0631-B1
Ronald F. Billings[1]
Severe outbreaks of the southern pine beetle, Dendroctonus frontalis, (or closely related species) developed in native forests of Pinus caribaea and P. oocarpa in Central America between 1999 and 2002. In total, more than 75,000 ha were destroyed, with major losses in Belize, Nicaragua, Honduras and Guatemala. Response to these outbreaks varied markedly among countries, based on the presence or absence of organized pest management programs. In March 2002, the author evaluated the status of bark beetle outbreaks in each affected country and made short- and long-term recommendations for pest management. With these recommendations and previous experiences in Honduras as a foundation, foresters and pest specialists from seven Central American countries met in August 2002 to jointly develop a regional strategic plan for bark beetles. The Central American Environment and Development Commission, consisting of the ministers of agriculture of each country, has approved this plan for implementation throughout Central America.
Native pine forests comprise an important natural resource in all Central American countries, except Costa Rica and Panama. These forests are home to increasing human populations and provide shelter, raw materials, protection of soil and water resources, a source of employment, local and national revenues, among other values. Central American pine forests are threatened periodically by a variety of natural and human-induced depredations: hurricanes, wildfires, shifting agriculture, and forest pest outbreaks.
In 2000 and 2001, a region-wide outbreak of native pine bark beetles of the genus Dendroctonus (Coleoptera: Curculionidae, subfamily Scolytinae) occurred in Central America, with major impacts in Belize, Nicaragua, Honduras, and Guatemala. This paper describes how each country responded to this most recent bark beetle outbreaks and how all Central American countries have jointly developed a regional strategy for forest pest management.
At least twelve species of Dendroctonus bark beetles inhabit pine forests of Mexico and Central America (Wood 1982). Among the most common and destructive species are D. frontalis, D. adjunctus, D. mexicanus, and D. valens. Adult beetles collected in Honduras, Nicaragua in 2001 and 2002 ranged in length from 2.8 - 4.2 mm and are believed to represent a single species, D. frontalis var. arizonicus (John Moser, USDA Forest Service, personal communication, Vité et al. 1975). According to recent genetic sequencing studies by Dr. Lawrence R. Kirkendall, a new species of Dendroctonus is believed responsible for the recent outbreak in Belize (Midtgaard and Thunes 2002). This new species is somewhat larger (3.0 to 5.0 mm in length) and is closely allied with both D. frontalis and the less common D. vitei.. The southern pine beetle, D. frontalis var. frontalis, is the most destructive insect pest of pine forests in the southern United States. In turn, D. frontalis var. arizonicus, distributed from Arizona to Nicaragua, has been the most destructive bark beetle in Honduras, Nicaragua, and El Salvador.
In Honduras from 1962-1965, D. frontalis destroyed more than 2 million ha. of mature pine forests (Hernandez Paz 1975). Due to the magnitude of the outbreak, coupled with the lack of roads, trained personnel, and financing, little direct control was carried out. The outbreak eventually collapsed of natural causes, but not before devastating nearly two-thirds of this country’s old-growth pine forests (Hernandez Paz 1975).
The destructive potential of D. frontalis is attributed to several factors (Thatcher et al. 1980): 1) a multivoline life cycle (with 8-10 overlapping generations per year in Central America) and females capable of establishing multiple broods; 2) a strong tendency to kill host trees in concentrated groups and ability to expand infestations rapidly in absence of intervention; and 3) capability to infest and kill even healthy pines older than five years of age as infestations expand.
Direct control methods currently used in Central America to address bark beetle outbreaks, in order of priority, are cut-and-leave, cut-and-remove, insecticide sprays, and pile-and-burn (Billings et al. 1996b). The latter two methods have been largely discontinued in the southern United States and are being used less frequently in most Central American countries. Cut-and-remove (salvage) consists of felling, removing and utilizing all infested trees plus adjacent uninfested trees to control individual infestations. Cut-and-leave (Billings et al. 1996b), an alternative control method used exclusively for D. frontalis, reduces timber losses in situations not accessible or feasible for prompt cut-and-remove (Billings 1995).
To apply cut-and-leave, all infested trees and adjacent uninfested trees within 10-30 m of recently-attacked trees are felled toward the center of the infestation and left on site. The width of the uninfested buffer strip is increased up to 100 m or more in case of massive infestations (more than 100 ha.) (Billings 2001b). Although not recommended, treated areas in Central America are often burned to further reduce brood survival. Cut-and-leave effectively disrupts pheromone production and mass aggregation of D. frontalis, processes required for infestation growth. Also, under sub-tropical conditions, interspecific competition from secondary bark beetles (Ips spp.) and solar heating reduces brood survival. (Billings 1982, 1995).
