September 2014
56
Nematodesharnessed for biological
pestmanagement
“G
oing green” and “environmentally friendly” are com-
mon termswe encounter increasingly frequent these
days. In the agro-chemical industry, the contamina-
tion of food by chemicals (i.e. pesticide residues)
and their safety to humans and the environment is a world-wide
public concern.
Thenatural enemies of insect pests includepredators (e.g., ladybird
beetles), parasites (e.g. wasps) and pathogens (disease-causing
microbes). The pathogen group is very diverse, comprising fungi,
viruses, bacteria, protozoa andnematodes.
Generally, producersare familiarwith the root-damagingnematodes
known as lesion- and root knot-nematodes. However, another group
of nematodes, the so-called entomopathogenic nematodes, does
not attack plants, but utilises insects as hosts.
These entomopathogenic nematodes are safe and environmentally
friendly, soil-dwelling insect parasites that occur globally in natural
and agricultural soils. They live in a symbiotic association with a
lethal bacterium, which the entomopathogenic nematodes release
into the insect host followingpenetration thereof.
This bacterium is very potent, capable of killing the insect within
48 hours. The bacterium then serves to digest the internal organs
of the host rendering it suitable as food source to aid nematode
developmentwithin thehost (i.e. productionof the infective juvenile
or IJ stage) (
Photo 1
).
It is for these reasons that scientists around the globe are conduct-
ing research to develop entomopathogenic nematodes based bio-
pesticide products. Such products hold a number of advantages
including: There exists no record of acquired or developed resist-
ance against entomopathogenic nematodes, safety towards mam-
mals, non-target organisms and the environment, sustained control
due toadurable IJ (non-feeding) stage, host-seekingabilities, persis-
tence in soil, rapid rate of insect mortality (48 hours), compatibility
with chemical pesticides and exemption from registration in many
countries.
The Insect Pathology unit at the ARC-Small Grain Institute (ARC-
SGI) curates a large collection of indigenous entomopathogenic
nematodes (>165 isolates) and have recently identified two new
species, published as
Steinernema tophus
n. sp. and
Steinernema
innovationi
n. sp.
Latter species was used as study organism in a PhD thesis by
Tshima Ramakuwela (co-author of this article). The study covered
aspects on the biology, mass production and formulation of the
nematode.
TSHIMARAMAKUWELA
and
JUSTINHATTING,
ARC-Small Grain Institute
1: The infective juvenile stageof an entomopathogenic nematode.
Photo: J.L. Hatting, ARC-SGI
2:Anadult beetleof the falsewireworm (
Gonocephalum simplex
) dissect-
ed to reveal thousandsof infective juveniles.
Photo: J.L. Hatting, ARC-SGI
FOCUS
Integratedpest control
Special
“
These
entomopathogenic
nematodes are safe
and environmentally
friendly, soil-dwelling
insect parasites.
“
