This Power point contains information on some major diseases of sweet potatoes.

1. DISEASES OF SWEET
POTATOES
Name: Ruth-Ann Morris
Course: Plant Pathology
1

2. Introduction
• Scientific Name: Ipomoea batatas.
• Family: Convolvulaceae.
• It is an herbaceous perennial.
• Grown for its edible storage root.
• The plants are grown in the form of creeping vines.
• Their average length is 13ft.
2

3. Sweet potatoes tubers
3

4. Sweet Potatoes Leaves and Flower
4

5. 6 Diseases of sweet potatoes
• 1. Black rot
• 2. Cercospora leaf spot
• 3. Fusarium Wilt
• 4. Rhizopus Soft Rot
• 5 Leaf stem and scab
• 6. Streptomyces ipomoea
5

6. Black Rot
• Caused by: The Ascomycete fungus (Ceratocystis
fimbriata).
• Symptoms: Stunted plants; wilting plants; yellowing
plants; dropping leaves; plant death; circular brown-
black patches of rot on tubers.
• Management: Plant only the clean and healthy
seeding materials. seed material should be treated
with an appropriate fungicide prior to planting. sweet
potato should not be planted in sites where sweet
potato has been grown during the previous 3-4 years.
6

7. Picture showing Black Rot
Yellowing in Sweet Potatoes leaves
7

8. Picture showing Black Rot
Circular brown-black patches of rot on tubers
8

9. Cercospora leaf spot
• Caused by: Cercospora bataticola
• Symptoms: Dark brown spots on both side of the leaves
with a light shade in the center.
• Management: Cultural practices that help prevent and
reduce disease incidence include: Avoid overwatering or
watering in the late evening to reduce free moisture. Avoid
overhead watering where the water can dislodge and
disperse spores to uninfected plants.
9

10. Picture showing Cercospora leaf spot
Spots on leaf
10

11. Fusarium Wilt
• Caused by: A strain of the fungus Fusarium oxysporum.
• Symptoms: yellowing of older leaves followed by wilting,
leaf drop, and stunting or dying of the plant. Discoloration
of the vascular tissues of the stem occurs earlier (dark
tanned rot in root).
• Management: Select only disease-free/ resistant roots for
seed; use cut transplants rather than slips; practice crop
rotation; treat seed roots with an appropriate fungicide
prior to planting.
11

12. Picture Showing Fusarium Wilt
Discoloration in stem
12

13. Rhizopus Soft Rot
• Caused by: The black bread mold fungus “Rhizopus
nigricans”
• Symptoms: Infected tissues become soft, stringy and
watery, with a fermentation odor, which causes decay
later on.
• Management: Since this disease occurs during post
harvesting, the crops should be properly handled and
stored in proper temperature.
13

14. Picture showing Rhizopus soft rot
Watery Sweet potato
14

15. Picture showing Rhizopus soft rot
Decaying Sweet potato
15

16. Leaf stem and scab
• Caused by: The fungus Sphaceloma batatas
• Symptoms: Scabby lesions form on stems, Small brown
lesions on leaf veins which become corky in texture and
cause veins to shrink causing leaves to curl.
• Management: Rotate sweet potato with other crops,
Avoid the use of overhead irrigation and good control of
the disease can be achieved licensed chemicals.
16

17. Picture Showing Leaf and Stem scab
Curling in leaves
17

18. Picture showing leaf and stem scab
Scab on stems
18

19. Streptomyces ipomoea
(Pox)
• Caused by: Bacterium
• Symptoms: Poor growth in plants, Circular dark brown
corky lesions on tubers, Cracked and distorted tubers.
• Management: The most effective method of controlling
the disease is through the use of resistant varieties of
sweet potato; if resistant varieties are not being used then
the soil should be maintained at a low pH which is
unfavorable to the pathogen.
19

20. Pictures showing Streptomyces
ipomoea
Lesions on tuber
20

21. Conclusion
• It can be concluded that most of these
disease in the sweet potato plants can all
be prevented or minimize by planting
disease free/ resistant varieties.
21

22. References
• Diseases of Sweetpotato. (n.d.). Diseases of
Sweetpotato. https://www.apsnet.org/edcenter/resources/commonna
mes/Pages/Sweetpotato.aspx
• Irish & sweet potato diseases. (2021, June 14). Home & Garden
Information Center | Clemson University, South Carolina.
https://hgic.clemson.edu/factsheet/irish-sweet-potato-diseases/
• Sweet potato | Diseases and pests, description, uses, propagation.
(n.d.). PlantVillage. https://plantvillage.psu.edu/topics/sweet-
potato/infos
22