CAN COFFEE VARIETY AFFECT THE POPULATION DYNAMICS OF COFFEE BERRY BORER

In the present study, we sought to describe CBB population dynamics across seven coffee plantations spanning a range of 68-1051 m above sea level (masl) in Sao Tome Island. We collected data on CBB infestation, position and development within the coffee berry, and mortality by the entomopathogenic fungus Beauveria bassiana

Biological control is the best option to control this pest, due to its economic and ecological efficiency, but all the factors that constitute the coffee ecosystem and its multiple interactions must be taken into account. It is essential to know the phenology of the crop in the different areas, especially that related to flowering periods and, therefore, the age of the fruits potentially susceptible to the CBB [18,46,35,47]. At the same time, it is necessary to know the biology and reproduction habits of the CBB, in order to determine the moments of greater susceptibility of the pest to the existing control practices, thus keeping it below the economic injury level [31,47]. In Sao Tome and Principe, the organic coffee plantation is predominant and the Biological Coffee Export Cooperative (CECAFEB) has shown enormous growth through the expansion of the domestic market.

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In the present study, we sought to describe CBB population dynamics across seven coffee plantations spanning a range of 68-1051 m above sea level (masl) in Sao Tome Island. We collected data on CBB infestation, position and development within the coffee berry, and mortality by the entomopathogenic fungus Beauveria bassiana.

Study Area:
Sao Tome Island is located at latitude 0° and longitude 6° 30' East with an area about 900 km² and is dominated by volcanic mountain, which culminates at 2024 masl. Sao Tome climate is sub-equatorial with very high rainfall. The average annual rainfall varies from 1000 mm in low zone (north and northeast) to more than 6000 mm in high zone (south and south-west). The driest months are June, July, and August and the wettest months are March, April, and May. The annual atmospheric humidity is 80% and annual average temperature at sea level is 25.4 °C[48,49].
The studies were conducted over 23 months (February 2018 through December 2019) in six coffee plantations of CECAFEB located in three regions (Districts) and one in the Center of Technological and Agricultural Investigation of Sao Tome and Principe-Experimental base of industrial crops (CIAT/STP-BECI). The cultural practices on these coffee plantations are: weeding, pruning and prophylactic harvesting, with no pesticide use.
São Nicolau and Brigroma: the agroforestry cultivation system prevails in the area with Robusta coffee trees associated with Erythrina, while in Poiso Alto Robusta coffee species is planted in an intensive cultivation system under full sunlight. São Carlos, CIAT/STP-BECI, Novo Destino and Bem-Posta: in these areas the agroforestry system of interplanting shade trees (Erythrina spp.) and some vegetables with coffee is predominant. More details of experimental coffee plantation are shown in Table 1.

Sampling borer populations:
The present study used the sampling procedure known as "Cenicafé method" in Colombia [50]. A brief description of the sampling method follows (1) divide the coffee farm into independent lots according to plantation age; (2) randomly select 30 coffee trees per lot (0.5-1.5 ha); (3) select a representative branch in the middle of the tree containing 30-100 developing berries (by visual estimation); (4) examine all green berries for CBB entry hole; (5) record the number of green berries, infested green berries and green berries with fungus Beauveria bassiana(EF)(equation 1); Beauveria bassiana level(Total infested green berries with EF )/(Total counted coffee berry)*100% (1) (6) repeat the process moving in a zig-zag pattern through the plantation; (7) calculate percent CBB infestation for each lot. In addition to infestation levels (equation 2), Infestation level(Total infested green berries with CBB )/(Total counted coffee berry)*100% (2) we assessed the position of the founding female CBB in the infested berries (equation 3).
Penetration rates(Total of coffee berry in position (AB or CD)/(Total counted coffee berry)*100% (3) For penetration rates of CBB, ~3 infested green berries per branch were collected and dissected to assess the position of the CBB inside. Infested berries were categorized as AB or CD depending on whether the CBB had penetrated the endosperm (CD position) or remained nearer the surface (AB position) [51,52,53]. To determine the developmental stage of CBB and the presence of parasitoids or predators, 100 infested berries were collected per site/sampling date, where 20 were opened and examined under 20x magnification using a stereoscope for screening and counting the stages of the biological cycle of the CBB [52,53]. The other infested fruits were placed in plastic cages to observe the emergence of parasitoids. Samples were taken monthly during the two years of field trial.

Statistical analyses:
Data analysis was carried out with IBM SPSS Statistics 23. Analyses of variance (ANOVA) were performed with variety as independent variable and the treatment means were subjected to Tukey"s HSD test (p<0.05), whenever appropriate. Correlation analysis (Pearson"s; r) was performed between infested green berry, AB position and Beauveria bassianato evaluate whether the presence of Beauveria bassiana is associated with the pest incidence assisting in its control and thus assisting in the eventual the decision-making process regarding CBB management.

