The document summarizes research on managing bean root rots (BRR) in a bean-based cropping system in Southwestern Uganda. It finds that: 1) BRR are a major problem for beans production and sorghum and peas in the system also suffer from root rots, likely playing a role in sustaining BRR pathogens. 2) Experiments show BRR pathogens infect and cause disease on beans, sorghum, and peas, suggesting these crops serve as alternate hosts. 3) Management practices like farmyard manure and inorganic fertilizers improved plant growth and yields but had minimal effect on disease levels, likely due to high pathogen populations in fields. Integrated approaches are needed to effectively

1. 1
MANAGEMENT OF BEAN ROOT ROTS IN THE BEAN-
BASED CROPPING SYSTEM IN SOUTHWESTERN
UGANDA
Walter OCIMATI
BSc Agric. (Hons)
Makerere University, P. O. Box 7062,
Kampala, Uganda

2. 2
•Common bean is an important food legume in Uganda
Introduction
•Production in southwestern (SW) highlands has declined
• Bean root rots (BRR) are the main cause for the decline
Ranks 3rd
Provides 25% calories,
45% dietary protein intake
Widely grown

3. 3
Problem statement
•Beans are often grown in crop mixtures
•BRR pathogenic Pythium spp. are
reported to be multi-host.
•The role of other crops in the SW farming system on BRR
occurrence is not known.
•These could potentially be responsible for sustaining BRR
disease.

4. 4
•RR could also be a serious problem on other crops, some
of which could be companion crops in bean intercrops.
•This is not fully investigated to date.
•BRR control practices could apply to the whole cropping
system
•Benefit beans, but also other crops in the cropping
system
ustification of the study

5. 5
Research objectives
•To determine the extent of RR on major crops
associated with beans as intercrops or in rotation.
•To determine the contribution of other crops in the
survival of BRR in the bean-based cropping system.
•To determine the effect of fungicides and application of
organic and inorganic fertilizers on RR occurrence on
major crops in the bean-based cropping system.

6. 6
Hypotheses
•The major crops in the bean-based cropping system do
not suffer from RR as is the case with beans.
•The major crops in the bean-based cropping system have
no influence on the survival of the BRR pathogens.
•Fungicides, organic & inorganic fertilizers do not affect
RR occurrence on other crops within the bean-based
cropping system.

7. The Extent of Root Rots on Major Crops
Associated with Bean Intercropping or
Rotations in Kabale, Uganda
7

8. Materials and methods
•Experiments done in the first & second rainy seasons of
2004 on farmers’ fields in Kabale district
•RR susceptible bean variety (K132) & bean inter/
rotation crops –maize, sorghum and peas used
•Crops were randomly assigned to experimental plots
•Measuring 3m x 4m in eight farmer fields
•A randomized complete block design (RCBD) used, each
field acting as a replicate/block.
8

9. •Both qualitative & quantitative data collected.
•Quantitative data included:
Plant stand (%) at 18, 36, 54 & 72 days after planting (DAP)
RR incidence (%)
RR severity at 36, 54 and 72 DAP (CIAT nine-point RR
severity scale (Abawi & Pastor Corralles, 1990) adapted ).
•ANOVA - using the GenStat 11th
Edition software.
•Means separated by LSD at p = 0.05.
9

10. Results
•Abnormal above & below
ground reactions were
evident
Peas Maize Sorghum
Sorghum
RR characteristic lesions - visible at 18 days (DAP)

11. 11Fig 1: Plant stand in beans, maize, sorghum & peas
Bean Maize
Sorghum Peas

12. 12
Crop Seasons
Days after planting (DAP)
36 54 72
Beans First season 8.43 8.57 D
Second season 8.5 6.81 D
CV% 7 15.3 D
LSD (5%) 0.773NS
1.537* -
Maize First season 2.29 4.9 5.3
Second season 4.14 4.14 5.09
CV% 26.5 16.2 11
LSD (5%) 1.116** 0.958NS
0.748NS
Sorghum First season 6.16 8.63 9
Second season 8.79 7.95 9
CV% 13.9 7.2 0
LSD (5%) 1.354** 0.783NS
-
Peas First season 3.46 6.86 7.6
Second season 4.01 5.67 4.56
CV% 29.2 30.7 25.8
LSD (5%) 1.445NS
2.516NS
2.017**
Table 1. RR severity in naturally infested fields

13. Discussion
• Beans & sorghum were more severely affected by RR
• Continuous cropping - results in a high build up of RR
• Crop rotation is rare, only dominance of crops shifts with
seasons.
• BRR pathogens (P. ultimum, P. pachycaule & F. solani) are reported
to affect peas & sorghum
• The RR burden in sorghum & peas could negatively impact on
the BRR problem and vice versa.
• The fight against RR in this region needs broadening
• The high RR in the second season - attributed to the humid
conditions that favour the survival RR pathogens.

