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Effect of Soil Solarization on Populations
of Chickpea Nematodes
C Akem, S Ahmed, B Bayaa, M Bellar, and
N Trabulsi (Germplasm Program, International Center
for Agricultural Research in the Dry Areas (ICARDA),
PO Box 5466, Aleppo, Syria)
Root-knot (Meloidogyne artiellia Franklin), lesion
(Pratylenchus thornei Sher et Allen) and cyst nematode
(Hetreodera ciceri Vovlas, Greco et Di Vito) are important
nematodes of chickpea (Cicer arietinum L.) in the West
Asia and North African (WANA) region (Di Vito et al.
1994). If not controlled, they can cause severe root
damage and crop losses. Resistance in chickpea cultivars
has been found for root-knot and lesion nematodes but
not for the cyst nematode (Greco and Di Vito 1993). Soil
solarization has been shown to be effective in nematode
control (Di Vito et al. 1991). However, its use is limited
because of low benefits and problems of large scale use
by resource poor farmers. Strip cropping of cereals with
legumes within the same field in the same season is a
common feature of the farming systems of WANA. In
such systems, solarization can be effective as a means of
nematode control in targeted plots within the strips.
Experiments were carried out at the ICARDA research
farm in Tel Hadya, Syria, during the 1996/97 cropping
season to study the efficacy of soil solarization on chickpea
nematode populations for possible use in nematode control.
Included in the 3 solarization treatments was a nematicide
application, Vydate L (active ingredient: Oxamyl). The
field plot used for the experiments had a known history
of severe nematode infestation on legumes. Root-knot,
lesion, and cyst nematodes were known to be prevalent
in this field.
Soil samples were collected to determine the population
of these nematodes in the plots before and after applying
the solarization treatments. The treatments consisted of
mulching 6 x 11 m plots with: 1) a single layer of
transparent polyethylene film 50 µm thick, 2) a double
layer of the transparent film, 3) a single layer of black
polyethylene film 50 urn thick, and 4) a spray treatment
with the nematicide, Vydate. The control plots were left
without any treatment. All treatments were replicated 3
times in a completely randomized block design. To improve
heat conductivity, the plots were irrigated (5-10 mm h -1 ,
for 3 5 hrs d -1 for 5 days) just before covering, and the
covers were kept in place for 8 weeks from mid-July till
mid-August. Soil temperatures before covering ranged
from 18°C to 25°C, and went up to 35-50°C during
covering at a depth of 5-10 cm.
Five soil samples were taken at random from each
plot for nematode population counts before and after
solarization. Root lesion and root-knot nematodes from
200 cm 1 soil sub-samples were extracted by Coolen's
method (1979). Cysts of H. ciceri were extracted from
200 g air-dried sub-samples using a Fenwick can. The
cysts were counted and egg numbers determined. Eight
weeks after removing the plastic mulch, the chickpea
cultivar F 82-150 C (Ghab 3) was planted on 4 row plots
spaced at 45 cm apart in each plot. Four weeks after
planting, the nematicide was spray-inoculated at 3 L ha -1 .
Soil samples were collected from the nematicide-treated
plots 4 weeks after the chemical application. Plots were
observed for visual differences based on foliar yellowing
symptoms and stunting. Destructive sampling was done
using 10 plants per plot, from which severity ratings
(1-9), were given for root-knot and lesion nematode
infections based on the root symptoms observed. Plots
were harvested at maturity.
The nematode population in the plots before and after
the treatments is shown in Table 1. The most effective
treatment was the use of double transparent polyethylene
mulch. This treatment eliminated the populations of the
lesion and cyst nematodes and drastically reduced the
population of the root-knot by 94%. Solarization with
the single layer transparent plastic was also effective in
nematode control. It also completely eliminated the
population of cyst nematode, drastically reduced the
populations of the root-knot, and lesion nematodes. The
black polyethylene covering was not as effective as the
transparent one in nematode control. It had no effect on
lesion nematode population, but reduced the population
of the root-knot nematode by 50% and that of the cyst
nematode by 85%. The nematicide application had virtually
no effect on any of the nematode populations.
Seed yield increased by more than 73% with the
double transparent covering, and by about 54% with
single covering. There were no significant yield differences
between the black covering and the nematicide treatments
ICPN 7, 2000 13