Wireworms are subterranean and seriously pestilent larvae of agricultural crops. In the absence of pest control products, organic crops are particularly vulnerable. Economic losses due to wireworm on organic farms are significant. For perspective, crop loss in conventionally-grown potato (where pest control products are used) in Prince Edward Island is estimated at $6M/year. Small-scale vegetable producers in BC report large crop losses or the inability to grow marketable produce. Control products and agricultural practices will be developed to address wireworm management in small-scale organic vegetable crops, to enable management of this pest and growth of the organic sector.
The nascent development of new control products offers hope for organic growers: i) biological and bioproduct controls, and innovation in specific application patterns have been used with success in Europe and experimentally in Canada; and ii) new formulations and uses of semiochemicals are promising for mating disruption and mass trapping of adult click beetles. Drawing on existing- and newly-developed technology, the aim is to fully develop these products and recommendations for their use, so that organic farmers can have access to a pest control product tools to combat wireworm infestations.
Drawing on decades of wireworm research experience and historical literature, it is understood that cropping and other farming practices affect wireworm populations through their action on several life stages: larvae (neonate and subsequent instars), pupae, eggs, and adults. Organic farmers are particularly adaptive to new cultivation techniques, and from findings arising from this research, there is opportunity to offer growers new cultivation practices to manage wireworms directly while conserving their natural enemies.
A multifaceted approach will address wireworm infestations, developing a range of products and practices targeting all stages of the wireworm life cycle. Biological control uses Metarhizium brunneum strain LRC112 and toxic frass of the black soldier fly to target wireworms and protect transplanted crops from their feeding. Both bio-based materials take advantage of an important wireworm trait: their attraction to carbon dioxide (CO2). Applied together with CO2-generating materials, wireworms will be lured to the control substances for improved targeting. Mass trapping takes advantage of pheromones for wireworm adults, or click beetles. Pheromones attract enormous numbers of male click beetles. Without males to mate with females, egg-laying and the input of new wireworm larvae ceases. In a similar way mating disruption takes advantage of pheromones in a granular form. Broadcast pheromone granules cause male beetles to become disoriented and unable to find female mates, with a similar outcome.
The development of cropping practices will complement the use of bioproducts. Trap crops are single rows of sacrificial crops, such as wheat, planted between the food crop to attract and concentrate wireworms, thereby protecting the food crop. Folk knowledge often refers to crop cultivation techniques such as timing of tillage to kill click beetle eggs and young larvae to reduce wireworm populations. Research aimed at testing these techniques will help answer why and how they work, laying the groundwork for their refinement into predictable and reliable pest control outcomes. The study of these practices will consider the effect on wireworm natural enemies such as beneficial ground beetles, adding conservation pest management to the range of management methods. Planting and harvest periods will be identified so that periods of intense wireworm feeding and crop damage are avoided.
While mechanically preventing wireworms from feeding on high value crops such as melons, tomatoes and cucurbits may seem obvious and simplistic, practical methods for farmers need identification and development. Plastic mulches and other mechanical methods of protecting crops will be identified along with recommendations for their use in a practical farm setting.
An emphasis on grower engagement, student and staff training, and knowledge transfer will serve to advance these sustainable pest management practices that are aimed at effective wireworm control while sustaining optimum environmental and human health.
Wireworms in Potato (Photo by Andrew Hammermeister)