Immature stages and adult of Hypothenemus hampei in developing coffee berries:
Immature stages (eggs, larvae and pupae) and adults of CBB were found throughout the sampling period. There were no differences among localities in average number of eggs (F=0.74; gl=6; p=0.62), larvae (F=1.42; gl=6; p=0.21) and pupae (F=1.48; gl=6; p=0.19) present in green, ripe and mature berry, but there was significant differences (F=3.42; gl=6; p=0.003) on the average number of CBB adults (Table 3).

Discussion:-
We investigated the population dynamics and infestation rates of the coffee berry borer in the Sao Tome Island, but due to irregular flowering we were unable to determine the number of seasonal CBB generations is unclear, we found infested green berry in all months sampled, and particularly from late May through October during the weeks following the main harvesting season and the formation of new green berries. The mean infestation across all seven sites was (11.5±3.5%), with two sites showing infestation <5% (Table 2), a value below the 5% economic injury level which estimated by several authors [54,55,56]. In this context, the pest was a limiting factor of organic coffee production in Sao Tome Island during the study period. Several factors can influence the CBB population dynamics, among them: precipitation, temperature, shading, altitude and harvest [56,57]. On the other hand, combinations of environmental factors and cultural practices such as daily rainfall, coffee variety, age of planting, and amount of CBB also influence the infestation [58]. In this trial the infestation rates differed across sites maybe due to a combination of elevation/microclimate/management and variety. Coffea arabica L. is more tolerant than C. canephoraPierre ex A. Froehner (Robusta) to the CBB,in contractssome studies report higher infestation and CBB populations in robusta [60,61,62], while others report higher numbers in arabica. Coffea arabica L. (var. Caturra) is more susceptible to the CBB [63], but in this trial C. arabica L. (var. Red Catuaí) was more susceptible. CBB infestation level between 7% and 52% were recorded in shading coffee plantations [64,65]. CBB infestation levels between 4% and 26% were recorded in full sunlight coffee plantationin PuertoRico [65]. Similar result (4%) was recorded in Poiso Alto (full sunlight).
On the other hand the incidence of Beauveria bassianawas rather low in Sao Tome Island. Under natural conditions, the Beauveria bassianaoccurs parasitizing low percentage of CBB [66]. The Beauveria bassianarates effected CBB varied from 0.23% to 0.47% in Rondônia, therefore lower than in other regions of Brazil [67]. CBB mean mortality by the Beauveria bassianaacross the entire 2016-2017 season in Ka"u was twice that observed in Kona (12% vs. 6%, respectively) in Hawaii [52]. However, the use of commercial formulations to control CBB infestations could be envisaged, if further research clarifies the conditions, and modalities of application.

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Infestation level and green berries with Beauveria bassianaper coffee branch were directly proportional. This was evidenced by the positive correlation observed ( Table 2).The highest infestations and activity of Beauveria bassianawere recorded in the months of lower rainfall in Sao Tome Island, particularly from late May through October during and in the weeks following the main harvesting season formation of new green berries ( Figures  1,2,3,4,5,6,7 and Table 4). The highest periods of berry infestation occurred from March to May, and again in late October through the end of harvesting in December. Although the highest green berries with Beauveria bassianaoccurred in September-October in Hawaii and Puerto Rico [52]. The highest periods of berry infestation was observed in May in Mina Gerais State [68].
We also found the highest mean number of eggs in Poiso Alto (562 masl), and larvae, pupae, and CBB adults in Brigroma (68 masl) ( Table 3). Maybe due to a combination of elevation and microclimate existent in these sites. Higher reproduction and dispersion of the CBB were found in low-elevation in Hawaii [51]. A lower occurrence of the CBB was observed in the high-elevation in Southern Colombia [69]. On the other hand, a decrease in the CBB population was observed at altitudes above 800 masl in Costa Rica [70]. A greater borer development was recorded in locations at 1.200 masl, with average temperatures above 21°C and less development in locations above 1.600 masl, with average temperatures below 19°C in Colombia [71]. A higher prevalence of the borer was recorded in coffee plantations located in low-elevation in southwestern Ethiopia [72].

Conclusions:-
From the results obtained, it can be concluded that the occurrence of CBB adults is a continuous process throughout the fruit ripening period, with a constant flow of new adults infesting fruit. The population dynamics of the CBB and infestation level show that there are more suitable periods for adopting practices aimed at reducing the CBB population in Sao Tome Island. Coffea arabica L. was more susceptible to CBB attack than C. canephoraPierre ex A. Froehner(Robusta). Beauveria bassianaactivity was more remarkable from late May through Octoberwhen the humidity is lower in Sao Tome Island. The CBB finds favorable conditions in the areas studied and probably in the other sites of Sao Tome Island.

Author Contributions:
Miclay Carvalho generated the idea for the paper, conducted field research, analyzed the data, and write the paper. Alex Lopes and Luís Santos helped conduct field research. Albino Bento, Pedro A Casquero, and Raul Narciso C. Guedes revised the manuscript for technical and scientific accuracy and organization.