A study was conducted to determine the factors influencing plant-parasitic nematode occurrence, abundance and distribution in the sugarcane fields. Four sugarcane growing zones; Nzoia, Mumias, West Kenya and Busia of Kenya were selected from which 81 fields randomly selected and sampled. Soil samples were taken from sugarcane rhizospheres and nematodes extracted from 200 cm3 soil using the modified Baermann funnel technique. Nematodes were then fixed and mounted on slides and identified to genera level using identification keys. Nematodes of the genera Pratylenchus, Scutellonema and Meloidogyne were predominant in the sugarcane belt of western Kenya with mean densities of 61, 54 and 39, respectively. Nzoia, which falls in a marginal sugarcane zone harboured the highest proportion of these plant parasitic nematodes (55%), while West Kenya zone had the least proportion (4%). Soil texture influenced nematodes with more than 50% occurring in sandy soils compared to other soil types. Build-up of plant parasitic nematodes occurred with subsequent ratoon crops up to the second ratoon before declining in the third ratoon. Anthropogenic effects were significant with 70% higher numbers of plant parasitic nematodes in the out-grower farms compared to the factory-managed farms. This study has revealed the influence of soil texture, crop cycle and anthropogenic factors on abundance and distribution of plant parasitic nematodes in western Kenya sugarcane zones. It has also set the justification of further work to determine the economic importance of the nematodes.
PDF Abstract XML References Citation
How to cite this article
Sugarcane, a tall perennial, thick stemmed grass is a complex hybrid between Saccharam officinarum L. and S. spontaneum L. (Cadet and Spaull, 2003). It is grown in more than 80 countries throughout the tropics and subtropics where it is among the principal sources of revenue, fiber and fuel. In many countries, sugarcane is used by peasant farmers to produce crude sugar and more than half of the cane grown in Brazil is used to produce ethyl alcohol (Stirling et al., 2005). In Kenya, sugarcane is an important cash crop earning farmers approximately US$ 100 million annually. However, the yields have been on a steady decline over the last decade from 91 t ha-1 in 1996 to 71 t ha-1 in 2005. A wide range of arthropod pests, fungi, bacteria, viruses plant parasitic nematodes and noxious weeds-individually or in complexes, cause significant losses in sugarcane (Cadet et al., 2003). Plant parasitic nematodes are one of the most common pests that have build-up over time and thus contributing to the decline in cane yield. Nematode diversity in sugarcane is greater than in most other cultivated crops with more than 48 genera of endo-and ectoparasitic nematodes having been recovered from the sugarcane rhizosphere (Cadet and Spaull, 2003).
The threat posed by nematodes is aggravated by the fact that sugarcane is a perennial crop which is grown under continuous monoculture. This aspect has been shown to favour the build-up of some selected pests and diseases to economic threshold levels (Mazhar et al., 2002). According to Cadet et al. (2003), yield losses due to pests and diseases in major crops are estimated at 20-50%, standing at 20-30% in sugarcane. Studies carried out in Pakistan, a tropical environment similar to Kenya showed that the damage caused by plant-parasitic nematodes is more serious and complex than in the temperate countries since the climate is suitable for nematode multiplication throughout the year (Maqbool et al., 2001). Surveys carried out in sugarcane growing areas of Kenya showed that lesion nematodes (Pratylenchus spp.) were widespread in this crop (Kandji et al., 2003). This study was therefore undertaken with the aim of determining the occurrence, abundance and distribution of nematodes in Nzoia, Mumias, West Kenya and Busia sugar cane zones.
MATERIALS AND METHODS
In this study, a total of 7 factors were hypothesized to influence occurrence, abundance and distribution of plant parasitic nematodes. These factors included; historical background, soil texture, Agro-Ecological Zone (AEZ), altitude, variety, crop cycle and crop management practices. A total of 81 samples were collected from randomly selected farms in four sugarcane production zones namely Nzoia, Mumias, Busia and West Kenya. A total of 20 sub-samples were taken from each farm and thoroughly mixed before drawing a composite sub-sample of about 1 kg which was transported to the laboratory. Extraction was done following the modified Baermann funnel technique described by Hooper et al. (2005). The effect of three soil textural classes, clay, clay loam and sandy clay on nematodes was evaluated. The influence of climatic factors on nematodes in the region was assessed by sampling three Agro-Ecological Zones (AEZs) namely lower midlands 2 (LM2), upper midlands 2 and 3 (UM2 and UM3) as described by Jaetzold and Schmidt (1983). The effect of the crop cycle was evaluated by taking samples from the plant crop, first ratoon, second ratoon, third and more ratoon crops. Anthropogenic factors were evaluated by assessing two sugarcane management practices; the management practices employed by the factories in the nucleus estates and that of the out-grower farmers. Factory managed nucleus estate farms were characterized by incorporation of organic substrates in the form of sugarcane baggasse and filtermud as opposed to farmer managed out-grower farms where no organic substrates were applied. All data collected were log transformed and subjected to General Linear Model and means separated by Duncan`s Multiple Range Test using SAS Release 8.1.
