The coffee berry borer is the most economically important coffee pest worldwide. This beetle reduces yields and quality of coffee, resulting in reduced income of coffee growers and the sustainability of coffee producing areas. In this project, the effectiveness of the entomopathogenic fungus Beauveria bassiana was studied at three commercial coffee farms located at different altitudes on the island of Hawaii. The results indicate that B. bassiana occurs naturally in the field, but applications of the commercial fungus should be sprayed early at the fruit development cycle and at the early stages of CBB attack to increase beetle mortality. With monthly applications, the effectiveness of Botanigard® was approximately 20% on average on all of the farms where trials were conducted. Botanigard® was less effective while beetles were in the C position (invasion and damage of the endosperm). Other management techniques, such as regular harvesting and sanitation, must be implemented to keep the coffee berry borer populations under an economic threshold level.
Coffee is one of Hawaii’s highest value agricultural products, ranking fifth in sales among the state’s agricultural industries. Coffee in Hawaii is grown from sea level to 762 meters a.s.l., and the largest contiguous area of production is in the Kona district of the Island of Hawaii (Bittenbender and Smith 1999, HDoA 2013). There are 820 coffee farms recorded in the state of Hawaii, of which 775 are located on the island of Hawaii with 2,549 hectares harvested; the majority of farms are located in the district of Kona. Forty-five coffee farms are located on other major Hawaiian islands, with 1,335 hectares harvested (HDoA 2013), and these contribute significantly to the total value of Hawaii’s coffee production. The farms located in the island of Hawaii are small and independently owned, and production procedures range from conventional approaches to organic production. According to the Hawaii Agricultural Statistics Service (HASS), the total acreage remained unchanged at 8,000 but harvested acreage declined 200 acres to 6,100 (HDoA 2012). The farm revenue for coffee is estimated at $34.4 million (parchment equivalent basis) for 2011/12. The CBB is a major concern for the coffee industry and limited sales are predicted (HDoA 2012).
The coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae), is a pest of immature and mature coffee berries and is the most economically important coffee pest worldwide due to the extensive destruction of the coffee seed that they inflict (Bustillo et al. 1998, Vega et al. 2009). The beetles feed and reproduce on the endosperm of the seed (Bustillo et al. 1998, Baker et al. 1992, Damon 2000, Vega et al. 2009). The life stages consist of eggs, larva, pupa, and adult and they occur inside the berry. The female lays two to three eggs per day for a period of 20 days. The colonizing female and larvae make galleries in the seed where they also feed. The founder female remains inside the fruit after oviposition until she dies. There is sibling mating among the adult progeny with a 10:1 sex ratio favoring females; therefore, when the new adult females emerge, they are already inseminated and ready to locate another berry in which to continue the cycle. Male insects do not fly and remain inside the berry. The life cycle varies according to the temperature: 21 days at 27°C, 32 days at 22°C, and 63 days at 19.2°C. Females can live 157 days and males may live for 20 to 87 days at (24.5 °C) (76 °F) (Bustillo et al. 1998, Damon 2002, Vega et al. 2009). Three types of damage have been reported; 1) premature fall of young berries, 2) infested ripe berries become vulnerable to fungus or bacterial infection, 3) reduction in both yield and quality of coffee, reducing the income of coffee growers (Damon 2000, Jaramillo et al. 2006). The coffee berry borer can cause bean yield losses of 30-35% with 100% of perforated berries at harvest time. Damage can be greater if harvest is delayed (Barrera 2008).
In August 2010, the coffee berry borer was reported in South Kona, Island of Hawaii (Burbano et al. 2011). The infestation has since extended and the beetle is now present from North Kona to the district of Kau, east side of the island and it is severely impacting farms and mill operators. Several farmers have stumped their coffee trees due to the devastating level of infestation. Economic losses for the region have been reported to exceed 30%. 2011 showed a significant increase in CBB damage compared with the 2010 harvest. Reports from the processing mills in Kona estimate the harvest losses to be over 40%. It is only a matter of time the pest finds its way to other Hawaii coffee growing areas on Oahu, Maui, Molokai, and Kauai.
