scientific conf

1. CULTURAL APPROACH FOR THE MANAGEMENT
OF RUSSIAN WHEAT APHID (diuraphis noxia
kurdjumov) INFESTATION ON SELECTED BREAD
WHEAT VARIETIES
• M.N. Njuguna., M. Macharia, H.G.Mwangi, J.K, Kamundia, I Koros,
and G. Ngotho.

2. Introduction
• Wheat is an important staple food crop ranking second after maize in
Kenya.- source of both food and feed (FAOSTAT, 2009).
• Domestic requirements - 1,750,000 MT against production - 442,000 MT
(USAID, 2014).
• Cereal aphids are among the most serious biotic constraint to wheat
production.
• RWA - most destructive causes 25-95% yield loss (Macharia et al., 2002).
• All commercial wheat varieties grown by farmers in Kenya are susceptible
to RWA (Macharia et al., 2002).
• Current control strategies use aphicides (Macharia et al. 2012),
• Hence there is need for development of an integrated approach in
management to reduce cost of production and safe the environment.

3. Methodology
• Studies were conducted to evaluate appropriate seeding and nitrogen
rates in the management of RWA at Njoro (2,164 m asl) in 2011, 2012
and 2013 crop seasons.
• The trial design- (RCBD) in a split plot arrangement replicated 3 times
Treatments:
 Wheat varieties- K. Tai, K. Kingbird, K Wren, K. Korongo, K. Hawk,
K. Sunbird, Robin, K. Eagle, and NBWII
Seed rates: (SR) 75, 100 and 125 kg/ha were assigned to the subplots.
Nitrogen rates - 75, 100 and 130 kg N/ha soil applied at
tillering.
 DAP (NPK 18:46:0) at 100 kg/ha to provide starter nutrients.

4. Methodology…
• Wheat was sown to coincide with RWA pick infestation period using plot
seeder.
• Crop management- recommendations (KARI, 2005)
No insecticide application done
• Five plants/plot were randomly selected, RWA identified and counted.
RWA symptoms identified:- were rolled flag leaf,
leaf/sheath purple coloration
and fish hook ears (Macharia et al. 2012).

5. Methodology…
• RWA counts were transformed (√x+1) (Gomez and Gomez 1984)
• Plots cut with a sickle and threshed by experimental plot thresher.
• Data collected: tillers, spikes, biomass, TKW, harvest index (HI) and
grain yield.
(Rashid, et al., 2007)
• Grain moisture adjusted to 12%, grain weight recorded;
1000 grains were counted and weighed.

6. Methodology…
•The data analysis (SAS, 1994).
•ANOVA-conducted among the treatment means.
•Means separated using Least Significant Difference (LSD).
•Yield benefits were calculated among different rates of N application
and seeding rates as follows
•GY Benefit =GY (N applied)-GY (no N applied)
•GY Benefit =GY (high SR) - GY (lowest SR)

7. Results and Discussions…
• Aphid counts were Significant (P<0.05) among varieties (Table 1).
K. Korongo - lowest RWA counts
- NBWII -highest RWA counts
RWA showed preference for NBWII, agrees with De Zutter et al.
(2012)
• Tillers/m2
and spikes/m2
, were significant (P<0.05) among the varieties.
Njoro BWII - highest tillers and spikes/m2
,
K. Wren and K. Kingbird -lowest tillers/m2
and
spikes/m2
.
• More tillers/spikes in NBWII did not lead to increased yield - probably
due to high RWA infestation

8. Results and Discussions…
• Yield components were significant (P<0.05) among varieties.
Robin- highest BM accumulation
 K Kingbird - lowest BM
K.Korongo - highest TKW and K Kingbird the lowest
• Grain yields were significant (P<0.05) among varieties was
Robin - gave the highest yield followed by K Korongo
Kingbird, K Eagle and NBWII – lowest yield
• The high vegetative growth and susceptibility to RWA observed in
NBWII may have caused the low grain yield.

