Pest & Disease Management in Organic Farming

Protecting crops from pests and diseases is the biggest challenge in organic farming. We use a variety of methods and techniques to manage pests(without synthetic chemical pesticides). We believe synthetic chemical insecticides and fungicides pose the biggest risk and are the biggest chunk of the problem to be eliminated in producing safe food.

There are two kinds of insects in the farm. Beneficial insects and harmful insects.

Thrips (Scirtothrips dorsalis Thripidae: Thysanoptera)

• Thrips are dark-colored insects that have fringed wings
• The nymph stage of a thrip is also dark in color.
• A female thrip lays 40-50 eggs inside the tissues of the leaves and the shoot of the plant.
• The life cycle of a thrip is given below

Damage symptoms

• Thrips suck sap from the bottom of the leaflets.
• This results in white-colored patches on the upper surface of the leaves and necrotic patches on the lower surface of the leaves.
• It consists of distortions of the young leaflets and patchy areas of necrotic tissue that puncture and split as the leaflets grow.
• Injury is normally seen on seedlings.

 

 

 

Leaf hopper

• Leaf hoppers are elongate, wedge-shaped green insects that are found under the surface of the leaves
• A female leaf hopper lays 15-30 eggs which lay within 4-10 days.
• The eggs of a leaf hopper are laid close to the midrib or in the petiole of the leaf.
• The number of leaf hoppers is high during August and September and February and March.

Damage symptoms

• Both adults and nymphs suck sap mostly from the lower surface of the leaves of plants that are young.
• The first symptom that is seen is the whitening of the veins.
• Yellow patches are then seen, especially at the tips of leaflets, probably caused by a reaction between the jassids salivary secretion and plant sap.
• Under severe infestation, the leaf tips become necrotic in a typical V shape giving the crop a scorched appearance known as ‘hopper burn‘.

Biological control for leaf hoppers

We should conserve bio-agents like:

• Praying Mantis
• Long Horned Grass Croppers
• Dragon Flies
• Spiders
• Green Muscardine Fungus

Red Hairy Caterpillar (albistriga)

• The adult stage of red hairy caterpillars is a medium-sized moth.
• The fore wings of a red hairy caterpillar are white with brownish streaks all over and yellowish streaks along the anterior margin and hind wings white with black markings. A yellow band is found on the head.
• In the wings of the moth, markings are red in color. On heavy rains, about a month after sowing in kharif season, white moths with black markings on the hind wings emerge out from the soil in the evening hours.
• A female Red hairy caterpillar lays about 600-700 eggs under the surface of the leaves. The eggs hatch after 2-3 days.
• A tiny greenish caterpillar comes out and feeds on the leaves sociably by scrapping on the lower surface of tender leaflets.
• A full grown larva measures 5 cm in length, reddish brown hairs all over the body arising on warts. The larval period is 40-50 days. With the receipt of showers, the grown up larva pupates in earthen cells at a depth of 10-20 cm.
• They pupate mostly along the field buds and in moist shady areas under the trees in the field and undergo pupal diapause till the next year.

Damage symptoms

• Later they feed voraciously on the leaves and main stem of plants.
• They march from field to field sociably.
• Severely affected field looks as though they are grazed by cattle. Sometimes it results in the total loss of pods.
• They also feed on sorghum, cotton, finger millet, castor, pulses and cowpea, etc.

Biological control

• Spray A-NPV (2X 10^5 PIB/I) and Bacillus thuringiensis.
• Release of Bracon hebetor@ 5000/ha. Two times at 7-10 days interval.
• Lady Bird (Coccinella sp) and Menochilus sexmaculata and parasitoids like Chelonus spp.
• Conserve the bio control population of Spiders, Long horned grasshoppers
• Praying mantis Robber fly, Ants, green lace wing,  Damsel flies/dragon flies, flower bugs, shield bugs, lady bird beetles, ground beetle, predatory cricket, earwig, braconids, trichogrammatids, NPV, green muscular fungus.
• Use 5% neem seed kernel extract on need basis.
• Inter cropping with pigeon pea, mung bean and soybean provides increase in population of spiders.
• Population of coccinellids is higher on groundnut with maize, mung bean and soybean and Chrysoperla spp. is higher with maize and soybean intercrops.

