Studies were carried out at the Department of Crop science, University of Nigeria Nsukka (UNN) to evaluate botanicals control of diseases associated with growth and germination of Moringa seeds. Five accessions of Moringa seeds collected from Imo, Enugu, Kogi, Plateau and Kaduna states of Nigeria were used. The following experiments were carried out: seed viability test, isolation of fungal pathogens, determination of phytochemicals, in vitro control of the pathogens with six botanicals, phytoxicity test of the botanicals on M. oleifera seeds and early growth study of the treated and untreated seeds. The viability test revealed significant (p < 0.05) differences in some of the germination traits of the five accessions of moringa seeds. Kaduna accession gave the highest number of days to first germination (approx. 6 days) followed by Jos and Imo with same value (approx. 4 days) and the lowest was Nsukka (approx. 3 days). The following organisms were isolated from the seed coats; namely, Aspergillius niger, A. flavus, A. glaucus, Fusarium oxysporium, Mucor spp, Cunnighamella spp, Penicillium digitatum. Only A. flavus was isolated from the cotyledon (seed without coat). The percentage disease incidence was highest in Kaduna (99.90%) on seed with coat and (89.75%) on seed without coat. Enugu accession had the lowest percentage disease incidence (10%) and (0%) for seed with coat and those without coat respectively. Aspergillius flavus had the highest percentage frequency of occurrence (16.31%) while the value for Fusaruim oxysporium and Mucor spp were lowest and statistically the same (0.27%). At both 50 and 70 grams/liter levels of concentration, Aspilia africana leaf extract showed the highest percentage growth inhibition for 14 days while the lowest was obtained in Cassia alata. Phytotoxicity test revealed that at 50 grams/liter O. gratissemum leaf extract significantly ( p < 0.05) gave the highest number of days to first germination (approx. 6 days) while A. africana leaf extracts gave the lowest (approx. 4 days). The main effects of Aspilia africana leaf extract treatment on plant height, stem girth, number of leaves, number of buds and number of nodes were significant (p , 0.05). The seedlings treated with Aspilia africana leaf extracts at 12 weeks after planting had higher plant height, stem girth, number of leaves, number of buds and number of nodes than the untreated. (Treated: 59.61, 3.21, 17.90, 4.51 and 18.18 cm) while the untreated gave lower values (untreated: 54.58, 3.19, 16.60, 4.27 and 15.89 cm) respectively. The duration of storage significantly (p < 0.05) affected the incidence of diseases on the fresh and stored Moringa oleifera leaf products. Two months of storage gave the highest percentage disease incidence (19.66%) which differed significantly (p < 0.05) from others. Zero storage (at harvest) gave the lowest value (0.92%). The result of the study shows that all the leaf extracts inhibited the growth of the fungal isolates but Aspilia africana leaf extract was more effective because it gave relatively less adverse effect to germination and growth of the Moringa oleifera seeds tested.
Moringa oleifera Lamarck belongs to the family of Moringaceae which consists of 13 species of deciduous trees (Keay, 1989; Price, 1985). Other species of Moringa in the family are M. arborea, M. berzian, M. concanensis, M. drouhaddi, M. hildebrandtii, M. longituba, M. ovalifolia, M. peregrina, M. pygmaea, M. rivae, M. ruspoliana and Moringa stenopetala. Moringa oleifera is the most cultivated among all the species in the family Moringaceae. It is a native of India but is widely distributed in many tropical and pacific regions, in West Africa as well as Central America and the Caribbean (Freiberger et al., 1998; Locket et al., 2000; Ramachandran et al., 1980 and Aregheore, 2002).
The common name of Moringa oleifera is Moringo in Malabar (a region in southern India) and it is believed to be the origin of the generic name (Jackson, 1990). It appears to have more names than any plant ever studied. It is known as Rawag in Arabic, Kelorin in Indonesian, Horse- radish tree, Drumstick tree in English (Hutchinson and Dalziel 1966), Ewe igbale (Ewe ile) in Yoruba, Zogallagandi (Zogalle) in Hausa, Okwe oyibo in Igbo (Gbile, 1984). The common names are Miracle tree, Life saver, Never die, etc. (Ofor et al., 2011). Every part of Moringa plant is useful; the root, seed, leaf, etc. (Fahey, 2005) and may be consumed raw, roasted, cooked, and processed domestically or industrially. The products of this tree have been reported to be useful to nutritionists, animal scientists, pathologists, entomologist, environmentalists, practitioners of natural medicine, etc. (Ofor et al., 2011).
Ogwo and Ogbonnaya (2010) presented Moringa oleifera as one of the few plants that have the capacity to meet the millennium goals in Nigeria in terms of food security. This is in response to the prediction of the Food and Agriculture Organization (FAO) that the world population may rise to about 10 billion in 2050. By 2008 statistics, almost 40% of the world population lived within the tropical zone and by 2060, 60% of the human population will be in the tropics due to high birth rates and migrations (Wikipedia, the free Encyclopedia, 2012). There is a need to increase production of useful plants like Moringa to ensure food security in the tropics. Though Moringa tree is widespread throughout the tropics, around farms and compounds and often used as fence especially in northern Nigeria, not much has been done to enhance its large scale production to ensure sustained availability (Ofor et al., 2011). One of the major challenges of large scale production is how to handle the pests and diseases of the plant. Farmers generally suffer great loss through pests and diseases especially through fungal infections which may not only inhibit the production of foliages, fruits and stems, but lower the overall quality and quantity of the cultivated crops. The known pests are caterpillars, budworms, borers and fruit flies. Most of the reported diseases of Moringa oleifera are fungal. They are
• The root rot (Diplodia spp)
• The papaya powders mildew (Levellula taurica (Lev) Arn)
• Pod rot disease (Drechslera haraiiensis)
Fungi are significant destroyers of foodstuffs, vegetables and grains during storage rendering them unfit for human consumption by retarding their nutritive value and often by producing mycotoxins (Janardhana et al., 1998; Marin et al., 1999). A significant portion of the agricultural produce in some countries and the world over become contaminated by fungus infected grains (Janardhana et al., 1998). The main toxic effect of fungi is genetoxicity, hapatoxicity, nephrotocity, carcinogencity, terratogencity, reproductive disorder and immune suppression (Hacey, 1988). More than 25% of the world cereals are contaminated with known mycotoxin and more than 300 fungi metabolites are reported to be toxic to man and animals (Galvano et al., 2001). A sizeable portion of the world population living below poverty line in the developing and under developed countries of Asia and Africa are suffering from health problems associated with consumption of contaminated grain and cereals (Majunder et al., 1977).
Plant disease invasion started when man began to devastate the ecosystem and then broke the food chain in ecology and that led to food shortage and famine across the world (Walker, 1969). The increase in demand for moringa and its products has undoubtedly increased the rate at which the plant is moved from one locality to another and this may contribute to more imbalances in ecosystem and may also mean exposition of these localities to new diseases. India had been enjoying disease free farming of Moringa except mild attacks of Diplodia spp. which occurs mainly in water logged conditions but recently, the threats of Drechslera haraiiensis and its rot ravages is described as a new disease in India. Its symptoms are observed all over the surface of the pods, more conspicuously at the stigmatic end. On the green pod, elliptical or elongated sunken spots with reddish brown raised margins can be observed. Diseased pods are shrunken to thinner dimensions at their stigmatic ends than healthy ones. In advanced stages of the disease development, the pods are rotten and dried up prematurely leaving uneven raised spots over them