Controle integrado de Spodoptera frugiperda (Smith & Abbott) utilizando-se o parasitóide Telenomus remus Nixon

This study was conducted in 1996 and 1997 to evaluate the efficiency of releasing Telenomus remus Nixon (around 200,000 adults/ha) alone or integrated to Spodoptera frugiperda (Smith & Abbott) Spodoptera frugiperda nuclear polyhedrosis virus (SFNPV) or to a selective insecticide to control the insect. The experimental design was a randomized complete block with six treatments and four replications. Leaf damage caused by the pest (visual scale from 0 to 5) and the grain yield were evaluated. In general, the damage was significantly higher in the check plots (average of 2.94) than in the other treatments (average of 1.04). Similarly, there was significant difference in yield between check plots (7,165 kg/ha) and the other treatments (9,084 kg/ha). There was no difference in ear length and damage caused to the ear among treatments.Este estudo foi conduzido em 1996 e 1997 para avaliar a eficiência da liberação de Telenomus remus Nixon (cerca de 200.000 adultos/ha), sozinho ou integrado ao vírus de poliedrose nuclear de Spodoptera frugiperda (VPNSf) ou a um inseticida químico seletivo, para o controle de Spodoptera frugiperda (Smith & Abbott). Os experimentos foram conduzidos em delineamento experimental de blocos ao acaso, com seis tratamentos e quatro repetições. Foram avaliados os danos provocados pela praga às folhas (escala de 0 a 5) e o rendimento de espigas. De maneira geral, os danos provocados pela praga foram significativamente superiores nas parcelas testemunhas (nota média de 2,94). Não houve diferença significativa entre os demais tratamentos (média 1,04). De maneira semelhante, houve diferença significativa no rendimento de espiga entre testemunha (7.165 kg/ha) e demais tratamentos (9.084 kg/ha). Não houve efeito dos tratamentos no comprimento da espiga e no dano às espigas

Age Polyethism in Atta sexdens (Linnaeus) (Hymenoptera: Formicidae)

This study aimed to verify age polyethism occurrence in medium-sized (cephalic capsule = 2.3 ± 0.21 mm) and small-sized (cc = 1.4 ± 0.10 mm) workers from Atta sexdens (Linnaeus) colonies. Four laboratory colonies were used, and they were maintained at 25 ± 2 °C, with 75 ± 3% relative humidity and a 12-hour photoperiod. Workers from these colonies were marked after their emergence and observed throughout their lifetime to determine which tasks they performed. The number of ants performing each activity was analyzed using linear mixed-effect models (LME), considering the temporal effect and the block design (colonies). We found that fungal garden maintenance tasks were frequent for both sizes, but their occurrence decreased significantly from the ninth week. The foraging activity occurred gradually in both sizes, with stabilization in the number of workers from the fourth week onwards and declined in the last three weeks of lifespan. Waste management tasks occurred throughout life but were more frequent during the first two weeks of life, in both medium and small workers. Therefore, age polyethism may be related to all activities; however, foraging tasks presented a distinct pattern compared to tasks in the fungus garden and refuse dump, where younger ants were more frequently observed

Recognition and Aggression of conspecific and heterospecific worker in Acromyrmex subterraneus subterraneus (Forel) (Hymenoptera: Formicidae)

Aggressive behavior is important for social insects because it makes possible for the colony to defend itself and the offspring from the action of invasive species. We studied the recognition and aggressiveness of the leaf-cutting ant Acromyrmex subterraneus subterraneus (Forel) to co-specific workers from other nest and heterospecific workers of Acromyrmex subterraneus molestans Santschi, Acromyrmex subterraneus brunneus (Forel) and Acromyrmex niger (Smith); and queens of their social parasite Acromyrmex ameliae De Souza, Soares and Della Lucia. Workers of other species were placed in contact with those of A. subterraneus subterraneus for three minutes and during this period the behavioral interactions were quantified. The aggressiveness index (AI) for each agonistic encounter was obtained. Acromyrmex subterraneus subterraneus workers exhibited greater aggressiveness against heterospecific than against conspecific competitors. Aggressiveness is connected to differences in the chemical profiles, which are larger in heterospecifics colonies

