EVALUATION OF TRAP CROPS AND INTEGRATED STRIGA MANAGEMENT IN THE CONTROL OF WITCH WEED (STRIGA HERMONTHICA (DEL.) BENTH) IN SORGHUM (SORGHUM BICOLOR L. MOENCH)

ABSTRACT

Field trials were conducted in 2012 and 2013 cropping seasons on a naturally heavily striga infested field at the research farm of Federal University of Technology, Gidan kwano campus Minna   to evaluate the effect of seed treatment, sowing date and trap crop in the management of Striga hermonthica. The  experiment  consisted  of two  varieties  of  sorghum (resistant  ICSV1002 and susceptible Gwari local varieties), three different concentration of Parkia pulp powder (0, 66 and

100 g/l) and one trap crop (soyabean variety TGX 1448-2E). Two sowing date (JUNE 15 and JULY

21) Were used in both years 2012 and 2013; the experiment was laid out in a randomized complete block design with three replications. The screen house experiment, evaluated the variability of ten soyabean, cowpea and groundnut varieties each,  with respect to their ability to induce suicidal germination  of  Striga  hermonthica  seeds.  The  experiment  was  3x10x2  factorial  laid  out  in completely randomized design with five replications. Factor A consisted of Striga seeds at three levels of inoculation (0, 2.5 and 5g) mixed with 20g of sterilized soil respectively. Factor B was 10 varieties of either soyabeans, cowpea or groundnut as trap crops. Factor C consisted of resistance (ICSV1002) and susceptible (local) sorghum varieties. In the laboratory assay, the ten soyabeans, cowpea and groundnut varieties each were screened for ability to stimulate the Striga seed germination in vitro, using cut root technique .The experimental design was completely randomized design (CRD) with four replications. In the field trial sorghum seeds soaked with 66g/l Parkia pulp concentration significantly (p < 0.05) reduced Striga attack and produced higher yield in 2012 and

2013 compared to those primed with 100 and 0g/l (control) .The sorghum seed planted in July significantly (p>0.05) had fewer Striga shoots and produced higher grain yield compared with those planted in June in 2012 and 2013. Intercropping sorghum with soyabeans significantly (p<0.05) reduced Striga attack per plot in both study years compared to sole sorghum. Among the ten soyabeans, cowpea and groundnut varieties  screened , soyabeans variety TGX 1448 -2E , cowpea variety ITO4K -217-5 and groundnut variety RMP-91 had fewer Striga shoot and produced higher grain yields compared to other varieties in the laboratory assay. The test crop (soyabeans, cowpea and groundnut) varieties screened showed significant differences in stimulant production in their ability to induce suicidal seed germination in Striga hermonthica. Soyabeans variety TGX 1448-2E, cowpea variety ITO4K-217-5 and groundnut variety RMP-91 gave the highest germination percentage compared to other varieties.

CHAPTER ONE

INTRODUCTION

Distribution, Production and Uses of Sorghum

It is believed that sorghum originated in Africa, more precisely in Ethiopia, between 5000 and 7000 years ago.From there it was distributed along the trade and shipping route around the African continent and through the middle East to India at least 3000 years ago (FAOSTAT, 2011).

FAO reported the United States of America as top sorghum producer with a harvest of 9.7 million tonnes followed by India, Nigeria, Sudan, and Ethiopia (FAOSTAT, 2011). The sub-Saharan Africa produces about 18million tonnes of sorghum annually making it the second most important cereal crop after maize (Zea mays L.) which is produced in about 27million hectares (Haussmann  et al., 2000,).

Nigeria is the leading sorghum producer in Africa followed by Sudan, Ethiopia and Burkina Faso. However, in terms of productivity, Egypt achieved the highest yields per unit area followed by Algeria, South Africa, Uganda and Ethiopia. Total sorghum productions from all sorghum producing countries were 55.6 million tonnes in 2010 (FAOSTAT, 2006). Globally, sorghum (Sorghum bicolor (L) Moench) is the fifth most important staple food crop after wheat, rice, maize, and barley (FAO,

2012). Sorghum is consumed by more than 70% of the population in the sub-saharan Africa (IITA,

2004). The crop is produced for its grain, which is used for food and stalks for fodder and building materials. In developing countries, sorghum is used primarily as animal feed and in the sugar, syrup and molasses industry (Dahlbert et al., 2004). Recent work has shown that sorghum and millet (Pennisetum glaucum (L.) R. Br) are rich in antioxidants and gluten-free, which make them an attractive alternative for wheat allergy sufferers (Dahlbert et al., 2004).

1.2.     Striga Problem in Sorghum

Striga hermonthica is the most troublesome among the six common Striga species reported in Nigeria, which has the highest potential of a serious economic damage in cereal production (Emechebe et al. 1991)

Striga hermonthica has been reported to reduce the yield of the crop by up to 100% in Nigeria when infestation occurs at an early stage (Ogborn, 1977). Striga problem has led to migration of peasant families to Striga free areas, shifting cultivation, farm abandonment or change of cropping pattern (Parker and Riches, 1993). Due to dwindling land resources, soil fertility problems and weed build up; the increase in crop output is becoming difficult day by day. In these circumstances, the only way to have more production is by increase in output per unit of land area (Khan et al., 2000). Dugje et al. (2006) reported in a survey, that 94% of farmers sorghum fields in North- East Nigeria were infested with S. hermonthica and that Striga control in sorghum is more challenging than other cereal crops because sorghum matures late compared to maize.

1.3      The trap crops

Soyabean

Soyabean is a legume; like all other peas and beans, lentils and peanuts, it belongs to the large botanical family leguminosae. It is a versatile grain legume because it has a variety of uses. The crop has ability to fix atmospheric nitrogen and therefore, improves soil fertility.

