Root sharpshooter on sugar cane

An important pest in sugarcane cultivation, the leafhopper Manaharva fimbriolata demand a lot discretion and attention. The appropriate choice of insecticide and method of application can make a difference in the integrated management of this insect.

In between the predominant pests that impact the degree of difficulty and cost in management integrated into sugar cane is the root planthopper (Manaharva fimbriolata). The main manifestations, such as records severe, occur in the states of São Paulo, Goiás, Minas Gerais, Mato Grosso and Mato Grosso do Sul, reducing productivity and quality of raw material

You problems with the pest have intensified both in areas of culture, in former pastures, as well as in places of renovation or according to fifth cut of sugarcane, with its impact being even greater on early sugarcane cultivars. sugar cane. The occurrence is not only associated with the history of the area, the presence of straw or not and the cultivation of more sensitive varieties, but rather the the entire production system, from management practices, climate and time of year to insecticides, applied doses and, mainly, application technology.

Mechanized harvesting increases the amount of straw which remains on the soil, preserving moisture, favoring growth population of leafhoppers.

The males of M. fimbriolata are colored reddish and the female with darker colors, reddish-brown and wings with almost black bands (Williams et al., 1969). Females oviposit in the straw and, mainly in the subsurface of the soil, mostly close to the stem of the plant.

At the dry period of the year, the eggs go into diapause, remaining like this until the soil moisture conditions are once again favorable. In conditions of high temperature and humidity, the nymphs emerge from the eggs about 15 days later. 20 days after laying, and head towards the roots, where they feed at the base of the culm sucking the plant's sap for 30 days to 40 days. During this period are always surrounded by a dense white foam, quite characteristic, whose main function is to protect the nymphs from desiccation. The total cycle of this insect lasts from 65 days to 80 days, with three generations being common annually during the rainy season.

Damage to sugar cane is caused mainly by the young forms of the root hopper, which extract a large amount of amount of water and nutrients from the roots. Adults also cause damage to plants, because, when they suck the sap from the leaves, they inject saliva into the stomata, a place where water and substances that will be transformed into nutrients are stored to the plant during photosynthesis. The saliva released, both by the nymphs like adult hairs, it is rich in enzymes and amino acids and helps the insect in food intake process. However, they are toxic to the plant, causing necrosis in leaf and root tissues (Williams et al., 1969). As a consequence of this, the culms become thin and the internodes shorten. Already In more severe attacks, the plant may present nutritional deficiency and dehydrate whole and dry (Dinardo-Miranda et al.,2003).

Productivity drops can reach 60%, in crops harvested at the end of the harvest. In areas harvested at the beginning of the harvest, losses are smaller, although the populations found in these areas are often higher compared to the others. This reveals that the crop harvested at the beginning of crops withstands the attack of the pest better, probably because the plants they are more developed, with several internodes. Furthermore, culture goes through a short period of water stress, between the end of the season when water leafhopper and harvest. Fields harvested at the end of the harvest suffer a greater damage, as its plants are poorly developed and after the insect attack, the long period of water stress until harvest does not favor the recovery of plants, causing damage caused by leafhoppers to be accentuated under these conditions (Dinardo-Miranda et al., 2001).

Since the leafhopper attack results in culms smaller, thinner and drier, often leading to death, also occur changes in the quality of sugar cane, generally with a reduction in values of pol and increase in fiber, as seen in Dinardo-Miranda et al.,2000.

To be successful in managing areas with leafhopper problems must encompass all available tools, as, For each cultivation situation, one of them is more suitable. The control chemical is a very valuable tool in the leafhopper management program, especially in sugarcane fields harvested from August onwards (middle to end of harvest), which suffer greater damage due to the pest attack, and in those severely infested (Dinardo-Miranda et al., 2000).

For reduce the levels of infestation present in the areas, it is essential to control first generations of the pest with the aim of reducing damage to sugarcane fields.

At region of the Triângulo Mineiro, more specifically in areas close to or to the around Frutal, Minas Gerais, the leafhopper is a great challenge for sugarcane production, even more so when associated with diseases such as red rot and orange rust, which significantly increase the cost of production.

 Studies carried out by Michel Fernandes, from Usina Cerradão, reveal that leafhopper control in the region of Frutal, Minas Gerais, proved to be unsatisfactory, probably due to the inadequate association of pest management system to insecticides and doses, as well as the low quality of application. In research, different insecticides were applied with tractor-driven sprayers with aerial application, simulating reality of different management systems.

In a new analysis, carried out in 2016, with the insecticide imidacloprid, applied via ratoon and pendant cutters, the results in efficiency surpassed by approximately 40% (number of nymphs per meter) when compared to other products tested in the modality via ratoon cutting. The percentage highlights the importance of the asset and the method of application for good integrated management of the root hopper. The results corroborate Dinardo-Miranda et al., 2009 who concluded that the insecticides imidacloprid and thiamethoxam showed greater efficiency in controlling leafhoppers when applied under lower initial infestations.

Roberto Estêvão Bragion from Toledo, Ourofino Agrociência; Michel Fernandes, Cerradão Plant; Ana Paula da Silva Martins Bonilha, Ourofino Agrociência; Marco Antonio Drebes da Cunha, Ourofino Agroscience

Article published in issue 232 of Cultivar Grandes Culturas, September, 2018