Ecological management of the leafminer in coffee

In the management of the miner, a pest of greatest importance for the coffee growing in regions with a hot and dry climate, it is important to increase the list of tools available to help reduce the population of this insect. In this sense, the use of natural predators and the adoption of windbreaks, such as those made up of Leucena and arboreal Guandu, have great potential for prevent infestations and help control them.

The miner, Leucoptera coffeella (Guérin-Méneville, 1842) (Lepidoptera: Lyonetiidae) is considered the most important pest for coffee plants in regions with hot climates and dry, overcoming the coffee borer Hypothenemus hampei (Ferrari, 1867) (Coleoptera: Curculionidae, Scolytinae). It's a plague exotic, whose region of origin is tropical Africa, introduced in Brazil probably in coffee seedlings (Coffea spp.) attacked and coming from the Antilles and Bourbon Island, in 1851. It is monophagous pest, which attacks only coffee plants.

O emergence of coffee rust in Brazil, Hemileia vastatrix, at the beginning of the 1970s can be considered a milestone for placing the miner in the status of plague. Coffee trees planted in appropriate spacing to high technology, in full sun, with the aim of controlling the disease, provide environments favorable for the multiplication of the insect, which develops well in conditions greater sunlight and low air humidity.

The adult insect is a small 6,5 mm moth wingspan, silvery-white in color and anterior and posterior wings fringed. When at rest the forewings cover the hindwings.

Place the eggs in upper surface of the leaves and the caterpillar, when hatching, penetrates directly to the inside of the sheet, without coming into contact with the outside. At this stage the caterpillar lives inside the lesion or mines it constructed, and when Fully developed it measures approximately 3,5 mm in length.

The injury caused by caterpillar has a darker center, as a result of the accumulation of excretions under the leaf epidermis. The upper epidermis of the leaf, at the site of the lesion, stands out easily.

In general, and especially during times of high infestation, the greatest number of lesions is found in the leaves of the upper third of the coffee tree due to greater insolation, temperature and wind, which removes moisture from the leaves and favors the pest.

After complete development the caterpillar leaves the leaf through the upper surface of the mine and with the help of a silk thread descends to the lower leaves to pupate in a cocoon constructed also with silk threads and in the shape of the letter X.

The evolutionary cycle of Egg to adult lasts between 19 days and 87 days, the shortest at temperatures higher, hence the severity of the plague in warmer regions. The phase of caterpillar, which is the one that causes damage, lasts from 9 days to 40 days, passing through three phases (ecdyses) and can occur in 8 to 12 generations per year.

Injuries or mines caused by caterpillars reduce the leaf's capacity for photosynthesis due to the reduction in area leaf. Also, in intense attack, the plant defoliates, from top to bottom. low due to the distribution of the pest, and as a result there is a reduction in production of coffee. Intensely defoliated crops can take up to two years to recover. recover.

Research shows that the level of control for L. coffeella between 26% and 36% of the leaf area is damaged, after which Losses begin to occur in coffee production.

In the south of Minas, it was found, in 1976, a reduction in coffee production of around 52% due to defoliation of 67% in October, when the biggest flowering of that year occurred. Subsequently, between 1987 and 1993, high losses were also observed, with reduction in production between 34,3% and 41,5%.

Conditions for the occurrence of the leaf miner

A The presence of the miner is conditioned by several factors: (1) climatic - temperature and rain mainly; (two) crop conditions - more crops airy areas are more likely to be attacked and (3) presence or absence of enemies natural - parasitoids, predators and entomopathogens (fungi and bacteria).

Seasons of the year with higher temperatures and greater water deficit are conditions conducive to the development of the pest. More airy crops, with greater spacing between plants are more predisposed to attack by leafminer. In general, coffee trees in higher altitude locations within the same coffee plantation are more subject to pest attack, as these locations provide conditions ideal conditions for its occurrence, such as greater exposure to winds and consequently greater insolation and lower air humidity.

To the The times when the largest populations of the pest are observed are the periods dry seasons of the year, starting in June and peaking in October, being lower before and after these months, generally, in the main coffee growing regions of Brazil. There are cases in which the population increases in March-April due to the summer in the month of January and/or February, as often occurs in cerrado coffee farming miner. Rainfall and relative humidity negatively influence the pest population, on the contrary, temperature has a positive influence.

