Anthracnose remains an important biotic factor constraining the efficient production of cowpeas in tropical and subtropical regions of the world especially in Nigeria. Correct and accurate identification of its causal organism is essential for tailoring appropriate control or management techniques for this impediment. So far, many Colletotrichum organisms have been reported as responsible for causing this disease in the crop. It appears that majority of these reports were predicated on morphological and colony characteristics of the pathogens from culture studies and/or in some cases, on uncritical assumption of host-specificity of the pathogens. This makes for the identity of the causal organism of anthracnose in the crop to be generally unclear, confusing and a subject of much scientific debate. In the Colletotrichum patho-system, it is known that different species could cause anthracnose of the same host. Since isolates, show overlapping ranges of morphological, colony and phenotypic characteristics, molecular diagnostic approaches such as sequence analysis of the internal transcribed spacer (ITS) region (1.8S and 5.8S; 5.8S and 28S genes) and sequence analysis of β tubulin genes which offer comparative variability for resolving phylogenetic relationships of Colletotrichum species; as well as sequence analysis of introns from two genes (glutamine synthase and glyceraldehydes-3-phosphate) and MAT1-2 mating sequences which have allowed differentiation of isolates from species complexes could play vital roles in discriminating the causal organism(s). Though cultural strategies, tolerant and resisitant varieties against the disease and chemical interventions are used in managing the disease; resistance have been reported to be only temporary due to variability of Colletotrichum pathogens. Chemical interventions are disadvantaged in being human and eco-health disruptive; in addition to the fact that Colletotrichum spp. have shown resistance to carbendazim, thiophenate-methyl and benomyl. This review peers into the economic importance of anthracnose of cowpeas, its causal agent(s), management strategies for the disease and elaborated the response of the anthracnose organisms to phyto-chemicals from tropical plants for Integrated Disease Management (IDM) programs.

Abstract. Enyiukwu DN, Amadioha AC, Ononuju CC. 2020. Histological aberrations and mode of damage of cowpea (Vigna unguiculata) by Colletotrichum destructivum. Nusantara Bioscience 13: 16-23. Leaf and stem of healthy 2-week old cowpea (Vigna unguiculata L. Walp.) seedlings were inoculated with spore suspension of the Colletotrichum destructivum O’Gara. Sections of the infection courts were prepared and examined under digital microscope. The results showed that the infection process began 12 hours after inoculation (hai) with the germination of spores of the fungus. Large multi-lobed primary hypha (somewhat spherical in shape) developed from the infection peg and remained inside a single epithelial cell for about 3 days. Towards the end of this time, the primary hyphae developed thin filamentous tentacles that punctured and branched into adjoining cells, initiating necrotrophic phase of the disease. During this period, typical anthracnose symptoms began to develop on the infected organs of the crop. The entire infection process lasted a maximum of 96 h, at the end of which acervulus that bore a single seta emerged on infected crop lesions. The mechanism of damage of the pathogen involved intra-cellular and inter-cellular colonization of the host tissues early and late in the disease cycle. The integrity of the affected tissues' cells was compromised by passage and colonization of Colletotrichum destructivum O’Gara evidenced by lack of clear-cut middle lamella and cell boundaries. Anthracnose affected cells dispossessed of vital nutrients became turbid, devoid of turgidity and vigor. Thus, these results have strong implications for plant health management in that effective environment-compliant control of the fungus should be initiated on or before the third day following arrival of the conidia of the pathogen on the crop. Seeds are major agents of introduction of Colletotrichum spp. to disease-free locations. Findings from this study also support that strong trans-border control of seeds of the crop should be maintained since the pathogen is known to be seed-borne and demonstrates sufficient cross-infection of crop plants. Key words: Hemibiotrophy,  Colletotrichum destructivum, Anthracnose, Cowpea,  Hyphal colonization