Mean population densities of plant-parasitic nematodes associated with sugarcane were variable (p≤0.05) among the four sugarcane zones in Western Kenya (Table 1). Among all zones, Nzoia was the most heavily infested followed by Mumias, Busia and West Kenya in decreasing order of infestation. The most dominant nematodes detected were of the genera Pratylenchus, Scutellonema and Meloidogyne with overall mean numbers of 61, 54 and 39 in 200 cm3 soil, respectively. Nematodes of the genera Rotylenchus, Aphelenchoides, Tylenchus and Helicotylenchus, showed moderate occurrence as compared to Paratylenchus, Hoplolaimus, Ditylenchus and Xiphinema amongst others whose occurrence was low in the sugarcane growing zones.
Soil texture had a significant effect on the distribution of plant-parasitic nematodes in the sugarcane zones studied (Table 2). Generally, sandy soils harboured more plant-parasitic nematodes compared to clay loam and clay soils which had lower nematode populations. Nematodes of the genera Pratylenchus, Scutellonema and Tylenchus were predominantly higher in sandy soils while Hopololaimus spp. and Tylenchorhynchus spp. were significantly higher in clay-loamy soils. Clay soils were significantly dominated by Ditylenchus spp., Paratylenchus spp. and Rotylenchus spp.
|Table 1:||Mean population densities of plant-parasitic nematodes associated with sugarcane crop in Nzoia, Mumias, West Kenya and Busia in western Kenya zones|
|*Significant at p≤0.05, **Significant at p≤0.01, NS: Not Significant, Means followed by the same letter(s) along rows are not significantly different|
|Table 2:||Effect of soil texture on the distribution of plant-parasitic nematodes associated with sugarcane in Western Kenya|
|*Significant at p≤0.05, **Significant at p≤0.01, NS: Not Significant, Means followed by the same letter(s) along rows are not significantly different|
|Table 3:||Effect of sugarcane crop cycle on the density of plant-parasitic nematodes in Western Kenya|
|*Significant at p≤0.05; **Significant at p≤0.01; NS: Not Significant, Means followed by the same letter(s) along rows are not significantly different|
The abundance of plant-parasitic nematodes was significantly influenced by the crop cycle (Table 3). Densities of nematodes of the genera Pratylenchus, Ditylenchus and Tylenchorhynchus steadily increased in the first two cycles of the crop (ratoon 1 and 2) followed by a rapid decline in the third and subsequent crop cycles. The populations of all other plant-parasitic genera that are frequently associated with sugarcane remained constant throughout the cropping cycles. Sugarcane management practices led to significant differences in numbers of plant parasitic nematodes associated with sugarcane in the study area (Table 4). Populations of plant-parasitic nematodes were significantly higher in out-grower farms compared to factory managed nucleus estates. With the exception of nematodes of the genus Hoplolaimus, numbers of nematodes of the other genera were higher in out-grower farms compared to factory-managed farms.
|Table 4:||Effect of management practices on the distribution of plant-parasitic nematodes in Western Kenya|
|*Significant at p≤0.05; **Significant at p≤0.01; NS: Not Significant, Data are means of 81 samples. Means followed by the same letter(s) along rows are not significantly different|
This study has demonstrated that nematodes of the genera Pratylenchus, Scutellonema and Meloidogyne are widespread in sugarcane fields of Western Kenya. These findings are in agreement with previous studies elsewhere (Cadet and Spaull, 2003; Cadet et al., 2003). Sugarcane is normally grown in a continuous monoculture with usually no more than a few months break between removing the last ratoon crop and replanting the field. This practice favours the development of relatively large number of some species, especially those that are highly pathogenic to sugarcane crop like Pratylenchus spp and Meloidogyne spp. (Mazhar et al., 2002). Previous studies on different crops have shown that root-knot and lesion nematodes are widespread and occur in large numbers in western Kenya (Desaeger and Rao, 2000). Lesion nematodes are widely recognized as pests of cereals while root-knot nematodes are devastating on leguminous and vegetable crops (Arim et al., 2006).
