Crops
Aphids
Several species of aphids * ( aphids ) can form colonies on the young leaflets of Cucurbitaceae and melon (figures 1 to 3), this from the nursery: Myzus persicae (Sulzer 1776) (figure 9), Aphis gossypii ( Glover 1877) (figure 10), Macrosiphum euphorbiae (Thomas 1878) (figure 11), Aulacorthum solani (Kaltenbach 1843) (figure 12) ... These polyphagous insects belong to the order Hemiptera, to the suborder Sternorrhyncha and to the superfamily Aphidoids. They develop quite frequently on melon in the form of colonies. they are especially formidable by their capacity 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 reported on melon in France: Aphis craccivora Koch; A. fabae Scopoli; A. nasturtii Kaltenbach; Smynthurodes betae Westwood ... To help you in recognizing aphid species, consult the INRAE site Encyclop'Aphid .
- Nature of damage
Nutritional punctures are the cause of chlorotic punctures and can deform young leaves which are rolled up and more or less swollen (Figures 1 to 3). A reduction in the growth of young shoots and even plants can be observed (Figure 4). In addition to aphid colonies, white moults and the presence of honeydew are often observed on the surface of the aerial organs of the melon, on which grows sooty mold (figures 6 to 8). It should be remembered that the latter can have several consequences, in particular a reduction in photosynthesis and leaf respiration and the soiling of the fruits thus rendered unmarketable.
- Biology
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 13). 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.
- 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 13). 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.
- Protection methods
Several protection methods are recommended to control the development of aphids on melon in France:
- use varieties resistant to clonization by Aphis gossypii .
- check the sanitary quality of the plants before and during their introduction into the shelter;
- produce the plants in an shelter insect- proof ;
- install canvases insect-proof at shelter openings;
- weed the greenhouse and its surroundings;
- detect the first pests thanks to the yellow sticky panels placed above the crop as soon as the plants are introduced;
- use auxiliaries under shelter, for example make a port of Aphidius colemani via relay plants (finger millet or barley), or of Aphidius colemani by dispersing the bottles;
- check the sanitary quality of the plants before and during their introduction into the shelter;
- produce the plants in an shelter insect- proof ;
- install canvases insect-proof at shelter openings;
- weed the greenhouse and its surroundings;
- detect the first pests thanks to the yellow sticky panels placed above the crop as soon as the plants are introduced;
- use auxiliaries under shelter, for example make a port of Aphidius colemani via relay plants (finger millet or barley), or of Aphidius colemani by dispersing the bottles;
- consider chemical protection (r) ( e-phy ) *, in particular if you use auxiliaries, choose products with low toxicity on them .
(r): resistance to insecticides or acaricides is known in these pests.
* Chemical control : The number of pesticides available for a given use is constantly changing, we advise you to always confirm your choice by consulting the e-phy site of the Ministry of Agriculture and Fisheries which is a catalog in line of plant protection products and their uses, fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.
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