Field Efficacy of Neem (Azadirachta indica A. Juss) for Managing Soil Arthropods and Cercospora Leaf Spots Damage for Increased Yield in Peanut

Abstract

Field efficacy of neem (Azadirachta indica A. Juss) for managing soil arthropods and Cercospora leaf spots damage to peanut was studied in Ghana from 2008 to 2010. Treatments consisted of neem kernel water extract (NKWE) and neem kernel powder (NKP) applied separately as soil drench at the rates of 10.5 and 21.0 kg/ha at either planting or pegging. Untreated control and chlorpyrifos treatment at pegging were included as checks. Results showed generally that the neem products at the concentrations tested were efficacious and comparable to chlorpyrifos in lowering populations of soil arthropods and severity of leaf spot diseases, leaf defoliation, and scarified and bored pod damage, resulting in increased pod yield in 2008 and 2009.

Full text

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Plant Protect. Sci. Vol. 49, 2013, No. 2: 65–72
Field Efficacy of Neem (Azadirachta indica A. Juss)
for Managing Soil Arthropods and Cercospora Leaf Spots
Damage for Increased Yield in Peanut
M ABUDULAI
1, A B. SALIFU1, D OPAREATAKORA1, M HARUNA1,
I I.Y. BABA1, I K. D 2, R L. BRANDENBURG 3 and D L. JORDAN 3
1CSIR-Savanna Agricultural Research Institute, Tamale, Ghana; 2University for Development
Studies, Tamale, Ghana; 3North Carolina State University, Raleigh, USA
Abstract
A M., S A.B., O-A D., H M., B I.I.Y., D I.K., B R.L.,
J D.L. (2013): Field efficacy of neem (Azadirachta indica A. Juss) for managing soil arthropods and
Cercospora leaf spots damage for increased yield in peanut. Plant Protect. Sci., 49: 65–72.
Field efficacy of neem (Azadirachta indica A. Juss) for managing soil arthropods and Cercospora leaf spots damage
to peanut was studied in Ghana from 2008 to 2010. Treatments consisted of neem kernel water extract (NKWE) and
neem kernel powder (NKP) applied separately as soil drench at the rates of 10.5 and 21.0 kg/ha at either planting or
pegging. Untreated control and chlorpyrifos treatment at pegging were included as checks. Results showed gener-
ally that the neem products at the concentrations tested were efficacious and comparable to chlorpyrifos in lowering
populations of soil arthropods and severity of leaf spot diseases, leaf defoliation, and scarified and bored pod damage,
resulting in increased pod yield in 2008 and 2009.
Keywords: Azadirachta indica A. Juss; Arachis hypogeaeL.; leaf spots; pest control
The soil arthropod pests, termite (Microtermes
and Odontotermes spp.), white grubs (Schyzoni-
cha spp.), millipedes (Peridontopyge spp.) and
wireworms (Heteroligus claudius), and the foliar
diseases, early leaf spot (Cercospora arachidicola
Hori) and late leaf spot (Cercosporidium persona-
tum (Berk. & M.A. Curtis) Deighton) are major
constraints to peanut (Arachis hypogeaeL.) pro-
duction in Ghana (U et al. 2001; A et
al. 2007, 2012). The arthropods damage plants by
penetrating and feeding on developing pegs, pods,
and seeds inside pods, resulting in yield loss ranging
between 30% and 70% in West Africa (J
et al. 1981; U et al. 1999, 2001; A et
al. 2012). Their feeding activity also predisposes
pods to infection by disease pathogens such as
the fungus, Aspergillus flavus (Link) (W-
 et al. 1990; L et al. 1991; W et
al. 1994). Also, early and late leaf spot diseases
that manifest as reddish brown to black necrotic
spots on leaves cause premature defoliation and
yield loss up to 70% in peanut (S & C-
 1997; W et al. 2000). Chemical
treatment is the conventional method for control
of pests and diseases in peanut (B
& H 1991; B & C 2008).
However, in many developing countries such as
Ghana farmers seldom control these pests in their
peanut fields, which may be attributed to limited
financial resources to use chemical control.
Products of the neem tree (Azadirachta indica A.