Phorid Flies Parasitizing Leaf-Cutting Ants: Their Occurrence, Parasitism Rates, Biology and the First Account of Multiparasitism

The leaf-cutting ants Atta sexdens (Linnaeus) and Atta laevigata (Smith) were parasitized by the following phorid flies: Apocephalus attophilus Borgmeier, Apocephalus vicosae Disney, Myrmosicarius grandicornis Borgmeier and species of Eibesfeldtphora Disney. It is also related here that the area of occurrence of phorids parasitizing A. sexdens was extended to include Central Brazil. The rate of parasitism on A. sexdens was three times lower than the rate found on A. laevigata; most common flies were, respectively, M. grandicornis in A. sexdens and A. attophilus in A. laevigata. This last phorid showed the shortest life span but the higher percentage of emergence. Multiparasitism on workers of A. sexdens and of A. laevigata involving three combinations of four phorid species was rare and is here related for the first time for leaf-cutting ants

Atratividade de Atta sexdens rubropilosa por plantas de eucalipto atacadas previamente ou não por Thyrinteina arnobia

The induced defense system of plants is activated after the occurrence of damage by a herbivore. The objective of this work was to evaluate whether plants of Eucalyptus grandis previously attacked by larvae of Thyrinteina arnobia become resistant to cutting by the leaf-cutting ant Atta sexdens rubropilosa. There was no significant difference in the lapse of time spent by the workers of this ant before they started cutting plants previously attacked or not. There was significant reduction in the size of leaf fragments cut by the ants. It was concluded that plants previously attacked were less attractive to the leaf cutter due to the activation of their induced defense system.O sistema de defesa induzido das plantas é ativado após a ocorrência do dano provocado por um herbívoro. O objetivo deste trabalho foi avaliar se plantas de eucalipto (Eucalyptus grandis) atacadas previamente por lagartas de Thyrinteina arnobia tornam-se resistentes ao corte de operárias de Atta sexdens rubropilosa. Não houve diferença significativa no tempo gasto por operárias dessa formiga em iniciar o corte em plantas atacadas ou não. Porém, houve diferença significativa no tamanho de fragmentos cortados. Concluiu-se que plantas previamente atacadas tornam-se menos atrativas para A. sexdens rubropilosa devido à ativação do seu sistema de defesa induzido

Eucalyptus growth under the effect of artificial defoliation

O objetivo deste trabalho foi avaliar os efeitos do desfolhamento total, realizado após o plantio e ao longo do primeiro ano de cultivo, sobre o crescimento de Eucalyptus grandis, desde a implantação até ao corte do povoamento. Foram avaliados cinco tratamentos: sem desfolhamento; um desfolhamento aos 56 dias após o plantio (DAP); dois desfolhamentos, aos 56 e 143 DAP; dois desfolhamentos, aos 56 e 267 DAP; e três desfolhamentos, aos 56, 143 e 278 DAP. Foram mensurados os diâmetros do tronco a 1,3 m e a altura total de 60 árvores por tratamento, em oito avaliações, do 21º ao 92º mês de cultivo. O crescimento médio em cada tratamento foi descrito por modelos de regressão não lineares e comparados por testes de identidade para comparar as tendências entre a testemunha e os demais tratamentos. O desfolhamento causou reduções significativas nas taxas de crescimento em diâmetro e altura das plantas, e diminuição expressiva no faturamento ao final da rotação, mesmo quando realizado uma única vez, no início do plantio. Maiores danos, no entanto, foram verificados após consecutivos desfolhamentos ao longo do primeiro ano de cultivo. A manutenção de áreas que tenham sofrido desfolhamento total na fase inicial de plantio pode tornar-se uma medida economicamente inviável.The objective of this work was to evaluate the effects of total defoliation at planting initial stages, and along the first year of cultivation, on Eucalyptus grandis growth, from planting to plantation cut. Five treatments were tested: without defoliation; one defoliation, at 56th day after planting (DAP); two defoliations, at 56th and 143rd DAP; two defoliations, at 56th and 267th DAP; and three defoliations, at 56th, 143rd and 278th DAP. Trunk diameter at 1.30-m height and the total height of 60 trees were measured from the 21st to the 92nd cultivation months. The average growth of each treatment was described by nonlinear models and compared by identity tests in order to estimate the tendencies between control and the other treatments in each variable. Defoliation significantly reduces diameter of the trunk and height growth rates, and expressively decreases the income at the plantation cut. However, greater losses were verified after consecutive defoliation, along the first cultivation year. Maintaining areas that suffered severe defoliations at initial planting stages can become economically unfeasible

