BIOLOGICAL PEST CONTROL IN THE NEOTROPICS
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In the Neotropics, including islands of the Caribbean, biological control represents the most economically viable, environmentally sound and self sustaining method of insect pest control, and it has been a source of beneficial natural enemies in California and elsewhere (Please refer to California Research #1, #2, #3). The earliest recorded effort of classical biological control in this region dates back to the beginning of the 19th Century when the coccinellids, Hippodamia convergens Guerin-Meneville and Rhizobius ventralis (Erichson) were introduced to Chile from California for the control of scale insects (Gonzalez & Rojas 1966). In 1904 natural enemies were introduced into Peru for the control of white scale, Pinnaspis strachani (Cooley), in cotton, and in 1980 Prospaltella (= Encarsia) berlesi (Howard) was introduced to Argentina to combat the white peach scale, Pseudaulacaspis pentagona (Targioni-Tozzetti) (Hagen & Franz 1973, Altieri et al. 1999). These efforts were supplemented by the establishment of specialized insectaries in Mexico in 1928, Chile in 1929 and later Peru, Argentina, Brazil, Colombia and Nicaragua. Most of this early work was concentrated on citrus pests, because citrus had marked the beginning of biological control efforts in 1888. This work was initiated by the Department of Biological Control, University of California, Riverside, which was for decades a world center for mass rearing and distribution of natural enemies of citrus pests. Other efforts were later initiated in sugarcane, apples, peaches, olives, alfalfa, cotton and other field crops.
The principal successes in classical biological control in the Neotropics include the citrus blackfly, Aleurocanthus woglumi Ashby in Mexico and Central America; the sugarcane borer, Diatraea saccharalis (F.) in Cuba, Peru, Brazil and the Caribbean; the cottony-cushion scale, Icerya purchasi (Maskell) in Chile; the woolly apple aphid, Eriosoma lanigerum (Hausm.) in Uruguay, Chile and Argentina; the black scale, Saissetia oleae (Olivier) controlled by Aspiditophagus (= Metaphycus) lounsbury (Howard) in Chile and Peru, and several species of mealybugs and scale insects in various countries (Gonzalez 1976, MacPhee et al. 1976).
Interest in biological control noticeably declined for about two decades following the advent of chemical insecticides after World War II. However, the environmental costs associated with many organochlorine insecticides, and the restrictions placed on residue levels of exported meats, vegetables and fruits by markets in Europe and the United States, precipitated a renewed interest in biological control, but mostly as a component of Integrated Pest Management.
Altieri et al. (1999) reviewed the pesticide situation in Latin America, specifically. Between 1980 and 1984 about 430 million U.S.$ worth of pesticides were imported, with expenditures expected to triple over the next decade, especially in Brazil, Mexico, Argentina and Colombia (Maltby 1980). Use of most organochlorine insecticides was expected to decline, but organophosphates, carbamates and especially pyrethroids was expected to increase, with most being imported from industrialized countries (gonzalez 1976). Cotton accounts for most of the insecticide use in Latin America at a level of about 6 kg. of pesticide per hectare. Several years ago in El Salvador and Guatemala, 75% of the total pesticide consumption was devoted to cotton which received up to 35 applications per season. Such an excessive number of treatments resulted in serious public health problems as well as ecological disturbances. Apple and pear orchards still receive up 8-16 treatments per season in the southern parts of this region (Chile, Argentina, Uruguay and southern Brazil), and most fruit trees in the tropical and subtropical areas are heavily treated for fruit fly control. Among the vegetable crops, tomatoes and potatoes account for the greatest pesticide use (Maltby 1980).
