A very large number of insects causing
damage to the groundnut crop have been recorded. Many insects, which
are minor pests at present, are likely to become important and major
ones in the near future. Such situations are noticed with Spodoptera
and jassids.
As groundnut is largely grown as a rainfed crop,
chemical control methods as far as feasible, have to be with dust formulations
of insecticides only.
Chemicals should not be used indiscriminately on
groundnut crop as soil application or application after pod formation
with insecticides like BHC are known to impart off-flavours not only
to the kernels but also to the oil.
Hence selection of a suitable insecticide is very
important in groundnut pest control. Information on some of these aspects
is very meager at present.
Recent surveys have shown that the groundnut crop
is mainly attacked by hairy caterpillars, leafminer, jassids, aphids,
Thrips, white grubs or root grubs, termites, stem borer, wire worms
and earwigs.
Severe infestation by certain leaf eating noctuid
caterpillars such as Spodoptera, Heliothes and Plusia was also
reported from certain pockets.
This polyphagous insect popularly known as bean
aphid or cowpea aphid feeds on a number of leguminous crops including
groundnut. Glyricidia maculata is a major alternate host.
It is considered to be a serious pest of rabi
groundnut than kharif groundnut crop. Colonies
of aphid nymphs and adults infest the tender shoots, flower stalks and
pegs in large numbers and suck the sap.
As a result of this feeding, curling of leaves and stunted growth
of plants is caused. In cases of infestation of flower stalks and pegs,
the pod formation is badly affected.
Aphids are also known as potential vectors of rosette
virus and peanut mottle virus. In this context, control of aphids assumes
added importance.
Control schedule
Aphids have to be controlled not only on groundnut crop but also on
other alternate hosts nearby to keep the groundnut crop healthy.
Spraying with any of the following chemicals will successfully control
the pest: endosulfan 0.04 per cent; methyl demeton 0.05 per cent; dimethoate
0.05 per cent; phosphamidon 0.02 per cent; monocrotophos 0.05 per cent.
Besides leaf miner/webber, the major defoliators
on groundnut are three noctuid caterpillars viz., the tobacco caterpillar
(Spodoptera litura Fb.), the gram caterpillar (Heliothes armigera
Hb.) and a semilopper (Plusia sp.).
Spodoptera litura Fb. Is a polyphagous pest
and the larvae are reported to cause severe defoliation to groundnut
crop both in kharif and rabi seasons.
The caterpillars are active at night and cause
extensive damage. During day time they hide underneath the plants, in
the cracks and crevices of the soil or beneath the fallen leaves, etc.,
and come up for feeding during the late evening hours.
Heliothes armigera Hb. Is also a polyphagous
pest and the larvae feed on leaves, tender stems and flowers of groundnut.
It feeds more extensively on flowers.
The semilooper (Plusia sp.) feeds on the
foliage and defoliates the plants.
All the three caterpillars, which were
known as minor pests, have become very serious pests on groundnut in
the recent years and are reported from several places.
Control schedule
The pests being nocturnal in their habits, control
operations have to be taken up either during early morning hours or
late evening hours or preferably during nights.
Spraying or dusting with a persistent insecticide
like carbaryl/ endosulfan/quinalphos at 0.1% gives satisfactory results
to control the pest.
Jassids appear in kharif crop in August
and reach a peak during September-October. In the rabi crop also
young seedlings are infested. Jassids, which were hitherto considered
as minor pests, have assumed major status in the recent years and are
causing considerable damage.
Adults and nymphs suck sap from the leaves and
leaf stalks of tender seedlings, which result in discolouration, and
wrinkling of leaves followed by sickly appearance and stunted growth
of plants.
The early vigour of the plants suffers due to jassid
infestation. In extreme cases of infestation, the margins of the leaves
show ‘hopper burn’ symptoms.
Disappearing of plants by jassids is known to affect
the pod filling adversely.
