Coffee borer control measures

A pest with the power to cause serious damage to coffee plantations, the coffee borer Hypothenemus hampei has behaved dynamically over the years in Brazil, at the same time that measures to combat the insect have improved with new strategies, tools and technologies . 

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The coffee borer, Hypothenemus hampei (Ferrari, 1867) (Coleoptera: Curculionidae, Scolytinae) is considered the second most important pest of the coffee plant Coffea spp. in most coffee growing regions in Brazil. Known in the country since 1922, until 1970 it was considered the main pest. It then became second or even third in importance, with the exception of the Zona da Mata of Minas Gerais, states of Espírito Santo and Rondônia. Furthermore, crops very close to large dams and irrigated coffee plantations, due to high humidity and temperature, provide ideal conditions for the insect's development and survival in the off-season. The adult female is a small, shiny black beetle, measuring approximately 1,7 mm in length and 0,7 mm in width.

The smaller male, approximately 1,2 mm long by 0,5 mm wide, cannot fly due to atrophied hindquarters. It always remains inside the fruits where it fertilizes the females. 

The female pierces the fruit, from green (pimbaon) to ripe (cherry) or almost dry (raisin), generally in the crown region, digging a gallery about 1 mm in diameter until reaching the seed. 

In the evolutionary cycle of the drill, the development of the male is faster (two larval instars) than the development of the female (three larval instars).

DAMAGE CAUSED

The damage is caused by larvae that live inside the coffee seed, where they feed, causing the fruit to fall, reduce the weight of the beans (quantitative damage) and reduce the quality of the coffee through changes in the type and sometimes the drink (qualitative damage). Generally, only one seed is attacked and rarely both, and the destruction of the fruit can therefore be partial or total. 

Initially the damage occurs with the falling of fruits (chumbinhos). For Coffea arabica L., it has already been found that the drill increases the percentage of natural fall in the order of 8% to 13% and for Coffea canephora Pierre & Froehner (‘Conillon’) is responsible for a fruit drop of around 46%, as this cultivar is more susceptible. Broached fruits that do not fall suffer weight reduction, which can reach 21% or 12,6 kg per 60 kg bag of processed coffee. The quality of the coffee is changed directly by the borer attack, going from type 2 to type 7 only with the increase in infestation, as 2 to 5 bored beans constitute a defect. Losses increase during the shelling operation due to the fragility of the attacked grain, which is broken and discarded when the shelling machine is ventilated.

The damage caused by the borer begins when the infestation reaches 7% to 10% in the fruits of the largest bloom (Figure 2). The quality of the coffee drink is not directly influenced by the borer attack, but indirectly by the ease that the damage provides for the penetration of microorganisms, such as fungi of the genus Fusarium e Penicillium, which are related to changes in the quality of the coffee drink.

DRILL MONITORING

In order for control to begin at the correct time, periodic sampling of the fruits must be carried out in the different plots of the crop, starting with the lowest and most humid parts.

Borer monitoring must begin during the insect's “transit” period, approximately three months after the major flowering (October), when the first borked fruits are observed in the rosettes, and carried out until April. During this “transit” period, the adult females of the insect abandon the remaining fruits from the previous harvest, where they were bred, fly and pierce developed green fruits (leads) from the following harvest.

CONTROL METHODS

Cultural control is perhaps the most efficient control method. Coffee plantations must be planted at spacings that allow greater aeration and light penetration in order to provide low air humidity inside, a condition that is unfavorable to the pest, in addition to allowing the circulation of sprayers attached to tractors.

Even more important as a cultural method is the harvesting of coffee, which must be very well done, and it must be avoided that fruits remain on the plants and on the ground, in which the borer can survive in the off-season (remaining fruits), especially if the off-season is rainy. After harvest, if there are many grains left on the plants and on the ground, it is recommended to transfer or collect the remaining fruits from the harvest.

Study carried out C. canephora CV. Conillon, in Espírito Santo, showed that, five months after harvest, around 72% of the remaining fruits were attacked by the borer, and in Rondônia close to 76%. These data highlight the importance of properly harvesting and transferring, especially in non-mechanized crops, where spraying is difficult to carry out.

Harvesting must always begin in the most infested plots, in order to avoid greater losses, as the borer has a great capacity for reproduction and, in years of high infestation, the last plots to be harvested will, without a doubt, present larger populations of drill and consequently greater losses.

Biological control

Although there are other forms of biological control, one of them lies in the use of entomopathogenic fungi beauveria bassiana (Bals. - Criv.) Vuill. Already found in Brazil, this fungus has been developed through research, but there is still no prospect of efficient use as the only control agent. 

Cloudy weather and high relative humidity (minimum 80%) are conditions that favor borer infection. B. bassiana. These conditions, ideal for the fungus, are not always found in coffee plantations with conventional spacing, which probably makes dense, shaded or wooded plantations promising for controlling the borer with the use of entomopathogenic fungi.

Commercial products containing the fungus B. bassiana as an ingredient are listed in Table 1.

Conventional chemical control

Chemical control is considered efficient and fast at spacings that allow the use of sprayers coupled to tractors, unlike dense and/or shaded coffee growing.

The chemical control tactic is often the only one available to keep the pest below the control level (NC) which is 3% to 5% of bored fruits, if possible even in those fruits where the borer has not reached the seed, where it will be killed by contact or ingestion with the applied insecticide, before it lays eggs.

As the attack is not uniformly distributed across a crop, control is recommended only in plots whose infestation has already reached the NC. Therefore, most of the time, control is not carried out across the entire crop, but is limited to a few plots. In irrigated crops, chemical control may be necessary in most fields.

The active ingredients and commercial products registered in Brazil for use on coffee plants to control the coffee borer are listed in Table 1. 

New research for chemical control of the coffee borer

 Several molecules being tested to control the coffee borer have been gaining prominence in the various coffee growing regions of Brazil, some in mixtures, such as the active ingredients metaflumizone (Verismo, Basf), ethiprole (Curbix - Bayer), ethiprole + imidacloprid (Bayer ), bifenthrin + acetamiprid (UPL 183 FP BR - UPL/United Phosphorus Limited), imidacloprid + bifenthrin (Galil - Adama), indoxacarb + novaluron (Plethora - Adama), already with promising results for the control of the coffee borer in Brazil. 

Paulo Rebelles Reis, Epamig Sul de Minas/EcoCentro

Article published in issue 211 of Cultivar Grandes Culturas.