Evaluating the effectiveness of mustard species and their concentrated extracts in reducing losses to wireworms in the Pacific Northwest, USA.

View the project final report

Commodities

• Agronomic: barley, canola, mustard, wheat

Practices

• Crop Production: cover crops, crop rotation

In recent years, cereal production in the Pacific Northwest and Intermountain regions of the USA has been threatened by the re-emergence of a devastating pest, known as wireworm. Neonicotinoid seed treatments, and until recently the only group of insecticides registered in cereals against wireworms, have failed to deliver acceptable levels of protection. There is currently an urgent need to develop alternative control methods to be used as components of an integrated pest management protocol against this pest. Cruciferous plants are known for their biocidal effects on a wide range of pest conditions (e.g. weeds, insects, pathogens) due to their glucosinolate contents. Here, in a series of greenhouse assays and field trials, we examined the effects of different mustard species as rotation/cover crops (soil incorporated), as well as their defatted seed meals in reducing wireworm populations, thus damage. For the first time, we also tested the efficacy of a newly developed concentrated seed meal extract (brown mustard) against wireworms. Further, we examined the potential impact of our treatments on the beneficial entomopathogenic nematodes, which are locally present as natural enemies of wireworms. This experiment was performed in one irrigated (yield data only) and one dryland (yield, wireworm, and entomopathogen estimates) field. In the greenhouse, the concentrated seed meal extracts of brown mustard caused significant mortality levels in wireworms (all application rates). In the field, the application of mustard treatment (brown or yellow mustard) did not result in a significant improvement in yield. In the irrigated field, however, plots treated with the concentrated extract of brown mustard tended to have higher yield. In our dryland plots, the brown mustard concentrated extract had a significantly negative impact on entomopathogenic nematode numbers.

The overall goal of this project is to explore an alternative integrated management tactic to control wireworms in cereal crops. We will achieve this goal through two complementary objectives. Our third objective is designed for effective delivery of findings to our regional stakeholders.

Objective 1: Evaluate the effect of mustard species including yellow (Sinapis alba) and brown (Brassica. juncea) mustard against wireworm, our sub-objectives are set as below:

1a. Investigate the effectiveness of cover crop (soil incorporated as green manure), defatted seed meals and concentrated extracts of yellow (S. alba) and brown (B. Juncea) mustard species to reduce wireworm damage in wheat under greenhouse conditions.

1b. Evaluate and compare the effectiveness of brown (B. juncea) and yellow (S. alba) mustard rotations, and mustard species products) in reducing wireworm damage to wheat.

Objective 2: Compare entomopathogenic nematode presence and infectivity following yellow and brown mustard treatments, and in relation to non-treated controls.

Objective 3: Disseminate findings to stakeholders and growers and promote adoption of successful IPM tactics against wireworms.

This project not only examines the effectiveness of alternative approaches to reduce wireworm pressure but also aims to increase growers’ knowledge of an alternative to paraphyletic application of synthetic insecticides to promote sustainability of our management practices.

Studies on the efficacy of mustard and mustard products have yielded conflicting results. The species of mustard and targeted wireworm, environmental conditions and timing of application have been proposed as potential variables that can explain the inconsistency in outcomes. In this proposal, focusing on a single wireworm species,  sugar beet wireworm, we will evaluate the efficacy of both yellow and brown mustard species, their seed meals, as well as the newly developed concentrated extracts for each of the two species (containing higher concentrations of glucosinolates), while taking into consideration, any potential side-effects on beneficial entomopathogenic nematodes.