Aphids  (Homoptera: Aphididae)                                                BACK

 Species complex

1.        Green peach aphid - Myzus persicae  (Sulzer): Light to dark green

2.        Cotton aphid - Aphis gossypii Glover: Pale yellow to brown, Grey black, or light to dark green

3.        Bean aphid - Aphis fabae  Theobald: Black to olive green

4.        Potato aphids - Macrosiphum euphorbiae (Thomas), Rhopalosiphum rufiabdominalis (Fitch) -   and Rhopalosiphoninus latysiphon Davidson: Pink to green forms

Myzus persicae            Aphis gossypii           Aphis fabae                                    Potato aphids                  

Distribution: All over India.

Host Range: Potato, cotton, cabbage, cauliflower, mustard and other solanaceous and cruciferous crops.

Nature of damage and symptoms:

·         Suck cell sap from tender leaves/shoots.

• Stunted growth and poor tuber formation.
• Under severe infestation the entire plant may dry up.
• Excrete honeydew which attracts sooty mould and interferes with photosynthesis.

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Typical potato leaf roll symptoms due to PLRV              Primary leaf roll symptoms (rolling and pigmentation of         Aphids infested potato plant

                                                                                        young top leaves) on potato plant

Identification:

·         Aphids are small (1 - 3 mm), soft-bodied insects that vary in color (green, pink, yellow, grey, or black).

·         Two cornicles (siphunculus) or "exhaust pipes" extend from the hind end of most aphids (Fig).

·         Most commonly seen in spring and autumn, aphids can be winged or wingless and are usually slow-moving.

·         Nymphs: 1- 1.5mm long, resembles adults but is smaller and always wingless.

·         Adults: About 2mm in length and ash grey in colour.

Figure : Identifying characters of aphids

Life cycle:

Among the aphid species infesting potato crop, M. persicae is the most studied and damaging as it is a potential vector of viruses.

·         It starts appearing on potato crop in the North- western plains of India from the second week of November and in the eastern plains in early December, reaching the critical level (20 aphids per 100 compound leaves) by the end of December in the former and during 1^st to 2^nd week of January in the later area (Fig ).

                        Population fluctuation of aphids in plains.

·         In the North- western higher hills and in North-eastern hills, the critical level generally reaches by the end of July (Fig ).

                    Population fluctuation of aphids in Hills.

·         In the plateau region of Maharashtra, aphid infestation remains almost negligible in Kharif crop while on Rabi crop, it appears in the second week of November and critical level reaches by the third week of December.

·         Reproduces through parthenogenetic vivipary however, during severe winter, sexual reproduction also occurs (Fig ).

                                                                Life cycle of aphids

·         Over-crowding coupled with high temperature and low humidity results in appearance of alates for migration.

·         There are 4 nymphal instars.

·         The nymphs mature in 10-15 days.

·         A single female can produce 40-45 young ones.

·         Total life cycle is completed in 10-45 days.

·         Most congenial conditions for aphid development and reproduction are 19-24^oC temperature with an average relative humidity of 67-85%.

·         Many generations in a year (multi-voltine). 

Management:

1.      Monitoring of aphids using yellow sticky traps and aphid count on 100 compound leaves.

2.      Growing potato crop by adopting the seed plot technique with the following precautions, i.e. planting of clean (virus free) potato seed procured from certified/reliable sources during aphid free/low aphid periods and adjusting planting dates as follows:

Ø  15^th Oct.   : North-Western Plains (Fig).

Ø  25^th Oct.   : Central Plains.

Ø  5^th Nov.    : North-Eastern Plains.

                                                Aphid population in relation to potato crop in NW plains.

3.      Maintaining an isolation of 50 m for seed crop.

4.      Timely rouging of virus infected plants well before they touch each other.

5.      Haulm (foliage) cutting of crop after desired maturity of crop but before the aphids cross the critical level of 20 aphids/100 compound leaves.

6.      Regular cutting of foliage re-growth so that the aphids could not build up on them.

7.      Conservation of natural enemies such as predators like coccinellids (Coccinella spp.), syrphids (Scaeva pyrastri, Eupodes frequens, Episyrphis balteatus, Metasyrphus confrator) and chrysopids (Chrysoperla carnea); and parasitoids like Aphidius spp.

        Coccinellid spp. feeding on aphids                                                                        Parasitized aphids

8.      Application of Pongamia glabra, Ageratum conyzoides, Vitex negundo, and Acorus calamus @ 2.0% for organic potato production.

9.      Spray of fine pulverized mica powder @ 0.2 % (2ml/lit) to repel the alates.

10.  Foliar application with dimethoate 30EC @1ml/lit of water or Imidacloprid 17.8EC @ 2ml/10 lit of water at a population level of 2 aphids/ 100 leaves. Repeat foliar spraying fortnightly if population exceeds. Spraying should be stopped at least 7 days before harvest.

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