Conserve bio-agents like:

• Spiders
• Long Horned grasshoppers
• Praying mantis
• Robber fly
• Ants
• Green lace wing
• Damsel flies/dragon flies
• Flower bugs
• Shield bugs
• Lady bird beetles
• Ground beetle
• Predatory cricket
• Earwig
• Braconids
• Trichogrammatids NPV
• Green Muscardine Fungus

Leaf miner

• Adult is dark brown with a white spot on the coastal margin of each forewing. The small hind wings are covered by fringe of minute hair.
• Adults are found briskly whirling around the plants in field and lay shiny transparent eggs singly on the under surface of leaflets.
• A female moth lays 150-200eggs that hatch in 2-3 days. The larvae are pale brown. Fully grown larva measures 6-8 mm. The larval period is 4-17 days.

The life cycle of a leaf hopper is given below:

Damage symptoms

• It prefers rain fed crop and bunch varieties. Young newly hatched green caterpillar mines into the leaflets and feed on green tissues resulting in brownish dried up patches.
• Later instars caterpillars fold the leaves together and feed on the green tissues by remaining inside.
• Severely infested crop presents a burnt up appearance. Caterpillars (or) pupae can be seen inside the mines and folded leaflets.
• It also attacks red gram and soybean.

Cultural Control for leaf miner

• Planting of cowpea or soybean as trap crop.
• Crop rotation with non-leguminous crop is advised in case of severe recurring problem.
• Crop rotation of groundnut with soybean and other leguminous crops should be avoided.

Mechanical control for leaf miner

• Install pheromone trap @ 5/ha for mass trapping.

Biological control for leaf miner

• Release Trichogramma Chilonis@ 50000/ha twice (7-10 days interval)
• Conserve the natural bio control population of spiders, long horned grasshoppers, praying mantis, robber fly, ants, green lace wing, damsel flies/dragon flies, flower bugs, shield bugs, lady bird beetles, ground beetle, predatory cricket, earwig, braconids, trichogrammatids, NPV, green muscular fungus.
• Mulching with rice straw causes reduction in leaf miner incidence and increase in percentage parasitism.
• Intercropping groundnut with Pennisetum glaucumenhanced the parasitoid Goniozus spp. on leaf miner.
• Spray neem based formulation @ 5%.

Tobacco caterpillar

• Adult moth is stout with wavy white markings on the brown fore wings and white hind wings with a brown patch along its margin.
• Eggs are laid in groups and covered with hairs on the leaves. The egg period is 4-5 days.
• Larva is stout, cylindrical, pale brownish with dark markings. The body may have row of dark spots or transverse and longitudinal grey and yellow bands. When fully grown, measures about 35-40 mm in length.
• The larval period is 14-21 days.
• It pupates in earthen cells in soil for 15 days. Life cycle is completed 30-40 days.
• ETL: 1-2 egg masses per meter crop row of 7-12 plants or pheromone trap catches exceed 100 moths per night, averaged over a week.

Damage symptoms

• Neonate, green caterpillars feed on the leaves voraciously and present an appearance to the field as if grazed by cattle. Since this pest is nocturnal in habit larvae hide under the plants, cracks and crevices of soil and debris during the day time. Faecal pellets are seen on the leaves and on the ground which is the indicator of the pest incidence.

Biological control for tobacco caterpillar

• • Conserve the natural bio control population of spiders, long horned grasshoppers, praying mantis, robber fly, ants, green lace wing, damsel flies/dragon flies, flower bugs, shield bugs, lady bird beetles, ground beetle, predatory cricket, earwig, braconids, trichogrammatids, NPV, green muscular fungus.
  • Release of Telenomus Remus @ 50000/ha. 4 times (7-10 days interval) based on pheromone trap catching.
  • Use SNPV @ 250 LE (6X 10^9/LE)/ha or B.T. @1 kg/ha, when large number of egg masses and early instars larvae are noticed.
  • Release Trichogramma Chilonis@ 50000/ha. 2 times (7-10 days interval) based on pheromone trap observation.
  • Release of Bracon hebetor@ 5000/ha. Two times at 7-10 days interval.
  • Spray insect pathogenic fungus Nomuraea rileyi@10^13 spores/ha for controlling early instars.
  • Release larval parasitoid Apanteles africanus @ 5000/ha.
  • Use 5% neem seed kernel extract on need basis.

  Cultural Control for Tobacco caterpillar

  • Planting castor or sunflower plants as trap crop for egg laying and destroying eggs or 1st stage larvae help in reducing the incidence.
  • The sunflower act as bird perches as well.

