A method using green coffee fruits (GFs) was developed to test the toxicity of insecticides against the coffee berry borer (CBB). Insecticides or toxic substances were applied to disinfected GFs before or after CBB infestation. Insect mortality, repellency, and reproductive capacity, in addition to other parameters, were evaluated.
Prior to recommending insecticides to treat the coffee berry borer (CBB) Hypothenemus hampei, it is valuable to know the mortality and repellency of these insecticides against adult insects or their impact on reproductive output. However, currently available methods assess adult mortality only, limiting the selection of novel insecticides with a different mode of action. In this work, different experimental methods were examined to identify the diverse effects on the CBB under laboratory conditions. For this, green coffee fruits (GFs) were collected and disinfected by immersion in sodium hypochlorite solution followed by UV light irradiation. In parallel, CBB adults from a colony were disinfected by immersion in sodium hypochlorite solution. To assess fruit protection (preinfestation), the fruits were placed in plastic boxes, and the insecticides were applied. Then, the CBB adults were released at a rate of two CBBs per GF. The GFs were left under controlled conditions to evaluate CBB infestation and survival after 1, 7, 15, and 21 days. To evaluate insecticide efficacy after CBB infestation (postinfestation), CBB adults were released to the GFs in a 2:1 ratio for 3 h at 21 °C. Infested fruits showing CBB adults with their abdomens partially exposed were selected and placed in 96-well racks, and the CBBs boring into the fruits were treated directly. After 20 days, the fruits were dissected, and the CBB biological stages inside each fruit were recorded. The GFs served as substrates that mimic natural conditions to evaluate toxic, chemical, and biological insecticides against the CBB.
The coffee berry borer (CBB), Hypothenemus hampei, was first detected in 1988 in Colombia and has since become the most important pest species of the coffee crop. CBB females leave the natal fruit already fertilized, seeking new fruits guided by the volatile chemicals that they emit1,2. A complete cycle is fulfilled within 23 days3 at a temperature of 25 °C. The cycle starts with the founder female penetrating the seed and laying eggs in the fruit endosperm. The eclosed larvae eat the seed. If the fruits are dissected at this point, it would be possible to observe both the founder female and her offspring. After 14 days, the larvae become pupae-generally, the pupae stage lasts 5 days. In the adult stage, the females copulate with their siblings, and the newly fertilized females fly away from the damaged fruits looking for new coffee fruits to start a new cycle4.
Both the penetration process and the result of larval feeding damage the coffee seed, decreasing the quality of the coffee beverage and significantly reducing the revenue; greater than 5% infestation in coffee plantations is generally considered the economic threshold.
CBB control is based on an integrated pest management (IPM) strategy, including cultural control and agronomic practices, natural biological agents, and the use of chemical insecticides, which requires safety conditions and timely application4.
To evaluate new insecticides for the control of the CBB, low-cost methodologies are needed that allow rapid results to be obtained. Both laboratory and field procedures are currently in use, including artificial diets containing coffee in which the insecticides are incorporated5,6, or spraying the insecticides on dry parchment coffee7,8,9. In addition, experiments carried out in the field using coffee tree branches covered with entomological sleeves have been reported10,11; however, these methods require intense labor and long evaluation periods.
A condition resembling natural field conditions, that is also fast and inexpensive, is the use of green or ripe coffee fruits. However, these fruits must be maintained under conditions suitable for developing the CBB, avoiding alterations and contaminants by microorganisms to maintain their quality and properties. To this end, different disinfectants have been used, as well as procedures involving heat and radiation7,9,12,13,14,15,16.
Additionally, the methods for insecticide evaluation against the CBB require simulations of adult females flying in search of fruits or penetrating those fruits17,18. For this, artificial fruit infestations have been carried out in the field8,11,19, although this process is labor-intensive and depends on environmental conditions.
Here, we describe a standardized methodology for the evaluation of products that can have different effects on the CBB under controlled environmental conditions that resemble field conditions.
In this protocol, disinfection of the fruits as well as the insects are critical steps. When fruits from the field are used in the laboratory, they frequently show high contamination and dehydration since microorganisms and mites are present in the epidermis7,15,16. Therefore, using fruits or insects that are not disinfected will cause insect death due to contamination caused by microorganisms, such as bacteria or fungi, thus in…
The authors have nothing to disclose.
The authors express their thanks to the National Federation of Coffee Growers of Colombia, the assistants of the Department of Entomology (Diana Marcela Giraldo, Gloria Patricia Naranjo), Experiment Station Naranjal, and Jhon Félix Trejos.
Beaker with spout, low form 500 mL | BRAND PP | BR87826 | |
Benchtop Shaker | New Brunswick Scientific Innova 4000 Incubator Shaker | ||
Dishwashing liquid soap-AXION | Colgate-Palmolive | AXION | |
Hood; Horizontal Laminar Flow Station | Terra Universal | Powder-Coated Steel, 1930 mm W x 1118 mm D x 1619 mm H, 120 V (https://www.terrauniversal.com/hood-horizontal-laminar-flow-station-9620-64a.html) | |
Insects CBB | BIOCAFE | (http://avispitas.blogspot.com/p/biocafe.html). | |
Multi Fold White paper towels | Familia | 73551 | |
Preval Spray unit | Preval Merck | Z365556-1KT | https://www.sigmaaldrich.com/CO/es/product/sigma/z365556?gclid=Cj0KCQiAweaNBhDEARIsAJ 5hwbfZOy1TWGj6huatFtRQt AzOyHe5-oBiKnOUK2T1exuuk WwJLdvxkvsaAjoYEALw_wcB |
Reversible Racks 96-Well | heathrowscientific | HEA2345A | https://www.heathrowscientific.com/reversible-racks-96-well-i-hea2345a |
Scalpel blades N 11 | Merck | S2771-100EA | |
Scalpel handles N3 | Merck | S2896-1EA | |
Sodium Hypochloride | The clorox company | Clorox | |
Stereo Microscope | Zeiss | Stemi 508 | https://www.zeiss.com/microscopy/int/products/stereo-zoom-microscopes/stemi-508.html |