Stimulating corn vitality to alleviate the effects of wireworm attacks

Wireworm attacks in corn (or maize) crops at the start of the cycle can cause significant damage. There is no curative method to control these pests. The possible levers for action include protecting the seed and appropriate soil preparation. Stimulating the vitality of young corn is a way of alleviating the damage caused by these pests, as explained below.

Wireworm attacks, a major risk for corn

Wireworms are the larval stage of click beetles, with only the larvae causing damage to crops. Corn (maize) is very vulnerable to wireworm damage from sowing until the 10 to 12-leaves stage. Before 6 and 8 leaves, seedlings attacked by the pests dry up and then die. After the 8-leaves stage, the plant is much less vulnerable but attacks can induce the reduction of ears.
Wireworm invasions generally occur in the fall (or autumn). The larvae attack the seeds, roots and young corn plants, with a risk of total destruction of the plant in the event of early, large-scale infestation.

These phenomena have an impact on crop yields:

• reductions in yields of 5 to 10 q/ha for corn grain and 0.5 to 1.5 t dry matter/ha for silage corn,
• 5 to 30% of corn crop surface areas are affected by the pest in Brittany, compared to a national average of 15%, with a risk of total destruction of the plant in the event of early, large-scale infestation.

What risk factors encourage wireworm attacks in young corn crops?

There is currently no curative method to effectively control wireworm. The only option is prevention. But, first and foremost, it is important to identify the risk factors for these pest attacks:

• Crops planted following grass, a fodder crop or set-aside without any soil tillage for at least two years are at major risk. Mild winters are also conducive to the survival of the pest.
• Excessively early sowing. The parasite will become established more slowly but more insidiously in the event of excessively early sowing. Dry, well-ventilated soil encourages wireworm movement, and hence activity.
• Slow establishment and growth of the plants at the start of the cycle. The more slowly the corn (maize) becomes established and grows at the start of the cycle, the greater the damage caused by wireworms. Conversely, favourable emergence of the corn crop followed by rapid growth protects it from attacks.

Consequently, supplying balanced nutrition to the young corn is a way of speeding up growth at the start of the cycle. In addition, developing the natural defence systems of the young plants helps boost their vitality. This will help them better withstand any wireworm attacks.

How to improve the vitality of young corn crops and prepare them to cope with wireworm attacks

Improving the vitality of young corn (maize) primarily involves optimising mineral nutrition and good development of natural defence systems. A few major avenues should be considered in this respect.

A balanced supply of zinc, manganese and sulphur. These minerals improve the plant’s reactivity to environmental stressors. Manganese regulates cell function. It is also essential for the synthesis of chlorophyll and therefore stimulates photosynthesis. Sulphur supplies elements required to form proteins. And the importance of zinc, which regulates growth, contributes to the synthesis of tryptophan and affects the synthesis of auxins, hormones that sustain maize growth, must not be overlooked. Phosphorus contributes to the formation of the ears at early stages and has a direct impact on yields. It is the least mobile element in the soil and is generally available in insufficient quantities when the crop’s requirements are at their peak.

Stimulating and developing the plant’s natural defence systems: thickening of the cell walls triggered by natural defence mechanisms creates a physical and mechanical barrier, which may contribute to the plant’s resistance against environmental attacks. Phytoalexins are either nzymes that directly attack the pathogen walls or enzymes controlling the synthesis of organic antimicrobial substances. Therefore they can help activate the plant’s natural defence mechanisms.

Be prepared to change your habits. We suggest a range of possible strategies: choose a later variety, boost the vitality of young corn plants and protect your seed against pests. Our experts are on hand to help you consider all the options. Don’t hesitate to contact them!