9. Variety K Tai K
Sunbird
K Wren K
Korongo
K Hawk K
Kingbird
Robin K Eagle NBWII MEAN LSD CV
(%)
2011
Aphids 3.3bc 3.6bc 3.6bac 2.8c 3.1bc 3.8ba 2.9bc 3.2bc 4.3a 3.4 0.88 2.11
Tillers/m2
111.1ba 116.9a 90.9c 120.5a 104.3bac 94.5bc 117.7a 114.4a 121.9a 110.2 18.3 1.97
Spikes/m2
82.2bdc 88.1bac 74.3dc 95.0ba 81.4bdc 71.0d 96.0ba 88.0bac 99.1a 86.1 15.8 1.97
Bio t/ha 5.1bdac 5.2bac 4.6de 5.5ba 5.3bac 4.2e 5.6a 4.8dc 4.9bdc 5.0 0.7 1.97
TKW 35.9dc 35.5ed 37.7ba 38.5a 36.4bdc 30.2f 37.2bac 33.9e 34.1e 35.5 1.6 1.97
HI 44.3 40.5 46.4 46.3 46.2 26.4 45.3 22.2 23.3 37.8 NS 1.97
YLD t/ha 2.2bc 2.1dc 2.1dc 2.5ba 2.4ba 1.1d 2.5a 1.1d 1.1d 1.9 0.3 1.97
2012
Aphids 3.9bc 4.4bc 4.4ac 3.0c 3.4bc 4.2ba 3.2bc 3.5bc 4.7a 3.9 0.97 2.11
Tillers/m2
122.2ba 128.6a 99.9.1c 132.6a 114.7bac 103.9bc 128.8a 125.8a 134.1a 121.2 20.1 1.97
Spikes/m2
90.4bdc 96.9bac 81.7dc 104.5ba 89.5bdc 78.1d 105.6ba 96.8bac 109.0a 94.7 17.4 1.97
Bio t/ha 5.6bdac 5.7bac 5.1de 6.1ba 5.8bac 4.6e 6.2a 5.2c 5.4bdc 5.5 0.6 1.97
TKW 39.5dc 39.1ed 41.5ba 42.4a 40.0bdc 33.2f 40.9bac 37.3e 37.5e 39.0 1.6 1.97
HI 48.2 44.3 51.0 51.2 51.1 29.4 50.3 24.6 25.9 36.1 NS 1.97
YLD t/ha 2.7bc 2.5dc 2.5dc 3.0ba 2.9ba 1.3d 3.1a 1.3d 1.3d 2.3 0.3 1.97
2013
Aphids 5.9b 5.5b 5.3cb 4.9d 4.9d 5.3cb 6.6a 6.0b 5.2cb 5.5 0.6 16.1
Tillers/m2
124.7bc 132.0bc 113.2c 112.1
c
158.8a 99.2c 116.5c 136.7a 153.5a 127.4 27.3 4.1
Spikes/m2
119.6ba 117.6bc 100.2d 101d 106.4d 86.8d 108.3d 126.7b 142.7a 112.0 13.3 2.3
Bio t/ha 6.5a 5.4b 5.6b 5.6b 5.3b 4.9cb 5.6b 5.7b 5.3b 5.7 0.6 1.9
TKW 31.8b 31.1c 33.1a 30.9d 30.7e 28.1i 29.2h 29.7g 30.2f 30.8 0.2 0.6
HI 44.9a 47.7a 43.0a 46.4a 40.9b 38.2b 38.2b 41.1b 41.4b 42.2 4.9 2.2
YLD t/ha 2.2cb 2.4b 2.4b 2.6b 2.1c 1.8d 3.1a 2.2cb 2.2cb 2.3 0.3 20.7
Table 1: Effect of aphid counts on yield and yield determinants of wheat varieties

10. Results and Discussions…
Effects of N application
•RWA: N rates were significant (P<0.05) on RWA densities (Table 2).
N at 100 kg/ha -highest RWA counts in the three seasons
N at 75 kg and 130 kg N/ha were not significantly (P>0.05) different
on RWA counts .
•This observation agrees with Sara et al. (2010) on improved crop
performance on higher N levels despite higher aphid infestation.
Yield and yield components:
•Nitrogen at 100 kg/ha increased tillers/m2
in 2011, 2012 and 2013 and
spikes/m2
in 2012 Haussain et al. (2008) findings.

11. Results and Discussions…
• N at 100kg N/ha - highest TKW and grain yields in the
three seasons.
• Although plots that received 100 kg N/ha had high
infestation, apparently N enhanced plants’ tolerance to
RWA hence high grain yield Silvina et al. (2005).
• Our observation agrees with Riedell, (2008) suggesting
that N fertilization may be a useful strategy for limiting
yield reduction caused by RWA in N deficient wheat crop

12. 2011
N rates 75 100 130 Mean Lsd (0.05) CV (%)
Aphids 3.3ba 3.7a 3.1b 3.4 0.6 1.97
Tillers/m2
106.5b 116.7a 107.6b 110.3 9.1 1.97
Biomass t/ha 4.9 5.2 5.0 5.0 NS 1.97
TKW 35.4b 36.5a 35.9b 35.9 0.6 1.97
Yield t/ha 2.0b 2.4a 2.2b 2.2 0.04 1.97
2012
Aphids 3.6b 4.1a 3.4b 3.7 0.7 1.97
Tillers/m2
117.5b 128.4a 118.4b 121.4 10.0 1.97
Spikes/m2
90.7b 99.7a 93.6b 94.4 6.1 1.97
TKW 38.9b 40.2a 37.0c 38.7 1.3 1.97
Yield t/ha 2.1b 2.5a 2.3b 2.4 0.03 1.97
2013
Aphids 5.6 5.7a 5.4 5.6 0.3 5.6
Tillers/m2
114.5b 151.1a 116.8b 127.4 27.3 4.1
Spikes/m2
106.5b 103.8b 125.8a 112.1 13.3 2.3
Biomass t/ha 5.5b 4.9c 6.6a 5.7 0.5 1.9
TKW 30.8 31.2 30.4 30.8 0.9 NS
HI 45.4a 42.6a 38.7b 42.2 4.9 2.2
Yield t/ha 2.1b 2.5a 2.4ba 2.3 0.25 20.8
Table 2: Effect of nitrogen on cereal aphid counts, yield and yield components
Means followed by the same letter in the same column are not significantly different at ( =0.05)Ɑ
Results and Discussions…