Mechanical Control for tobacco caterpillar

• Install light trap.
• Use pheromone traps (5/ha) to monitor moth population.
• Install 10-12 bird perches per ha.

Gram Pod Borer

• Adult is brown colored moth with ‘V’ shaped speck on forewings and dull black border on the hind wing.
• Eggs are laid singly on host plant. The egg period is 5-7 days. Larva is greenish with dark brown to grey lines. Color varies with kind of host plant.
• The larval period is 14-20 days. It pupates in soil and pupal stage lasts for 10 days. Cannibalism is common among larvae.
• Damage symptoms
• Small or large irregular feeding holes on the leaves. Presence of pale green or rose or brown or chocolate colored caterpillars with dorsal and later stripes and hairs on the body.
• Caterpillars also damage the fruiting bodies by entering into them.

Cultural control  for Gram pod borers

• Deep summer ploughing.
• Inter crop one row of red gram for every 5 or 6 rows

Mechanical Control for gram pod borers

• Install light trap.
• Use pheromone traps (5/ha) to monitor moth population.
• Install 10-12 bird perches per ha.
• Collection of egg masses/early instars larvae from trap crops.

Biological control for Gram pod borers

• • Use Trichogramma Chilonis @ 1 lakh/ha or Chrysoperla carnea @ 50000/ha at 40 and 50 days after sowing of groundnut can effectively check the pest.
  • Apply H-NPV @ 250 LE/ha or B.t (Bacillus thuringiensis) 1 kg/ha or 5% NSKE for monitoring eggs and early instars larvae.
  • Conserve the natural bio control population of spiders, long horned grasshoppers, praying mantis, robber fly, ants, green lace wing, damsel flies/dragon flies, flower bugs, shield bugs, lady bird beetles, ground beetle, predatory cricket, earwig, braconids, trichogrammatids, NPV, green muscular fungus.

  White grubs

  

• The dark brown adult beetles renter the soil to hide and lay eggs.
• Female lays 20 – 80 white, roundish eggs in clusters. Egg period 9 – 11 days.
• Grubs are white and translucent. Pupates in soil and remain as pupae until the following year. The adult beetles emerge with the first monsoon showers.

Biological control of white grubs

• Conserve braconids, dragon flies, trichogrammatids, NPV, green muscardine fungus.

• Termites

  

• The queen produces thousands of eggs over the lifetime.
• After mating, the new queen starts laying eggs in about a week.
• Eggs are laid in a crevice by digging a hole in the soil or by excavating a tunnel in wood.
• Once the nuptial chamber is constructed the king and queen will mate.
• Initially, the queen lays only a few eggs which are looked after by her and the king.
• The eggs are normally laid singly.
• Incubation takes from 24 to 90 days.
• There are normally seven nymphal instars (stages) in established colonies but the number varies depending on temperature, age of colony, size of colony and relative humidity. The nymphs may grow into soldiers or workers.

Damage symptoms

• The termite is endemic in red and sandy soils.
• All termites eat cellulose (e.g. from dead plant fiber) and many termites cultivate a fungus within the nest, which is a source of food (especially proteins) for the queen, king and the young.
• Wilting of plants in patches
• Termites penetrate and hollow out the tap root and stem thus kill the plant.
• Bore holes into pods and damage the seed.
• It removes the soft corky tissue between the veins of pods causing scarification, weaken the shells, make them liable to entry and growth of Aspergillus flavus that produces aflatoxins.

Pod bugs

• The adult is dark brown, approximately 10 mm long and 2 mm wide. In the field, the females lay their eggs singly in the soil or on groundnut haulms.
• But in storage eggs are laid loosely among the groundnuts. A female bug may lay up to 105 eggs. The egg period is 4-5 days.
• The first instar nymphs have a bright red abdomen, later instar become progressively darker.
• Both nymphs and adults feed on kernels by piercing the pods with their rostrum.
• The nymphal period is 23-29 days. Since it is nocturnal in habit, it hides under weeds, cracks and crevices in soil and debris during day time.

Damage symptoms

• It is a serious pest at pod maturity stage, pod harvesting stage and harvested produce in the threshing floor.
• Both nymphs and adults suck the sap from the pod in the field and produce at threshing floor.
• Freshly harvested pods have shriveled kernels.

Biological Control for pod bugs

• Set up light traps to attract and kill the bugs.
• Keep the crop refuse in the field along irrigation channel to attract the bugs which can be killed by dusting.
• Dust the groundnut stored in the gunny bugs with Malathion 4D.