Effects of sugarcane ripeners on corn crops

An important tool to help sugarcane producers accelerate the supply of raw materials at the beginning of the harvest, ripeners present adverse results when in contact with corn plants. Therefore, discretion and close attention to problems with drift are necessary when using this product in areas close to other crops.

The aerial application of phytosanitary products has been widely used in several crops that require treatment at an earlier stage of the cycle, where ground traffic by spraying machines is impossible. One of these crops is sugar cane, which requires spraying from ripeners in order to accelerate the maturation of cultivars to supply the flow of raw materials necessary for the start of the harvest. When applying these products aerially, the spraying must reach its target without causing drift, ensuring the safety of neighboring crops. However, due to the height of the sugarcane fields, in many cases spraying is carried out above the thermal inversion point, which increases the chances of drift occurring. The damage caused by drift depends on the concentration and quantity of the active ingredient in the respective adopted products that reach the crops. As you move away from the application range of phytosanitary products, the damage caused by drift decreases, as well as its concentration. Generally speaking, in cases of terrestrial application, the drift is around 3% to 5% of the applied product, with approximately half of the drift occurring being deposited in the first 15 meters, decreasing rapidly as the distance increases in relation to the product. to the application range. As for aerial application, information is non-existent in the scientific community.

With the objective of evaluating the effect of drift of sugarcane ripeners on corn crops when occurring in vegetative stages of development (V4 and V8), research was conducted at the Federal University of Goiás, Jataí Regional, with the aim of clarifying the agrarian community about the influence of sugarcane ripeners on corn cultivation. The ripeners tested were ethephon (475,2 g a.i./ha), glyphosate (216 g a.i./ha) and sulfometuron methyl (15 g a.i./ha), with proportions of 3%, 6%, 9%, 12%, 25%, 50% and 100% of the dose as a ripener for each situation. Applications of concentrations above 12% of the dose as a ripener were considered application errors, which is characterized as off-target application.

The drift of ethephon and glyphosate ripeners did not cause visual effects on corn plants at any of the doses tested up to the limit of 12% of the recommended dose as ripener. At 21 DAA (days after application) of ethephon, a reduction in size was observed in plants subjected to the application error (100% of the dose as ripener) at the V8 development stage (Figure 1). At 21 DAA of glyphosate, a reduction in the size and yellowing of the leaves was observed in plants subjected to application error (100% of the dose as a ripener) at the V4 development stage (Figure 2). Errors in the application of glyphosate at the V8 development stage of the corn crop presented greater damage to the crop compared to the application error at the V4 stage (Figure 3). Decreased productivity was evidenced for application errors above 25% of ethephon at the V8 development stage, application errors of 100% glyphosate at the V4 development stage and application errors of 25% and 50% glyphosate at the development stage V8. Furthermore, errors in applying 100% glyphosate at the V8 development stage resulted in the death of corn plants (Figure 4).

Visual symptoms of phytotoxicity were observed in corn plants from the drift of 3% sulfometuron methyl, with the drifts of 6%, 9% and 12% being more aggressive, at 21 DAA in the V4 development stage (Figure 5). Furthermore, plant death was evidenced by the error in applying 25% sulfometuron methyl at 42 DAA at the V4 development stage (Figure 6). At 21 DAA of sulfometuron methyl at the V8 development stage, pointer necrosis began to occur from 9% of drift, progressing to plant death at 42 DAA (Figures 7 and 8). Grain productivity was compromised by the drift of 3% of sulfometuron methyl, with an application error of more than 25% at the V4 development stage causing plant death (Figure 1). On the other hand, from the 9% drift in the V8 development stage, plant death has already occurred. Reduction in corn cob size was characterized by 3% sulfometuron methyl drift occurring at the V4 and V8 developmental stages. Uneven grain filling and ear deformation were observed for 9% and 12% sulfometuron methyl drift occurring at the V4 developmental stage (Figure 9).

In general, greater sensitivity of the corn crop to ripeners was observed when the crop was at a more advanced vegetative stage of development. In this context, the ripener sulfometuron methyl proved to be phytotoxic to corn crops even at low doses. And the ripeners ethephon and glyphosate presented themselves as good ripener options to be applied in sugarcane fields located close to corn growing areas, as long as there are no application errors.

When making decisions to apply ripening agents, the crops grown in adjacent areas as well as their stages of development must be taken into account, given the risk of drift of these products. Therefore, when the sugarcane crop is located close to corn planting areas, it is necessary to be careful about choosing a ripener that is less aggressive if there is a potential for drift to occur.  

Patrícia Aparecida de Carvalho Felisberto, Paulo César Timossi, Guilherme Felisberto and Andréia Rodrigues Ramos, Federal University of Goiás – UFG – Jataí Regional

Article published in issue 201 of Cultivar Grandes Culturas.