Although there has been general concern about the environmental and public health impact of pesticides and their toxic residues in the region, comparatively little information is available on the dimensions of environmental contamination (Burton & Philogene 1984). This lack has led to the belief that pesticides are not likely to cause sufficient environmental disruption or to seriously affect the continued growth of agriculture (Murdoch 1980). What data is available, however, contradicts this viewpoint (Leonard 1986). Between 1971 and 1976 more than 19,000 pesticide poisonings were reported in Central America, mostly in Guatemala and El Salvador. In Nicaragua more than 3,000 cases of poisoning and over 400 deaths occurred yearly from 1962-1972. In Costa Rica pesticide poisonings averaged about 550 per year. Parathion has been largely responsible for intoxication in many countries (Almeida & Pereira 1963). Organochlorine concentrations in human blood, fat tissue and mothers' milk had also reached alarming levels in many countries (ICAITI 1977). The few pesticide surveys conducted in ecosystems of the area have basically confirmed trends observed elsewhere. In cotton growing areas of Central America, malaria resurgence has reoccurred mainly due to the fact that mosquitoes have developed pesticide resistance (Leonard 1986). Residues of organochlorine insecticides have been detected in fish and several other invertebrate species, especially in estuaries and areas near cotton fields (Giam et al. 1971). Up to 1970 over 35 cases of insecticide resistance had already been detected, including important cotton, banana and stored grain pests (Gonzalez 1976).
The growing use of pesticides is influenced by government subsidies which lower the costs to farmers. In countries such as Honduras, Colombia and Ecuador, the rate of subsidies can be as high as 45% of retail costs (Repetto 1985).
Argentina.--From 1900 to 1979, 46 natural enemy species were imported to control 21 pest species. Of these 18 became established and 14 achieved partial control and four achieved complete control. Seven of the 21 main pests targeted are under permanent biological control. Among the successful introductions are Prospaltella (Encarsia) berlesi against the white peach scale, Aphelinus mali (Haldeman) against the woolly apple aphid and Rodolia cardinalis (Mulsant) against the cottony-cushion scale.
Brazil.--There have been several natural enemies imported into Brazil against a limited number of hosts. Aphelinus mali introduced in 1923 gave substantial control of the woolly apple aphid, and P. berlesi has achieved complete control of the white peach scale since 1921. Poor results were obtained with the introduction of Prorops nasuta Waterston and Tetrastichus giffardianus Silv. against the coffee berry borer Hypothenemus hampei (Ferris) and the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), respectively (Clausen 1978). Three species of tachinids Lixophaga diatraeae (Townsend), Metagonistylum minense Townsend, and Paratheresia claripalpis (Wulp) have been released against the sugar cane borer and are still being used in plantations. Apanteles flavipes (Cam.) was introduced and achieved up to 62% parasitization in south central Brazil (Macedo 1983). In 1978 a large biological control program against cereal aphids was initiated in southern Brazil. Fourteen species of hymenopterous parasites and two coccinellids, Hippodamia quinquesignata Kirvy and Coccinella septempunctata L. were introduced from Europe and Chile. Good adaptation and significant impact was observed on Sitobium avenae (L.) by Aphidius uzbekistanicus Luzhetski and Aphidius rhophalosiphi de Stephani, and on S. avenae and Metopolophium dirhodum (Walker) by Praon volucre (Haliday) (Gassen 1983). As of 1991 there are active programs in cassava, soybean, coffee and cotton.
Central America.--The only recorded cases of classical biological control in this portion of Latin America are those directed against the citrus blackfly, Aleurocanthus woglumi Ashby, which was introduced into Panama and Costa Rico in the 1920's. Eretmocerus serius was introduced into Panama in 1931 and to Costa Rica in 1933-34 (Clausen 1978). Since then the pest has been under excellent biological control (Elizondo 1987). The citrus blackfly also invaded El Salvador around 1965, and the introduction of Encarsia opulenta in 1971 brought about a complete control of the pest (Quezada 1974). A recent effort against Mediterranean fruit fly was made in Costa Rica by F. Gilstrap (pers. commun.) of Texas A. & M. University. Parasitoids from Cameroon, West Africa were liberated in coffee plantations at Turrialba, with some field reproduction being reported. This work which was supported by the U. S. Dept. of Agriculture, was unfortunately terminated before a thorough appraisal could be made.
