Aphid damage on Chenopodiaceae

Chenopodiaceae of large-scale crops 

The aphids are highly prominent pests of sugar beet which they can affect by transmitting two viral diseases: severe yellow and mild yellow. The severe beet yellows virus (BYV) is transmitted mainly by two species, the green peach aphid (Myzus persicae) and the black bean aphid (Aphis fabae), by the semi-persistent mode. The beet mild yellowing virus (BMYV) is principally transmitted by Myzus persicae through the persistent mode. These viruses can be hosted by more than 100 plant species in which they can spend the winter when there are no beet crops. The aphids become viruliferous after ingesting viral particles on infected plants. Just one piercing action by the feeding aphid coming from a contaminated plant is enough for the disease to be transmitted. The symptoms are shown by general fading of the leaf veins, then by a lemon yellow colouring over the whole of the blade. The older leaves become orangey yellow. The disease spreads more or less rapidly over the whole plot starting from the first infection foci. In the field, the two yellow viruses are often associated. The resulting yield losses can reach 15-20 t/ha.

 Since 1992, seed treatment with a systemic insecticide has been bringing protection for the beet for 70-80 days and makes it hardly worthwhile applying any supplementary foliar treatment. These yellow viruses appear to be mastered even though localized foci do appear regularly at a local scale. 

Chenopodiaceae of market-garden crops

On spinach, the cucumber mosaic virus (CMV) is a deforming disease expressed as chlorosis, with broad chlorotic patches on leaves, leading to withering of the whole plant. It is transmitted by the non-persistent mode by numerous species of aphids including Aphis fabae and Myzus persicae. The aphids do not cause extensive direct damage except when the plant is very young. The presence of a colony can occasionally prevent full release of the product onto the market.

On beetroot, the same diseases are found as on large-scale crops: the severe beet yellow virus (BYV) and the beet mild yellowing virus (BMYV) are transmitted in equal measure by the aphids Myzus persicae and Aphis fabae. Myzus persicae are present mainly on leaves of the heart of the plant, but do not cause direct damage. Aphis fabae,in dense colonies on the underside of leaves, lead to crinkling and extensive fading of the leaves.