14. The Contribution of other Crops in
the Survival of Bean Root Rots in the
Bean-based Cropping System
14

15. Materials and methods
• Study done under screen house at NARL –Kawanda in 2005
• BRR pathogens Pythium spp. & Fusarium spp. separately
cultured
• Grown on autoclaved millet in 500ml bottles over 2 weeks.
• To mimic the field pathogen complex, Pythium spp. (mixed
4:4:1 of P. ultimum: P. salpingophorum: P. torulosum (v/v)) was
mixed with Fusarium spp. in the ratio of 4:1 (v/v).
• The culture mixture was then mixed with pre-sterilized soil
in a ratio of 1:8v/v in 42cm x 72cm wooden flats
15

16. •Inoculum allowed to establish for 18 days.
•Two rows of each crop (beans (K131), maize, sorghum &
peas) planted & replicated thrice.
•Plants were periodically watered.
•A repeat experiment conducted in the same year 2005.
•RR incidence & severity was assessed as in objective 1.
•Data analysed as in objective 1.
16

17. Crops Seasons
Root rot incidence (%) Root rot severity
18 DAP 36 DAP 54 DAP 72 DAP 36 DAP 54 DAP 72 DAP
Beans First trial 100 100 100 100 4.3 3.83 8.75
Repeat trial 100 100 100 100 6.7 4.67 7.5
CV% 0 0 0 0 36.4 3.9 9.2
LSD(5%) - - - - 25.40NS
2.12NS
9.53NS
Maize First trial 33.3 33 67 12.5 1.5 2.58 1.5
Repeat trial 33.3 67 50 100 2.5 1.83 3
CV% 0 66.6 85.5 22.2 16.7 34 0
LSD(5%) - 423.1NS
635.5NS
158.8NS
4.25NS
9.53NS
-
Sorghum First trial 100 100 100 100 5.5 5.17 7.25
Repeat trial 100 100 100 100 6.33 5.67 5.25
CV% 0 0 0 0 2.8 15.4 16
LSD(5%) - - - - 2.12NS
10.59NS
12.71NS
Peas First trial 83.3 33 83.3 100 2.17 3.08 8.5
Repeat trial 100 67 33.3 100 1.67 1.83 6
CV% 18.2 66.6 28.6 0 43.5 23.7 3.4
LSD(5%) 211.8NS
423.1NS
212.2NS
- 10.59NS
7.41NS
3.18NS
Table 2. Percentage root rot incidence & root rot severity in
artificially inoculated soils in screen house trials at Kawanda in 2005.
Table 2. Percentage root rot incidence & root rot severity in
artificially inoculated soils in screen house trials at Kawanda in 2005.
Results

18. Discussion
• RR lesions were visible on all the crops.
• Beans, sorghum and peas, respectively were more
susceptible.
• Sorghum/peas possibly play a role as alternate hosts affecting
survival/inoculum density of BRR pathogens & BRR
severity.
• Similar observations were reported by Gichuru (2008)
• P. Ultimum colonised & infected sorghum & pea roots but not
maize (Gichuru 2008) 18

19. Effects of Fungicides, Organic and
Inorganic Fertilizers on Root Rots of Major
Crops in the Bean-based Cropping System
19

20. Materials and methods
•Study conducted on farm and in a screen house
•Farm evaluation- in the first & second cropping seasons
of 2004 on farmers’ fields in Kabale district.
•8 farmer fields each acting as a block/ replicate used
•Each field divided into 20 plots of 3m x 4m
•RCBD with split plots used
•RR management practices randomly assigned to subplots
•Component crops assigned to main plots 20

