Mealybug parasitoids

populations Mealybug in the vineyard are generally well controlled by their natural enemies. Present in colonies on the twigs, mealybugs are easily accessible for the laying of female parasitoids. However, the presence of ants (which feed on the honeydew produced by the cochineals), if they constitute large populations, can be a gene for the auxiliaries.

The primary parasitoids of mealybugs are mainly related to two families of Chalcidian Hymenoptera (with always very reduced wing venation) (Figure 1), Encyrtidae and Aphelinidae, and the genera concerned are specialized on a particular family of cochineal.

• Encyrtidae

The Encyrtidae constitute one of the most important families of the Chalcidians, and the second in terms of success in terms of biological control, here mainly directed against mealybugs.

They are small Hymenoptera (1-2 mm on average, figure 2), with a compact body, not showing any apparent constriction between the thorax and the abdomen (which normally characterizes the apocritic Hymenoptera ). Many encyrtids have a more or less pronounced metallic luster (as is the case with Blastothrix ) or on the contrary are devoid of it, their body is then partly yellow, brown or even black (case of Metaphycus and Anagyrus for example).

The antennae almost always have 11 segments in the female. On the other hand, the tibia of the middle leg is provided with a very developed apical spur, in relation to their aptitude for jumping, allowing them to make very large leaps. Males of encrtides are often very different, and for this reason, difficult to associate with females.

The egg is usually inserted into the host. Encirtid larvae being internal parasites, the species have adapted, on the one hand to avoid the immune reactions of their hosts (encystment attempts), on the other hand to be able to breathe inside a medium. liquid. Pupation usually takes place in the host. It is the mature larva or nymph in the host that overwinters.

• Aphelinidae

They are also very small insects (0.5-1 mm) with an equally compact body, for the same reasons as in the encyrtidae. They never show a metallic sheen, their body being either entirely yellow, or entirely dark brown, or even with a mixture of the two colors (figure 3). The antennae are 3 to 8 articles, the marginal vein of the forewing is long, but the stigma is very short. The ovipositor is not very visible.

Aphelinids are mainly parasitoids of sap-sucking biting hemiptera living in colonies, such as aphids, whiteflies and mealybugs. The larvae which give rise to females are endoparasites, on the other hand those which give rise to males can be ectoparasites. Adults feed on the excretions of their hosts or their hemolymph through voluntary injury by means of their ovipositor (a behavior called host-feeding). The adult emerges from the host by cutting an opening in the integument of the mummified host (Figure 4). It is the mature larva or pupa that overwinters.

Aphelinids constitute a family of medium importance in terms of biodiversity but the first in biological control for the success of programs, almost always directed against sucking stinging hemiptera (whiteflies, aphids and mealybugs ).

• The most frequently observed species
  

Heliococcus bohemicus generally and more the Pseudococcidae : the procession of parasitoids is quite well known and belongs to the family of the Encyrtidae. Ericydnus sipylus (Walker, 1837) (Figure 2), Anagyrus szodensis Erdös 1957, and Leptomastidea bifasciata (Mayr, 1876) are the auxiliaries that provide most of the regulation of this species.

The Coccidae or lecanins are parasitized by two families of Chalcidoidea hymenoptera: Encyrtidae (genera Metaphycus and Blastothrix ) and Aphelinidae (genus Coccophagus , figures 3 and 4).

Recognition of species is a matter for specialists, but genera, provided one is interested in a specific host, can be determined by neophytes with existing documentation.

Bibliography

G. Delvare, C. Villemant (2011) Simplified key for identifying families of hymenoptera containing auxiliaries present in the vineyard. In: Auxiliary fauna of the vineyards of France, Eds France Agricole-Dunod

G. Sentenac (2013) Biological control of grapevine mealybugs. Ecophytopic-Viticulture

G. Sentenac, P. Kuntzmann, L. Perez, A. Gili, P. Kreiter (2011) Biological control of Heliococcus bohemicus Sulc. (Hemiptera: Pseudococcidae) with the natural enemy Ericydnus sipylus (Walker) (Hymenoptera: Encyrtidae). IOBC/WPRS Bulletin 67: 31-40

R. Sforza et al (2003) Inventory and evaluation of mealybug antagonists on grapevine: prospects for biological control. Phytoma, 558, 42-46

Universal Chalcidoidea Database - Notes on families. Site web du Natural History Museum