CUTTING PREFERENCE OF Eucalyptus spp. BY THE LEAF-CUTTING ANT Acromyrmex laticeps nigrosetosus FOREL, 1908 (HYMENOPTERA: FORMICIDAE) UNDER LABORATORY CONDITIONS

O objetivo deste trabalho foi avaliar a prefer\ueancia de corte das oper\ue1rias de Acromyrmex laticeps nigrosetosus Forel, 1908, em tr\ueas esp\ue9cies e um clone de eucalipto. Plantas de Eucalyptus urophylla S.T. Blake, 1977, Eucalyptus cloeziana F. Muell., 1878, Eucalyptus camaldulensis Dehnh., 1832, e o Clone 129 foram oferecidas, simultaneamente, para tr\ueas col\uf4nias de Acromyrmex laticeps nigrosetosus Forel, 1908. O bioensaio finalizou 6 horas ap\uf3s o seu in\uedcio ou at\ue9 que uma das col\uf4nias cortasse todas as folhas de um dos eucaliptos oferecidos. As col\uf4nias cortaram e carregaram, em m\ue9dia, 0,453g \ub1 0,064 de Eucalyptus camaldulensis; 0,384g \ub1 0,052 do Clone 129; 0,341g \ub1 0,054 de Eucalyptus urophylla e 0,102 \ub1 0,027 de Eucalyptus cloeziana, sendo essa \ufaltima a esp\ue9cie menos preferida para o corte. Por outro lado, n\ue3o houve diferen\ue7a significativa entre a quantidade de folhas cortadas nos outros eucaliptos.The objective of this research was to evaluate the cutting preference of Acromyrmex laticeps nigrosetosus workers among three species and a Clone of eucalypt. The seedlings of Eucalyptus spp. were offered simultaneously to three colonies of this leaf-cutting ant under laboratory conditions. The assay ended six hours after initial offering or until the workers of a colony cut all leaves of a certain eucalyptus species. On the average, colonies cut and carried 0.453g \ub1 0.064 of Eucalyptus camaldulensis; 0.384g \ub1 0.052 of Clone 129; 0.341g \ub1 0.054 of Eucalyptus urophylla and 0.102g \ub1 0.027 of Eucalyptus cloeziana. This last species was the least preferred for cutting and carrying. On the other hand, there was no significant difference among the amount of leaves cut from the other eucalypts