Control schedule
Spraying with methyl parathion/endosulfan/malathion/
carbaryl /dimethoate (all @ 0.05%) and phosphamidon 0.02 per cent or
dusting with carbaryl/endosulfan/malathion at 20-25 kg/ha is suggested
for jassid control.
This is another serious and fairly specific pest
of groundnut although it has been reported to infest other crops such
as soybean, redgram and green gram.
The pest is also recorded on two wild shrubs Psoralea
corylifolia and Cassia thora. Serious damage by the pest
is felt mostly in deccan plateau and plains of South India.
The pest appears both in kharif and rabi
crops. Drought conditions with intermittent occasional showers favour
multiplication of the pest whilst heavy wash out the pest.
Dark headed green caterpillars mine into the leaves
as a result of which dried blisters appear on the leaf surface.
Sometimes the leaf is folded and in some cases
the nearby leaves are brought together and webbed.
The caterpillars feed on the tissues of the leaf
in between the upper and the lower epidermis skeletonising the leaf.
In severe cases of infestation, the dried skeletonised
leaves give burnt appearance.
Control schedule
The moths are highly phototropic and hence light
traps or bonfires will be useful to attract them and destroy them.
When once the larva mines into the leaf it will
be in comparative safety against chemicals, particularly the dust forms.
Hence the most rational approach is to treat the crop with penetrating
sprays of contact insecticides timing the same either with the light
trap information or with the first appearance of a few mines and larval
chambers on the plants. Hence vigilance on the part of the farmer goes
a long way in the control of this pest.
The following chemicals are recommended for spraying:
carbaryl 0.2 per cent; endosulfan 0.04 per cent, dimethoate 0.03 per
cent; quinalphos 0.05 per cent; formothion 0.05 per cent; methyl demeton
0.04 per cent, phosphamidon 0.02 per cent, methyl parathion 0.05 per
cent and chlorpyrifos 0.05 per cent.
Depending on the need, spraying may be repeated
with a different insecticide.
The larvae of wireworms (Coleoptera tenebrionidae) bore into
the immature pods by making a hold on the shell and feed on kernels
inside. The incidence is confined to rainfed groundnut.
Similarly, the larvae and adults of earwigs (Euborellia stali
Dohrn) bore through the immature pods and feed on the kernels.
Both the pod feeding insects are abundant in pesticide free areas.
Soils treated with insecticides either for the control of root grubs
or termites will generally be free from wireworms or earwigs.
The groundnut crop is also attacked by the blister beetles (Mylabris
pustulata Thumb) which feed on flowers and the ash weevils (Myllocerus
sp.) which feed on the foliage. The damage however is minor and
hence do not generally warrant any control measures.
Red hairy caterpillars (Amsacta
albistriga Wlk. And A.moorei Butler)
These are the most injurious leaf eating pests of the groundnut crop.
The caterpillars in all their stages feed on the leaves and defoliate
the plants. These are mainly pests of the kharif crop.
The caterpillars are polyphagous and feed on a variety of crops such
as sorghum, pearl millet, finger millet, pulses, cotton, castor, etc.,
and a number of weeds besides groundnut.
From the hibernating underground pupae, moths emerge with the receipt
of first monsoon rains in June-July and start laying eggs in one or
two days The eggs are laid in masses and the quite conspicuous due to
their creamy colour.
The caterpillars feed gregariously in early stages but spread when
they grow old. In their grown up stage, the larvae march from field
to field completely browsing the plants on their way leaving only the
stubbles.
By about November, full grown larvae enter the soil for pupation.
Only two or three generations are found per year.
Generally, it is the second and the third broods that cause considerable
damage to groundnut crop in south India.
The Bihar hairy caterpillar (Diacrisia obligua HL.) also occurs
on groundnut along with red hairy caterpillar and causes the same type
of damage. Other details regarding the life cycle and habits are similar.
