Distribution, Density, and Abundance of Parthenium Weed (Parthenium hysterophorus L.) at Kuala Muda, Malaysia

Knowledge of distribution, density, and abundance of weed in a place is a prerequisite for its proper management. Parthenium hazard is a national agenda in Malaysia, and Kedah is the worst infested state in the country. Despite it, the distribution and abundance of the weed is not systematically documented. Periodical weed surveys were conducted at Kuala Muda, Kedah, during March and September 2015 to identify infested locations, to determine density, abundance, and severity of infestation, and to do mapping of weed distribution of the area. Geographic locations were recorded using a GPS.Weed density was measured following the list count quadrat method. (e mapping of weed infestation was done by the ArcGIS software using data of GPS and weed density. Different letters were used to indicate the severity of infestation. Results indicated that in Kuala Muda, sixteen sites are infested having average weed density of 10.6 weeds/m. (e highest density was noted at Kg. Kongsi 6 (24.3 plants/m). (e relative density was highest at Semeling (27.25%) followed by Kg. Kongsi 6 (23.14%). (e average severity of infestation was viewed as the medium. Parthenium abundance and relative density increased by 18.0% and 27%, respectively, in the second survey conducted. (e intervention of concerned authority to tackle the weed problem using integrated weed management approach is emphasized.


Introduction
e most obnoxious, allergenic, and environmental pollutant weed, Parthenium hysterophorus L. (locally called as Rumpai Miang Mexico) is an invasive alien species in Malaysia. e weed scientists of Universiti Malaysia Kelantan detected it for the first time at Batang Kali, Selangor, in 2013 [1][2][3]. At present, ten states of Malaysia are invaded by the weed, and the state Kedah is the worst infested area [4,5]. e weed has harmful impacts on crop production, livestock production, human and animal health, and biodiversity [6,7]. e weed spreads very fast through transport, agricultural implements, crop seeds, compost, and organic manures. It also spreads through flood water, wind pressure, and tyre-carried mud of vehicles [8]. It is essential to know the critical analytical characters such as density, frequency, and abundance of the species if we want to know its dominance in a community. Weed density measures the number of the species in a unit area, sometimes expressed as a percentage. Frequency is the number of times the species occur in the sampling unit, or it is the degree of dispersal of the species. e abundance of a species is the total number of the species present in the weed community and is a relative measure [9]. e severity of weed infestation usually regards the percentage of area covered by the species. e study of weed distribution, abundance, and severity over time are helpful in determining how a population changes over time in response to agronomic practices and agroclimatic conditions [5]. erefore, it is essential to identify the parthenium infested locations, that is, the geographical range of the weed, its abundance, and severity of infestation in the study site. e primary objective of the study was to accurately identify the areas with parthenium populations and quantify their abundance and severity of infestation. It is intended that the scientists, land managers, and the inhabitants can foresee those areas, potentially subject to parthenium invasion, understand the biology of invasion process, and thereby develop the appropriate weed management plans.
A regular weed monitoring is needed to control the weed sustainably. Weed monitoring involves repetitive surveys to track weed populations over time. e comparisons between different periodic surveys can help to elucidate the effect of new weed control technologies on weed species shift. Our preliminary investigation indicated that the weed is scattered in various areas of Batang Kali (Selangor) and Sungai Petani (Kedah), but detailed information was not documented from elsewhere [2,5].

Procedure of Weed Survey.
e field surveys were conducted throughout Kuala Muda subdistrict, Kedah, during March and September 2015.
e observation was made alongside the highways and major roads of the study sites with an interval of 500 meters. e farmland, wasteland, and river bank around the survey spots were also considered in the survey following the list quadrat method [9,10]. e geographical coordinates were recorded using a GPS. When parthenium was observed at a density of at least one plant per 10 m 2 area, it was considered as presence of the weed.

Determination of Relative Density and Abundance of Parthenium Weed.
e weed density was measured by placing a quadrat (1 m 2 size) randomly on the survey spots following the list quadrat method [10]. Ten quadrats were placed at each site of the survey spots. Parthenium weed and other weed species within each quadrat were counted [11]. Parthenium weed density and frequency were calculated based on the formulae as applied by Tauseef et al. [12] and Nkoa et al. [5]. Whereas the relative density was determined using the equations of Yakubu et al. [13] and Knox et al. [14]. e abundance of parthenium weed invasion was determined based on the formula of Kilewa and Rashid [15]: density � total number of parthenium weed in a quadrat total area of a quadrat 1 m 2 ( ) × 100, frequency � number of quadrats with parthenium weed total number of quadrats used in each spot × 100, relative density � total number of parthenium weed total number of all weed species × 100, abundance � total number of parthenium weed in all quadrats total number of quadrats in which parthenium weed occurred . (1)

Mapping the Distribution of Parthenium Infestation and the Percentage of Area Coverage (Severity Class)
. e information on parthenium distribution and severity of infestation marked on the base maps of Kedah following the technique of Cooksey and Sheley [16]. e mapping of parthenium weed distribution was done by measuring the percentage of area coverage completed by visual estimate within the quadrat according to Philippoff and Cox [17]. e severity of infestation is categorized and presented in Table 1.
All the data of infested areas were transferred into a digital map using Geographic Information System (GIS) software, ArcGIS [16]. e distribution, density, and percentage of coverage by the parthenium weed were considered in mapping the weed infestation.  Figure 2(a)). e difference in intensity of infestation is due to natural selection as no other extra influence has worked here to make difference.

