Anderson Mathias Holtz

Searching behaviour of an omnivorous predator for novel and native host plants of its herbivores: a study on arthropod colonization of eucalyptus in Brazil

Adaptation to novel host plants is a much‐studied process in arthropod herbivores, but not in their predators. This is surprising, considering the attention that has been given to the role of predators in host range expansion in herbivores; the enemy‐free space hypothesis suggests that plants may be included in the host range of herbivores because of lower predation and parasitism rates on the novel host plants. This effect can only be important if natural enemies do not follow their prey to the novel host plant, at least not immediately, thus allowing the herbivores to adapt to the novel host plant. Hence, depending on the speed with which natural enemies follow their prey to a new host plant, enemy‐free space on novel host plants may only exist for a limited period. This situation may presently be occurring in a system consisting of the herbivorous moth Thyrinteina arnobia Stoll (Lepidoptera: Geometridae) that attacks various species of Myrtaceae, such as guava (Psidium guajava L.) and jaboticaba (Myrciaria spp.), in Brazil. Since the introduction of eucalyptus (Myrtaceae) species into this country some 100 years ago, the moth has included this plant species in its host range and frequently causes outbreaks, a phenomenon that does not occur on the native host plant species. This suggests that the natural enemies that attack the herbivore on native species are not very effective on the novel host. We tested this hypothesis by studying the searching behaviour of one of the natural enemies, the omnivorous predatory bug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae). When offered a choice between plants of the two species, the predators (originally collected in eucalyptus plantations) preferred guava to eucalyptus when both plant species were clean, infested with herbivores, or damaged by herbivores but with herbivores removed prior to the experiments. The bugs preferred herbivore‐damaged to clean guava, and showed a slight preference for damaged to clean eucalyptus. These results may explain the lack of impact of predatory arthropods on herbivore populations on eucalyptus and suggests that eucalyptus may offer an enemy‐free space for herbivores.

FERTILIZANTE ORGANOMINERAL E ARGILA SILICATADA COMO INDUTORES DE RESISTÊNCIA Á VARÍOLA DO MAMOEIRO

A variola ou pinta preta e um dos mais serios problemas para cultura do mamoeiro e seu controle e baseado na aplicacao excessiva de produtos quimicos. O objetivo deste trabalho foi avaliar o efeito da aplicacao de fertilizante organomineral e argila silicatada na inducao de resistencia a variola em plantas de mamao, avaliando-se a incidencia e severidade. Os tratamentos receberam aplicacoes foliares do fertilizante organomineral (T2), argila silicatada (T3), fertilizante organomineral mais argila silicatada (T4) e agua na testemunha (T1). As avaliacoes foram realizadas 5 dias apos a 6a, 9a e 12a aplicacao foliar dos produtos. Os tratamentos 2, 3 e 4 proporcionaram significativa reducao da incidencia e severidade da doenca. Contudo, maior reducao da incidencia e severidade foi observada quando se associou fertilizante organomineral mais argila silicatada (T3). A aplicacao destes produtos e uma medida eficaz e economicamente viavel para o manejo da variola em cultivos de mamao.

SURVIVAL AND REPRODUCTION OF Podisus nigrispinus (HETEROPTERA: PENTATOMIDAE): EFFECTS OF PREY SCARCITY AND PLANT FEEDING

The spined soldier bug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) is a generalist predator that can alternatively feed on plant tissue to survive under prey scarcity. This research aimed to evaluate the effects of plant feeding forced by a shortage of prey on the survival and reproduction of P. nigrispinus on Eucalyptus urophylla S.T. Blake�(Myrtaceae)�plantsinthefield.� Podisus nigrispinus adults were enclosed on branches of eucalyptus by using gauze bags. These adults were fed daily with Tenebrio molitor pupae (T1) or after 5 (T2), 10 (T3) or 15 (T4) days from mating to simulate prey shortage. The pre-oviposition period, number of egg masses, number and viability of eggs and longevity of females were evaluated. Females of P. nigrispinus had a longer pre-oviposition period and produced lower number of egg masses as the period of prey shortage increased. However, the average number of eggs per egg mass, emergence of nymphs and longevity of P. nigrispinus females were not affected by prey shortage. Females of P. nigrispinuscansurvive�15�dayswithoutpreybyfeedingoneucalyptusleavesandifitfindsprey� afterwards can still reproduce. This shows that plant feeding is a successful incidental strategy to survive periods of foodscarcity�(andthusincreasetheefficiency)�ofthispredatorasabiologicalcontrolagent.