Control Schedule
As the incidence of these pests is widespread
and the damage is devastating, a large scale campaign approach for control
is necessary on the following lines:
Moths, which are highly phototropic, emerge from the soil with the
commencement of rains in June-July. Therefore, setting up of light traps
or bonfires help in attracting the moths and destroying them before
the moths lay the eggs.
Egg masses, which are creamy or yellowish in colour, are quite conspicuous
over the green background of the leaf. Collection of such masses has
to be done and destroyed.
Since the caterpillars in their early instars are gregarious in their
feeding habit, collecting the leaves on which they are feeding along
with egg mass collection and destroying them is necessary.
Dusting with carbaryl or parathion or endosulfan @ 25-30 kg/ha a week
after large scale emergence of moths controls the early instars of the
caterpillars. However, control of grown up larvae is difficult due to
thick growth of hair on their bodies. Spraying with DDVP, fenitrothion,
endosulfan, dimethoate or formothion @ 0.1 per cent may control the
grown up larvae to a satisfactory extent.
As the caterpillars in their full grown stage have the habit of marching
from one field to another in large numbers, digging straight cut trenches
of 30 x 20 cm across the direction of marching of the pest and application
of 5 per cent malathion dust in the trench is recommended to prevent
marching. The larvae in the course of their march fall into these trenches,
come in contact with the insecticides and are killed. Alternately, the
caterpillars in the trenches may be collected and burnt.
Red headed hairy caterpillars
Trap crop: Sow the redgram and cowpea in borders to kill the young
larva.
Dusting of malathion only on the trap crop.
Preparation of baits
Broken wheat grains 10 kgs + jaggery 1 kg + monocrotophos/methomy/100
ml (13-15 kgs/acre).
Preparation methodology
Moisten the wheat brain and spread jaggery solution then farms a bran,
then mix the chemical by using hand gloves.
Pack them in a plastic cover, keep it in overnight.
In the morning spread the bait in the field, it gives very good control
for 4-5th instar larva.
This beetle pest is recorded throughout India but
is serious only in pockets in South India.
The grub of this beetle bores into the stem of
the groundnut plant and often travel downwards tunneling the main root
and killing the plant.
Besides groundnut, it attacks a number of other
leguminous plants like cowpea, redgram, horsegram, etc.
Control schedule
Spraying with a persistent insecticide like carbaryl/endosulfan
@ 0.1 pr cent or application of phorate/carbofuran granules to the soil
@ 1.5 kg a.i./ha is suggested for effective control.
There are several insects, which cause substantial
losses to stored groundnut pods on kernels. Both adults and nymphs of
pod sucking bug [Elasmolomus (Aphanus) sordidus F.] suck the
oil from the kernels piercing through the shells of just harvested as
well as dry pods in storage. The quality of oil is reduced and the damaged
kernels later turn rancid.
The larvae of the rice moth (Corcyra cephalonica
Stnt.) adults and grubs of red flour beetle (Tribolium castaneum
Host.), the larvae of the fig moth (Cadra coutella Walk.) and
the larvae of Indian meal moth (Plodia interpunctella Bb.) are
some of the common insects that damage the groundnut pods and kernels
in storage and cause extensive losses both in quantity and quality.
Thorough drying of pods and storage containers
before storing is a pre-requisite.
Spraying the storage godowns with 0.1 per cent
malathion has to be done to eradicate the carry over population of the
pests.
Dusting 5 per cent malathion as a thin film on
the bags in which the pods are stored serves as a preventive.
For the effective control of storage pests,
fumigation with methyl bromide for 24 hours is recommended if the godowns
are air tight.
Termite damage to groundnut crop is more common
in light red and clay soils where rainfall is scanty Two types of damage
are caused by the termites. The best known is the scarification of the
underground pods. This weakens the shells and makes them liable to crack
facilitating entry and growth of toxic fungus, Aspergillus flavus
into kernels.
The second type of damage is the feeding on the
tap root of the plant. The termites enter the root and work up the stem
hollowing and filling the same with mud particles. In this way the termites
reach the upper part of the plant also. Finally plants wilt and die.