Owing to the fact that the coffee berry borer has only recently invaded Hawaii, management techniques are limited and there is urgency for a strategic plan to reduce populations. The insect-pathogenic fungus Beauveria bassiana (formulated a Botanigard, Mycotrol O)was licensed for use in February 2011 by the Hawaii Department of Agriculture (HDoA). This fungus has shown to cause high mortality of the coffee berry borer in Latin America (De la Rosa et al. 1997). In Hawaii, B. bassiana is sprayed on a calendar basis, without any science-based data upon which to base decisions to make applications. Frequency of application and timing of first applications are thus made arbitrarily. Kona coffee is grown at different elevations, ranging from 213 m to 609 m above sea level, and fruit production is perennial (Bittenbender and Smith. 1999) which facilitates the establishment and reproduction of the coffee berry borer and results in frequent fungus applications as growers are concerned that they will incur complete crop losses. These factors clearly show the need to achieve a greater understanding of the effect of B. bassiana on the coffee berry borer with special reference to timing of applications and the effects of local environmental conditions on the effectiveness of the product.
The objectives addressed by this project were:
(a) determine the effectiveness of three rates of Botanigard® as a control measure for the CBB at different agroclimatic zones in Kona,
(b) determine the effectiveness of Botanigard® upon the position of the CBB female in the coffee berry, and
(c) disseminate and publish the results of this study.
This study was conducted in the Kona district of the Island of Hawaii. In April 2013, three commercial coffee farms were chosen at different elevations. Plantations consisted of mature coffee trees between 5 and 15 years old, and all were of a Guatemalan variety locally known as Kona typica (Coffea arabica). Coffee trees were planted at an average of 1.6 m apart within plants, and rows were spaced 3.4 m apart. The landscape, environmental conditions, crop, and CBB management varied among the farms.
Farm one was located in Honaunau at 145 m a.s.l. (N19°28.320’ W 155°54. 428’). The surrounding vegetation was feral coffee, commercial coffee farms, christmas berry trees (Schinus terebinthifolius), Leucaena leucocephala, and macadamia (Macadamia integrifolia). This farm was characterized by limited rainfall and a rocky soil. The CBB management program here was focused in the use of baited traps and no pesticides were used in this farm.
Farm two was located in Keauhou at 538 m a.s.l. (N 19°33.361’ W 155°55.730’). The surrounding vegetation of this farm was mango (Mangifera indica), eucalyptus (Eucalyptus sideroxylon A. Cunn. ex Woolls), christmas berry trees, avocado (Persea Americana Mill), Koa (Acacia koa A. Gray), macadamia, and ohia lehua (Metrosideros polymorpha Gaud). Trees were planted on a rocky soil and without irrigation. The CBB management was focused on the use of baited traps and Beauveria bassiana.
Farm three was located in Captain Cook at 763 m a.s.l. (N19°29.727’ W 155°53.503’). This farm was surrounded by feral coffee, Eucalyptus spp., macadamia, christmas trees, avocado, mango, koa, and ohia. Coffee trees were not harvested for several seasons, and there was no input of fertilizer or pruning. This lack of crop management combined with the humidity and frequent rainfall facilitated high infestations of CBB.
A randomized complete block experimental design was made on each farm with four treatments and the control (untreated trees) and three replicates per treatment. Blocks were chosen randomly in each farm, with approximately 70 m buffer rows of coffee trees among blocks. The treatments consisted of three rates of Botanigard®; 8, 24, and 32 oz plus 8 oz of Widespread® Max per acre, Widespread® Max alone, and the control or untreated trees. The treatments were assigned at random within blocks with approximately 10 m among treatments. Each experimental unit consisted of one plot with ten plants in a row per treatment. Each plant was marked with a color ribbon for identification.
Treatments were applied approximately two months after flowering, at a time where coffee berry borer was observed initially attacking the coffee berries, and several times through the study (see figures for spraying dates). Treatments were sprayed early in the morning between 06:00 and 08:00 h with a calibrated backpack sprayer (Solo backpack sprayer-4 gallon, 90 PSI, model # 425), thoroughly covering the upper and lower surfaces of the branches. To avoid any residual effect within sprayers from previous applications, the treatment spray order was surfactant, low, medium, and high dose and the backpack sprayer was rinsed with water several times before and after each treatment application.
To assess the level of CBB infestation and presence of B. bassiana, four branches located in the middle part of the plant, on the four cardinal directions, were sampled in each plant as described by Baker 1999.