Juss) from all parts of the plant have demonstrated
efficacy against many pest species including ar-
thropod pests and diseases of crops. The principal
active ingredient, Azadirachtin, is however more
concentrated in the kernel, which makes it the most
effective part of the plant (S 1990;
G 2000). Neem acts on insects in several
ways including contact toxicity, repelling adults
and larvae, disrupting developmental processes,

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and disrupting adult behaviour such as mating
(M 2004; I 2006). Neem also acts
systemically because of absorption by roots and
translocation to plant parts when applied into soil
or sprayed on the plant (T & P
2006; T et al. 2006). Laboratory and field
studies have demonstrated efficacy of neem ex-
tracts against soil pests such as termites (C
& M 1981; L & W 1988; U et
al. 2001; C & N 2010). Neem has
also been reported to inhibit spore germination
and mycelial growth of leaf disease fungi (K &
H 1994; B et al. 1995; G
2000). However, the application of neem extracts
for control of soil pests and leaf spot diseases of
field peanut is yet to be explored. There is the need
to harness the pesticidal activity in this promising
natural product that abounds in Ghana and other
parts of sub-Saharan Africa for control of peanut
pests. Therefore, the objective of this study was
to evaluate neem kernel water extract and neem
kernel powder for managing soil arthropod pests
and Cercospora leaf spot diseases of field peanut
for increased yield.
MATERIAL AND METHODS
The study was conducted at the research farm
of the CSIR-Savanna Agricultural Research Insti-
tute located at Nyankpala (9o42'N, 0o92'W, and
184 m a.s.l.) and on farm at Bagurugu (9o53'N,
0o43'W, and 168m a.s.l.), both in the northern
region of Ghana from 2008–2010 crop seasons.
The experimental lay out was a randomised com-
plete block design and treatments were replicated
four times. Plots consisted of six rows 5 m long
with spacing of 0.4 m between rows and 0.1 m
between plants in a row. The peanut cv. Chinese
was used and planted on June 25th 2008, June 10th
2009, and June 21st 2010 at Nyankpala and on June
23rd 2008, June 25th 2009, and June 8th 2010 at
Bagurugu. Treatments consisted of neem kernel
water extract (NKWE) and neem kernel powder
(NKP) applied separately each at the rates of 10.5
and 21.0 kg/ha at either planting or pegging stage
(50 days after planting) of the crop. Untreated
control and the standard treatment at pegging
with chlorpyrifos (B & H
1991) were included as checks. All treatments
were applied into the soil as soil drench along
planting rows.
Preparation of neem kernel powder and neem
kernel water extracts. Neem kernel powder and
extracts were prepared from air-dried seeds col-
lected from neem trees on the research farm at
Nyankpala. The dried seeds were decorticated to
remove the shells to obtain the kernels. The ker-
nels were then pounded in a mortar using a pestle
to obtain the NKP. The NKWE was prepared by
soaking the NKP in ordinary tap water and allowed
to stand for 24hours. The mixture was strained
through a muslin cloth to obtain the filtrate or ex-
tract that was put in a knapsack for spraying. The
quantities of NKP were the same as those used to
prepare the NKWE for the different concentrations
expressed per ha.
Data collection. Randomly selected samples of
5 plants were dug with the associated soil around
the root zone for soil arthropod pests. The samples
were taken at harvest from within the outer two
rows of each plot and data on the numbers of pests
on plants and soil samples were recorded. Samples
of 100 pods were taken to determine numbers of
pods that were scarified (fibrous tissue surrounding
pods removed) or bored into by soil pests and were
converted to percentages. Severity of early and late
leaf spot diseases and percentage defoliation were
assessed at harvest on 10 randomly selected plants
using the Florida scale of 1–10 where 1 represents
no leaf spot and 10 represents plants completely
defoliated and killed by leaf spot (C et al.
1997). The middle four rows of each plot were
harvested to determine yield.
Statistical analyses. The data were subjected
to analysis of variance (ANOVA) using the general
linear models procedure of SAS (SAS Institute
1998). Where a significant treatment effect was
measured by ANOVA, means were separated using
Fisher’s protected Least Significance Difference
(LSD) test at P < 0.05. Percentage data for pod
damage and defoliation were transformed using
arcsin(x) or square root (x + 0.5) as appropriate
prior to analysis.
