Cowpea diseases Sanag University

cowpea diseases research in sanaag region somaliland

1. CHAPTER TREE COW PEA DISAESES

2. SEEDLING MORTALITY ANTHRACNOSE PYTHIUM STEM ROT SCLEROTIUM STEM ROT FUSARIUM WILT BROWN RUST BLACK SPOT (LEAF SMUT) POWDERY MILDEW BACTERIAL CANCER COWPEA (SEVERE) MOSAIC VIRUS (CSMV) List of cow pea diseases

3. Causal agent: Pthujam aphanidermatum Distribution and Importance : the Causal fungi are global. Seedling mortality has been investigated only in Nigeria but the disease probably occurs elsewhere. Seventy five per cent mortality of cowpea seedlings has been found with in 21 days after sowing. Disease occurrence is highest during cool, wet , cloudy weather. SEEDLING MORTALITY

4. Symptoms : Both pre and post-emergence mortality occur; in the latter case, symptoms can be observed on the hypocotyls. The reddish brown lesions caused by C solani are usually limited to the collar region of the leaves and seeds.

5. Spread and controls: These pathogens are abundant in soil where the humid environment is favourable for their activity. Management options Corp rotation Field sanitation Seed treatment with chloroneb seed dressing ( 2g/kg).

6. Causal agent: Colletotrichum lindemuthianum Distribution and Importance: The pathogen is widely distributed, being present in almost all areas where beans ( Phaseolus vulgaris) are grown. The disease is particularly severe in monocropped cowpeas in which it can cause up to 50 percent loss in yield. ANTHRACNOSE

7. All aboveground parts can be affected but anthracnose is chiefly a stem disease in cowpea. Individual lesions are lenticular to sunken, and dark to brown in colour. Lesion size and spreading depend on varietal susceptibility . Highly susceptible lines develop large spreading lesions which rapidly merge to stems , branches and petioles. Anthracriose can be distinguished from covering by the presence of black shield, and from the related brown stain fungi by the shape of the (C). Symptoms

8. Primary inoculum may come from seed (40% seed transmission) or from diseased plant debris. Secondary spread is rapid during cool, wet weather. The disease may be controlled by using clean seed , applicaion of mancozeb (0.2 percent ) or by growing resistant varieties . Spread and Control

9. Causal agent: Pythium aphaniderinatum Distribution and Importance: Worldwide . In Nigeria, field rate in cowpea normally ranges between 0.5 -10.0 percent , although occasional incidences of up to 30 percent have been observed. PYTHIUM STEM ROT

10. Pythiurn stem rot is characterized by a grey-green water soaked rope of the stem spreading from soil level Edge to and sometimes including the lower portions of the lower branches. During periods of high humidity copious growth of white, cottony Mycelia occurs at the stem base. Infected plants quickly wilt and die . Symptoms

11. Probably not seed transmitted. Principally soil-borne. sanitation Crop rotation Bi-weekly applications of captafol effectively control the disease, actually increase its frequency. Spread and Control

12. Causal agent: Corticiurn rolfsii = Sclerotium rolfsii ) Distribution and Importance : The pathogen is widespread in moist tropics and warm temperate areas but the disease is of minor importance on cowpea. SCLEROTIUM STEM ROT

13. The causal fungus infects the centres of stems producing a follower of silky white myceliam and large round sclerotia which are initially white and slowly darken. Infected plants wilt and die. The mycelium and presence of sclerotia serve to distinguish this disease from Pythium stem rot which it otherwise resembles. Occasionally , concentric leaf spots are also encouraged by C. rolfsii Symptoms

14. C . rolfsii is an unspecific parasite capable of extensive Parasitic growth in surface layers of soil, continuing on crop residues and weed hosts. The sclerotia are spread by cultivation, wind and water, and rarely as toxins among seed. Control may be achieved by cultural means. Spread and Control

15. Causal agent : Fusurium oxysporurn Distribution and importance: fairly wide spread , being reported from North and south America, Asia and Australia. Constantly recorded in tropical Africa, Locally damaging . Hosts include cowpea and soybean. FUSARIUM WILT