CARACTERÍSTICAS BIOLÓGICAS DE TRICHOGRAMMA EXIGUUM EM OVOS DE ANAGASTA KUEHNIELLA E SITOTROGA CEREALELLA

O objetivo deste trabalho foi obter informacoes sobre alguns aspectos biologicos de Trichogramma exiguum Pinto & Platiner, (Hymenoptera: Trichogrammatidae) criado nos hospedeiros alternativos Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) e Sitotroga cerealella Oliver (Lepidoptera: Gelechiidae), visando a producao desses parasitoides para utilizacao no controle biologico de pragas. A maior taxa de parasitismo de T. exiguum foi encontrada em ovos de A. kuehniella. A viabilidade foi superior em ovos de S. cerealella. A razao sexual foi semelhante para ambos os hospedeiros alternativos. Estes resultados demonstram que ambos hospedeiros alternativos podem ser utilizados na criacao massal de T. exiguum, porem levando em consideracao a importância da taxa de parasitismo, A. kuehniella demonstrou maior aptidao.

Selection of Trichogramma species for controlling the Diamondback moth

Biological characteristics of the egg parasitoids Trichogramma acacioi, T. atopovirilia, and T. bennetti were studied to select the one with better performance on the control of the Diamondback moth, Plutella xylostella. Parasitism rate, viability, and sex ratio were studied. Parasitism rate ranged from 1.67 to 41.33%. T. atopovirilia and T. acacioi were respectively the most and less aggressive species. The viability ranged from 6.20% for T. acacioi to 53.34% for T. atopovirilia. There were no differences on sex ratio (P < 0.05) that remained above 0,88. T. atopovirilia was the species with best performance in the laboratory when rearing on the Diamondback moth eggs.

Influência do substrato alimentar sobre o desenvolvimento de Diaphania hyalinata L. (Lepidoptera: Crambidae)

The aim of this research was to evaluate the biological behaviour of melonworm at different natural and artificial diets. Squash cultivar jacare, cucumber, summer squash and an artificial diets developed by Hensley & Hammond for the sugarcane borer were tried. The research was carried out in the Laboratorio de Entomologia do Centro de Ciencias Agrarias of the Universidade Federal do Espirito Santo, in climatized room at 25 ± 1oC, relative humidity of 70 ± 10% and 14h photofase. The caterpillars fed on each substrate during the whole life cycle. Differences in duration of the larval period, larvae and pupae survival, adult longevity and number of eggs were registered between the substrates. The results show that the best diet for rearing is the artificial one. Between the natural diets the cucumber showed the best results.

DETERMINAÇÃO DA CONCENTRAÇÃO LETAL MÉDIA (CL 50) DE BEAUVERIA BASSIANA PARA O CONTROLE DE BREVICORYNE BRASSICAE

The cabbage aphid is one of the main curses of Brassicas in general, and the search for healthier foods has been stimulating the development of techniques inside of the maintainable handling, as the microbial control. The objective of this work was determine concentrations of the microbial B. bassiana for the handling of the cabbage aphid. Nymphs of B. brassicae were inoculated in submerged cabbage leaves in fungic suspensions , of the commercial product Boveril®, in the concentrations of 0.05, 0.08, 0.12, 0.31, 0.50, 1.0, 1.5, 2.0 grams per liter of distilled water plus adhesive espalhante Hai-Teem®, and maintained 26.0 ± 1.0°C and UR of 75.0 ± 5%. There was an increment of the mortality in function of the increase of the concentration, because, to smallest concentration (0.05g/L) it presented reduced effect of control 14% of confirmed mortality. However, the concentrations of 1.0-2.0g/L of water provided a superior mortality of 85%. The value found for CL50 was of 0.233g/L. In that way the microbial control of the cabbage aphid can be economical and biologically viable for the handling of this pest in brassicas cultivations.