RESULTS
Nyankpala. In 2008, chlorpyrifos and A. in-
dica treatments, irrespective of whether used as
powder or water extract and time of application,
significantly (P < 0.05) lowered populations of
millipedes, white grubs, and termites compared
with untreated control (Table 1). In 2009, only

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Plant Protect. Sci. Vol. 49, 2013, No. 2: 65–72
millipede populations were generally lowered
by the treatments. Populations of millipedes and
termites recorded in 2010 were not significantly
different (P > 0.05) among the treatments (Table 1).
Also, chlorpyrifos and A. indica treatments inde-
pendent of the form used and time of application
significantly (P < 0.05) lowered severity of both
early and late leaf spot diseases, and percentage
defoliation compared with untreated control in
2009 and 2010 (Table 2).
In 2008, percentage scarified pods caused princi-
pally by termites was significantly (P < 0.05) lower
in chlorpyrifos and A. indica treatments than un-
treated control (Table 3). Also, percentage bored
Table 1. Effect of neem kernel water extract (NKWE) and neem kernel powder (NKP) soil treatment of peanut at
planting or pegging on abundance of soil arthropod pests (Nyankpala, 2008–2010)
Treatment Rate
(kg/ha) Timing Millipedes Whitegrubs Termites
2008 2009 2010 2008 2009 2010 2008 2009 2010
NKWE
10.5 planting 0.0b0.3bc 2.0 0.3b0.0 – 0.0b–0.5
pegging 0.0b0.0c1.5 0.0b0.8 – 12.5b–2.5
21.0 planting 0.0b0.5a–c 1.3 0.3b0.0 – 52.5b–1.5
pegging 0.0b0.0c0.5 0.0b0.3 – 7.5b–5.5
NKP
10.5 planting 0.3b0.0c1.5 0.0b0.3 – 3.8b–0.0
pegging 0.0b0.3bc 0.5 0.0b0.0 – 6.3b–3.8
21.0 planting 0.3b0.8ab 3.0 0.3b0.5 – 32.5b–4.0
pegging 0.0b0.3bc 2.0 0.0b0.5 – 0.0b–0.0
Chlorpyrifos 2.0 pegging 0.3b0.0c0.5 0.0b0.0 – 25.0b–2.5
Untreated –2.3a1.0a2.0 0.8a1.0 –200.0a– 17.5
P > F–0.0001 0.0179 0.4630 0.0577 0.1355 –0.0314 –0.0933
CV (%) –19.1 24.4 39.1 21.6 30.9 –69.2 –30.7
– pest was not recorded for the year; means within a column followed by the same letters are not signicantly different according
to Fisher’s Protected LSD test at P < 0.05
Table 2. Effect of neem kernel water extract (NKWE) and neem kernel powder (NKP) soil treatment of peanut at
planting or pegging on severity of early and late leaf spots, and percentage defoliation (Nyankpala, 2009 and 2010)
Treatment Rate
(kg/ha) Timing Early leaf spots Late leaf spots Defoliation (%)
2009 2010 2009 2010 2009 2010
NKWE
NKWE
10.5 planting 3.3b4.9b4.3b5.9b61.3bc 60.0bc
pegging 3.3b4.9b4.3b5.9b61.3bc 65.0b
21.0 planting 3.3b4.2de 4.4b5.2cd 63.8b53.8de
pegging 3.3b4.8b4.3b5.8b62.5b58.8cd
NKP
NKP
10.5 planting 3.3b4.8b4.3b5.8b63.8b61.3bc
pegging 3.3b4.7bc 4.4b5.6bc 60.0bc 57.5cd
21.0 planting 3.1b4.6bcd 4.2b5.7bc 55.0c58.8cd
pegging 3.2b4.4cde 4.3b5.6bc 58.8bc 56.3cd
Chlorpyrifos 2.0 pegging 3.2b4.0e4.2b5.0d58.8bc 50.0c
Untreated –4.2a5.5a5.4a7.2a75.0a75.0a
P > F–< 0.0001 < 0.0001 < 0.0001 < 0.0001 0.0012 < 0.0001
CV (%) 14.3 6.3 11.0 5.7 8.0 6.3
