To get aphid control programs off to the best start in bedding crops, Paul Koole – technical team coordinator for Biobest North America - urges growers to take a preventative approach and start releasing Aphidius-System and Ervi-System now. “There is very little tolerance for aphids in bedding crops,” he says. “Customers know if there is one aphid on their plants, there are soon likely to be hundreds.
“Ornamental growers should assume they are going to get aphid issues soon, particularly if they have overwintered plants in the corner of the greenhouse or there are weeds. It doesn’t pay to wait,” he warns.
“To optimize control, nurseries need to adopt a preventative approach and aim to release Aphidius colemani and Aphidius ervi weekly. The first aphid species to appear is usually the Foxglove Aphid (Aulacorthum solani); later on it is often, although not exclusively, the Green Peach Aphid (Myzus persicae). These two parasitoids control both these aphid species.
“Nurseries that keep scouting records over several seasons will know when they typically experience a sudden increase in aphids,” says Paul. “This data is extremely useful to forecast when to increase the parasitoid rates to optimise control. It’s good practice to increase the rates of Aphidius-System and Ervi-System approximately two weeks ahead of this rapid rise.”
Ornamental growers around the world are increasingly turning to biological options in a bid to improve sustainability, by minimizing the impact on the environment, and to maintain the efficacy of remaining chemical active ingredients.
“At the end of the day, plants never benefit from being sprayed with chemicals as it stunts growth,” explains Paul. “However, if the aphid population gets out of control, growers often resort to spraying pest hotspots. Before selecting which chemical to use, speak to your Biobest adviser to check product compatibility with biological control programs at work in the crop.”
In situations where the grower is unsure exactly which aphid species are in the crop, Biobest has Aphidius-Mix-System, containing both A. colemani and A. ervi in a single product. For situations where aphid species other than Foxglove Aphid and the Green Peach Aphid have been scouted, there is Aphi-Mix-System. This also contains Aphelinus abdominalis and Aphidius matricariae – a mix of four parasitoids that control all common aphid species.