Nzoia sugar zone was more heavily infested with nematodes compared to the other zones within the study site. Part of Nzoia lies in marginal sugarcane areas (UM2 and UM3) as opposed to the entire Mumias zone which lies within the ideal sugarcane zone in LM1 (Jaetzold and Schmidt, 1983). It is conceivable that the conditions experienced in marginal sugarcane areas are more favourable for multiplication of nematodes and hence the high density observed in Nzoia as compared to Mumias Scheme. In addition, unthrifty crops growing in marginal areas are more vulnerable to attack by nematodes (Walker, 2004). Busia zone is the most recently established sugarcane production zone so that the nematode numbers are yet to build up in the fields. In the West Kenya zone, sugarcane is established using cane tops, this practice combined with the long period the crop stays in the field, is thought to cause accelerated yield decline. Ploughing the sugarcane under after only one ratoon crop may be a viable option to manage nematodes (Agyarko and Asante, 2005). The frequent disruptions of the nematode cycles may have limited their multiplication leading to the less numbers observed (Desaeger and Rao, 2000). Sugarcane in West Kenya and Busia is produced wholly by out-grower farmers where extended fallow periods between subsequent crops are common. According to Agyarko and Asante (2005) periodic fallowing has contributed to the reduced numbers of nematodes.
This study has also shown that soil texture is a major factor that influences abundance and distribution of plant parasitic nematodes. The higher numbers of plant-parasitic nematodes associated with sandy soils could be attributed to high porosity and aeration that favour nematode mobility. The poor drainage associated with clay soils may explain the low numbers of nematodes recovered from these soils. Similar studies have revealed that the effect of soil texture on the distribution of some of the nematodes is more than that of climatic or topographic factors (Mateille et al., 2002; Cadet et al., 2003). According to Cadet and Spaull (2003), it is the quantity of sand and organic matter in soil that appears to affect the distribution of nematodes associated with sugarcane. It has been suggested that sandy soils enable easy movement of nematodes and provide optimum aeration which leads to increased pathogenicity. The negative effect of nematodes on plants is aggravated by the fact that sandy soils have a lower water and nutrient holding capacity (Avendaño et al., 2004).
Generally, higher nematode numbers were recorded in the out-grower farms as compared to the factory-managed nucleus estates. Bagasse and filter press mud are applied in nucleus estates on a routine basis and may account for nematode suppression as well as increase in sugarcane yields (Akhtar and Malik, 2000). According to Maqbool et al. (2001), the quality of planting material, especially the varieties, may be a contributing factor to the differences that occurred between the two management types. Indeed in Western Kenya, factory-managed farms use certified seed that is well treated and most likely free from nematodes as opposed to the individual farmers.
This study showed that numbers of plant parasitic nematodes increased steadily in the ratoon crops and then declined after the third ratoon. Increase in nematode numbers could be due to multiplication of the nematodes as a result of continuous presence of susceptible crops (Kratochvil et al., 2004). According to Quader et al. (2001) populations of plant parasitic nematodes were continuously building up in Australasian vineyard fields mainly due to the perennial nature of the crop. Loss of plant growth vigour coupled with competition among the nematodes, for limited reserves could explain the decline (Akhtar and Malik, 2000). In addition, the subsequent build-up of microorganisms that are antagonistic to nematodes partly results in their decline after the third ratoon (Kiewnick and Sikora, 2004; Tiyagi and Shamim, 2004).
Sugarcane fields in the western sugarcane zones of Kenya were heavily infested with plant parasitic nematodes with the predominant ones being in the genera Pratylenchus, Scutellonema and Meloidogyne. The marginal sugarcane zone in Nzoia is more heavily infested with nematodes than the other zones. Sandy soils are more suitable for plant parasitic nematodes and application of organic amendments in the form of sugarcane bagasse and filter mud could account for the lower numbers of plant parasitic nematodes in sugarcane fields under the management of sugarcane factories. More work is required to determine the economic importance of the nematodes associated with sugarcane in Kenya.