Leaf spot disease severity scores were rated on 10 plants using the Florida scale of 1–10 based on visual observations (C
et al. 1997); means within a column followed by the same letters are not significantly different according to Fisher’s Protected
LSD test at P < 0.05

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pods was significantly (P < 0.05) lower in treated
than untreated plots. Moreover, pod yield was
significantly (P < 0.05) greater in treated than un-
treated plots except for plots that were treated with
10.5 kg/ha NKWE or at pegging with 21.0 kg/ha
NKWE. Yield generally was higher in chlorpyri-
fos and the NKP treatments. In 2009, percentage
scarified pods was not significantly different (P>
0.05) among the treatments. However, percentage
bored pods was significantly (P< 0.05) lower in
chlorpyrifos and A. indica treatments than control
except plots that were treated at pegging with
21.0 kg/ha NKP. Pod yield for the year was not
significantly different (P > 0.05) among the treat-
ments. In 2010, lower percentage scarified pods
was recorded in chlorpyrifos and plots treated
Table 3. Effect of neem kernel water extract (NKWE) and neem kernel powder (NKP) soil treatment of peanut at
planting or pegging on percentage scarified and bored pods and pod yield (Nyankpala, 2008–2010)
Treatment Rate
(kg/ha) Timing Scarified pods (%) Bored pods (%) Pod yield (kg/ha)
2008 2009 2010 2008 2009 2010 2008 2009 1010
NKWE
10.5 planting 7.5b3.8 7.5ab 1.3b10.3bc 5.3bcd 954.1bc 1615.6 1471.9
pegging 4.8b4.0 3.0c2.5b10.3bc 7.3b1013.8bc 1471.9 1543.8
21.0 planting 7.8b6.3 8.3a2.0b 9.0 c 6.3bc 1113.1ab 1521.9 1643.8
pegging 7.8b1.8 5.5abc 1.3b 9.8bc 5.5bcd 1016.1bc 1537.5 1559.4
NKP
10.5 planting 7.5b3.5 7.5ab 1.5b10.8bc 5.8bcd 1280.0a1365.6 1637.5
pegging 4.0b4.3 5.0bc 3.0b11.3bc 4.8bcd 1093.4ab 1378.1 1556.3
21.0 planting 7.0b4.5 6.5ab 1.8b 6.8cd 4.0cd 1078.9ab 1440.6 1491.7
pegging 7.0b2.8 5.5abc 2.5b12.5ab 5.8bcd 1159.5ab 1521.9 1545.8
Chlorpyrifos 2.0 pegging 7.8b1.3 3.0c1.5b 3.5d2.8d1138.6ab 1790.6 1565.6
Untreated – – 15.3a7.8 8.5a8.0a17.3a13.5a800.9c1440.0 1153.1
P > F–0.0245 0.1460 0.0058 0.0315 0.0008 < 0.0001 0.0382 0.1227 0.3356
CV (%) 48.2 36.5 35.4 34.1 16.0 36.1 8.0 12.2 16.7
Means within a column followed by the same letters are not significantly different according to Fisher’s Protected LSD test at
P < 0.05
Table 4. Effect of neem kernel water extract (NKWE) and neem kernel powder (NKP) soil treatment of peanut at
planting or pegging on abundance of soil arthropod pests (Bagurugu, 2008–2010)
Treatment Rate
(kg/ha) Timing Millipedes Whitegrubs Termites
2008 2009 2010 2008 2009 2010 2008 2009 2010
NKWE
10.5 planting 0.8ab 0.0 13 0.3 0.3 0.3b0.0 7.5 12.5
pegging 0.0c0.5 0.0 0.0 0.3 0.5b0.0 0.0 5.0
21.0 planting 0.8ab 0.5 1.3 0.0 0.3 0.3b0.0 0.0 0.0
pegging 0.3bc 0.8 0.3 0.0 0.3 0.5b0.0 25.0 0.0
NKP
10.5 planting 0.5bc 0.8 0.8 0.3 0.0 0.3b0.0 0.0 12.5
pegging 0.3bc 0.5 1.0 0.0 0.3 0.0b0.0 0.0 0.0
21.0 planting 0.8ab 0.8 1.0 0.5 0.3 0.0b0.0 0.0 5.0
