach | 30 | 90 | 358.0 |
Okra | 100 | 100 | 880.0 |
Fallow Field | 100 | 100 | 910.0 |
Mean | 48 | 87.5 | 489.9 |
S.E. (+/−) | 7.85 | 5.2 | 72.17 |
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Squash | 90 | 100 | 674.9 |
Tomatoes | 75 | 100 | 836.4 |
Cabbage | 10 | 50 | 360.0 |
Spinach | 25 | 100 | 365.6 |
Bodie Bean | 10 | 100 | 207.8 |
Cauliflower | 10 | 50 | 215.8 |
Mean | 36 | 83 | 443.4 |
S.E. (+/−) | 2.45 | 2.07 | 6.5 |
There was no significant difference in the mean Importance Value Index (IVI) of
In the wet season (Table 1), there were variations within the same crops due to different levels of weed management, e.g. cauliflower with two hand weedings and no herbicides had a higher IVI (417.1) than a crop of similar age with treatments of one hand weeding and pre-emergence herbicide (262.5); similar trends for tomato and cabbage were observed at the same growth stage, but under different levels of weed management. The application of pre-emergence herbicides reduced the IVI for
Crops with shrub-type architecture, e.g. hot and sweet peppers, had no competitive plant height advantage over leafy vegetable crops under similar levels of weed management. Both types of crops had an IVI below the mean value recorded for the wet season.
In both the wet and dry seasons, the IVI of leafy vegetable crops was lower than the mean IVI. This is due mainly to the close spacing used at planting and the intensity and thoroughness of the hand-weeding operations practised by the farmers.
A field prepared for planting, but subsequently abandoned, showed an IVI of 910.0 (wet season) and gave an indication of the weed’s dominance. The high IVI (880.0) for okra in the wet season was due to the wide spacing as well as the absence of any weed management operations. The
In the fields surveyed, adequate irrigation facilities were available to all farmers during the dry season. Adequate water supply was the main factor determining the lack of shift in
4.1. Incidence of P. hysterophorus during different seasons
There was no significant difference between visual estimates (VE) for
There were no changes in abundance (Ap) between seasons.
Wet season density (Dp) in Aranguez (5.24) did not differ significantly from that of other vegetable-growing areas (5.6). The Dp for
The IVI indicated that there were no shifts in the
5. Crop loss assessment
Farmers found that the presence of the weed within or around the field can result in a reduction of the market yield of cabbage and cauliflower. It was observed that damage to marketable curds of cauliflower caused by the larvae of
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VE | 47.69 | 36.66 |
Ap | 5.77 | 5.25 |
Dp | 5.24 | 3.99 |
Fp | 87.69 | 83.3 |
RDi | 58.88 | 56.8 |
RDp | 415.61 | 340.0 |
F4RFp | 66.31 | 61.36 |
IVI | 489.99 | 443.43 |
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VE | 43.87 | 1.78 | 35.58 | 1.23 |
Ap | 7.46 | 1.11 | 15.50 | 1.67 |
Dp | 5.6 | 0.66 | 15.04 | 1.68 |
Fp | 65.32 | 14.96 | 88.4 | 1.15 |
RDi | 53.02 | 9.04 | 44.4 | 1.81 |
RDp | 412.0 | 37.46 | 284.73 | 4.51 |
F4RFp | 58.43 | 5.9 | 59.48 | 1.03 |
IVI | 491.19 | 37.92 | 378.5 | 4.76 |
6. Competitive effect of Parthenium on selected crops
A high density of
Failure to plant lettuce and celery on
No significant reduction in yield was reported by farmers for vining crops, e.g. pumpkin, squash, or cucumber and staked bodibean which withstood the weed competition. However, early hand weeding was essential for bush-type cowpea bodi to prevent yield reductions by 25 to 50%.
Studies conducted on soil amended with unburnt and burnt residues of
The reduction in crop yield and quality is probably due to the competitive ability and allelopathic potential of
7. Weed economic assessment
An economic analysis was performed on
Over time, the DN option had the most rapid increase in population, followed by the EB and then by CM. The IMA displayed the slowest increase in the invasive population during that time.
Quantifying the benefits for each management option proposed for the control of
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Do Nothing (DN) | ⋅ no weed control ⋅ allow weed to grow and spread ⋅ population density (6% of the carrying capacity) |
Current Management (CM) | ⋅ maintain the ⋅ chemical control of the weeds (paraquat and glyphosate post-emergence) |
Integrated Management Approach (IMA) | ⋅ chemical control ⋅ manual ⋅ mechanical control methods (hoe and plough, cutting and hand weeding or uprooting of weeds) |
Exploitation of Benefits (EB) | ⋅ determine benefits – medicinal value, enhancement of crop productivity ⋅ bioremediation (heavy metals) ⋅ dyes and handicraft production |
The costs associated were different for each management option and included labour and capital costs (tool, safety gear and machinery). Herbicide cost included the purchase of chemicals, based on market prices, and machine service cost included the servicing of the whacker on a per-service basis (Table 6).