16. Leaves of infected plants are wilting and yellowed and in young plants a rapid wilt leads to death. Older plants are stunted, leaves turn yellow and then fall and the plant gradually wilts. The vascular tissue is typically necrotic ,and it is this symptoms and the presence of characteristic spores, which distinguish the disease from the stem rots. Symptoms

17. The pathogen Is soil-borne and probably also seed transmitted. Control is best achieved through: Sanitation Crop rotation Seed treatment with suitable fungicides and growing resistant varieties. Spread and Control:

18. Causal agent : Uromyces appendiculatus Distribution and Importance : World wide. Highly susceptible lines can be almost completely defoliated by mid-flowering time so that yield loss is probably severe. BROWN RUST

19. Spots development on leaf surfaces , releasing powdery, reddish-brown spores. The spots may be surrounded by yellow haloes, then by rings of secondary spots. The color of the spots becomes black as the pigmented pores develop. The fruiting stage occasionally causes a stem rust disease. Symptoms

20. Rust is not seed borne . The dispersal of rust is favoured by cloudy , humid weather with heavy droplets, and temperature of 21-27°C. spores are distributed principally by wind. Control of rust may be achieved by spray and by the use of resistant varieties/hybrid is the best control measure, through the presence of numerous pathogenic races. Spread and Control:

21. Causal agent: Protomycopsis phaseoli Distribution and importance: This disease is widely distributed on cowpeas in tropical Africa and Jamaica, and on cowpeas, beans and other legumes in India and Nepal. The disease is of major economic importance on cowpea in Brazil where yield losses of 30-40% are reported. BLACK SPOT (LEAF SMUT)

22. Dark ash-grey to black circular discrete leaf spots 6-8mm diameter, surrounded by narrow yellow haloes. The leaf spots enlarge (to 10mm or more), becoming greenish-grey, irregular and diffuse severe infections cause pre mature defoliation. Symptoms

23. Black spot survive in plant debris for at least two years but lower their viability when buried. The fungus is not seed-borne. Control measures would include R otation , destruction of crop residues , and U se of fungicides . Resistant varieties have been identified to use. Spread and control

24. Causal apen t: Erysiphe polygoni apparently of greater importance in tropical America, and India than it is in Africa . Disease severity often greater under of dry shady conditions . POWDERY MILDEW

25. Mycelium forms Artificial, scattered, spreading patches/covers, it white first turning greyish , on leaves and other plant parts . Symptoms

26. Not known; not seed-borne . Mycelium is known to be tolerant of low humidity . Survival possibly as active infection. To control use resistant varieties and suitable fungicides Spread and Control:

27. Causal agent: Xanthomonas vignicola Distribution and Importance: A widespread and important disease of cowpea in tropical Africa, America and India. Seedling mortality resulting from seed-borne infection may be up to 60 percent . Yield losses from field infection have not been estimated. BACTERIAL BLIGHT (CANKER )

28. The initial symptoms of bacterial blight are tiny water soaked dots on leaves. These dots remain small and the surrounding tissue dies. developing a brown to orange coloration with a yellow halo. On heavily infected ,leaves the dead spots merge so that large areas of leaf are affected. The pathogen also infects the stem, causing cracking (stem canker), and causes water soaking of pods from where the pathogen enters the seed. Symptoms

29. The disease spread rapidly during heavy rainfall, and during over head irrigation. The pathogen is seed borne, and probably survives on diseased cop residues . Methods of control include: T he use of clean seed or seed treatment and R esistant varieties. Spread and Control:

30. Distribution and Importance: widespread in tropical and sub-tropical areas of Africa and America . In Brazil,yield losses of 60-80% are caused by CSMV COWPEA (SEVERE) MOSAIC VIRUS (CSMV)

31. Symptoms: A kind of mosaics spread and Control: Sap , and seed-borne ( 10%) and transmitted by several beetles including Ceratoma spp , and other common weeds in tropical areas may act as lakes of CSMV . Resistant cowpea varieties are available