pegging 0.0c0.5 0.8 0.0 0.5 0.0b0.0 62.5 5.0
Chlorpyrifos 2.0 pegging 0.0c0.3 0.5 0.0 0.0 0.0b0.0 25.0 0.0
Untreated –1.5a1.3 1.0 0.8 1.0 1.3a 12.8 15.0 5.0
P > F–0.0038 0.4755 0.1141 0.1861 0.2816 0.0065 0.3873 0.4923 0.8697
CV (%) 24.7 32.9 27.7 26.0 27.8 24.0 34.1 87.7 53.3
Means within a column followed by the same letters are not significantly different according to Fisher’s Protected LSD test at
P < 0.05

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Plant Protect. Sci. Vol. 49, 2013, No. 2: 65–72
at pegging with 10.5 kg/ha NKWE or 10.5 kg/ha
NKP compared with untreated control. Also, per-
centage bored pods was significantly (P< 0.05)
lower in chlorpyrifos and A. indica treatments
compared with control. However, there were no
significant differences (P > 0.05) in pod yield among
the treatments.
Bagurugu. In 2008, chlorpyrifos and A. indica
treatments significantly (P < 0.05) lowered popula-
tions of millipede compared with control except
for plots that were treated at planting with 10.5
or 21.0kg/ha NKWE or 21.0 kg/ha NKP (Table4).
There were however no significant differences
(P>0.05) among the treatments in populations of
white grubs and termites. In 2009, there were no
significant differences (P > 0.05) among the treat-
ments in the populations of all the three aforemen-
tioned arthropods. In 2010, populations of white
grubs were lower in chlorpyrifos and A. indica
treatments than untreated control. Millipede and
termite populations were not significantly differ-
ent (P > 0.05) among the treatments.
In 2009, significantly (P < 0.05) lower severity of
early leaf spots was recorded in chlorpyrifos treat-
ments and plots treated at planting with 10.5kg/ha
NKWE or at either planting or pegging with 21.0kg/ha
NKWE compared with control (Table5). Also, lower
severity of late leaf spots was recorded in chlorpyri-
fos and A. indica treatments than control except for
plots that were treated at pegging with 10.5 kg/ha
NKWE, or at planting with either 10.5 or 21.0 kg/ha
NKP. Nonetheless, percentage defoliation was lower
in chlorpyrifos and all A.indica treatments. In 2010,
severity of both early and late leaf spots and per-
centage defoliation were lower in chlorpyrifos and
A.indica treated plots compared with control.
In 2008, percentage scarified pods was signifi-
cantly (P < 0.05) lower in chlorpyrifos and A. in-
dica treatments compared with control except for
plots that were treated at planting with 10.5kg/ha
NKP (Table 6). Percentage bored pods was also
significantly (P < 0.05) lower in chlorpyrifos and
A. indica treatments than control. Pod yield dur-
ing the year was significantly (P < 0.05) higher in
chlorpyrifos and A. indica treatments than control
except for plots that were treated with 10.5 kg/ha
NKWE at planting. In 2009, percentage scarified
pods and percentage bored pods were signifi-
cantly (P < 0.05) lower in chlorpyrifos and A.in-
dica treatments compared with control (Table6).
