Several species of aphids * ( aphids ) can form colonies on young tomato leaflets (figures 1 to 3), this from the nursery: Macrosiphum euphorbiae (Thomas 1878) (figure 5), Myzus persicae (Sulzer 1776) (figure 6 ), Aphis gossypii ( Glover 1877) (figure 7), Aulacorthum solani (Kaltenbach 1843) (figure 8). These polyphagous insects belong to the order Hemiptera, the suborder Sternorrhyncha and the superfamily Aphidoidea. They develop quite frequently on the tomato as colonies, but they do not have the same development dynamics as whiteflies. On tomatoes, they are especially formidable by their ability to transmit several Viroses . In addition, the chemical control of populations of these pests is often problematic because of their possible resistance to several insecticides.

* Other species signalees on tomate en France: Aphis craccivora Koch; A. beans Walker; A. frangulae Kaltenbacb; A. cress Kaltenbacb; Aulacorthum circumflex (Buckton); Myzns ascanicus Doncaster; M. sure (Walker); Marcus host Laing; Rhopalosipmonimus latysiphon (Davidson); Smynthurodes tying Westwood ...
 

Nutritional punctures are the cause of chlorotic punctures and can distort young leaflets (Figures 4 and 5). A reduction in the growth of young shoots, or even plants, can be observed. Besides aphid colonies, often observed the white driven and the presence of honeydew on the surface of above tomato, on which develops Sooty mold (sooty mold). It should be remembered that the latter can have several consequences, in particular a reduction in photosynthesis and leaf respiration and the soiling of fruits thus rendered unmarketable.

These insects have a rather complicated life cycle, with the possibility for adults of some species to change host in winter. We find eggs, founders of populations, adults, among them, winged viviparous females or not, 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.

- Forms of conservation and / or alternative hosts : it is often the eggs, laid in particular on many weeds at the approach of winter, which allow these insects to spend the winter. They can, of course, survive under heated shelters on existing crops, in the form of viviparous females in particular.

- Developmental stages : the 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.

Young larvae form, which immediately feed on the sap and molt 4 times before giving birth to the adult. White moults (exuviae) on vegetation indicate the presence of aphids in the crop. The adults are winged (1) or not; in the latter case, we speak of “wingless” individuals (2) (figure 11). 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 leaf blade, feed through their rostrum. The excess sugar contained in the sap is rejected in the form of honeydew.

- Dispersion in the crop : a few plants scattered throughout the crop on which aphid colonies quickly gain importance constitute the first outbreaks. First wingless, aphids start by visiting 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.

- Favorable development conditions : these insects appreciate mild temperatures and summer conditions in shelters.
 

 

Last change : 04/13/21