Since 1982, the author has served periodically as a consultant for bark beetle control in Central America. In March 2002, he evaluated the current bark beetle situation and control program in Honduras, Nicaragua, Guatemala, El Salvador, and Belize (Billings and Schmidtke 2002). He found that the extent of pine forests, the impact of bark beetles, and the response by governmental forestry agencies to bark beetle outbreaks varied markedly among countries.
Honduras
Honduras has 2.8 million ha of pine forests (Silviagro S. de R. L. 1996), consisting principally of Pinus caribaea, P. oocarpa, and P. tecunumanii (= P. patula var. tecunumanii). Pinus caribaea grows from sea level up to elevations of 600-800 m; P. oocarpa is found between 500 and 1,200 m; and P. tecunumanii is found at higher elevations, primarily above 1,200 m.
In 1982, an infestation of D. frontalis developed in north central Honduras, threatening the country’s forest resource. At request of the Honduran Forestry Development Corporation (Corporación Hondureña de Desarrollo Forestal or COHDEFOR), the author evaluated the outbreak. He provided field training to control crews, introduced cut-and-leave (or buffer-cutting) as the preferred alternative to pile-and-burn and insecticides to treat infestations, initiated a record-keeping system, and made recommendations for establishing a permanent bark beetle management program (Billings 1982). Additional visits have been made since then to evaluate the effectiveness of the management program and to provide additional pest management training (Billings 1988, 2001a). Color-illustrated field guides (Billings et al. 1990, 1996 a, b) on bark beetle management were prepared and published in Spanish for use in Honduras and, more recently, throughout Central America.
A key to success in Honduras was designating and training a national pest coordinator (role fulfilled by the same individual since 1982) and forest protection coordinators in each forest department. The latter are experienced foresters or technicians that coordinate detection and control programs for both fires and bark beetles at the local level.
The forestry school (Escuela Nacional de Ciencias Forestales or ESNACIFOR) in Siguatepeque is recognized throughout Central America for its forestry curricula and training programs. Most of the forest technicians involved in bark beetle control programs in Central America have either graduated from ESNACIFOR or attended at least one of the school’s training courses in bark beetle biology, detection, evaluation, and control.
As a result of COHDEFOR’s commitment to following the author’s recommendations (Billings 1982, 1988), Honduras now has the most comprehensive bark beetle management program in Central America. From 1984 through 2001, a total of 9,877 SPB infestations were detected in Honduras and 73% were controlled, primarily with cut-and-leave or cut-and-remove. The average size of controlled infestations was 2.1 ha./infestation (compared to 8.6 and 21.2 ha./infestation in 1982 and 1983, prior to implementation of the program). This track record suggested that Honduras should serve as the model for development of pest management programs in other Central American countries.
Belize
In 2000 and 2001, over 26,000 ha. of mature pine stands (Pinus caribaea and P. tecunumanii) in the Mountain Pine Ridge Forest Reserve suffered nearly 100% mortality from an outbreak of Dendroctonus spp. (Billings and Schmidtke 2002, Midtgaard and Thunes 2002). This was the first bark beetle outbreak in Belize in ca. 50 years. The casual agent is an undescribed species, closely related to both D. frontalis and D. vitei (Midtgaard and Thunes 2002), with attack dynamics similar to those of D. frontalis. The devastated area represents about 70% of the entire Forest Reserve and about 85% of its pine forests. Little direct control was applied and, by March 2002, the beetle outbreak had largely subsided (Billings and Schmidtke 2002).
Guatemala
Guatemala has 602,000 ha. of pine forests (Sharma 1992). Historically, the most severe bark beetle problems have occurred in the Altiplano Region and have involved Dendroctonus adjunctus infesting Pinus hartwegii (= P. rudis). From 1975-80, an outbreak of D. adjunctus killed an estimated 100,000 ha. of pine forests (Vité 1980). During the last decade, several small infestations of D. frontalis and D. valens have been detected and controlled in the Sierra de las Minas Biosphere Reserve in southeastern Guatemala, without causing major resource losses.
