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Farmers in Brazil should monitor the corn crop for caterpillar attack
Jan. 12, 2017
Farmers need to be aware of the pest attack on the corn crop. The corn caterpillar is the main pest present in the crop at this time when the maize of the first crop is in the vegetative phase.
"To avoid compromising productivity, we need to monitor so that farmers can take a proper decision," said Brazilian agricultural research corporation, (Embrapa) Milho and Sorgo researchers.
Currently, the transgenic maize, or simply Bt maize, has been planted on 5.3 million hectares of the country. This represents about 82 percent of the first corn cropped area, according to a survey conducted by Céleres.
However, the use of this technology over vast parts of the crop does not relieve the producer of the task of continuing to monitor for pests, mainly because of reduced resistance or efficacy of Bt maize against the carcass caterpillar.
It is a reality in the main maize producing regions of the country. Researchers explained that the key is to maintain vigilance and constantly monitor crops.
According to the researcher, the pest can affect the crop to an extent where additional measures to control it become necessary. One can opt for biological controls by releasing beneficial insects in the crop, also known as natural enemies, such as the Trichogramma wasp, or resort to use of bio-insecticides. Also, chemical control measures in the form of applying insecticides are an option. Such control measures should be used when the occurrence of the pest reaches a level where it causes harm and biological controls are no longer viable. This can be verified through monitoring.
Basically, two forms of monitoring are advocated. The first is to use pheromone traps, and the second is field monitoring.
"In the first case, a device in the trap exudes the "scent” of the female moth to attract the male. In this case, it is necessary to check the traps frequently. When captures of three moths are observed, it is a sign that the critical level of infestation has been reached. At this stage, the producer needs to take into account which management measures he has to pursue. A trap can monitor around five hectares," explained the researcher.
On the other hand, field-based monitoring focuses on injuries (scraped or damaged leaves) caused by the carcass caterpillar to maize plants. In this case, the farmer needs to divide the crop into plots and adopt a strategy for monitoring.
"It is necessary to be aware of the maximum level of plants with injuries, 20 percent, to take a decision to deploy chemical control measures," the researcher advised.
From this point onwards, plants grow larger and become less vulnerable to pest infestation. "In addition, when the caterpillar is very large, it is difficult to control it through any measure. It is worth mentioning that the damage caused by the carcass caterpillar in the plant can lead to a 40 percent fall in productivity."
Source: AgroNews
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