Bayer: Complementary integrative measures must be adopted to control leafhopper in corn production

According to Embrapa, the proliferation of the leafhopper (Dalbulus maidis), the insect vector and disseminator of corn stunting complex, could reduce grain production by up to 70%, bringing losses to rural producers. Being aware of the problem, specialists and entities in the sector aim to make farmers conscious of the need to adopt preventive measures in an integrated manner, with a view to controlling the pest. One of the essential actions is the elimination of voluntary corn plants (Tiguera or guaxo), in order to combat stunting.

The indicators of issues affecting crop are visible: dead plants, bending with the wind and empty or malformed grains, due to the stunting complex. Tiguera corn is usually the only type of unaffected corn in agricultural areas after the harvest of corn lost during the harvesting process, as well as parts of cobs with corn grains that are born naturally, randomly, in agricultural areas.

"It serves as a green bridge between one crop and another, sheltering both the insect and the causative agents of the diseases: red stunting, yellow stunting (pale) and the fine stripe virus (stripe virus). That is why it needs to be eliminated,″ stressed Bayer corn specialist Paulo Garollo. "By feeding on a plant contaminated with one of the diseases, the leafhopper can become infected and transmit the three agents together,″ he said.

According to Garollo, the biggest problem is that this pest is resistant. Studies by Embrapa showed that in plants, such as millet, the spittlebug survives for up to five weeks without feeding, enough time to wait for tiguera corn to appear and make the green bridge for the next harvest. "That is why it is important to control the corn as soon as it appears using graminicide herbicides," he stressed.

According to the Bayer specialist, it is possible to prevent the appearance of the pest by adopting integrated measures, which need to start long before the eradication of tiguera corn. "The producer must use seed treatment, chemical and biological defensive applications strategically, as well as corn hybrids that are more tolerant to the stunting complex, and adjust the planting time by avoiding late plantings, and not carry out consecutive corn plantings,″ he said.

Another important point mentioned by Garollo is that during the harvest, producers must pay attention to the proper adjustment of machines, preventing many grains from falling into the field, or even breaking ears containing grains that will germinate. "This germination can happen up to 15 days later, so it is necessary to monitor areas after the harvest," he affirmed. And in regions that go through extended periods of drought during the winter, corn can wait for the rain to increase, as is the case in areas such as the Midwest and Southeast, in Minas Gerais.

Time determines chemical pest control

Graminicide herbicides can be used for the chemical control of the pest, but it is necessary to observe the phenological stage of tiguera corn, as the herbicides are effective when applied in the first vegetative stages of the plant when there are two to three leaves. "The later and more advanced the growth of guaxa plants, the more difficult the control will be, as expenses tend to increase as well, making the damage greater,″ Garollo said.

According to the specialist, both graminicides from the chemical group, Aryloxy-Phenoxy Propionates (FOPs), and Oxime Cyclohexanediones (DIMs) are very effective in controlling corn stalk up to the four-leaf vegetative stage. "But if the producer decides to control tiguera corn at later phenological stages, he will have to use graminicides at higher dosages according to the specific stage at the time of application, and likely with a preference for FOPs, which are more effective at field level in corn plants, in relation to DIMs, for example,″ he stressed.

Despite being complex, producers have allies when it comes to fighting the pest. "To monitor what is happening, they should seek the guidance of an agronomist and follow the rules for applying what is prescribed while observing the appropriate weather conditions, and choosing the right application tip, drop coverage, pressure, volume of syrup, among other details. Therefore, adopting combined measures is essential to interrupt this cycle," he said in conclusion.