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Aphids in general

Melon and cotton aphid (Aphis gossypii)


Aphis gossypii

Melon and cotton aphid beneath a leaf from cucumber. The population will grow quickly (Aphis gossypii)
Photo: Magnus Gammelgaard


Aphis gossypii

Mark the different colours
Those aphids are nymphs from the same mother (Aphis gossypii)
Photo: Magnus Gammelgaard


Aphis gossypii

Curling shoots and sticky shining covering of the leaves, are the normal resulting, symptoms of aphids attack.
Here on the houseplant Kallonchoe. (Aphis gossypii)

Photo: Magnus Gammelgaard


Symptoms:

Just like a lot of other aphids, the melon and cotton aphid, also attack where the concentrations of amino acids are highest and that is at the end of newly developed shoots.
The result of the sucking is curling and deformed leaves. If the leaves are very thin, they are rolling tight and the aphids are well protected against different kinds of changes in the environmental conditions. Also the aphids are able to transmit different kind of plant virus.

The melon and cotton aphid are in Danish called "Black aphids", but the colouring can be very variable from black to bluish, greenish and yellow. Often you can see a great variation in colouring, in individuals in the same population.
Individuals in the adult stages are 1- 2 mm long and has normally darker colour than the young ones.
It is not always certain that black aphids in greenhouses are belonging to the species Aphids gossypii. It is often necessary to have expert knowledge, to make the right diagnosis.

Aphis gossypii
Colony of melon and cotton aphid. (Aphis gossypii).
Photo: Magnus Gammelgaard


Biology:

The melon and cotton aphid are not native in Denmark, but are imported from the south. They are not able to owe winter in Denmark.
In Denmark the aphids are giving birth to young ones without any pre going mating ("virgin-birth"). When the population has reached a large number, nymphs witch will develop wings are born and as adults they are able to disperse to other plants, for establishing new colonies. Optimum tempeture for this aphid is from 21-27 degrees centigrade. It is not only cucumbers with are to bee attacked from this aphid. In greenhouses you often will se it on sweet pepper and tomatoes. Also it is very common on many ornamentals and often will see it in many of our ordinary pot plants.

From abroad it is known as The melon and cotton aphid ……………………………….

Take a look at the. 
"Insectkingdom" to locate melon and cotton aphid.




On this close up you can se that the aphids are coated with a wax layer, which make them "waterproof". (Aphis gossypii).
Photo: Magnus Gammelgaard


Control:

The melon and cotton aphid has in general attracted a lot of extension from Danish growers, because this species is characterised to be resistant, to a lot of the normally used insecticides.
Especially the active ingredient pirimicarb, which is normally used for aphid control, will not work at the Aphids gossypii.
Therefore the use of natural and biological control on this species, is very widespread.
Different species of parasitoids, lacewings, ladybirds, syrphids, bugs, gall midges and a some insect pathogenic fungi can be used for controlling this aphid.
One relatively new insecticide (imidacloprid) however is very effective for controlling this specimen.

You can read more about aphids control i general at the: bladluseng.htm


Opdateret d. 14.1.2012
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