Results and Discussion
However, during the second survey, all the villages had "medium" level of infestation signposted by "M," and Kg. Semeling had a high level of infestation designated by "H." It is mentioned here that the personnel from Department of Agriculture (DOA), Kedah, sprayed with glyphosate twice (trade name: Knockdown) between the surveys. Although the above-ground parts of the weed were destroyed, a vast number of seeds remained within the soil and emerged later with higher energy. at is why the infestation level was higher in the second survey ( Figure 2(b)). Probably the weed seedbank of parthenium was encouraged after herbicide spraying above ground. Worku [19] stated that parthenium became the major weed in Ethiopia, India, and Australia within a short period, even after herbicide sprays. erefore, continuous monitoring and control measures are needed for an extended period.

Parthenium Preference according to Habitat. In Kuala
Muda, most of the infestations are noticed along roadsides, residential areas, wasteland, and crop farms ( Figure 3). When parthenium is prevalent on roadsides, it is subject to quick spread through wind pressure of moving transports [20]. According to Ayele et al. [21], parthenium weed was introduced to Ethiopia in the year 1968 through cereals consignment. However, another form of introduction occurred to eastern Ethiopia in the year 1976 through weed seeds attached to the army transport at the time of Ethio-Somali war.
When parthenium grows in the wasteland, it usually remains undisturbed and leads the plant to produce a higher number of seeds. Parthenium growth in the residential area is dangerous to the inhabitants. e children who play with the weed are prone to be infected by parthenium showy white flowers which cause allergy. People may inhale the pollen from the parthenium flowers during breathing which might adversely affect their respiratory system. e weed surveyors noticed many parthenium plants in front of mosques and Hindu temples, which are also risky for the people who come for worships. e dominance of parthenium weed in crop farms may lead to its contamination with crop seeds which leads to its further spread. Upadhyay et al. [22] commented that parthenium weed commonly grows near the roadsides, in farms, and paddocks. Adnan et al. [11] also noted that most of the habitats infested by the parthenium weed are alongside road, the fields for crop cultivation, and wasteland rather than alongside water canal.
Presence of parthenium near cattle farm is risky for the cattle. If the cattle graze on the parthenium infested land, the animals might be infected with skin dermatitis due to close contact with the weed. When parthenium is abundant along the river bank or watercourses, the spread of the weed may occur due to the mixing of parthenium weed seeds with river water. All these information indicate the risks of the parthenium weed at Kuala Muda.

Density and Abundance of Parthenium Weed at Different
Sites.
e density, relative density, frequency, abundance, and other parameters of parthenium weed infestation at Kuala Muda, Kedah, are shown in Table 2.  Table 2).
It is not clear to us that why such a variability in parthenium density exists among different villages. Since the people of all these villages were unaware about this invasive species [4], the discrepancy in weed densities might be due to natural selection. More or less similar ranking of weed frequency was noticed in different survey sites. For example, the highest frequency was noted in Kg. Kongsi 6, Kg. Penghulu Him, Kg. Telok, Taman, and Cahaya Baiduri, and    Table 2). ere was more or less similar weed frequency noticed in the second survey, and the highest was in Kg. Kongsi 6 followed by Kg. Sungai Tok Rawang, Kg. Zainal Abidin, and Kg. Semeling. e lowest weed frequency was in Batu Dua, Pokok Terap, and Kg. Banggol. Higher frequency and density of parthenium weed caused its abundance also higher in both the surveys in Kuala Muda, Kedah. From Table 2, it is obvious that the value of weed abundance increased the most in Teluk Wang Besar (85.23%) followed by Taman Nilam Sari (75.0%) and Pokok Terap (52.38%). However, there were decreases in parthenium abundance in some locations, especially in Taman Songket Indah (35.09% decrease). While an average impact of the weed distribution considered, it is clear that on an average, more than 18.0% increase in weed abundance and 28.0% increase in relative density were observed in the second survey. Nkoa et al. [5] stated that the weed abundance is related to weed number (density) or frequency, which might have influenced the abundance positively in this study.
From the data of percent area coverage, the severity of infestation is regarded as "M" in most of the sites, except in Kg. Teluk Wang Besar which is regarded as trace (T) and Batu Dua, Pokok Terap, Taman Nilam Sari, and Kg. Banggol are regarded as low (L) infested areas. However, the percent coverage in the second survey increased, and the severity of infestation is regarded as "M" in those sites. However, the severity of the weed is regarded as high (H) in Kg. Semeling. e overall differences between the two surveys in March and September 2015 were statistically significant (P < 0.05) (Figure 9).      When the comparison is made between the two surveys, it was obvious that the parthenium weed density was not different. However, the weed abundance as regarded by percent coverage was higher in September than in March 2015 (Figures 6 and 9). Parthenium weed spreads very fast just like wildfire in the forest. erefore, the increase in weed abundance in Kuala Muda, Kedah, is a matter of great concern to the authority of the country. e control of the weed should follow an integrated approach including prevention, chemical control, physical control, and biological control. e involvement of all stakeholders, for example, researchers, policymakers, administrators, and community people, should be ensured.

Conclusion
e status of weed density and abundance in Kuala Muda, Kedah, Malaysia, is in a critical stage of infestation and needs quick action to tackle the problem sustainably. Timely control of the weed by adopting appropriate methods especially with an integrated weed management approach is essential.

Data Availability
Data are available from the corresponding author upon email request. importance value index (IVI) of the weeds in cotton crop