Ecological management of the miner

A predation, that is, the natural control of leafminer caterpillars carried out mainly by predatory wasps (Hymenoptera: Vespidae) presents approximately 70% of efficiency. Around 18% of natural control is carried out by microhymenoptera parasitoids.

The preservation of vegetation areas natural environment close to coffee plantations can play an important role in the strategy conservation and increase of predatory and parasitoid wasps. Areas of natural or regenerated vegetation adjacent to crops allows species sensitive to cultural practices find refuge in its interior. A definition of management tactics for these plants close to coffee crops could be used as one of the complementary strategies in regulating population of pest arthropods, contributing to the gradual reduction of dependence on plant protection products, promoting development sustainable development of the coffee agroecosystem. The use of legume strips (Fabaceae) trees (alleys) as windbreaks can reduce pest attacks by offering barriers that will make it difficult for insects that are propagated by the wind, modify the microclimate making it unfavorable to pests such as the leaf miner and increase the incidence of natural enemies by offering shelter and alternative food.

Research

The study of the influence of legume alleys (Fabaceae) trees, or windbreaks, in the incidence of leaf miner in coffee trees was object of research. The work was carried out at the Epamig Experimental Farm, in São Sebastião do Paraíso/Minas Gerais. The coffee tree strain was used Topaz, low in size, densely spaced in the row (3,4m x 0,5 m). The Fabaceae used as alleys, or windbreaks, were the arboreal Guandu (Cajanus cajan), Glyricidea (Gliricidia sepium), Leucena (Leucaena leucocephala) and Acacia (Acacia mangium), planted perpendicular to the direction of the winds predominant. Assessments of the incidence of leafminer were carried out monthly between the months of April, the beginning of the infestation, and October, the peak of pest in the region, by counting mined leaves. The incidence of predation by wasps was assessed by counting "predated" mines, by observing the tears made by the wasp in the lesions. Also which species of wasps were present were determined, which was done by capture of specimens with yellow sticky traps (24cm x 9,5cm) distributed in the plots in October of each year (pest peak), placed hanging in the center of each plot and at the same height as the plants of coffee tree.

Search results

They are presented and discussed the results obtained in 2009 after pruning the alleys at the height of the coffee trees in the previous year (2008) and in 2010 with the legumes already in their normal size.

In 2009, after pruning the alleys in the height of coffee trees in the previous year, the level of leaf miner control (NC = 30% of mined leaves) was observed from the month of May until the end of September in all treatments, with a reduction in mined leaves only in October with the beginning of rain in the region, when a new leafing on coffee trees. Therefore, no difference was observed between the effect of the different types of windbreaks and the control or control treatment without windbreaks (Fig. 1).

In 2010, with legumes already at normal size, it was observed that coffee trees with influence of Acacia and Gliricidia, showed lower pest infestation until the month of July, equaling the witness, and those under the influence of Guandu and Leucena until the end of September, a period in which the rains, showed that there would be no need to use any other pest control measure beyond that naturally exercised by enemies natural conditions and microclimate conditions provided by these two legumes, Leucena and Guandu (Fig. 2).

Species of predatory wasps (Hymenoptera: Vespidae) most abundant in the experimental area were Polybia scutellaris (44,7%), Brachygastra lecheguana (23,8%), Protonectarina sylverae (10,5%) (Fig. 8), Polybia ignobilis (7,9%), Polybia sericea (2,6%) e Polybia sp. (10,5%).

Cost benefit

The results allow us to conclude that windbreaks, such as those made up of Leucena and tree pigeon pea are efficient in preventing infestation of leafminer, either by making it difficult for insects to enter coffee plantations, constituting a physical barrier, either by conserving natural enemies close to the coffee trees, or for providing unfavorable microclimate conditions for the pest in the coffee plantation under influence of windbreaks. In addition to these results, from the point of view of reduction of pest attack, multiple-use plants that serve as Windbreaks can be used as firewood to dry coffee in dryers mechanical and mulching, in the latter case incorporating nutrients into the coffee trees, after the decision to prune them, making coffee cultivation more self-sustainable.

Article published in issue 219 of Cultivar Grandes Culturas, August, 2017.