Pod yield during the year was significantly (P <
0.05) higher in chlorpyrifos treatments and plots
treated at pegging with 10.5 or 21.0 kg/ha NKWE,
or at either planting or pegging with 21.0 kg/ha
NKP compared with control. In 2010, percentage
scarified pods was significantly (P < 0.05) lower in
chlorpyrifos treatments and plots treated at pegging
with 10.5kg/ha NKWE, at planting with 21.0 kg/ha
Table 5. Effect of neem kernel water extract (NKWE) and neem kernel powder (NKP) soil treatment of peanut at
planting or pegging on severity of early and late leaf spots, and percentage defoliation (Bagurugu, 2009 and 2010)
Treatment Rate
(kg/h) Timing Early leaf spots Late leaf spots Defoliation (%)
2009 2010 2009 2010 2009 2010
NKWE
10.5 planting 3.6bcd 5.1b4.8bcd 6.2b63.8b62.5b
pegging 3.7abc 4.8bc 5.1ab 5.8bc 63.8b57.5bc
21.0 planting 3.5bcd 3.9de 4.7cd 4.9d65.0b52.5cd
pegging 3.3cd 4.3cde 6.9bcd 5.3cd 65.0b53.8c
NKP
10.5 planting 3.7abc 4.7bc 5.1ab 5.5c60.0b56.3c
pegging 3.8ab 4.6bc 4.9bcd 5.5c60.0bc 55.0c
21.0 planting 3.7abc 4.5bcd 5.0abc 5.3cd 56.3c55.0c
pegging 3.7abc 4.6bc 4.9bcd 5.5c60.0bc 57.5bc
Chlorpyrifos 2.0 pegging 3.2d3.8e4.6d4.8d56.3c47.5d
Untreated –4.0a6.5a5.4a7.8a75.0a82.5a
P > F–0.0114 < 0.0001 0.0085 < 0.0001 < 0.0001 < 0.0001
CV (%) 12.4 9.7 9.8 7.0 6.6 6.3
Leaf spot disease severity scores were rated on 10 plants using the Florida scale of 1–10 based on visual observations (C
et al. 1997); means within a column followed by the same letters are not significantly different according to Fisher’s Protected
LSD test at P < 0.05

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NKWE or 10.5 kg/ha NKP, or at pegging with
21.0kg/ha NKP compared with control. Percentage
bored pods during the year was also significantly
(P < 0.05) lower in chlorpyrifos and A. indica
treatments than control. There were, however, no
significant differences (P > 0.05) detected in pod
yield among the treatments (Table 6).
DISCUSSION
Peanut pest management relies heavily on chem-
ical-based crop protection strategies. However,
chemical control is very expensive and not sus-
tainable for farmers in developing countries like
Ghana. Extracts from A. indica that is indigenous
to Ghana and occurs abundantly in the wild have
shown pesticidal effects that could be exploited for
control of pests and diseases in peanut. In addi-
tion to being a cheaper source of biopesticide, the
extracts are also thought to be less detrimental to
the environment compared to synthetic pesticides
(I 2006). Although peanut farmers in Ghana
appreciate the yield-limiting effects of attack by
soil arthropod pests and leaf spot diseases, they
seldom apply protection for their crops due largely
to financial limitations for chemical protection
that is recommended for control (A et
al. 2009). It was against this background that this
study was conducted to evaluate the efficacy of
neem kernel water extract and powder for manag-
ing damage by soil arthropod pests and leaf spot
diseases to boost peanut yield in Ghana.
Results from the study showed that both the
NKWE and NSP tested were efficacious against
the soil arthropod pests and leaf spot diseases at-
tacking peanut in Ghana. At Nyankpala, A. indica
products at the concentrations tested showed
efficacy comparable to chlorpyrifos in lowering
populations of millipedes, white grubs, and ter-
mites in 2008 and millipedes in 2009. Populations
of millipedes and white grubs were also lowered by
the A. indica treatments at Bagurugu in 2008 and
2010, respectively. In a soil dip bioassay, R et
al. (2009) reported that the neem-based product,
Azatin, exhibited high toxicity to the white grub
larvae Popillia japonica Newsman, Rhizotrogus
majalis (Razoumowsky), and Anomala orientalis
Waterhouse. Also, C and N (2010)
reported that azadirachtin treated soil was repel-
lent to wireworms and lowered their populations
than untreated controls. Furthermore, U et
al. (2009) reported that soil treatment with neem
seed powder and extract lowered populations of
the flea beetle Ootheca mutabilis (Shalberg) on
fluted pumpkin, Telfaria occidentalis (Hoof L.)