In 2000 and 2001, bark beetles, believed to be D. frontalis, killed nearly 3,000 ha. (40%) of the P. caribaea forests in the Petén Region of northeastern Guatemala. A total of 341 individual infestations were detected and average size after containment was ca. 9 ha. Due to a delayed response by the two government forestry agencies (Consejo Nacional de Areas Protegidas and the Instituto Nacional de Bosques), many infestations were larger than 10 ha. before controls were initiated. A variety of control methods was used, including cut-and-remove, chemical control, and cut-and-leave. The outbreak had subsided by March, 2002 (Billings and Schmidtke 2002).
Nicaragua
The range of Central America’s native pines ends in northern Nicaragua. This country supports 5.4 million ha. of native forests, but only 500,327 ha. of pines, primarily P. caribaea, P. oocarpa and P. tecunumanii. Nicaragua has been significantly impacted by natural disasters, including earthquakes, hurricanes, wildfires and bark beetle outbreaks. Since 1998, a major outbreak of D. frontalis killed over 32,581 ha. of pine forests, almost exclusively within the northern province of Nueva Segovia.
In May 2001, with the author’s technical assistance and emergency funds provided by the U.S. Department of Agriculture Hurricane Mitch Project and subsequently by the Nicaraguan government, an organized control effort was carried out to address the most recent outbreak. Under supervision of trained foresters, fifty local chainsaw crews installed extensive buffer strips (up to 200 m wide and 13 km long) to stop the spread of massive infestations. Then, cut-and-leave was used to treat smaller infestations as they were detected (Billings 2001b).
According to the Insitiuto Nacional Forestal (INAFOR), 5,600 ha. were treated, involving the felling of 1.4 million trees (575,421 cubic m). As a result of the aggressive, albeit delayed, control effort, over 35,000 ha. (53%) of the pine resource in the Department of Nueva Segovia were saved from potential destruction. The beetle outbreak has now been contained, although less than 30% of the felled timber and 5% of all the dead trees were salvaged (largely by skidding logs to available roads with teams of oxen). Beetle-affected areas became high risks for wildfires due to heavy fuel loads. There is also concern that treated areas will be converted to agricultural or grazing uses and not regenerated in pine forests.
El Salvador
Among the seven countries, El Salvador has the smallest amount of forest cover remaining with just 25,000 ha. of pines (Sharma 1992), coupled with the highest human population density (290 persons/square km). Both bark beetle outbreaks and fires threaten these fragmented forests. In 2000 and 2001, D. frontalis infested some 600 ha. of pines adjacent to the border with Honduras. The Forest and Wildlife Service (Servicio Forestal y de Fauna) has used cut-and-leave and cut-and-remove to keep losses to reasonable levels in areas where the few trained field crews are available.
The extensive loss of pine resources in Central America to bark beetles can be attributed to several common factors: 1) an abundance of dense unmanaged pine stands, weakened by frequent fires, resin extraction, and drought, 2) failure of forestry agencies to recognize and respond to the beetle outbreak in early stages of development (Nicaragua, Belize, Guatemala), 3) lack of forestry personnel trained in pest management (or rapid turnover or loss of trained personnel due to budget shortfalls, low salaries, or changes in governments), 4) insufficient funding to initiate and maintain detection and suppression programs, 5) lack of access to infestations, and 6) inadequate markets for beetle-killed trees. It is possible that Hurricane Mitch in 1998 further predisposed the region’s forests to bark beetle outbreaks.
In August 2002, in accordance with recommendations of Billings and Schmidtke (2002), a 5-day workshop was conducted in Siguatepeque, Honduras. The Norwegian Forest Trust, Inter-American Development Bank, USDA Foreign Agricultural Service, U. S. Agency for International Development, and the Texas Forest Service provided technical and/or financial support. Selected foresters or technicians with responsibilities in forest protection from each Central American country were brought together to develop a regional strategy for management of forest pests and wildfires in Central America.
The strategic plan that workshop participants proposed for forest pests involves establishment of a regional forest pest sub-committee organized under the forests committee of the Central American Environmental and Development Commission (CCAD). The CCAD consists of the ministers of agriculture from each country. The Forest Pest Sub-committee, made up of each country’s national pest coordinator, will meet periodically to standardize prevention and control programs, develop record-keeping systems, and share experiences in forest health programs. An Internet web page will be developed to share information throughout the region.
Recommendations also included initiation of bark beetle research within the region’s educational institutions, training of forestry personnel and forest landowners in pest management, and increased public awareness of forest pests. The plan calls for each country to establish (or maintain) a forest protection department with qualified staffs and a budgeted program to address pest problems. The strategic plan calls for detection, evaluation and prompt suppression of expanding infestations (Billings et al. 1990, Billings 1996 a, b) and maintaining permanent records of pest outbreaks and control efforts, approaches that have proven effective for two decades in Honduras.