For each sample, the following variables were measured: total number of berries per branch, number of berries infested by the CBB, number of fruits infested by the CBB, and the beetles showing signs of mycosis. Fruits with the fungus were marked with a water-proof marker and recorded before and after treatment application to identify them in subsequent samples. The total number of new infested and uninfested berries was recorded approximately every month for four months subsequent to the application of the treatments. Additionally, 100 infested berries were randomly collected per replicate and treatment in each farm. Berries were placed separately into labeled paper bags and stored in a cooler with ice pack and transported to the laboratory. Each infested berry was dissected under a microscope and the number of live and dead CBB females showing signs of mycosis due to B. bassiana and the position of the colonizing female were recorded. The female positions inside the berry were recorded as: position A (the female is starting to penetrate the exocarp and the abdomen is visible (Fig. 1A); position B (the female has penetrated the berry and a slightly damage of the endosperm is observed but the beetle has not yet oviposited (Fig. 1B); and position C (the female has invaded the endosperm and immature stages are observed in the galleries) (Fig. 1C). Sampling and dissection was carried out approximately every month for four months after treatment application.
The percentage of infested berries, presence of fungus, percentages of females in each position (A, B and C), and mortality and survival of female were calculated at each sample date. Mean percentages of dead CBB female were compared among treatments and analyzed by ANOVA using the general linear model (GLM), followed by pairwise comparisons of means using a Tukey test with a = 0.05 (SAS Institute, 2002).
Natural infestation of CBB before treatments application
Before treatment applications, the percentage of dead CBB caused by natural B. bassiana were Honaunau (145 m asl) 5.07 % (SE = 5.36), Keauhou (538 m asl) 13.65 % (SE = 6.43), and Captain Cook (763 m asl) 26.76 % (SE = 6.68 (Fig. 2). The highest percentage of mycosis was observed at the farm located at the higher elevation.
Mortality of CBB after fungus application
The percentage of dead CBB after the application of B. bassiana at different elevations is shown in Figure 3 (A, B, and C). At the farm located in Honaunau at 145 m, the mean percentage of CBB mortality caused by B. bassiana was 14.56, 10.67, and 12.57% with 8, 24, and 32 ounces per acre respectively (Fig. 3-A). The mean percentage of CBB mortality with four applications of Botanigard® in four months was 12.63%. At the farm located in Keauhou at 538 m, percentage of CBB mortality caused by B. bassiana was significant higher with 32 oz (36.48%) than 8 oz (25.83%) and 24 oz (24.77%) per acre (Fig.3-B). The mean percentage of CBB mortality with four applications of Botanigard® in four months was 30.02%. At the farm located in Captain Cook at 763 m, the mean percentage of CBB mortality was 47.01, 49.91, and 50.66% with 8, 24, and 32 oz per acre respectively (Fig. 3-C). The overall mean percentage CBB mortality with five applications of Botanigard® in four months was 49.22%. The percentage of mycosis caused by B. bassiana was higher at the farm located at 763 m than for the other farms located at 145 m and 538 m. Wild Beauveria bassiana was present in the control and Widespread® Max plots in all the three farms, mycosis varied from 0.0 to 20%.
Percentage infestation, berries with fungus, and dead females
The highest infestation of CBB was observed at the farm located at the highest elevation (763 m). The higher levels of infestation were observed in July and August (Fig 4. A-C).
Effect of Botanigard® upon the position of the CBB female in the coffee berry
The effectiveness of B. bassiana upon CBB female mortality was significantly related to the position of CBB inside the fruit in all the farms. There were significantly higher numbers of dead CBB females in position A than position B and C (Tukey test, P < 0.0001).
At the farm located in Honaunau at 145 m, the mean percentage of dead females at position A was (78.33 %), position B (9.16 %), and position C (9.16 %) (Fig. 5-A). At the farm located in Keauhou at 538 m, the percentage of dead females at position A was (85%), position B (11.22 %), and C (3.11 %) (Fig. 5-B). At the farm located in Captain Cook at 763 m, the mean percentage of dead females at position A was (75. 92 %), position B (14.02 %), and C (9.45 %) (Fig. 5-C).