The Net Present Value (NPV) represents the overall net benefit of a project to society. The Benefit Cost Ratio (BCR) is the ratio of the NPV of benefits associated with an activity, relative to the NPV of the costs of the same activity. The discounted future costs and benefits to present value used a discount rate of 5% and the project length is assumed to be 10 years. Cost-effective (CE) analysis is an approach often used to rank intervention options when monetary benefits cannot be derived from key categories in a given project. CE is the NPV of the monetized costs of the intervention divided by the effectiveness of the project option measured in physical units. The smaller the CE ratio, the greater is the cost-effectiveness of an intervention.
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Agricultural Crops | $/kg | 10.00 | 335 | 335 | 335 | 335 |
Research Crops | $/kg | 25 | 8,087 | 8,087 | 8,087 | 8,087 | |
Human Health | $/report | 200 | 24 | 24 | 24 | 24 | |
Biodiversity | $/m3 | 50 | 5,280 | 5,280 | 5,280 | 5,280 | |
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Labour | $/day | 200 | 0 | 36 | 72 | 270 |
Initial Capital Cost | $/unit | 1 | 0 | 1,775 | 8,670 | 9,000 | |
Herbicides | $/litre | 20 | 0 | 16 | 16 | 0 | |
Machine Service | $/service | 200 | 0 | 0 | 3 | 0 | |
Research | $/hour | 30 | 0 | 0 | 0 | 600 |
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Do Nothing | $0 | 3 | 1.0 | 3 | 0 | - |
Current Management | $230,822 | 2 | 5.7 | 1 | −1,218 | 1 |
Integrated Management Approach | $390,354 | 1 | 4.9 | 2 | −1,668 | 2 |
Exploitation of Benefits | −$222,021 | 4 | 0.5 | 4 | −24,079 | 3 |
The cost–benefit analysis for the four different management options disclosed that the CM option yielded the greatest benefit for each dollar of costs and thus was most efficient on funds (Figure 3). The CM option also ranked first in cost-effectiveness being the option with the least cost per physical unit of benefit (Table 6 and 7). The ‘Integrated Management Approach’ (IMA) ranked first in NPV. Therefore, this option yielded the most benefit to society in terms of managing the spread of
8. Management of Parthenium hysterophorus
Because of its negative impact on the natural and agroecosystem, it is necessary to manage
8.1. Prevention and containment
The best methods of weed management is prevention and containment.
Difficulties in the preventive method could be further exacerbated through the easy spread of seeds through vehicles, machinery, the trading and transport of goods, animals grazing on infested fields and the transportation of sand, soil and compost from infested areas to uninfested areas. These are potential risks for further spread and hence should be controlled through an adoption of quarantine measures involving the adoption of inspection and wash-down procedures.
8.2. Mechanical control
Manual removal of
Other mechanical treatments, such as grading, mowing, slashing and ploughing, are also considered inappropriate since they may also promote seed spread as well as rapid regeneration from lateral shoots close to the ground [28; 29]. Ploughing the weed before the plants reach the flowering stage may be effective. Although burning is not promoted as a control strategy, it has been used to control the first flush of emergent weeds at the beginning of the rains in Australia but is only considered a short-term control measure [30]. Burning has been shown to create open niches in the landscape, into which larger number of
8.3. Cultural control
This is considered one of the most cost-effective methods, but it is practical only on small farms or where it is part of an integrated weed management strategy. Farmers have used almost every conceivable practice to reduce the infestation on their holding such as hand weeding, brush cutting and even digging out the weed. In all cases, there is a rapid regrowth from both stumps or re-emergence from the existing seed banks.
Mulching using plant stubble is often used for general weed control, but this is on a limited scale. However, this has not proven to be effective in areas where the seed bank is predominantly
The use of pre-emergence herbicides (pendimethalin, oxyfluorfen or alachlor) and a post-emergence herbicide (propaquizafop) in combination with cultural practices such as hand weeding or black polythene mulch has been shown to be effective. The pre-emergent application of oxyfluorfen followed by soil covering with black polythene mulch recorded the least weed count, dry weight of weeds, higher weed control efficiency and favoured the head initiation, early yield, fresh weight and dry weight of heads and highest economic yield, which was at par with treatment with pendimethalin followed by black polythene mulch [30].