Upon completion of the workshop, the regional pest management strategy was presented to and approved by members of CCAD. The heads of the forestry agencies, who make up a subordinate group of CCAD, also were in attendance. It is envisioned that these forestry heads will return with the framework and administrative support needed to implement the regional pest management strategy in their respective countries.
Billings, R.F. 1982. Evaluation and recommendations for control of the 1982 outbreak of Dendroctonus in the pine forests of Honduras. Unpublished report submitted to USDA Office of International Cooperation and Development and US Agency for International Development. 26 p.
Billings, R.F. 1988. Evaluation of the southern pine beetle outbreak and control program in Honduras: 1982-1988. Unpublished report submitted to USDA Office of International Cooperation and Development and US Agency for International Development. 23 p.
Billings, R.F. 1995. Direct control of the southern pine beetle: Rationale, effectiveness at the landscape level, and implications for future use of semiochemicals. IUFRO Joint Conference entitled “Behavior, population dynamics, and control and its rationale.” Maui, Hawaii. Feb. 6-11, 1994.
Billings, R.F. 2001 a. Evaluación de la plaga del gorgojo descortezador del pino (Dendroctonus frontalis) en los pinares de Honduras con recomendaciones para su control. Unpublished report prepared for Corporación Hondureña de Desarrollo Forestal, USDA Foreign Agricultural Service, Hurricane Mitch Project. 17 p.
Billings, R.F. 2001 b. Evaluación de la plaga del gorgojo descortezador del pino (Dendroctonus frontalis) en los pinares de Nicaragua y recomendaciones para su control. Unpublished report prepared for Instituto Nacional Forestal de Nicaragua, USDA Foreign Agricultural Service, Hurricane Mitch Project. 32 p.
Billings, R.F. and P. Schmidtke. 2002. Central American southern pine beetle/fire assessment. Unpublished report prepared for U.S. Agency for International Development and the USDA Foreign Agricultural Service, Washington, D.C. 45 p.
Billings, R,F,, J.E. Flores L., and R.S. Cameron. 1996a. Los escarabajos descortezadores del pino, con énfasis en Dendroctonus frontalis: Guía para la detección aérea. Texas Forest Service Publ. 149. 27 p.
Billings, R,F,, J.E. Flores L., and R.S. Cameron. 1996b. Los escarabajos descortezadores del pino, con énfasis en Dendroctonus frontalis: Métodos de control directo. Texas Forest Service Publ. 150. 27 p.
Billings, R.F., H.A. Pase III, and J.E. Flores L. 1990. Los escarabajos descortezadores del pino, con énfasis en Dendroctonus frontalis: Guia de campo para la inspección terrestre. Texas Forest Service Publ. 146. 19 p.
Hernandez Paz, M. 1975. El gorgojo de la corteza, plaga principal de los pinares. Pub1. 1, Corporación Hondureña de Desarrollo Forestal. 13 p.
Midtgaard, F., and K.H. Thunes. 2002. Pine bark beetles in the Mountain Pine Ridge Forest Reserve, Belize: Description of the species and how to monitor and combat the beetle infestations. Field Manual. Norwegian Forestry Group, Inter-American Development Bank. 18 p.
Sharma, N.P. (ed.). 1992. Managing the world’s forests: Looking for balance between conservation and development. Kendall/Hunt Publishing Co., Dubuque, Iowa. 605 p.
Silviagro S. de R.L. 1996. Analisis del sub-sector forestal de Honduras. Corporación Hondureña-Alemana, Programa Social Forestal. Tegucigalpa, Honduras. 496 p.
Thatcher, R.C., J.L. Searcy, J.E. Coster, and G.D. Hertel (eds). 1980. The Southern Pine Beetle. USDA Forest Service Tech. Bull. 1631. 266 p.
Vité, J.P. 1980. Planificación del control de la plaga del Dendroctonus (in Guatemala). P. 51-69. In: Planificación del control de la plaga del Dendroctonus y del aprovechamiento de la madera dañada. FAO Report TCP/GUA/8003.
Vité, J.P., R. Lühl, P.R. Hughes, and J.A.A. Renwick. 1975. Pine bark beetles of the genus Dendroctonus: Pest problems in Central America. FAO Plant Protection Bull. 23: 178-184.
Wood, S.L. 1982. The bark and ambrosia beetles of North and Central America (Coleoptera: Scolytidae), a taxonomic monograph. Great Basin Naturalist Memoirs No. 6. 1359 p.
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