Drought and pesticides ban compound aphid infestation

This summer, aphids – those small, sap-sucking insects which infest potatoes and other key agricultural crops – have been appearing on Czech farms in alarming numbers. While drought is a factor, efforts to save the honeybee are also behind the infestations.

Aphid, photo: André Karwath, Wikimedia Commons, CC BY-SA 2.5

Due in large part to the mild, dry weather this May and June, which followed upon a wet winter, the tiny but ravenous aphids have been breeding earlier than usual. As such, they have been dining on crops when still in the seedling stage –and less able than mature plants to survive an onslaught.

Particularly invasive has been the “peach-potato” species of aphid, which despite the name, attacks most varieties of fruits and vegetables. Under the right conditions, up to 30 generations of aphids can spawn in a year, according to Jan Sitek of the Central Institute for Supervising and Testing in Agriculture.

"With aphids, everything happens quickly. They multiply quite rapidly. A week of good weather is enough to see an infestation – aphids definitely thrive in dry weather, so the number of outbreaks increases with a lack of rain. These insects eat leaves, of course, and also damage plants’ ability to take in water. But apart from that, aphids are quite harmful in that they transmit viral diseases, which is particularly bad for potato seedlings."

Aphids, photo: Thomas Bresson, Wikimedia Commons, CC BY 3.0

Climate specialists say the Czech Republic is drier than it has been in at least 80 years, with droughts ever more frequent. In April the government approved two billion crowns in compensation to farmers who suffered losses due to a particularly long drought in 2017, while the Ministry of Agriculture has earmarked over 140 million crowns for building new irrigation systems to try to maximise the use of what rainwater there is.

In the Czech Republic, where this summer the potato aphid is proving as ubiquitous as the staple itself is at traditional meals, many farmers are no doubt praying for rain.

The weather aside, the growing number of aphids also may stem from recent measures introduced across Europe to protect the health of honeybees and other vital pollinators. To that end, a two-year EU-wide ban on using certain pesticides on flowering crops, such as oilseed rape, was introduced in December 2013.

But while good for the honeybee, that ban on neonicotinoids – extended this year to cover all outdoor crops – has made it easier for agricultural pests to breed. Compounding the problem here, the Czech Republic is a major producer of both oilseed rape and sunflowers, both ideal breeding grounds for aphids.