21. •Management practices included:-
farmyard manure (FYM, at 5t/ha),
green manure (GM, at 5t/ha),
inorganic fertilizer (NPK 17:17:17, at 50Kg of N, P and K),
fungicide (Ridomil Gold MZ 68 WP; 4% Metalaxyl-M & 64%
Macozeb; seed dressed at 2.5Kg/ha),
an un-amended control (C).
•Data collected included:
Plant stand (%), RR incidence (%), RR severity as in objective 1.
Plant vigour at 36 DAP (CIAT 1–9 vegetative adaptation scale)
Dry matter (g) at flowering stage.
•Data analysis – as in objective 1 & 2 21

22. • In the parallel screen house soils were inoculated with
BRR pathogens (Pythium spp. & Fusarium spp.)
• Inoculum prepared as in objective 2.
• NPK, FYM, GM, Metalaxyl-M & control allocated
randomly to the fifteen wooden flats with infested soil.
• FYM, GM -applied at 151.2g/wooden flat, NPK at 8.89g.
• GM, FYM - allowed to set for 14 days before planting.
• Data collected on RR incidence, severity, plant vigor and
dry matter & analysed as in the field experiment.
22

23. NPK
Results
• In most cases plant stand, RR incidence & severity were not
significantly improved by the management options.
• Their impact was least observed on beans & sorghum
• FYM & Ridomil had lower incidences & severities early in
the season, while GM exacerbated the RR problem.
23
Control
Ridomil
GM
FYM
FYM
GM
Ridomil
NPKControl
Beans Maize

24. NPK
Control
Ridomil
NPKControl
Treatment/Crop
Dry matter yield (g)
Beans Maize Sorghum Peas
Control 12.3a 15.1 2.0 15.8a
FYM 19.0b 22.6 4.2 28.6c
GM 11.8a 17.0 2.7 17.1ab
Ridomil Gold MZ 68 WP
10.2a 16.7 2.0 19.2ab
NPK 20.2b 20.6 3.1 23.3bc
CV% 52.6 68.1 133.1 45.7
Table 3. Effect of BRR management practices on mean DM yield
in beans, maize, sorghum and peas in farmer fields infested with
RR pathogens.
• FYM & NPK improved plant vigor & dry matter (DM)
yield

25. 25
NPK
Control
Ridomil
NPKControl
Crop/ Treatment
Dry matter yield (g)
Beans Maize Sorghum Peas
Control 3.33a 6.88a 2.64a 2.64
FYM 8.20b 13.91b 3.72b 3.03
GM 3.76a 7.01a 2.70ab 2.57
Ridomil Gold MZ 68 WP
4.00a 6.15a 2.71ab 2.90
NPK 5.22a 23.88c 3.40ab 2.73
CV% 31.4 15 21.7 13.6
LSD (5%) 2.426** 2.735*** 1.038NS
0.602NS
Table . Effect of BRR management practices on mean dry matter yield
in beans, maize, sorghum & peas in screen house trials with soils
artificially inoculated with Pythium spp. & Fusarium spp. in a ratio of 3:1

26. Discussion
• RR management options improved plant vigour & DM
• Had minimal effect on disease incidence & severity
• High soil pathogen population possibly masked their effect
• Benefits from soil amendments could reasonably improve if soil
pathogen population was below a certain threshold.
• These amendments need to be evaluated over several seasons.
• Some GM increase RR effects- possibly the case with Crotalaria spp.
• Increasing the time between the incorporation of Medicago GM &
the sowing the crop reduced the severity of disease. 26

27. Conclusions
•RR are still a major problem to beans in SW Uganda
•Sorghum & peas in this cropping system suffer from RR.
•The RR burden in sorghum & peas warrant intervention.
•Sorghum & peas are potential alternate hosts to BRR
pathogens.
•BRR management practices are also effective in
management of RR in other crops in the system.
27

28. Recommendations
• RR organisms in the RR complex of these crops (especially
sorghum & peas) in SW need to be identified.
• Sorghum/ peas intercropping/ rotation with beans
discouraged.
• Cross infection studies are needed.
• A systems approach instead of the current commodity
approach should be adopted for managing RR.
• The optimum period between GM application & planting
needs to be determined.
• FYM & GM need to be evaluated over several seasons. 28

29. Acknowledgments
• Dr. Geoffrey TUSIIME,
• Dr. Robin BURUCHARA,
• Dr. Fina OPIO and Michael A. UGEN
29

30. Thank you
30