Project Code: PRR07-030
Christine Noronha - Agriculture and Agri-Food Canada
To evaluate the impact of rotational crops used in potato production on larval populations of wireworms and on the behaviour of adult click beetles within agricultural fields
Summary of Results
Wireworms, the larvae of click beetles, have become a serious threat to many agricultural crops worldwide. Because of their subterranean feeding habits, wireworms can cause catastrophic crop losses due to stand and yield reduction, and due to cosmetic injuries. Typically, the problem is most severe in fields that have had a recent history of pasture or cereal crops; when these crops are removed, wireworms remaining in the field then feed on many higher value crops planted in rotation. Due to their long life cycles (2-6 years depending on the species), damage by wireworms can continue for several years.
Cultural practices, such as crop rotation or leaving a field fallow, can be used as a strategy to reduce pest populations. The crops used in a rotation play an important role in the management of wireworms, mainly because some crops, such as small grains and clover which are common rotation crops, are good hosts for wireworms. There are, however, certain crops such as mustard that are inadequate hosts for wireworms. In Canada, wireworm populations are increasing due to the regulatory phase out of certain older pesticides which previously kept the pest in check. In order to manage populations in a sustainable and environmentally-safe manner, it is important to develop and utilize alternative management strategies.
The study was conducted at two 20-acre fields in Canoe Cove and Hazelbrook in Prince Edward Island during 2007-2009. Both fields had potatoes planted in 2006. For the following two years (2007 and 2008), each field was divided into four sections and each section was planted with one of the following crops: alfalfa (Medicago sativa), buckwheat (Fagopyrum esculentum), brown mustard (Brassica juncea), or the common standard rotation of barley (Hordeum vulgare) under-seeded to clover (Trifolium pratense). In 2009, all crops were ploughed and the entire fields were planted with potatoes, with an insecticide applied in-furrow at planting. At the end of the season, potato tubers were harvested and evaluated for wireworm damage.
The study concluded that brown mustard and buckwheat grown in rotation for two consecutive years reduced wireworm damage to potato daughter tubers during the third year and increased the percentage of marketable tubers for the processing market, without reducing total yield. Although not statistically significant, the reduction in damage was greater following brown mustard compared to buckwheat.
Planting brown mustard or buckwheat for two years in wireworm-infested fields, followed by potatoes planted with an in-furrow insecticide in year three, could help reduce damage to the daughter tubers.
The results of this study highlight the importance of integrating alternative solutions to pesticides, such as crop rotation, in the management of wireworms. In this context, the use of crop rotation, along with other alternative strategies as they become available, can help reduce the reliance on insecticide products for growing potatoes, thus leading to a reduced risk approach for the control of wireworms.
Information from this study and other projects related to wireworm management are included in a factsheet by the AAFC’s Pest Management Centre entitled Reduced - risk Wireworm Management in Potato.