cowpea diseases research in sanaag region somaliland

1. COW PEA DISAESES

2. 
1. SEEDLING MORTALITY
2. ANTHRACNOSE
3. PYTHIUM STEM ROT
4. SCLEROTIUM STEM ROT
5. FUSARIUM WILT
6. BROWN RUST
7. BLACK SPOT (LEAF SMUT)
8. POWDERY MILDEW
9. BACTERIAL CANCER
10. 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. 

6. 
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).

7. 
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

8. 
 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

9. 

10. 
 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

11. 
 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

12. 
 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

13. 
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

14. 

15. 
 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

16. 
 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

17. 

18. 
 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

19. 
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

20. 
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

21. 

22. 
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:

23. 
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

24. 
 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

25. 

26. 
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:

27. 
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)

28. 
 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

29. 
 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
 Rotation,
 destruction of crop residues, and
 Use of fungicides.
 Resistant varieties have been identified to use.
Spread and control

30. 
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

31. 
Mycelium forms Artificial, scattered, spreading
patches/covers, it white first turning greyish, on leaves
and other plant parts .
Symptoms

32. 

33. 
 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:

34. 
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)

35. 
 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

36. 
 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:
 The use of clean seed or seed treatment and
 Resistant varieties.
Spread and Control:

37. 
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)

38. 
 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