Melon and cotton aphid

Aphis gossypii

General

• The aphid Aphis gossypii is widely distributed throughout the world. This aphid is a major pest of plants in the Cucurbitaceae family due to its ability to transmit viruses.

• In Guyana, A. gossypii is also found on tomatoes, aubergines, okra, dachines, citrus fruits and papayas.
   

• Distribution in the Overseas Departments:

• Extremely polyphagous, the A. gossypii develops on more than 92 botanical families.

• Observed in the open field as well as under shelters.

Symptoms, damage

• Aphids produce honeydew causing sooty mold to appear on the foliage of infested plants. These fungi when they are in abundance, can limit photosynthesis and lead to a reduction in yield. Sooty mold, if it develops on the fruits, can lead to a reduction in production, but a simple washing can remove it.
• Aphis gossypii is also known to be an excellent virus vector in cucurbits.
• In Guyana, it is capable of transmitting the following viruses on cucumber:
  - Zucchini yellow mosaic virus (ZYMV), Zucchini yellow mosaic virus
  - Papaya ringspot virus (PRSV), Papaya ringspot virus
  - Cucumber mosaic virus (CMV), Cucumber mosaic virus.
• Early attacks by this virus can lead to the total loss of production.

Biology

• In hot climates, Aphis gossypii multiply by parthenogenesis: reproduction takes place without fertilization. The eggs are produced directly by the adult female.
• The optimum temperature for reproduction is 20 – 25°C: the female then produces an average of 2.8 larvae per day. The aphid reaches maturity after 5 days.
• The color of A. gossypii can vary from yellow to dark green. The female, 2 mm long, has 2 black cornicles, the antennae are shorter than the body. The ends of the legs are brown.
• Aphids are usually located on the underside of leaves, often in association with ants guarding them.

Protection

• Weed the crop and its surroundings.
• Check the sanitary quality of the plants before and during their introduction into the crop or shelter.
• shelter insect-proof
• Install  canvases  insect-proof at shelter openings.
• Detect the first pests thanks to the yellow sticky panels placed above the crop as soon as the plants are introduced.
• Several auxiliaries have an action on the aphid Aphis gossypii . Auxiliary predators: ladybug and hoverfly larvae eat aphids. Some parasitoid wasps, Aphelinus spp. are known to lay their eggs in aphids.
• The presence of these natural auxiliaries can be favoured:
  - For Aphelinus and adult Syrphid flies, flower nectar is an important food source that can be provided by spontaneous flora as well as the planting of flower strips.
  - For ladybugs, planting sorghum can promote their presence because this plant can harbor the grass aphid ( Rhopalosiphum maidis ) on which ladybird larvae feed. This specific grass aphid is a source of food for ladybirds and does not attack the main crop (Source Bio Savane).
• Proper management of fertilization by limiting excess inputs limits the susceptibility of plants to attacks by aphids and other pests.
• are Insecticides approved against aphids on cucurbits, however, many resistance phenomena are to be deplored and these broad-spectrum products also kill auxiliary fauna. In addition, an insecticide treatment can sometimes be accompanied by the spread of a viral disease: a consequence of hyperactivity of vector aphids on the treated plot.