On farms where the soil seed bank was dominated by
Other cultural methods include the use of competitive cover crops (
8.4. Chemical control
It is important that
Several herbicides (Table 8) have been used by farmers for control of
Agricultural Extension Workers have reported for several years the inability of both glyphosate and gramoxone to control
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Bromoxynil | Buctril | Post-Em | 5 |
Glufosinate ammonium | Basta | Post-Em | 5 |
Oxadiazon | Ronstar | Pre-Em | 4 |
Ioxynil + 2,4-D ester | Actril D | Pre-Em | 4 |
Paraquat | Gramoxone | Post-Em | 0 |
Glyphosate | Round-up | Post-Em | 0 |
Alachlor | Pilarzo | Post-Em | 5 |
Dinitroaniline | Butralin | Post-Em | 5 |
Diphenamid | Enide | Pre-Em | 4 |
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Oxyfluorfen + Quizalofop ethyl | Pre-Em | 4 | [32] |
Atrazine + Pendimethalin | Pre-Em | 4 | [33] |
Pendimethalin fb 2,4-D sodium salt | Pre-Em | 4 | |
Metsulfuron methyl | Pre-Em | 4 | |
Oxyfluorfen | Pre-Em |
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[34] |
Glyphosate + Isoproturon | Post-Em | 5 | [35] |
Chwastox + Buctril | Post-Em | 4 | [35] |
Imazapyr 6.86 | Post-Em | 3 | |
Metsulfuron-methyl 36 g a.i. ha-1 3.93 | Pre-Em | 3 | |
Metsulfuron-methyl 4.6 g a.i. ha-1 2.59 | Post-Em | 3 | |
Atrazine 2.54 | Post-Em | 2 | |
Imazapic 240 g a.i. ha-1 2.44 | Post-Em | 22 | |
Metsulfuron-methyl 36 g a.i. ha-1 1.79 | Post-Em | 2 | |
Imazapic 1.59 | Post-Em | 2 | |
2,4-D (D.M.A. salt) + Dicamba (D.M.A. salt) | Post-Em | 4 | [24] |
Atrazine + Dicamba | Post-Em | 5 | |
Atrazine + 2,4-D (D.M.A. salt) | Post-Em | 5 | |
Atrazine + 2,4-D (Na salt) | Post-Em | 5 | |
Pretilachlor | Pre-Em | 3 | [33; 34] |
Oxyfluorfen + 2,4-D | Pre-Em | 3 | |
Oxadiazon | Pre-Em | 4 | |
Thiobencarb + 2,4-D | Pre-Em | 4 | |
Oxyfluorfen | Pre-Em | 4 | |
Anilofos + 2,4-D | Post-Em | 4 | |
Butachlor + 2,4-D | Post-Em | 5 | |
Atrazine | Post-Em | 33 | [30; 32; 33] |
Metribuzin | Post-Em | 3 | |
Chlorimuron | Post-Em | 3 | |
Glufosinate ammonium | Post-Em | 5 | |
Paraquat | Post-Em | 0 | |
Glyphosate | Post-Em | 0 |
8.5. Biological control
There are no current biocontrol strategies for the management of
Other biocontrol agents, which have been reported to show some level of control in Ethiopia, are the stem-galling moth
Pathogens such as
The weed is not grazed by animals or other wild life.
9. Allelopathic plant species with potential in controlling P. hysterophorus
There are several studies reporting the use of crude extracts, plant residues and purified compounds of allelopathic plants (crops, grasses, broadleaf weeds and trees) for controlling the germination, growth and physiology of
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Root and shoot | Momilactones A and B, phenolic acids, 5,7,4’-trihydroxy-3’,5”- dimethoxyflavone and 3-isoprophyl-5-acetoxy cyclohexene-2-one-1 | Reduced germination and root/shoot growth | [40–42] |
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Root and shoot | Benzoic, p-hydroxy benzoic, vanillic, m-coumaric, p-coumaric, gallic, caffeic, ferulic and chlorogenic acids | Reduced germination and root/shoot growth | [40; 41] |
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Root and leaves | Phenols and terpenoides | Reduced germination and root growth | [40; 43; 44] |
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Aqueous extracts of all parts, especially root and shoot extracts | Caffeic, ferulic, p-hydroxybenzoic, p-coumaric, vanillic, chlorogenic and syringic acids | Reduced germination and root/shoot growth | [45; 46] |
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Leaves | Maximum inhibition of biological activities including seed germination and multiplication | [47] | |
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Shoot and root | Reduced germination, shoot-cut bioassay, seedling bioassay and chloropyll | ||
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Leaves | Reduced vegetative and reproductive growth | [48] | |
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Leaves | Reduced germination, biomass, protein and pigment content | [49] | |
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Leaves and roots | Withaferin A | Reduced germination and plant growth | [50; 51] |
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Leaves | Phenolic acids, tannins, flavonides and eucalypt oils | Reduced germination | [52; 53] |
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Leaves | Monoterpenes (cineole, citronellol, citronellal and linalool) | Reduced germination and chlorophyll content | [54] |
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Leaves | Gallic, benzoic, p-coumaric, p-hydroxybenzoic vanillic, and trans-cinamic acid | Reduced germination and dry biomass | [55] |
10. Potential for management by utilization
There are reports of innovative uses of
More recently, it has been found to confer many health benefits such as a remedy for skin inflammation, rheumatic pain, diarrhoea, urinary tract infections, dysentery, malaria and neuralgia [17]. Extracts from the flowers have shown significant antitumor activity [62; 63]. It has been used as a remedy for inflammation, eczema, skin rashes, herpes, rheumatic pain, cold, heart problems and gynaecological ailments [17]. It has prospects in nanomedicine to be used in applications of eco-friendly nanoparticles in bactericidal, wound healing and other medical and electronic applications [17]. It has the potential to remove heavy metals such as nickel, cadmium, cresol and dyes from the environment, eradication of aquatic weeds such as salvinia (
11. Conclusion
Due to its invasive capacity and allelopathicproperties,
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