Soil application of carbofuran 3% CG @ 4.0 kg/acre, remove and destroy root rot/wilt affected plants. During this week attack of aphids and thrips is seen in cotton crop.
Fusarium wilt: Fusarium oxysporum f.sp. vasinfectum
Symptoms
- Initial symptoms on young seedlings are yellowing and browning of cotyledons, followed by brown ring on the petiole.
- Finally wilting & drying of the seedling occurs. Symptom at later stages includes loss of turgidity, yellowing, drooping and wilting starting from older leaves.
- Browning or blackening of vascular tissues occurs on the stem and spreads upwards and downwards. Infected plants appear stunted with fewer bolls.
Management
- Treat the acid-delinted seeds with Carboxin or Carbendazim at 4 g/kg.
- Remove and burn the infected plant debris in the soil after deep summer ploughing during June-July.
- Apply increased doses of potash with a balanced dose of nitrogenous and phosphatic fertilizers.
- Apply heavy doses of farm yard manure or other organic manures at 100t/ha.
Spot drench with 0.05 % Benomyl or 0.1 % Carbendazim.
Aphids
Description of Insect
Nymphs are small, yellowish or brownish on the undersurface of the leaves and on the terminal shoots and are mostly wingless. Adults are yellowish brown to black, 1.25 mm long with black cornicles and yellowish green abdominal tip. Both apterous (0.9-1.8 mm) and winged form (1.1-1.8mm) occur together.
Nature of Damage and Symptoms
Fig: 1&2- Colonies on undersurface of leaves.
Fig: 3- Black coating on boll & lint “Stickiness” of lint.
Fig: 4- Leaf crumbling and downward curling.
- Both adults & nymphs suck sap from tender leaves, twigs & buds and weaken the plants.
- Indirectly decreases cotton fiber quality as a result of sticky cotton due to deposition of honey dew on open bolls.
- Complete reduction in reproductive growth.
Life History
Aphids live in colonies and the females multiply parthenogenetically and viviparously. In a day female may give birth to 8-22 nymphs. Nymphal period lasts for 7-9 days and the adults live for 12-20 days. In all, the pest has 12-14 generations per year. It is a polyphagous pest. Aphids produce sugary excretion called ‘honey dew’ on which sooty mould grows. Ant activity is associated due to the honey excretion by aphids. Ants transmit aphids from plant to plant. Aphids have a large host range with varying durations of development and reproductive rate.
Thrips
Description of Insect
- Eggs are minute, kidney shaped laid in slits in leaf tissues. Incubation period is 5 days.
- Nymphs are creamy to pale yellow in color, resemble adults but wingless. Nymphal Period: 5 days. Pupal period: 4-6 days.
- Adults are straw colored, yellowish brown and elongated
Nature of Damage and Symptoms
- Shrivelling of leaves due to scrapping of epidermis and desapping.
- Attackedterminal buds –have ragged edges.
- Silvery shine on the under surface of leaves.
Life History
Thrips thrive on the weeds during the off-season and migrate to cotton as soon as the seedlings emerge above ground. Males are rare and the reproduction is parthenogenetic. Eggs hatch in 5 days time, nymphal and pupal period lasts for 5 and 4-6 days, respectively. The preimaginal stage is spent in soil without feeding. The adults survive for 2-4 weeks. Life cycle of T. tabaci from egg to adult lasts for 13-19 days and they have about 15 overlapping generations per year including their development on wild plants. Thrips inhabit on leaves of cotton up to mid season and colonise on bolls during the late season.
Management-
- ETL: 50 nymphs or adults/50 leaves
- Seed treatment with imidacloprid 70 WS 7g/kg protect the crop from aphids, leafhoppers and thripsupto 8 weeks
- Spray any one of the following insecticides (500 l spray fluid/ha)
- Imidacloprid 200 SL @100 ml
- Methyl demeton 25 EC 500ml/ha
- Dimethoate 30 EC 500ml/ha
- NSKE 5% @ 2 kg/ha
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