Scale insects are stinging, sucking insects belonging to the order Hemiptera and the Coccoidea superfamily. The tomato is especially affected by a few mealybugs belonging to the Pseudococcidae family. Mealybugs of this family lack a horny shield (a kind of shell), and the body is usually covered with a white mealy secretion. They also have lateral waxy filaments clearly visible at the periphery of the body, and a cottony secretion containing the eggs can sometimes be noticed at the end of the abdomen. We will be particularly interested here in Pseudococcus viburni (Signoret) (syn. Pseudococcus affinis [Maskell]) which was introduced in the Netherlands at the beginning of 1990, and began to be observed in France from 1997. This mealybug is found now in a significant number of shelters spread over several French production regions.
 

Plant growth is reduced because of the numerous punctures and food sucks exerted by the larvae and the females present, especially on the stem. Honeydew and Fumagine cover the surface of the aerial organs of the tomato (Figures 1 to 3). Sooty mold, by reducing photosynthesis and respiration, causes yellowing and leaf damage. It also spots the fruits or alters their coloring, making them unmarketable (Figure 3).
 

P. viburni presents several stages of development: egg, 3 larval stages, and adult (figure 4).

- Forms of conservation and / or alternative hosts : P. viburni tolerates cold fairly well and spends the winter as a non-diapausing nymph in the soil. It can be maintained on other alternative hosts, in particular on potatoes, apple trees, lemon trees, grapevines.

- Developmental stages: the eggs (figure 4-1) are laid inside a white waxy ovisac. After hatching, the first instar larvae (Figure 4-2) disperse on infested plants. After the second larval stage (figure 4-3), this insect will form two successive false nymphs in which the males will undergo a metamorphosis. These have the appearance of small winged midges, whose life is ephemeral. Females (Figure 4-4) (Figures 5 and 6), measuring 4 mm in length, do not undergo metamorphosis and therefore do not change shape. The pinkish color of their body is masked by white mealy wax.

- Dispersion in the culture : this cochineal is mainly disseminated by the plant material. The workers during cultivation operations, the animals contribute to its dispersion.

- Favorable development conditions : P. viburni seems to have found in France, in greenhouses, conditions entirely favorable to its development.
 

Last change : 07/08/21