Abstract. Enyiukwu DN, Amadioha AC, Ononuju CC. 2021. Evaluation of some pesticides of plant origin for control of anthracnose disease (Colletotrichum destructivum O’Gara) in cowpea. Asian J Agric 5: 4-11. Anthracnose is a common disease of cowpea in many bean growing areas of the world. This study evaluated the effects of Alchornea cordifolia, Tabernaemontana pachysiphon, and Lantana camara as low-input biopesticides for control of the disease. The experiment was laid out in randomized complete block design (RCBD) made up of 14 treatments with 4 replications. The results indicated that all the plant materials irrespective of carrier solvent and concentrations of application significantly (P?0.05) minimized the incidence and severity of the disease, as well as improved the yield and yield parameters of the treated crop than the control. Amongst all evaluated dosages of the plant materials, 50-100 % concentration of L. camara gave the best disease control and yield improvement of the crop, followed by full strength of T. pachysiphon and A. cordifolia was the least. However, comparative to benomyl a standard fungicide, the plant-derived pesticides demonstrated lower fungitoxicity against the pathogen apart from 50-100 % extracts of L. camara which were statistically (P?0.05) at par with the effects of the fungicide. Therefore, all the plant extracts could be used at higher doses as prophylactics to stem the disease; however, L. camara could be applied at lower doses to achieve the same level of control. These plant materials overall could therefore contribute as effective bio-fungicides towards improving productivity of cowpea in the humid tropics.

Brown spot disease, caused by Helminthosporium oryzae, is worldwide problem capable of causing considerable damage to paddy in the nursery, field or grain yield. The disease is seed borne, and thus can be transmitted through infected seeds and crop residues, alternate hosts and contaminated irrigation water. The objective of this study was to evaluate the effect of plant extracts on radial growth of Helminthosporium oryzae on rice plants. An in-vitro experiment was conducted at the Plant Pathology Laboratory of National Root Crop Research Institute, Umudike, Abia State, in Nigeria. Treatments included water and alcohol extracts of Azardiractha indica (Neem leaves), Piper guinensis (seeds), Garcinia cola (Bitter cola seeds), Ocimum gratissimum (leaf) and Vernonia amygdalina (leaf); and synthetic fungicide (Benomyl) at a concentrations of 10, 25 and 30% of the extract applied to H. oryzae in culture. The test materials were administered on Helminthosporium oryzae, sourced from rice seeds and infected shoot system of rice. Alcohol extract of Piper guineensis had the highest radial growth inhibition (89.89%) by the fifth day, but was not significantly different from Azardiractha indica, which had an inhibition value of 81.02%. The least effective plant extract was Ocimum gratssimum with radial inhibition of 11.50%, which occurred also on the fifth day. Plant extracts were as effective as the synthetic fungicide in inhibiting growth of the test fungus. Therefore, the effective extracts, all of which are readily available to the farmers, should be promoted instead of the synthetic fungicides, which are in limited supply and invariably expensive for rice farmers in Nigeria.

The effect of agricultural wastes and a botanical on root knot nematode (Meloidogyne spp) on okra (Abelmoschus esculentus L. Moench) was investigated in pot experiment. The experiment was laid out in a completely randomized design with five treatments each replicated five times. The treatments included: sawdust, oil palm sludge, cassava peels, bitter leaf powder, carbofuran plus untreated control. All the treatments except oil palm sludge and nematicide were applied at the rate of 20 g each. Oil palm sludge was applied at the rate of 20 ml while the nematicide at 3.0 g ai per plant. The plants were inoculated with 2000 nematode eggs (Meloidogyne spp.) three weeks after emergence. Treatments and fertilizer were applied one and three weeks after inoculation respectively. Eight weeks after treatment application, the experiment was terminated and the following collected; fresh and dry shoot weight, plant height, number of leaves, number of galls, population of nematode eggs in the roots and nematode population in the soil. Results obtained indicated non-significant difference between the treatments in the parameters recorded except plants treated with bitter leaf and nematicide in some cases. Generally, results from bitter leaf were better and compared favourably with the nematicide treated plants.