A new strain of Myzus persicae aphid, genotype R, which is less susceptible to chemicals has been identified in sweet pepper crops in Belgium, the Netherlands and Germany.
“IPM control strategies for this problem pest of sweet peppers tend to centre on a multi-pronged biological approach, with the occasional use of chemical controls to knock back populations,” explains Biobest IPM and Pollination Specialist, Arno Hellemons. “To combat the genotype R strain, growers need to follow a robust preventative and curative biological approach.”
Well adapted to develop resistance
“With the ability to reproduce rapidly, particularly at higher temperatures, aphids are well adapted to build up resistance to chemicals,” explains Arno. “Systemic aphicides are often applied via drip irrigation. If the chemical isn’t taken up by the plant in sufficient quantities, aphids can develop resistance to the active ingredient. Meanwhile, weeds growing inside the greenhouse act as secondary hosts, enabling the pest population to quickly build up.”
“As genotype R is less susceptible to conventional chemicals, there are reports of young pepper plants arriving on nurseries already infested with this new strain,” he warns. “The resulting pest colonies have been observed to be smaller, but to produce winged individuals more quickly; the upshot is that genotype R can spread faster through the crop.”
Natural enemies maintain effectiveness
On a positive note, Arno says; “Of course, Myzus persicae genotype R is not resistant to natural enemies – parasitoid (mixes), lacewing, hoverfly and ladybird controls.”
As with all biocontrol programmes, routine crop monitoring and scouting are essential to keep track of the aphid species present, as well as their population size.
Preventative parasitoids
“In geographical areas where the small green Myzus persicae genotype R is prevalent, we recommend growers start with a preventative approach - introducing the standard aphid parasitoids Aphidius-System and Aphidoletes-System,” says Arno. “If larger aphid species are found to be present, these can be effectively targeted with Ervi-System.”
Curative hoverflies and brown lacewing
“Once several aphid hotspots have been scouted, growers should switch to a curative programme; our complementary hoverfly controls, Eupeodes-System and Sphaerophoria-System, in combination with our robust brown lacewing, Micromus-System,” he explains. “This switch should ideally happen long before sticky honeydew or sooty mould are found in the crop.”
“While to-date Myzus persicae genotype R has been identified in several sweet pepper crops in northern Europe, it is likely to spread to other countries. As such, pepper growers should remain vigilant.”