discription of entomopathogenic nematodes

1. By Shariqa Aisha.
University of Kashmir
Department of Bioresources

2. Outline
 Introduction
 History
 Global Distribution
 Pathogenicity
 Life cycle
 Mode of Action
 Host Range
 Mode of Application
 Advantages
 Limitations

3.  Nematodes are simple round worms.
 These are colorless, unsegmented, and lacking
appendages.
 Nematodes mat be free-living, predaceous, and
parasitic.
 Nematodes pathogenic to insects are referred to as
Entomopathogenic Nematodes.
 they possess an optimal balance of biological
control.
 Entomopathogenic nematodes are extraordinarily
lethal to many important insect pests, yet are safe
for plants and animals.

4.  The first Entomopathogenic Nematode was described by Steiner in
1923 as Aplectana kraussei ( Steinernema kraussei).
 In 1928, Dutky found Neoaplectana carpocapsae.
 In 1929, Steiner gave the systematic position of second
entomopathogenic nematode, Neoaplectana glaseri.
 Heterorhabiditis bacteriophora, was first time described In 1976 by
Pionar.
 The infective juvenile (IJ) stage, were found to transmit a specific Gram-
negative baterium in the anterior intestine to the homeceol of insect
hosts ( Poinar et. Al 1977).

6.  Entomopathgenic nematodes enter through
the insects natural body openings, the
mouth, anus, or respiratory inlets(spiracles).
 Heterorhabditis species penetrate through
the intersegmental membranes by stretching
away at these with a special tooth.
 In the insects blood, infective juvenile
releases a highly specialized symbiotic
bacterium.
 These symbiotic bacteria multiply rapidly
produce toxins that cause septicemia.

7.  Nematodes complete 2-3 generations inside the host.
 Over 100,000 nematodes exist an infected insect.
 The cycle of entry of infective juveniles into the insect host to
emerge of new batch of infective juveniles takes about 10-14 days.

9.  Simple life-cycle includes the egg, four juvenile stages
and an adult.
 Infective juvenile ( third stage) called dauer larvae is
resistant to environmental conditions.
 EPN locate their insect hosts in the soil by detecting
chemical cues such as excretory products and
carbobdioxide gradient.
 One generation from egg to egg typically takers from
4-7 days.

12.  The juvenile stage releases the cells of their symbiotic bacteria from
their intestines into the homoceol of the insect.
 The bacteria multiply in the insect homolymph and the infected host
usually dies within 24-48 hours.
 Once released, nematodes actively seek out the insect hosts. When a
host has been located, the nematodes penetrate into the insect
through body openings and release symbiotic bacteria that multiply
and rapidly kill the insect.
 Subsequently, nematodes feed upon the host , and mature into the
adults, which mate and produce the next generation.
 The life cycle is completed within a few weeks, and hundreds of
thousands of nematodes emerge in search of hosts.

14.  In laboratory tests, S. carpocapsae alone infected more than 250 species of
insects from over 75 families in 11 orders.
 Some nematode species may search for hosts at or near soil surface( e.g., S.
carpocapsae and S. scapterisci).
 Others are adapted to search deeper in the soil profile “ cruiser” ( e.g., H.
bacteriophora and S. glaseri).

15. Some appropriate nematode host targets are known:
 S. scapterisci against mole crickets;
 S. carpocapsae against cutworms and other mobile caterpillar pests;
 S. riobrave against cutworms and other noctuid larvae and pupae and citrus
weevils;
 S. feltiae against sawfly larvae and fungus gnat maggots; and
 H. bacteriophora against white grubs and other sedentary soil-dwelling
beetle larvae.

19.  Apply in the late evening. Nematodes are very sensitive to destruction
by bright sunlight and to desiccation if they are applied to plant foliage.
 Apply during the initial stage of pest damage.
 Light irrigation after application.
 Add adjuvants like glycerol, liquid paraffin.
 They can be applied with conventional chemical application equipment,
but screens in nozzles should be removed when applying nematodes
with a back-pack sprayer or spray rig.
 Nematodes should be reapplied on seven day intervals if damage
continues.
 Relative humidity should be high, ambient temperature should neither
be extremely hot or cold, soil temperature should be between 10 to 35
°C.

20. o High reproductive potential.
o Highly virulent( kill the host within 48 hours).
o Viable up to 3-6 months ( refrigerated at 10° C).
o Broad host range ( safe to vertebrates).
o Easy application using spray equipment's.
o Compatible with many chemical pesticides.
o Environmentally safe and acceptable.
o EPN seek out and kill all stages of harmful soil-dwelling insects.

21. o Nematode based insecticides- inactivated if stored in hot.
o Cannot left in spray tanks for long periods.
o Incompatible with many of the chemicals.
o Certain species cannot applied in high pressure equipment.
o Different species require different screen sizes.