The Kenya Sugar Research Foundation (KESREF) is acknowledged for funding this study.
- Agyarko, K. and J.S. Asante, 2005. Nematode dynamics in soil amended with neem leaves and Poultry manure. Asian J. Plant Sci., 4: 426-428.
- Akhtar, M. and A. Malik, 2000. Roles of organic soil amendments and soil organisms in the biological control of plant-parasitic nematodes: A review. Bioresour. Technol., 74: 35-47.
- Arim, O.J., J.W. Waceke, S.W. Waudo and J.W. Kimenju, 2006. Effects of Canavalia ensiformis and Mucuna pruriens intercrops on Pratylenchus zeae damage and yield of maize in subsistence agriculture. Plant Soil, 284: 243-251.
- Avendaño, F., F.J. Pierce and H. Melakeberhan, 2004. The relationship between soybean cyst nematode seasonal population dynamics and soil texture. Earth Environ. Sci., 6: 511-525.
- Cadet, P. and V.W. Spaull, 2003. Effect of nematodes on the sustained production of sugarcane in South Africa. Field Crop Res., 83: 91-100.
- Cadet, P., S. Berry and V. Spaull, 2003. Mapping of interactions between soil factors and nematodes. Eur. J. Soil Biol., 40: 77-86.
- Desaeger, J. and M.R. Rao, 2000. The root-knot nematode (Meloidogyne spp.) problem in Sesbania fallows and the scope for management in Western Kenya. Agrof. Syst., 47: 273-288.
- Hooper, D.J., J. Hallmann and S.A. Subbotin, 2005. Methods for Extraction, Processing and Detection of Plant and Soil Nematodes. In: Plant Parasitic Nematodes in Subtropical and Tropical Agriculture, Luc, M., R.A. Sikora and J. Bridge (Eds.)., 2nd Edn., CAB International Publisher, UK, ISBN: 9781845931445, pp: 53-86.
- Jaetzold, R. and H. Schmidt, 1982. Farm Management Handbook of Kenya, Part A. Vol. II. West Kenya (Nyanza and Western Provinces) Kenya, pp: 397.
- Kandji, S., Ogol, C. and A. Alain, 2003. Crop damage by nematodes in improved-fallow fields in western Kenya. Agrofor. Syst., 57: 51-57.
- Kiewnick, S, and R. A Sikora, 2004. Optimizing the efficacy of Paecilomyces lilacinus (strain 251) for the control of root-knot nematodes. Commun. Agric. Applied Biol. Sci., 69: 373-380.
- Kratochvil, R.J., S. Sardanelli, K. Everts and E. Gallagher, 2004. Evaluation of crop rotation and other cultural practices for management of root-knot and lesion nematodes. Agron. J., 96: 1419-1428.
- Akhtar, M., N.N. Elahi and M. Ashraf, 2001. Morphological characters of some exotic sugarcane varieties. Pak. J. Biol. Sci., 4: 471-476.
- Mateille, T., D.L. Trudgill, C. Trivino, G. Bala, A. Sawadogo and E. Vouyoukalou, 2002. Multisite survey of soil interactions with infestation of root-knot nematodes (Meloidogyne spp.) by Pasteuria penetrans. Soil Biol. Biochem., 34: 1417-1424.
- Qureshi, M.A., R.S. Ahmed, G.S. Shah, A.L. Khanzada and K.I. Rajput, 2002. Studies on chemical control of plant parasitic nematodes associated with sugarcane Saccharum officinarum linn. Plant Pathol. J., 1: 44-47.
- Quader, M., I.T. Riley and G.E. Walker, 2001. Distribution pattern of root-knot nematodes (Meloidogyne spp.) in South Australian vineyards. Aust. Plant Pathol., 30: 357-360.
- Stirling, G.R., E.J. Wilson, A.M. Stirling, C.E. Pankhurs, P.W. Moody, M.J. Bell and N. Halpin, 2005. Amendments of sugarcane trash induce suppressiveness to plant-parasitic nematodes in a sugarcane soil. Aust. Plant Pathol., 34: 203-211.
- Tiyagi, S.A. and A. Shamim, 2004. Biological control of plant parasitic nematodes associated with chickpea using oil cakes and Paecilomyces lilacinus. Indian J. Nematol., 34: 44-48.