-The objective of this work was to evaluate the natural attack by Acromyrmex crassispinus in initial Pinus taeda plantations without control measures against ants, as well as the effect of defoliation in seedlings of P. taeda. Evaluations of the attack of leaf-cutting ants on P. taeda plantations were done monthly in the first six months, then 9 and 12 months after planting. The percentages of plants that were naturally attacked by ants were registered. The effect of defoliation was evaluated by artificial defoliation, simulating the natural patterns of attack by A. crassispinus on P. taeda seedlings. The natural attack of A. crassispinus was greater during the first months after planting, being more intense in the first 30 days. Artificial defoliation indicated that there were no significant losses in diameter and height in plants with less than 75% defoliation. However, there were significant losses in diameter and height in plants with 100% defoliation, independently of the cut of the apical meristem, and also plant death. The control of leaf-cutting ants in P. taeda plantings, in which A. crassispinus is the most frequent leaf-cutting ant, should be intense only at the beginning of planting, since the most severe attacks occur during this time.Index terms: Acromyrmex crassispinus, Pinus taeda, artificial defoliation, forest pest. Ataque de formigas cortadeiras em plantios iniciais de pinus e crescimento de plantas desfolhadasResumo -O objetivo deste trabalho foi avaliar o ataque natural de Acromyrmex crassispinus em plantios iniciais de Pinus taeda sem controle contra formigas, bem como o efeito da desfolha em mudas de P. taeda. As avaliações do ataque de formigas cortadeiras em plantios de P. taeda foram realizadas mensalmente nos primeiros seis meses, depois aos 9 e 12 meses após o plantio. As percentagens de plantas naturalmente atacadas por formigas foram registradas. O efeito da desfolha foi avaliado por meio do desfolhamento artificial, ao se simularem os ciclos naturais de ataque de A. crassispinus em mudas de P. taeda. O ataque natural de A. crassispinus foi maior nos primeiros meses após o plantio, tendo sido mais intenso durante os primeiros 30 dias. A desfolha artificial indicou que não houve perdas significativas no diâmetro e na altura de plantas com menos de 75% de desfolha. No entanto, observaram-se perdas significativas no diâmetro e na altura de plantas 100% desfolhadas, independentemente do corte da gema apical, e também a morte de plantas. O controle de formigas cortadeiras em plantios de P. taeda, em que A. crassispinus é a formiga cortadeira mais frequente, deve ser intenso somente no início do plantio, pois os ataques mais severos ocorrem neste período.Termos para indexação: Acromyrmex crassispinus, Pinus taeda, desfolha artificial, praga florestal.
Leaf-cutting ants are well-known insects due to their remarkable activity as herbivores and the considerable economic damage they cause to many crops. The identification of season and time of day when leaf-cutting ants are most active is an important tool, not just to understand the foraging ecology of these ants, but also to optimize their control in plantation areas where they were pests. Thus, the aims of this study are to evaluate the daily foraging activity of leaf-cutting ant species of the genus Acromyrmex, which occur in forest plantations in Southern Brazil. Foraging activity of Acromyrmex crassispinus (Forel) and Acromyrmex subterraneus subterraneus (Forel) were correlated with weather conditions, and it was more intense during spring and summer. Workers that forage at night are significantly heavier than workers that forage during the day. This study showed that A. crassispinus and A. subterraneus subterraneus did not forage at temperatures below 10-11°C. Then, the use of granulated baits to control these leaf-cutting ants species where they were pests should be done just under favorable conditions of temperature for Acromyrmex foraging activity (over 12°C), to ensure maximum collection of baits by ants and the least left-over baits.