Soyabean is used in the manufacture of cooking oil, margarine, salad dressing, milk, flour, paints, vanishes, linoleum, rubber fabric, soap, printing ink, spaghetti, baby food, milk of plant origin and meat substitutes and high protein beverages in the industry(Abdo and King, 1967, Metcalf and  Alkins,  1980).  Soyabean  is  known to  be  a  source of calcium which contributes to  bone development and reduce the problem of major bone disease called osteoporosis. It is also a source of iron, zinc, phosphorous, vitamin A, C and B6, thiamine, riboflavin and niacin. Its inclusion in diet

helps to decrease cholesterol by an average of 13% and consequently reduce heart disease risk by

54%. Isoflavones present in soyabean prevent menopause diseases while genisten and daidzein also produced by this crop prevent cancer disease (Anon, 1999).

Cowpea

Cowpea is leguminous crop that  is widely grown in Africa under marginal production systems. Cowpea is able to perform well even in marginal soils due to its ability to fix substantial nitrogen in the soil (Hall, et al., 2003). Cowpea is an important source of affordable protein, B vitamins, and minerals. Inadequate intake of protein in the diet is one of the factors that contribute to high prevalence of malnutrition in developing countries.

Cowpea is widely grown as an intercrop with cereals, through improved breeding lines and agronomic practices. There is potential for increased production of cowpea despite the prevailing production challeng

es of declining soil fertility, unreliable rainfall, pest and diseases (Singh,  2005).

Groundnut

Groundnuts (Arachis hypogaea), also known as peanuts or monkey nuts, are the edible seeds of a legume plant that grow to maturity in the ground. It is cultivated in nearly 100 countries, with over 90% of which are developing countries, (Hall et al., 2003).

The nuts are high in edible oil content (40-50%) and protein (25%), and also serve as a good source of a variety of essential vitamins and minerals. They can be consumed directly or processed into oil or cake/meal, confectionary products or snack food. The kernels can be used for human consumption, vines as fodder for cattle, and nitrogen fixed from its roots as nutrients for the soil.

1.5     Statement of the problem

Striga control is more difficult and complicated than the control of other weeds. This is due mainly to its biology, because of Striga seeds after ripening requirements, not all are pre-conditioned

for germination at the same time thus necessitating persistent control.Striga problem has led to migration of peasant families to Striga free areas, shifting cultivation, farm abandonment or change of cropping pattern (Parker and Riches, 1993).

As population pressure and demand for food production increase, land use intensified. With greater use of monocropping and little or no fallow, populations of these parasites have gradually increased  and  become  threats  to  food  production (Doggett, 1984).Various methods  have  been recommended for  the  control of Striga  in  sorghum,  including  cultural practices  such as  hand weeding, planting of trap crops, planting of Striga tolerant or resistant varieties and chemical or herbicide treatments such as the use of high levels of chemical fertilizers especially nitrogen and ethylene gas to induce suicidal germination and herbicides, which give some reasonable results but are prohibitively expensive or are either incompatible with the cropping system  for the resource poor farmer in Striga-stricken areas of Nigeria (Kuchinda et al., 2003).

Despite these efforts, there has been limited success and no single known control method is effective in control of Striga in sorghum. The variability within and between Striga species and the diversity of African farming systems is also contributing to constraint in Striga control.Strigahermonthica is difficult to control because of the build-up of a large reserve of it in the soil which remains viable for many years (Kanampiu et al., 2003).

Figure 1: General life cycle of Striga species

1.6 Justification

The various control methods such as land preparation, hand-pulling, hoe-weeding, trap cropping have been tried out singly over the years with no conclusive and consistent results for the peasant farmer, partly because of huge amounts of seeds that  accumulate over time  in the seed bank (Oswald, 2004). Furthermore, variability within and between Striga species and the diversity of African farming systems,and other methods of control such as the use of high levels of chemical fertilizers especially nitrogenous, ethylene gas to induce suicidal germination and herbicides, which give some reasonable results, are prohibitively expensive for the resource poor farmer in Striga– stricken areas of Nigeria (Kuchinda et al., 2003). This has aroused interest in a more integrated

approach among researchers. Dashiell et al., (2000) also reported that Striga control is likely to be achieved  by  combining  a  range  of  individual  component  technologies  into  a  programme  of integrated Striga Control (ISC) to provide more flexible and sustainable control over a wide range of biophysical and socio-economic environments.Schulz et al., (2003) also reported that single control options for S. hermonthica will not be as effective as combining a range of individual technologies into integrated packages.

An alternative control approach against Striga would be the use of natural products that would inhibit or induce the germination of Striga seeds in order to deplete the Striga seed bank in the soil. Screen house evaluation of Azadirachta indica (neem) and Parkia biglobosa (locust bean) to control S.hermonthica revealed that products based on the two species were effective to reduce Strigaemergence (Marley, et al., 2004; Kolo  et al., 2005, Kolo and Mamudu 2008).

An integrated Striga management package of combining host seed treatment, different dates of planting and trap crop was considered in this research. So there is need for further investigation with respect to the natural product and the trap crops used in this research with S. hermonthica strain from other locations in Nigeria.

1.4 Objectives

The objectives of this research therefore were to:

i.    Determine the effectiveness of seed treatment, sowing date and intercropping system in integrated management of Striga hermonthica in sorghum;

ii.    Evaluate the priming effect of Parkia pulp in the control of S.hermonthica in a Guinea savanna ecosystem; and

iii.    Evaluate the variability of ten soyabean, cowpea and ground nut species each with respect to the ability of their root exudates to stimulate the germination of Striga hermonthica seeds.

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