This presentation summarizes information about root-knot disease caused by the nematode Meloidogyne incognita in Gerbera plants. It causes large losses to commercial floriculture, reducing yields by 30% in exotic varieties and 50% in Indian varieties. The life cycle and symptoms of the disease are described. Integrated management strategies include crop rotation, soil solarization, flooding, and use of biological agents like Trichoderma and Bacillus subtilis or chemical nematicides.

1. College of Agriculture,
Chiplima, OUAT
Presentation on Root-knot disease of
Gerbera
Course Title NEM-121
Course Name Introductory Nematology
Submitted to:
Dr. Swatilekha Mohanta
Associate Professor,
Department of Nematology,
College of Agricure, Chiplima,
OUAT
Submitted by:
Anup Aurojyoti Nayak, 2nd year, B.Sc. (Hons.)
Agriculture, 18131039
Satyam Sahu, 2nd year, B.Sc. (Hons.) Agriculture,
18131040

2. Root-knot Disease
The root-knot disease or crown gall disease is an
infection in various crop plants caused by the
Nematode species of Meloidogyne.
In Gerbera, it is a major plant parasite that results in
large scale losses to commercial floriculture.
The estimated loss in cultivation of Exotic varieties
and Indian varieties is 30% and 50% respectively.
Economic threshold level is 1 J2 juvenile/1 gram of
soil.

3. History
Root-knot disease was first reported by Berkeley in cucumbers of a
glasshouse in England in the year 1855.
In India, the disease was first reported by Barber in Tea plantations
of Kerala in the year 1901.
Until 1949, the root knot nematodes were considered to be a single
species. After that, Chitwood classified them into four major species.
These species are: M. incognita, M. javanica, M. hapla and M.
arenaria.
The M. incognita is the most important pest of Gerbera.

4. Distribution
The nematodes are distributed worldwide and are obligate parasites of
the roots of thousands of plant species.
They exist in soil in areas of hot climate or short winters.
About 2000 plants worldwide are susceptible to infection by root-knot
nematode.
Casual Organism
Out of more than 100 species, M. incognita, M. javanica, M. arenaria and
M. hapla are serious problem of most vegetables, fruit plants, pulses,
fiber crops, oilseeds, plantation crops, cash crops, flowers and
ornamentals.
M. hapla is restricted to temperate areas and high altitude of tropical and
sub-tropical zones.

5. Phylum Nematoda
Class Secernentea
Order Tylenchida
Sub - Order Tylenchina
Super Family Tylenchoidea
Family Heteroderidae
Genus Meloidogyne
Taxonomic Classification

6. Morphology
The nematode is sexually dimorphic.
Females are pear shaped with no posterior
protuberance.
Their stylet ranges from 15-16 microns long,
and knobs are rounded and offset.
Perineal pattern is oval to rounded, typically
with high dorsal arch, striae usually wavy and
lateral field absent or weakly demarcated.
Males have a not offset head with an elevated
labial disc without lateral lips.
Male
Female

7. Their stylet range from 23-26 microns long
and knobs are rounded to oval and offset.
The J2 juvenile has a body length of 350-
450 microns.
Their tail has rounded tip and range from
43-65 microns in length with 6-14 microns
long hyaline region.
Infective Stage: J2 Juvenile
The J3 and J4 stages are also known as
the “spikelet stages” due to the presence
of spike-like structures.

8. Life Cycle
The Root-knot nematode is a sexually dimorphic species. The females are
saccate or pear shaped and the males and juveniles are vermiform in
shape.
The reproduction is parthenogenetic.
Adult females secrete a gelatinous matrix or egg sac from six unicellular
rectal glands inside which it lays eggs.
The J1 juvenile develops inside the egg and the first moult occurs within
the egg shell giving rise to the J2 juvenile.
This juvenile has stylet through which it punctures the egg shell and
hatches out.

9. Life Cycle of M. incognita

10. The J2 moves freely in the soil in search of a host. It is the infective
stage of the nematode.
Usually, the nematode infects the meristematic region behind the root
cap. It secretes Protease enzyme that breaks down cell protein into
amino acids. Among amino acids, Tryptophan causes hormonal
imbalance in cell leading to formation of root galls.
Within 24 hours of feeding, giant cells are formed.
The J2 juvenile undergoes 3 moults to form young males and females.
J3 and J4 are resting stages. The young females become gravid within
7 days while young males leave the roots and exist as free-living
forms.
Life cycle is completed in 25-30 days at 25-27° C temp

11. Spread of Disease
The above ground symptoms include:
Stunted plant growth and yellowing of the
foliage.
Incipient wilting during hot, dry weather
conditions particularly in broad leaf crops.
Under sized fruits and reduced yield.
Plant mortality is rare, but occurs with
secondary infections.

12. The below ground symptoms include:
Formation of root galls or knots is diagnostic of
root-knot infection.
In some severe cases, the roots appear
swollen.
Infection spreads through infected soil,
irrigation water and farm implements.
In some severe cases, it forms a disease
complex with the fungus Rhizoctonia solani
that causes rotting of the roots.

13. Integrated Nematode Management
Deep summer ploughing: 2-3 deep ploughings at 10-15 days interval during
May-June is effective in killing different stages of nematodes due to
desiccation to high temperature in tropical areas.
Soil Solarisation: Soil is covered with polythene sheets for 3-4 weeks to
increase the soil temperature.
Crop Rotation: Instead of continuous cultivation of gerbera, non-host plants
such as Marigold should be grown. The “Calcutta Yellow” variety has
nematostatic/nematocidal properties. Solanaceous crops contain
Dodecanoic acid and Myristic acid which are antagonistic effect on
Nematodes.
Flooding: Submerging the field in water creates an anaerobic condition
unfavourable for nematodes.

14. Biological control agents: Trichoderma viridae, Pseudomonas flourescens,
Bacillus subtilis are some microbes that can be used for the control of
root-knot nematode population in the soil. Bacillus subtilis in particular has
been successful in Gerbera cultivation.
The required dose is 10g/kg seeds. Soil drenching can be done as well.
Chemical treatments: Soil drenching and fumigation are done. Earlier,
Methyl Bromide served as an excellent fumigant but is banned now.
Nursery bed is treated with Carbofuran 3G or Phorate 10G @ 0.3g
A.I./m2.
Main field is treated with Carbofuran/Cartap Hydrochloride @ 1-2 kg
A.I./m2.

15. THANK YOU
“The policy of protecting crops from pests by means of sprays,
powders and so forth is unscientific and unsound as, even when
successful, such procedure merely preserves the unfit and obscures
the real problem - how to grow healthy crops.”
-Sir Albert Howard