Aspectos biológicos de Thyrinteina arnobia (Lep.: Geometriadae) provenientes de lagartas criadas em folhas de Eucalyptus cloeziana ou de Psidium guajava sob condições de campo

Eucalyptus plantations in Brazil may be damaged by native insects of many orders including Orthoptera, Coleoptera and Lepidoptera. These insects feed on Brazilian tree species of the family Myrtaceae to which the genus Eucalyptus belongs. The Lepidoptera Thyrinteina arnobia Stoll (Lepidoptera: Geometridae) is the most harmful defoliator of Eucalyptus in Brazil. The objective of this work was to evaluate biological aspects of T. arnobia adults originated from caterpillars fed on guava or eucalyptus plants. Adults of T. arnobia originated from caterpillars reared with eucalyptus or guava leaves presented significant differences for most biological aspects evaluated, except for duration of preoviposition and oviposition periods and sex ratio. This shows that species feeding on host plants related to eucalyptus can cause considerable damage in reforestation with species of this genus. T. arnobia insects are still undergoing an imposed adaptation process to eucalyptus plants and likely feed on these plants to escape from pressure by physical and chemical barriers of Brazilian native Myrtaceae.

Parasitoids follow herbivorous insects to a novel host plant, generalist predators less so

The ‘enemy‐free space’ hypothesis predicts that herbivorous insects can escape their natural enemies by switching to a novel host plant, with consequences for the evolution of host plant specialisation. However, if natural enemies follow herbivores to their novel host plants, enemy‐free space may only be temporary. We tested this by studying the colonisation of the introduced tree Eucalyptus grandis (Hill) Maiden (Myrtaceae) by insects in Brazil, where various species of herbivores have added eucalyptus to their host plant range, which consists of native myrtaceous species such as guava. Some herbivores, for example, Thyrinteina leucoceraea Ringe (Lepidoptera: Geometridae), cause outbreaks in eucalyptus plantations but not on guava, possibly because eucalyptus offers enemy‐free space. We sampled herbivores (mainly Lepidoptera species) and natural enemies on eucalyptus and guava and assessed parasitism of Lepidoptera larvae on both host plant species during ca. 2 years. Overall, predators were encountered more frequently on guava than on eucalyptus. In contrast, parasitoids were encountered equally and parasitism rates of Lepidoptera larvae were similar on both host plants. This indicates that herbivores may escape some enemies by moving to a novel host plant. However, this escape may be temporary and may vary with time. We argue that studying temporal and spatial patterns of enemy‐free space and the response of natural enemies to host use changes of their herbivorous prey is essential for understanding the role of natural enemies in the evolution of host plant use by herbivorous arthropods.

Controle alternativo de Planococcus citri (Risso, 1813) com extratos aquosos de pinhão-manso

The Planococcus citri (Risso, 1813) (Hemiptera: Pseudococcidae) is a phytosanitary problem in the coffees cultivation. The most used type of control for this pest is the chemical one, which leads to the selection of resistant individuals, as well as social and environmental problems. Therefore, it is necessary to control the alternative. Thus, this paper had the aim of studying the potential insecticide in different parts of the plant Jatropha curcas , in some concentrations, over the P. citri . Dices of leaf containing 10 P. citri (nymphs and adults) were directly and indirectly sprayed with the Potter Towers assistance, on the pressure at 15 Lb/pol2, applying 6 mL of solution per repetition. Seven concentrations of oil and extracts were tested, and the mortality was evaluated in function of time. All physic nuts structures in both routes of administration showed satisfactory mortality P. citri , reaching 91.6% mortality at the concentrations of 1.5, 2.0 e 3.0% oil in the direct application.