Crops
Aphids
General
- Polyphagous insects of worldwide distribution belong to the order Hemiptera, the suborder Sternorrhyncha and the superfamily Aphidoidea.
- Very common and very damaging on vegetable crops, developing quite frequently on plants in the form of colonies.
- Particularly formidable virus vectors (CMV, etc.) for certain vegetable crops.
- Several species encountered belonging to different genera: Aphis, Myzus, Macrosiphum, Aulacorthum, etc.
- Existence of populations resistant to chemical insecticides due to their intensive use.
- Observed in the open field and under shelters.
- Organs attacked : leaves, stems, fruits.
- Symptoms :
- Chlorotic punctures, 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).
- >>> More pictures
- Signs : Presence of larvae and adults on affected organs (Figures 2, 10 to 15). In addition to aphid colonies, white molts are frequently observed on the surface of aerial organs, as well as the presence of honeydew rapidly colonized by opportunistic fungi that cause sooty mold (figures). Remember that the latter leads to a reduction in photosynthesis and leaf respiration and makes the productions non-marketable.
- Possible confusion :
*: to help you recognize aphid species, consult the INRAE site Encyclop'Aphid .
Biology
- Development cycle : quite complicated involving eggs, founders of populations, adults, among them, winged or non-winged viviparous females, and winged males. The length of the cycle varies depending on the species, the nature of the host plant and its condition, and climatic conditions.
- Eggs laid on various hosts, herbaceous or woody, hatch and give rise to founders. Subsequently, over a long period of time, viviparous females are found in the colonies. Eggs and viviparous females allow aphids to survive.
- Formation of young larvae which immediately feed on the sap and moult 4 times before giving birth to the adult. White moults (exuviae) on 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 rejected in the form of honeydew.
- Dispersion : possible via wingless birds which move on plants and visit neighboring plants. As soon as the adults appear (during outbreaks), they disperse in the crop or in nearby plots. Plants and workers can contribute to their spread.
- Appreciate the mild temperatures and the summer conditions of the shelters.
Protection
- Weed the crop and its surroundings.
- Produce the seedlings in an nursery insect-proof .
- Check the sanitary quality of the plants before and during their introduction into the crop 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 into closed shelters if available.
- Reason the chemical protection, in particular 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.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10