Aphid in Cotton

Cotton Insect Pest APHIDS

Aphid in Cotton

Common Name : Aphids

Local Name : Mawa

Scientific Name : Aphis gossypii Glover 

Family : Aphididae

Order : Homoptera

Pest Category: Sap feeder 

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Distribution and status:           India, occasionally serious.

Host plants:                                Cotton, Bhendi, Brinjal, Chillies, Guava

ETL:                                             5% of Infested Plants.

Description of Insect Stages:

Nymph: 

          Nymphs are small, yellowish or brownish on the undersurface of the leaves and on the

Aphids are Nymph Stage

terminal shoots and are mostly wingless.

Adult: 

            Adults are yellowish-brown to black, 1.25 mm long with black cornicles and yellowish-green abdominal tip. Both operate (0.9-1.8 mm) and alates (1.1-1.8 mm) occur together.

Bionomics:

           

Aphids On Cotton Plant Leaves in Nymph & Adult Stager

                The aphids are greenish-brown, soft-bodied and small insects.  The alate, as well as apterous females, multiply parthenogenetically and viviparously.  A single female may produce 8-22 nymphs in a day which become adults in about 7-9 days. They are often attended by ants for the sweet honeydew secretion.  Winged forms may be seen under crowded conditions.

Nature of Damage: 

          Aphids are phloem feeders, causing direct leaf c rumpling and downward curling with a severe attack. Indirectly decreases cotton fiber quality as a result of sticky cotton due to deposits of honeydew on open bolls. Younger plants suffer more attack than older plants. Aggregating populations are seen at the terminal buds and largest populations are found below leaves of the lower third of plants where they are partially protected from sunlight and higher temperature.

Aphids are Adult Stage

Symptoms:

        Leaves show downward crumpling. Leaves are shiny with honeydew or darkened by sooty mold growing on the honeydew. Contamination of lint with honeydew and associated fungi leads to poor quality cotton. The activity of ants on the aphid-infested plants is common

Life History:

             Aphids live in colonies and the alate as well as apterous females multiply parthenogenetically and viviparously. In a day female may give birth to 8-22 nymphs. Nymphal the 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 'honeydew' on which sooty mold grows. Ant activity is associated due to the honey

Aphids are Affected in Cotton Plant Leaves

 excretion by aphids. Ants transmit aphids from plant to plant. Aphids have a large host range with varying durations of development and reproductive rate.

Seasonal Dynamics:   Aphid infestations on cotton commence after the true leaves emerge and their field distribution is often clumped Typically aphid infestations will develop along with areas downwind from bunds and occasionally spotty within fields. It is to be noted that fields receiving regular insecticide treatments continue to have damage due to aphids for a long period of time over the fields
without insecticide applications wherein aphid cause damage for a short period of time but quickly brought under control by natural enemies. High levels of aphid populations develop on late than early-planted cotton. Excessive nitrogenous fertilizer

applications stimulate faster development of aphids.

Pest Management Options:

             Management of aphids during very early crop growth the stage should be attempted with a view to maintain optimum plant stand. Assessment of overall field conditions are necessary before opting for management against aphids. Insecticides of neonicotinoid group such as imidacloprid and thiamethoxam applied as seed treatment is efficient in suppressing the population of aphids on the crop for a maximum period of 45 to 50 days. However, 'prevention is better than cure' approach of pre-sowing seed treatment with systemic insecticides aids in attaining proper plant stand however they also cause luxuriant plant growth leading to a higher attack by thrips during pre-flowering stage, especially when there are dry periods. Therefore, keeping a close watch of crop growth and weather conditions, post-emergence sucking pest management should be done on a need basis. Crops should not be sprayed with insecticides considering the populations of aphids on plants. This is because aphids occur in aggregations and distributed randomly in a field, initially. As they breed, the population spreads to adjacent plants and the proportion of aphid infested plants in the field increases. The aphidophagous coccinellids and syrphids, and the generalist predator Chrysoperla carnea offer significant control of aphids during the early crop growth period. Under such situations, even if the pest numbers are high, insecticidal sprays need not be given. Spraying the crop should be done only when cupping and curling of rd the leaves on the top 1/3 portion of the plant and aphids all over the plant are seen, and the active growth of the plants is inhibited in at least 25 % plants of the field. Await and watch attitude is a must in cotton pest management to succeed by doing nothing e.g. the decision of spraying insecticides against the high population of aphids would be no use when heavy rains occur. The applied insecticide goes waste, but with natural reduction of pests due to rain. A spray of 5 % neem seed kernel extract prepared on-farm or crude neem oil spray @ 1% suppresses also the aphid population in addition to other sucking pests during the pre squaring crop stage. While using neem products, detergent/soap powder @ 1 gm/liter of spray fluid is to be added for getting uniform spray suspension. Chemical insecticides such as Imidacloprid 200 SL @ 0.5 ml/lit and Thiamethoxam 25 WG @ 1-1.5 gm/lit of water can be used only when there are symptoms, indicative of a high aphid population. The conventional systemic insecticides should be alternated if more than one spray of systemic insecticides is to be sprayed. Sprays should be undertaken when the population of aphids is high. Aphid attack during late season coinciding with the boll opening can be managed using the conventional insecticides like Endosulfan @ two ml/ lit of water. Pyrethroids cause resurgence of aphids on the crop and hence care should be taken against the control of pink bollworm. In such a situation a spray of anyone organophosphorus insecticidal compound is to be followed for aphid suppression. Insecticidal control is more successful in late than the early population of aphids. The table of the spray volumes for field use at different crop growth stages is given below.

Acetamiprid 20 SP 50 g	Fluvalinate 25EC 200-400 ml
NSKE 5% kg/ha or Azadirachtin 0.03% 500 ml	Imidacloprid 70 WG 30-35 g or 30.5 SC 60-75 ml or 17.8 SL  100 -125 ml
Buprofezin 25 SC 1.0 L	Profenofos 50 EC 1.0 L
Diafenthiuron 50 WP 600 g	Thiacloprid 21.7 SC 100-125 ml
Fipronil 5 SC 1.5-2.0 L	Thiamethoxam 25 WG 100 g
Methyl demeton 500 ml	Dimethoate 500 ml
Monocrotophos 1000 ml

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