Chile.--As in other South American countries, A. mali was imported against E. lanigerum and R. cardinalis against I. purchasi and Icerya palmeri Riley & Howard (Hagen & Franz 1973). In Chile between 1903-1984, ca. 66 species of beneficial insects were introduced against several pest species of crops such as citrus, grapes, peach, apple and potato. Forty two of these species became adapted and established. Sixty percent of the targeted pests are under complete or substantial control, 38% of the introduced predators and 24% of the parasitoids are responsible for maintaining pests at relatively low population densities. Recent efforts at the La Cruz experiment station have resulted in substantial control of whiteflies by Amitus spiniferus (Brιthes), various lepidopterous pests by Trichogramma spp., alfalfa aphid Acyrthosiphon pisum (Harris) by Aphidius smithi Sharma & Subba Rao, and Pieris brassicae (L.) by Apanteles glomeratus (L.). It is estimated that biological control of several pests , i.e., Aonidiella sp. and several species of Aphididae and the purple scale, Lepidosaphes beckii (Newmann) have saved the Chilean citrus industry ca. $US900,000 per year in pesticide costs (Gonzalez & Rojas 1966, Zuniga 1985).
Colombia.--Aphelinus mali was introduced from the United States in 1933 and complete control of Eriosoma lanigerum was obtained. In neighboring Venezuela, R. cardinalis was introduced in 1941 for control of Icerya purchasi. Recent attempts to control Diatraea saccharalis have involved the introduction and mass release of the Peruvian race of Paratheresia claripalpis Wulp. which has a shorter life cycle than the native race (Hagen & Franz 1973).
Cuba.--A most outstanding biological control success was the 1930 introduction of Eretmocerus serius Silv. against the citrus blackfly. Full economic control was rapidly attained (Hagen & Franz 1973).
Mexico.--In 1935 E. serius was introduced against the citrus blackfly. It became established and controlled the pest mostly in humid areas. A further search for parasitoids was made in semi-arid regions of asia and four additional parasitoids were found and established, three of which became dominant in both humid and dry climates. Amitus hesperidium Silvestri became by far the most effective parasitoid, which was then extensively released in the 1950's by the newly organized Departamento de Control Biolσgico de Defensa Agrνcola (Hagen & Franz 1973).
Several parasitoids were introduced during 1954-55 from Hawaii for the control of the Mexican fruit fly, Anastrepha ludens (Loew) which is native to Mexico. A large scale production program was initiated, and in five years more than 7 million Aceratoneuromyia indica (Silv.) were released. This parasitoid quickly became established, accounting for parasitization of up to 80% and lowered fruit damage to about 30% in Morelos, Oaxaca, Veracruz, Michoacαn and other states (Clausen 1978).
Aphytis holoxanthus DeBach was released against the Florida red scale Chrysomphalus aonidum (L.) in 1957 in Morelos and infestations in citrus groves were drastically reduced within one year. Releases in 1954 of Aphytis lepidosaphes Compere against the purple scale also resulted in effective biological control (Clausen 1978). In Baja California the woolly whitefly has been controlled with parasitoids originally introduced to California.
Peru.--The woolly apple aphid was controlled by A. mali and cottony-cushion scale by Rodolia cardinalis. The black scale was controlled by three imported parasitoids from the United States. Cotton white scale biological control was achieved with several parasitoids once cultivation practices were altered. There have been altogether 12 cases of successful classical biological control in Peru: one case in cotton, five in citrus, two in olive one in alfalfa and one in sugarcane (Aguilar 1980). The most recent successes were in the 1970's with the introduction of Aphytis roseni DeBach and Cales noacki Howard against Selenaspidus articulatus Morgan and Aleurothrixus floccosus (Maskell) on citrus. Aphidius smithi was also introduced against Acrythosiphon pisum (Harris) in alfalfa. At the national insectary CICIU, the yearly production of Trichogramma was 131 million wasps in 1976 which were distributed over ca. 1,300 ha. at a rate of 100,000 wasps per ha. (Klein Koch 1977).
