Two-spotted spider mite causes 20% losses in Brazilian cotton

If left unchecked, the two-spotted spider mite (Tetranychus urticae) can cause estimated losses of 20% in cotton crops, equivalent to more than 1,000 kg of fiber per hectare. 

This projection comes from researcher Jacob Crosariol Netto of IMA (Mato Grosso Cotton Institute). It considers just 10% of infested cotton plants in an area with a productive potential of 5,200 kilograms per hectare.

Crosariol Netto emphasized that the pest, considered secondary until about five years ago, has gained prominence in cotton management. "It was a pest that arrived at the end of the cycle, in dry conditions, or from mid to late season. It required some care, but producers could easily manage and coexist with it. Today, the two-spotted spider mite is present throughout the cotton cycle," he explained.

According to him, field studies in some regions of the Brazilian state of Mato Grosso indicate that excessive use of fungicides for foliar diseases and low-selectivity insecticides eliminates the two-spotted spider mite's natural enemies. "These molecules don't control the mite and accelerate its reproductive cycle. This causes their populations to multiply and resurge very quickly," the researcher emphasized.

Crosariol Netto recommends that this scenario requires specific care regarding acaricide applications and other protective measures. "In the past, we made two or three applications of these products. Today, we reach up to 12 applications per season, depending on the region of Mato Grosso state," he revealed.

Crosariol Netto was one of the professionals responsible for conducting trials related to the active ingredient fenpyroximate of acaricide from Sipcam Nichino Brasil, which was recently registered with regulatory agencies for two-spotted spider mite control. According to the IMA researcher's assessment, when integrated into crop management systems and rotated with other actives, the Italian-Japanese company's solution showed control efficacy above 80%.

"We must apply under control conditions when the spider mite population is at the ideal level, with 10% of plants infested," the researcher emphasized. "Existing solutions, like fenpyroximate, also require good application technology because the mite settles on the underside of the leaf to feed, and we need to reach the target with good droplet distribution," he pointed out.

Crosariol Netto also highlighted that effective management of the two-spotted spider mite required constant crop monitoring and the pursuit of alternative resources capable of deterring the pest. "By choosing cultivars with better health to avoid diseases and, consequently, decrease fungicide use, we reduce the imbalance regarding natural enemies of the two-spotted spider mite," he stated.

"The pest is growing. We depend heavily on the effectiveness of active ingredient rotation because the two-spotted spider mite's development cycle is rapid. If sequential applications of the same active ingredient are made in the crop, more resistant populations will be selected. However, with structured management, it's possible to coexist well with the pest," Netto said in conclusion.

(Editing by Leonardo Gottems, reporter for AgroPages)