13. Results and Discussions
Effects of Seed rates
•RWA: Seeding rates significantly (P<0.05) influenced RWA counts
(Table 3).
SR-75 kg/ha - highest aphid counts
SR - at 100 kg/ha -lowest aphid counts
•Low plant densities are more susceptible to aphid attacks
(Infonet biovision 2013)
Yield and yield components
SR had significant (P<0.05) effect on spikes/m2
, BM, HI and grain yield but not
tillers/m2
in 2011.
SR at 125 kg/ha - spikes/m2
in 2011 and 2012
and BM followed by SR at 100 kg/ha.

14. 2011
Seed Rates kg/ha
Yield Components
75 100 125 Mean Lsd (0.05) CV (%)
Aphids 3.7a 2.9b 3.4ba 3.3 0.05 2.03
Spikes/m2
79.0b 86.9ba 91.7a 85.9 91.1 1.97
Biomass t/ha 4.9c 5.0b 5.2a 5.0 0.04 1.97
HI 44.0b 45.0a 43c 44 1.0 1.97
Yield t/ha 2.1ba 2.3a 2.3a 2.2 0.14 1.97
2012
Aphids 4.0a 3.2c 3.7b 3.6 0.05 2.03
Spikes/m2
86.9b 95.6ba 100.9a 94.5 9.12 1.97
Biomass t/ha 5.4c 5.5b 6.1a 5.6 0.03 1.97
HI 48.0b 50.1a 47.2b 48.4 2.0 1.97
Yield t/ha 2.4 2.5 2.5 2.4 NS 1.97
2013
Aphids 5.7a 5.0b 5.6a 5.5 0.36 21
Tillers/m2
116.3 138.9 127.1 127.4 0.5 4.0
Spikes/m2
105.3c 114.0b 116.9a 112.1 0.36 2.3
Biomass t/ha 5.5b 5.8a 5.7a 5.7 0.11 1.9
TKW 30.7b 30.9a 30.6b 30.8 0.14 0.6
HI 40.9c 43.6a 42.2b 42.2 0.32 2.2
Yield t/ha 2.2 2.5 2.4 2.3 0.25 2.1
Table 3: Effect of seeding rates on cereal aphid counts, yield and yield components
Means followed by the same letter in the same column are not significantly different at ( =0.05)Ɑ
Results and Discussions

15. Season/year 2011 2012 2013
N kg/ha 75 100 130 75 100 130 75 100 130
Grain yield kg/ha 2.0 2.4 2.2 2.1 2.4 2.3 2.1 2.5 2.4
Grain yield benefit
(kg/ha)
400 200 300 200 400 300
Seeding rates kg/ha 75 100 125 75 100 125 75 100 125
Grain yield kg/ha 2.1 2.3 2.3 2.4 2.5 2.5 2.2 2.4 2.5
Grain yield benefit
(kg/ha)
200 200 100 100 200 300
Table 4: Yield benefits due to Nitrogen application and seeding rates
Results and Discussions

16. Conclusion
 RWA infestation varied with variety
K. Korongo –least most attacked & NBWII most affected.
Robin - highest grain yield.
NBWII - lowest grain yield.
 N appeared to improve plants tolerance to aphid infestation
Highest aphid infestation – recorded at 100 N kg/ha
 Aphid counts varied with seeding rates, highest counts - recorded in lowest
seeding rate (75 kg/ha).
> 100 kg N/ha and 100 kg seed/ha - not beneficial to the grower
increase grain yield.
 Optimum N and SR may be a useful strategy for limiting both yield reduction
and increased cost of production (pesticides use) caused by RWA in wheat
crop.

17. Recommendations and Acknowledgement
• Recommendation
• Moderate seeding rate (100 kg/ha ) and (100 kg N/ha) could be used as
an integrated strategy in the management of RWA in wheat production
by farmers.
• Acknowledgement
• Authors acknowledge with appreciation the Eastern Africa Agricultural
Productivity Program (EAAPP) and KALRO Director General through
the Centre Director , KALRO- Njoro for facilitating this study.