There were, of course, many more introductions in the Neotropics against fruit flies, coffee berry borer, oriental fruit moth, etc., but documentation is lacking (Clausen 1978). Countries not mentioned sustained little biological control activity. For instance, introductions of natural enemies in countries surrounding Uruguay resulted in complete biological control of cottony-cushion scale and white peach scale in that country also.
There are few research centers totally devoted to biological control in the Neotropics. Earlier in this century, there were only three centers: the INTA Castelar Insectary in Argentina, INIA's experimental substation in La Cruz, Chile and the Centro de Introducciσn y Crνa de Insectos Utiles (CICIU) in Lima, Peru. In Argentina the U. S. Dept. of Agriculture opened a subsidiary laboratory of biological control of weeds in Hurlingham near Buenos Aires, which although mostly devoted to quarantine and selectivity studies of weed herbivores for introduction into the United States, sponsored activities which led to the successful biological control of the water hyacinth, Eichornia crassipes Solms by Neochetina bruchi Hust. in the La Rioja region. In 1970 the Universidad de Tucuman established in San Miguel de Tucuman the Centro de Investigaciones Sobre Regulaciones de Poblaciones de Organismos Nocivos (CIRPON), a center devoted to the integrated and biological control of citrus and soybean pests. CIRPON also conducts regular training courses in IPM, biological control and agroecology with participation from graduates from all over Argentina. In Brazil four laboratories and 23 multiplication units were established by the Programa Nacional de Melhoramiento de Cana de Azucar, for the mass rearing and release of Apanteles flavipes and tachinid parasitoids for sugarcane borers. Brazil's agricultural research center, EMBRAPA, has also built insectaries and laboratory facilities in southern Brazil to support the cereal aphid biological control program initiated in the late 1970's.
In Colombia private sugarcane plantations have organized small insectaries for the mass rearing of sugarcane borer parasitoids and Trichogramma wasps. In Mexico, the government established a national system (CRIA) for the mass production of Trichogramma spp. and other beneficial organisms. Otherwise private or government groups have variously initiated small efforts to deal with specific pest problems. Examples are the projects in Venezuela against Diatraea spp. which resulted in 50% damage reduction following the introduction of Metagonistylum minense Townsend (Clausen 1978), the releases of two predators in the Dominican Republic against the coconut scale in 1937 (Gomez-Menor 1937), and in Colombia against cypress sawfly (Drooz et al. 1977).
There is a long and rich tradition of biological control in Latin America, especially in Chile, Argentina, Peru, Brazil, Colombia and Mexico. The early success of biological control of citrus pests obtained in California triggered a number of introductions into the citrus growing areas of the continent, thus promoting wide interest in biological control. Other projects followed such as those in sugarcane, cotton, peaches, olives and wheat. The current economic and social juncture in the region calls for more lo input approaches to agriculture. Classical biological control should be at the forefront of any sustainable agricultural development effort, complemented by agroecosystem management schemes (i.e., intercropping, crop rotations, cover crops), that not only aid biological control agents but that conserve the soil and make the agroecosystems less dependent on fertilizers, herbicides and other chemical inputs.
There is a successful case of biological control of Oxydia trychiata (Guenee) in Colombia regulated by Telenomus alsophilae Viereck from eastern North America (Bustillo & Drooz 1977, Drooz et al. 1977).
A number of economically important arthropod pests in the Neotropics could probably be controlled with the establishment of key natural enemies. Following is a list of such possibilities:
The list could unquestionably be greatly enlarged were additional studies made in the respective areas, the present one reflecting a disproportionate attention in Central America.