Resumo -O objetivo deste trabalho foi avaliar a densidade e o tamanho dos formigueiros de Acromyrmex crassispinus, ao longo do ano, em plantios de Pinus taeda de diferentes idades. Os experimentos foram realizados, em Rio Negrinho e em Três Barras, SC, em talhões de P. taeda com diferentes idades (recém-plantado, três anos e seis anos de idade). Em cada tratamento, foram demarcadas três parcelas de 1 ha. Os formigueiros foram classifi cados em três classes de tamanho: classe I, até 30 cm de diâmetro; classe II, 31 a 60 cm; e classe III, mais que 61 cm. A densidade de formigueiros de A. crassispinus foi menor no início do desenvolvimento da fl oresta, praticamente duplicou nos plantios com três anos, e reduziu quando a fl oresta estava com seis anos. A maior densidade de formigueiros ocorreu no período de dezembro a abril. Os formigueiros aumentaram de tamanho com a idade do pínus Termos para indexação: Formicidae, formigas cortadeiras, praga fl orestal, refl orestamentos. Density and size of Acromyrmex crassispinus nests in Pinus taeda plantationsAbstract -The objective of this work was to evaluate the density and size of Acromyrmex crassispinus nests in Pinus taeda plantations along the year. The experiments were carried out in Rio Negrinho and Três Barras, SC, Brazil, in P. taeda plantations of different ages (recently planted and three and six years old). Three plots of one hectare were delimited in each treatment. The nests were classifi ed according to three size classes: class I, up to 30 cm diameter; class II, 31 up to 60 cm; class III, above 61 cm. The density of A. crassispinus nests was low in recently planted areas, nearly twofold in three year-old plantations, and it reduced when the forest was six years old. The greatest nest density occurred in the period from December to April. The nests size increased along with the age of the P. taeda plantations.Index terms: Formicidae, leaf-cutting ants, forest pests, reforestation. IntroduçãoA produção e o aproveitamento da madeira são importantes, pois existe uma crescente demanda do produto como matéria-prima em vários segmentos produtivos. As plantações comerciais visam a suprir essa demanda. A área cultivada com espécies fl orestais, no Brasil, corresponde a aproximadamente 5,6 milhões de hectares, sendo 3,4 milhões de hectares com Eucalyptus spp., 1,8 milhão de hectares com Pinus spp. e 326 mil hectares com outras espécies. No Sul do país, cerca de 80% das fl orestas plantadas são constituídas de Pinus taeda L., devido à sua alta produtividade e qualidade de matéria-prima (Sociedade Brasileira de Silvicultura, 2006).Entre os problemas silviculturais dessas fl orestas implantadas, sobressaem as formigas cortadeiras dos gêneros Atta (saúvas) e Acromyrmex (quenquéns), que alcançaram o nível de praga pela magnitude dos prejuízos que causam aos plantios fl orestais.As saúvas e as quenquéns usam exclusivamente substratos vegetais para o cultivo do fungo que utilizam na alimentação, destacando-se como formigas cortadeiras de importância econômica. São nocivas a...
Acromyrmex species primarily attack Pinus taeda plantations during the first months after planting, with more intense damage in the first 30 days. 2 We evaluated potential damage by Acromyrmex crassispinus and Acromyrmex subterraneus in 30-day-old P. taeda plantations in southern Brazil by assessing the number of attacked plants and the distance reached by each colony, along with the losses in plant development resulting from different levels of defoliation. 3 Both species were significant pests in newly established pine plantations. A single colony can attack a substantial number of seedlings (up to 453 seedlings). Colonies with larger nests attacked more plants and ranged farther; A. crassispinus reached 59 m and A. subterraneus 87 m. 4 After 10 years, no significant losses in plant development were seen in seedlings defoliated less than 50% at 30 days after planting. But when defoliation of the young plants attained 75%, 100%, and 100%, including the cut of the apical meristem, volume losses reached 32%, 37%, and 43%, respectively. 5 Leaf-cutting ant controls should be carried out in plantations of P. taeda within 30 days of planting to avoid attacks. When seedlings are defoliated more than 75%, they should be replanted to avoid future losses in final wood volume.
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