Identifying And Controlling Wireworm Infestations

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The bad news is that you can’t eliminate wireworm once they’re in your field, but the good news is you can protect your crop with a seed treatment the following year.

Syngenta Crop Protection Canada

Wireworms can have a devastating effect on cereal crops, resulting in poor emergence, compromised stand establishment and significantly reduced yields. Traditionally wireworms have been a problem in brown soil regions of the Prairies, but damage is now also occurring in the dark brown and black soil zones.

The effects of wireworms are frequently mistaken for poor seed or poor germination. This is because damage begins in small patches which can be associated with wet or dry soil conditions, and because wireworms live underground where they aren’t seen.

Meanwhile, damaged plants start to wilt and die, resulting in thin stands. When plant stands are severely reduced, weed management will also become a concern due to lack of crop competition and second flushes of weeds. The long life cycle in the larvae stage and underground habit of wireworms make them difficult to control. If there is one wireworm in a field, there are likely more. As the larvae pupate and emerge as adults they lay more eggs and the populations continue to grow.

Meanwhile, larval feeding and activity are influenced by temperature and moisture conditions. Cool, wet conditions force the wireworms to the surface to feed on germinating seed, whereas hot dry weather forces them deeper into the soil. Due to the long cycle in the larvae stage, damage can continue for 5-7 years in the same field before the insect emerges as an adult.

Unfortunately, once the crop is in the ground, there’s nothing that can be done to stop wireworm damage. However, you can take steps now to prevent them from causing damage to future crops.

Prevention and management

Find out for sure if you’ve got wireworm. Before planting, use a bait trap to determine if your field is infested. Take either a mixture of oatmeal, honey and water, or freshly cut potatoes, or germinating wheat/ corn, and place in a nylon sack. Bury the traps 10-15 cm underneath the soil in areas where thin stands were observed the previous year, marking down exactly where your traps are buried. After 10-14 days, dig up the traps to see if wireworms are there. The results won’t reflect the severity of the problem but they will confirm the pest’s presence.

You can also scout for wireworms in the spring by looking at perennial weeds such as dandelions, as wireworms will feed off plants omitting carbon dioxide. When scouting, look for long, cylindrical, copper-brown, hardened bodies.

Throughout the growing season, if you see row damage or spotty unproductive areas, dig up your plants and look for bite marks and evidence of chewing in the main root section. Watch for symptoms such as partially eaten seeds, shredded stems just above the crown, yellow and wilted leaves, withering or dead main shoots, or any wilted or dead plants along a section of crop row.

Use the right seed treatment

The bad news is that you can’t eliminate wireworm once they’re in your field, but the good news is you can protect your crop with a seed treatment the following year. A dual-purpose seed treatment that includes both insecticide and fungicide, such as Cruiser Maxx Cereals, will provide the best protection. As with all crop protection products, it’s important to apply seed treatment at the correct rate; where there is a history of wireworm damage, a higher rate of application may be required. Producers with wireworms in their fields have reported a 5-7 per cent yield increase from the use of seed treatments as a control method. A seed treatment can also provide protection against seed and soil-borne diseases which can improve emergence, stand establishment and yield.

Adhere to best practices

Aside from seed treatment, there’s little that can be done to keep wireworm away from your crop. However, consider the big picture when it comes to getting your best yield and making the best long-term decisions for your farm. For example, no-till farming will make your field a friendly environment for wireworm, but the benefits of minimizing soil erosion, soil moisture conservation, and improved soil quality far outweigh trying to starve newly hatched wireworms by plowing fields. Similarly, crop rotation is not an effective control measure as wireworm can survive for up to one year without a suitable food crop, but it is nonetheless a valuable practice to reduce leaf diseases and incorporate herbicide rotations.

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