Ant Community Evolution According to Aging in Brazilian Cocoa Tree Plantations

Agriculture is frequently held accountable for the depletion of biotic diversity, although a few agroforestry systems support the conservation of a number of organisms. Cocoa farming is noteworthy as an example of an agricultural activity that benefits or maintains species richness. However, the mechanism by which the biodiversity persists throughout the entire process of plant development remains obscure. In Southeastern Bahia, Brazil, cacao tree plantations support the conservation of a large amount of organisms native to the Atlantic Forest, between them the ants. This study aims at recording the relationship between cocoa tree development and ant community structure. The experiment was carried out in a series of six cocoa tree plantations aged one, three, four, eight, fifteen and 33 years, distributed across the experimental grounds of the Cocoa Research Center at Ilhéus. 1,500 ant samples were collected using the sampling techniques: hand collection, honey and sardine baits, entomological blanket and “pitfall”. Highest values for diversity and richness were reported in the 15-years-old cocoa plantation. No significant correlations between diversity, richness or plant age were reported. Considering the faunistic composition, a statistical similarity was observed between the plantations close in age to one another. Plant aging did not exert any influence on the diversity gradient and richness in the succession process of the ant community. In young plantations, there are low differences between the ants found on the ground and the ones found on the young cocoa trees. In older plantations, the ant community divides in two distinct assemblages on the ground and on the trees. The variations observed in the ant community along the plant development were likely caused by the structural organization of the dominant species mosaic

Crescimento de eucalipto sob efeito de desfolhamento artificial

O objetivo deste trabalho foi avaliar os efeitos do desfolhamento total, realizado após o plantio e ao longo do primeiro ano de cultivo, sobre o crescimento de Eucalyptus grandis, desde a implantação até ao corte do povoamento. Foram avaliados cinco tratamentos: sem desfolhamento; um desfolhamento aos 56 dias após o plantio (DAP); dois desfolhamentos, aos 56 e 143 DAP; dois desfolhamentos, aos 56 e 267 DAP; e três desfolhamentos, aos 56, 143 e 278 DAP. Foram mensurados os diâmetros do tronco a 1,3 m e a altura total de 60 árvores por tratamento, em oito avaliações, do 21º ao 92º mês de cultivo. O crescimento médio em cada tratamento foi descrito por modelos de regressão não lineares e comparados por testes de identidade para comparar as tendências entre a testemunha e os demais tratamentos. O desfolhamento causou reduções significativas nas taxas de crescimento em diâmetro e altura das plantas, e diminuição expressiva no faturamento ao final da rotação, mesmo quando realizado uma única vez, no início do plantio. Maiores danos, no entanto, foram verificados após consecutivos desfolhamentos ao longo do primeiro ano de cultivo. A manutenção de áreas que tenham sofrido desfolhamento total na fase inicial de plantio pode tornar-se uma medida economicamente inviável.The objective of this work was to evaluate the effects of total defoliation at planting initial stages, and along the first year of cultivation, on Eucalyptus grandis growth, from planting to plantation cut. Five treatments were tested: without defoliation; one defoliation, at 56th day after planting (DAP); two defoliations, at 56th and 143th DAP; two defoliations, at 56th and 267th DAP; and three defoliations, at 56th, 143th and 278th DAP. Trunk diameter at 1.30-m height and the total height of 60 trees were measured from the 21st to the 92th cultivation months. The average growth of each treatment was described by nonlinear models and compared by identity tests in order to estimate the tendencies between control and the other treatments in each variable. Defoliation significantly reduces diameter of the trunk and height growth rates, and expressively decreases the income at the plantation cut. However, greater losses were verified after consecutive defoliation, along the first cultivation year. Maintaining areas that suffered severe defoliations at initial planting stages can become economically unfeasible

Population survey of Acromyrmex subterraneus subterraneus Forel, 1893 (Hymenoptera: formicidae)

Nests of Acromyrmrex subterraneus sub terraneus were excavated in two localities of Minas Gerais to estimate their population. All the nests had flve entrance holes which were destroyed by methyl bromide application. Twenty four hours after, the fungus culture and the ants present in the Chambers were collected and weighed. In the entomology laboratory at the Federal University of Viçosa Six samples of identical weight were taken from each nest and the number of eggs, larvae, pupae and adults was counted. Total weight of the nests ranged from 1,30og to 2,684 g. Egg percentage varied from 62% to 21.1%; larvae averaged between 0.6 to 5.4 % and pupae from 70% to 843% %. The total number of individuals varied from 10,248 to 20,872. In general, the number of minor workers that are involved in fungal and brood care was about 9,4 times lower than the number of foragers. A positive significant correlation ( r=0.896) was found between the number of pupae and that of adults