in Nigeria. J et al. (2008) also reported that
soil application of crude neem formulations sig-
nificantly reduced the invasion of tomato roots by
root-knot nematodes. In the present study, early
Table 6. Effect of neem kernel water extract (NKWE) and neem kernel powder (NKP) soil treatment of peanut at
planting or pegging on percentage scarified and bored pods and pod yield (Bagurugu, 2008–2010)
Treatment Rate
(kg/ha) Timing Scarified pods (%) Bored pods (%) Pod yield (kg/ha)
2008 2009 2010 2008 2009 2010 2008 2009 1010
NKWE
10.5 planting 2.3b5.8b4.8ab 2.0b5.5cd 3.8bc 909.4bc 1440.6cd 1681.3
pegging 1.3bc 5.3b1.3c2.8b8.8bc 3.0c1034.4ab 1484.4bc 1665.6
21.0 planting 2.0bc 4.7b3.3bc 3.3b9.5bc 4.0bc 1106.3a1416.7cd 1625.0
pegging 2.3b5.3b4.3abc 1.8b6.5cd 3.8bc 1121.9a1509.4bc 1503.1
NKP
10.5 planting 2.8ab 5.3b3.8bc 3.3b12.0b5.8b1006.3ab 1441.8cd 1656.3
pegging 1.8bc 3.3b4.3abc 4.0b9.3bc 5.8b1078.1ab 1465.8cd 1412.5
21.0 planting 2.0bc 4.5b4.5ab 3.3b8.5bc 5.0bc 1147.2a1595.8b1615.6
pegging 2.5b2.8b3.3bc 1.8b8.8bc 3.3c1121.9a1518.8bc 1543.3
Chlorpyrifos 2.0 pegging 0.5c0.8b1.8bc 1.5b2.3d0.3d1053.1ab 1884.4a1806.3
Untreated - – 5.0a13.8a7.3a10.0a18.8a9.8a768.8c1356.3d1354.7
P > F–0.0080 0.0039 0.0394 0.0111 < 0.0011 < 0.0001 0.0083 < 0.0001 0.0718
CV (%) 25.6 68.3 56.5 33.5 33.4 38.3 12.5 15.1 11.9
Means within a column followed by the same letters are not significantly different according to Fisher’s Protected LSD test at
P < 0.05

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Plant Protect. Sci. Vol. 49, 2013, No. 2: 65–72
and late leaf spot severity and percentage defolia-
tion were also generally lowered by the NKWE
and NKP treatments. This is consistent with the
report that A. indica treatment inhibited spore
germination and mycelial growth of fungal leaf
disease (K & H 1994; B et al.
1995; G 2000).
Percentages of scarified and bored pods were
always lower in chlorpyrifos and A. indica treat-
ments, with the exception of the results for 2009 at
Nyankpala. The lower damage resulted in increased
yield at Nyankpala in 2008 and at Bagurugu in
2008 and 2009. Data from this study are in agree-
ment with those of U et al. (2009). They
reported that soil treatment of A. indica products
significantly lowered damage to fluted pumpkin
leaves by O. mutabilis and resulted in increased
yield over untreated control. Although, all the
A.indica treatments in the present study were
generally effective at the concentrations tested,
the higher concentrations showed more efficacy in
lowering damage and improving yield. Pod dam-
age and yield from plots treated with the lower
concentration of 10.5 kg/ha NKWE especially at
planting was usually not different from untreated
control. Several workers have reported that the
activity of A. indica was concentration dependent
(S 1990; A et al. 2003). For
control of leaf spots, however, the lower concen-
trations of 10.5 kg/ha NKWE effectively lowered
severity of the disease especially when applied at
planting.
In conclusion, the study demonstrated the ef-
fectiveness of A. indica products for lowering
damage by soil arthropods and leaf spot diseases
for increased peanut yield in Ghana. The results
also confirmed the systemic effect of A. indica
treatments reported by T and P
(2006) and T et al. (2006). These findings
are important for farmers in Ghana who could
now exploit the potential of A. indica for control
of pests in their peanut fields with possible exten-
sion of the technology to other crops.
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Received for publication June 4, 2012
Accepted after corrections November 5, 2012
Corresponding author:
M A, Ph.D, CSIR-Savanna Agricultural Research Institute, P.O. Box 52, Tamale, Ghana;
E-mail: mabudulai@yahoo.com or mabudulai11@gmail.com