This is the first study that evaluates the effectiveness of B. bassiana on the coffee berry borer in the field in Hawaii. The cryptic behavior of the coffee berry borer made this insect difficult to control since all stages of its life cycle occur inside the berries, and the only time for any product to be effective against the beetles is before they penetrate the berry and excavate the galleries in the endosperm. The results of this study show that the level of infestation of the CBB and the effectiveness of the fungus varied at all the farms. With monthly spraying, the effectiveness of Botanigard® was approximately 20% in all of the farms, on average. The presence of B. bassiana in the control plots was caused by natural infestation, and higher mycosis was observed at the farm located at the higher altitude. The effectiveness of B. bassiana was mediated by the female position inside the berry. Monitoring of CBB infestations must be conducted to obtain higher mortality rates through careful timing of B. bassiana applications.
Educational & Outreach Activities
The results of this study were presented at the Hawaii Coffee Association (HCA) annual meeting on Kauai, July 2013 (http://www.hawaiicoffeeassoc.org/Resources/Documents/CTAHR%20Update%202013.pdf) and several seminars in the CTHAR extension office in Kainaliu, Hawaii were presented.
We disseminated information on this project through coffee workshops, meetings, and field days that were organized with collaboration of the extension agents from the Island of Hawaii, coffee associations such as Hawaii Coffee Association (HCA), Hawaii Coffee Growers Association (HCGA), Kona Coffee Farmers Association (KCFA), and Kau growers.
A poster was presented at the 24th international conference on coffee science and the Kona Coffee Expo in 2012. In addition, results of this study were presented at the HCA meeting held in July 2012. A manuscript will be published in a peer-reviewed journal.
There are several native strains of Beauveria bassiana present in the field in Hawaii. This entomopathogenic fungus is a natural mortality factor of the coffee berry borer and it is present in all the farms that have CBB. Its abundance depends on several factors, such as level of CBB infestation, weather conditions, and the altitude of the farm (which is inversely correlated with temperature). The results of this research show that B. bassiana has potential as a management option to reduce CBB infestation with monthly applications. Other management techniques such as monitoring, frequent harvest, removal, and destruction of berries after the harvest season need to be combined in an integrated management program.
An online survey was provided to the coffee farmers of the island of Hawaii with the collaboration of H.C. Bittenbender, coffee specialist, and Andrea Kawabata, extension agent in Kona (CTAHR). The survey assessed how the coffee farmers manage the CBB, what strategies are they using, how they are implementing these strategies, the damage levels they are experiencing, and how the damage levels fluctuate through the harvest season. Regarding specifically the use of B. bassiana, in 2012, 80% of the farmers sprayed the fungus and 16% did not spray, compared to 75% who sprayed the fungus and 24% who did not spray in 2011. In 2012, 48% of the farmers mentioned that they started spraying in February or March, 10% sprayed year-round. In 2011, 18% started spraying May and 14% in April. Spray frequency showed that the farmers spray the fungus every four or six weeks.
In 2012, 38 % of farmers sprayed less than 16 oz. of Beauveria per acre per application, 28 % used 16oz, and 28% use 32 oz. In 2011 most sprayed 32 oz./acre. Beauveria rate per acre per application is decreasing while Beauveria per acre per year is increasing. Farmers use a silicone based surfactant. A typical spray solution is 0.3% surfactant, 4 oz. in 24 gallon spray solution. Farmers also mentioned that spraying BotaniGard® is extremely effective and with six applications per year produce good results. Additionally, they mentioned that the combination of sanitation (removing and destroying infested berries from the field), use of baited traps, and early application of the fungus have been very effective at knocking it down the CBB population.
Areas needing additional study
There are several strains of B. bassiana present in Hawaii. Since the most effective strain in the laboratory is not always the most effective strain in the field, strains adapted to local conditions in Hawaii should be tested in the laboratory and under field conditions. The effectiveness of B. bassiana is highly affected by temperature (correlated with altitude) and humidity. Most of the coffee farms on the Big Island (Hawaii) are located in areas where the coffee berry borer reproduction is favored by biotic and abiotic factors such as temperature, landscape characteristics, wild coffee, and cultural practices. The amount of surfactant actually used by farmers and its effectiveness on the survival of the fungus in the field should be studied. A cost benefit analysis that compares the effectiveness of the management techniques actually available for the coffee berry borer versus a frequent harvest and the removal and destruction of infested berries after the harvest season should be conducted. An exclusive coffee berry borer education team that provides an integrated management practices program through hands-on farm workshops disseminated by county and periodically year-round, especially during the growing and harvest season, is urgently needed.