Rhopalosiphum maidis

Scientific Name Rhopalosiphum maidis
Common Names English: Corn leaf aphid, German: Grüne Maisblattlaus, Spanish: Pulgón del maíz, French: Puceron vert du maïs
Description Adults are about 2 mm (0.078 inch) long and dark blueish-green to black in color; their siphunculi are short and thick.

Biology

Damage

An early infestation is often discovered when aphids are found on leaves that have not yet unfolded, or on the not yet emerged tassels. The growing colonies will spread mainly on the undersides of leaves, which start to show yellowish-brown spots after a while. If infestation is heavy, the leaves may wilt and curl, especially on young plants.

Without treatment, the aphids can then spread over all aerial parts of their host.

Colonies on the tassels may sometimes become so dense that the aphids and their excretions interfere with pollination.
The aphids produce large quantities of honeydew, which covers all plant parts beneath the feeding sites. This can attract ants and some other pests such as corn earworm moths; but most importantly, it provides a substrate for the growth of sooty mold. The aphid's capacity for direct damage is less significant than its role as a vector of many viruses of cereals and other crops, e.g. BYDV and cucumber mosaic virus.

Lifecycle

As R. maidis is primarily a species of warm areas, it mostly reproduces parthenogenetically. Accordingly, populations consist almost completely of winged and wingless females; males are rarely observed, and then only in cooler climates. The aphid appears to be anholocyclic and always viviparous, as overwintering eggs have not been described so far. Rhopalosiphum maidis is found worldwide, throughout the tropics and subtropics, where it is most common, but also in warmer temperate regions as well.

In areas where temperatures during the cold season are too low for R. maidis to overwinter, it may immigrate from the South in the spring and attack young plants. The aphid's development rate, lifespan and quantity of offspring are essentially determined by temperature and host plant quality. Under optimal conditions, more than 40 nymphs per female and up to 50 generations per year are possible.

Occurrence

Additional Crop Information

Mainly corn, but also sorghum, barley, rye, wheat, sugar cane and other graminaceous hosts; occasionally tobacco, hemp, potato, cucurbits, papaya and others.

Agricultural Importance

While low densities are not harmful in themselves, they are quite sufficient for spreading dangerous viruses.

Control

Integrated Crop Management

Like other aphids, R. maidis has a considerable reproductive potential. Its population density can increase rapidly, so careful monitoring is essential.

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