Crops
Aphids
General
- Polyphagous insects with worldwide distribution belong to the order Hemiptera, the suborder Sternorrhyncha and the superfamily Aphidoideae.
- Very frequent and very damaging on vegetable crops, especially in sub-tropical, tropical and equatorial production zones, developing fairly frequently on plants in the form of colonies.
- vectors Virus (CMV, ZYMV, etc.) particularly dangerous for certain vegetable crops.
- Several species encountered*:
- Aphis gossypii (Glover 1877).
- Aphis craccivora Koch).
- Lipaphis erysimi (Kaltenbach, 1843).
- Myzus persicae (Sulzer 1776).
- Macrosiphum euphorbiae (Thomas 1878).
- Aulacorthum solani (Kaltenbach 1843).
- To be completed
- Existence of populations resistant to chemical insecticides due to their intensive use.
- Observed in the open field and under shelter.
- Susceptible botanical family(ies)* :
| Aphis gossypii | Solanacées | Cucurbits |
| Composed | Brassicas | |
| Vegetables | ||
| Aphis craccivora | Solanacées | Composed |
| Myzus persicae | Solanacées | Cucurbits |
| Composed | Brassicas | |
| Vegetables |
- Affected production area :
| Aphis gossypii | Mayotte | Reunion |
| Guyana | Guadeloupe and Martinique | |
| New Caledonia | French Polynesia | |
| Aphis craccivora | Mayotte | Reunion |
| Guyana | Guadeloupe and Martinique | |
| New Caledonia | French Polynesia | |
| Myzus persicae | Reunion | Guadeloupe and Martinique |
| New Caledonia | French Polynesia |
- Organs attacked
| Leaves | Fruits | Rods |
Damage
- Symptoms :
- Chlorotic pitting, various deformations of the young leaves which are rolled up and more or less blistered following the nutritional bites of aphids (figures ).
- Reduced growth of young shoots and even plants (figure ).
- Signs : Presence of larvae and adults on the affected organs (figures 2, 10 to 15). In addition to aphid colonies, white moults are frequently observed on the surface of aerial organs, as well as the presence of honeydew rapidly colonized by opportunistic fungi causing sooty mold (figures ). Remember that the latter leads to a reduction in photosynthesis and leaf respiration and makes production unmarketable.
- Possible confusion :
Biology
- Development cycle : quite complicated involving eggs, population founders, adults, among them viviparous females, winged or not, and winged males. The length of the cycle varies according to the species, the nature of the host plant and its state, and climatic conditions.
- Eggs laid on various hosts, herbaceous or woody, hatch and give rise to foundresses. Subsequently, for a long period, viviparous females are found within the colonies. Eggs and viviparous females allow aphids to perpetuate themselves.
- Formation of young larvae which immediately feed on the sap and moult 4 times before giving birth to the adult. White moults (exuviae) on the vegetation indicate the presence of aphids in the crop.
- Winged or non-winged adults (in the latter case we speak of “wingless” individuals)(2) (figure ). Each individual can give birth to 40-100 offspring depending on the host and climatic conditions in particular.
- Larvae and adults often present on the underside of the blade, feeding through their rostrum. The excess sugar contained in the sap is released in the form of honeydew.
- Dispersal : possible via the wingless which moves on the plants and visits the neighboring plants. As soon as the adults appear (during pullulations), they disperse in the crop or in nearby plots. Plants and workers can contribute to their spread.
- Appreciate mild temperatures and summer shelter conditions.
Protection
- Use varieties resistant to colonization by Aphis gossypii in the case of a melon crop
- Weed the crop and its surroundings.
- Produce the seedlings in an nursery insect-proof .
- Control the sanitary quality of the plants before and during their introduction into the culture or shelter.
- Install canvases insect-proof at shelter openings when weather conditions allow.
- When growing under cover, detect the first pests using sticky yellow panels placed above the crop as soon as the plants are introduced.
- Favor natural enemies in field crops or under open shelters.
- Introduce auxiliaries in closed shelters if available.
- Reason chemical protection * ( e-phy ), especially if you use auxiliaries or biopesticides .
- Treat plants before uprooting in the presence of high pest populations so as not to contaminate nearby host crops.
*: resistance to insecticides or acaricides is known in these pests.
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