"If [a grower] has only spotted small aphids, like the green peach aphid (Myzus persicae) and the cotton aphid (Aphis gosypii), he can rely on two parasitic wasps as part of a curative strategy: Aphidius colemani, complemented with Aphidius matricariae. However small, these aphid species are notorious for their rapid distribution," said Wesley Akkermans, sustainable crop management specialist at Biobest.
For bigger species, such as the glasshouse potato aphid (Aulacorthum solani) and the potato aphid (Macrosiphum euphorbiae), Akkermans advises the use of Aphidius ervi and Aphelinus abdominalis as biocontrols.
"The parasitic wasps are always introduced as mummies. These need to be put on damp, shady spots
between the crops to guarantee the best result, preferably close to an aphid hot spot," he said.
If growers are unable to identify which aphid species are present, or if they wish to maintain a thorough preventive strategy, they can opt for a mixture of the four mentioned Aphidius species in the same package.
In addition, the parasitic gall midge Aphidoletes aphidimyza is a strong complementary weapon against aphids.
"Its progeny eats literally every aphid species," says Wesley. "Moreover, thanks to the large cucumber
leaves, the larvae have an excellent mobility. Only a few larvae per leaf is already enough to destroy a complete aphid population."
For maximum protection Biopest recommends combining the parasitic gall midge with the four Aphidius species.