Finland is experiencing a longer and warmer summer than normal which is threatening their potato crops. The warmer temperatures have led to increases in the prevalence of the Colorado potato beetle which has been attempting to establish in Finland for the past decade. The Colorado potato beetle itself is a highly effective reproducer and necessitates a wide range of control methods to prevent its spread.
The Colorado potato beetle (Leptinotarsa decemlineata) is an important and potentially devastating crop pest. The Plantwise distribution map shows that it is present in North America and Central Europe but has not yet been able to establish a population in Scandinavia. This is due to the vigilance of national authorities in early detection and control measures being enforced.
Despite the control measures in place the Finnish Food Safety Authority (EVIRA) have recently detected a record number of beetles in the country’s potato fields. EVIRA believe that the unusually long and warm summer has worked in favour of the beetles.
The beetles emerge from the soil and begin to eat the potato plant leaves before laying their eggs. The summer weather conditions are important in their development, with the hot weather accelerating their growth. This means that they will lay their eggs earlier and that these new offspring will develop quicker than normal. The increased offspring development may lead to multiple generations of the beetle emerging in the same season with the potential to significantly reduce crop yields.
The Colorado potato beetle is a highly effective reproducer and one beetle can produce hundreds of offspring in a single season. These beetles were recently sighted in September when the potatoes were being harvested. During the day they are found at the top parts of the potato plants before they burrow back into the ground overnight. They are found on small household allotments as well as large farms and the presence of round holes in the ground are a sign that the beetles have pupated.
If the beetles are not controlled or destroyed then devastating crop losses can occur after only a few summers. The most efficient way to control them is to collect them by hand, however there are a range of alternative options. The Plantwise datasheet on the Colorado potato beetle has a large amount of information on methods to control them. A simple control is crop rotation which delays the colonisation of the farmer’s potato crops by the beetle. If the beetle reaches the potato crop later then they will be unable to produce more offspring until later in the potato season. Biological controls, using Edovum puttleri (an exotic egg parasitoid), have had limited success in eastern USA and have been largely discontinued due to the high cost.
More information on Finland’s response to the Colorado potato beetle can be found on the EVIRA website.