Control schedule
In places where regular termite incidence is noticed,
repeated deep ploughings during summer months for successive years discourage
termite buildup.
Where other soil inhibiting insects such as root
grubs, wire-worms earwigs, etc., are also a problem along with termites,
application of phorate/carbofuron granules to the soil @ 1.5 kg a.i/ha
gives beneficial results besides controlling all the early season occurring
pests of groundnut such as jassids, Thrips, etc.
Where specific control measure for termites is
required, application of lindane dust to the soil @ 20-25 kg/ha gives
satisfactory control of the termites.
Three species of Thrips occur on groundnut and
all the three are polyphagous and hence not host specific. Scirtothrips
dorsalis Hood commonly known as chilli Thrips, occur on groundnut
in kharif and rabi seasons.
Nymphs and adults feed on tender foliage causing
yellowish green patches on the upper surface and brown necrotic areas
on the lower surface of the leaves.
Severe curling also occurs among the affected
leaflets. These Thrips are known as vectors of yellow spot virus.
Caliothrips indicus Bagnall known as the
groundnut Thrips are a menace to the groundnut crop particularly in
South India.
They are very prolific in rate of multiplication
and pass through several generations in a year.
Nymphs and adults through their concentrated feeding
make the tender foliage spotted and pale.
Feeding is generally confined to lower leaves.
In severe cases of infestation the foliage dries up.
The adults and nymphs of Frankliniella schultzei
Trybom feed on the tender foliage resulting in heavy scarring and stunted
growth of the plant.
These Thrips occur in both kharif and rabi
seasons and are established as vectors of bud necrosis disease caused
by tomato spotted virus.
Control schedule
Although Thrips are considered as minor pests,
prompt control is necessary as they are vectors of serious viral diseases.
For control of Thrips, spraying with dimethoate
/ monocrotophos /malathion/methyl demetion - @ 0.05 per cent and phosphamidon
0.02 per cent is suggested.
White grubs or root grubs are the larvae of the
cockchafer beetles and are nationally important pests.
The grubs feed on the roots and fine rootlets of
the plant, which results in wilting and death. Hence, the damage becomes
evident only when the plants are wilted and killed.
The grubs also feed on the tender pods of the
plant after pod formation and in this type of attack no external symptoms
of damage are seen.
The adult beetles emerge out of the soil with the
onset of heavy monsoon showers in June-July and feed during nights on
the foliage of trees like neem, acacia, zizyphus, tamarind, moringa,
etc.
During day time they hide in the soil and lay the
eggs. Grubs hatch from these eggs in about 7-10 days feed on the roots
of plants. Besides groundnut, root grubs also feed on the roots of sugarcane,
chillies, sorghum, maize, redgram, pearl millet, etc., and cause damage.
The grubs are found mostly in the 5-10 cm layer of the soil and prefer
sandy loams and river bed soils to black soil or pebbled soil.
By about November, full grown larvae migrate to
a considerable depth in the soil for pupation.
The pupal stage lasts for about a fortnight and
the beetles after emergence remain in diapause in the soil till the
next monsoon in June-July and thus there is only one generation in a
year.
Control schedule
As the pest in its adult stage diapauses in the
deeper layers of the soil, exposing the adults by deep ploughing during
summer months in a good practice.
As the adults on emergence from the soil feed on
the foliage of certain nearby trees, pruning the branches of trees and
spraying them in the night with a persistent insecticide such as carbaryl/endosulfan
all @ 0.1 per cent results in the mortality of some adults before egg
laying.
Adults are highly phototropic and hence setting
up bonfires in fields may attract them and destroy them.
Application of granular insecticides such as phorate/carbofuran
@ 1.5 kg a.i/ha to the soil at the time of sowing effectively controls
not only the root grubs but also other soil insects like termites and
plant sucking insects like jassids, Thrips, etc., and keeps the crop
free from insect attack for a period about 20-30 days.
Insect Management
