-The objective of this work was to screen plants with insecticide activity, in order to isolate, identify and assess the bioactivity of insecticide compounds present in these plants, against Coleoptera pests of stored products: Oryzaephilus surinamensis L. (Silvanidae), Rhyzopertha dominica F. (Bostrichidae) and Sitophilus zeamais Mots. (Curculionidae). The plant species used were: basil (Ocimum selloi Benth.), rue (Ruta graveolens L.), lion's ear (Leonotis nepetifolia (L.) R.Br.), jimson weed (Datura stramonium L.), baleeira herb (Cordia verbenacea L.), mint (Mentha piperita L.), wild balsam apple (Mormodica charantia L.), and billy goat weed or mentrasto (Ageratum conyzoides L.). The insecticide activity of hexane and ethanol extracts from those plants on R. dominica was evaluated. Among them, only hexane extract of A. conyzoides showed insecticide activity; the hexane extract of this species was successively fractionated by silica gel column chromatography, for isolation and purification of the active compounds. Compounds 5,6,7,8,3',4', 5,6,7,8,3'-pentamethoxy-4',5'-methilenedioxyflavone and coumarin were identified. However, only coumarin showed insecticide activity against three insect pests (LD 50 from 2.72 to 39.71 mg g -1 a.i.). The increasing order of insects susceptibility to coumarin was R. dominica, S. zeamais and O. surinamensis.Index terms: natural insecticide, pest management, alternative control, secondary metabolites. Compostos de plantas com atividade inseticida a coleópteros-praga de produtos armazenadosResumo -O objetivo deste trabalho foi selecionar plantas com atividade inseticida, para isolar, identificar e avaliar a bioatividade de compostos inseticidas presentes nessas plantas, contra as seguintes pragas de produtos armazenados da ordem Coleoptera: Sitophilus zeamais Mots. (Curculionidae), Rhyzopertha dominica F. (Bostrichidae) e Oryzaephilus surinamensis L. (Silvanidae). As espécies de plantas usadas foram: anis (Ocimum selloi Benth), arruda (Ruta graveolens L.), cordão-de-frade (Leonotis nepetifolia L.), datura (Datura stramonium L.), erva baleeira (Cordia verbenacea L.), hortelã (Mentha piperita L.), melão-de-são-caetano (Mormodica charantia L.) e mentrasto (Ageratum conyzoides L.). Avaliou-se a toxicidade dos extratos hexânico e etanólico dessas plantas sobre R. dominica. Somente o extrato hexânico de A. conyzoides apresentou atividade inseticida. O extrato hexânico desta planta foi fracionado, sucessivamente, por cromatografia de coluna de sílica gel, para isolamento e purificação dos compostos ativos. Os compostos 5,6,7,8,3',4', 5,6,7,8,5'-metilenodioxiflavona e cumarina foram identificados. Entretanto, somente a cumarina apresentou atividade inseticida às três espécies de insetos (DL 50 de 2,72 a 39,71 mg g -1 de i.a.). A ordem crescente de suscetibilidade à cumarina foi R. dominica, S. zeamais e O. surinamensis.Termos para indexação: inseticida natural, manejo de pragas, controle alternativo, metabolito secundário.

Background: The deployment of entomopathogenic fungi (EPF) for the control of crop pests is an important alternative to synthetic pesticides. Despite recent advances in EPF formulations and application techniques, their efficacy is still limited by abiotic and biotic factors. Entomopathogenic fungi naturally colonize plant tissues or they can be artificially inoculated, protecting the plants from insect attack. Beauveria bassiana is the most widely used fungal biological control agent and has potential as an endophyte to protect a range of crops. Although B. bassiana is known to be pathogenic to the South American tomato pinworm, Tuta absoluta (Meyrick), this fungus could be more efficient when deployed as an endophyte to protect tomato plants from attack. Methods: Three B. bassiana isolates were screened for virulence against T. absoluta larvae by application of conidia to leaf surfaces. Following confirmation of virulence, tomato plants were then exposed to conidial suspensions using a forced uptake technique. Only one isolate, LPP139, colonized the leaves. Seedlings were then inoculated with LPP139 and the presence of the fungus in different plant tissues was monitored over 30 days. Possible effects of B. bassiana endophytic colonization on plant development were also evaluated. Following confirmation of endophytic colonization of leaf tissues, T. absoluta 2nd or 3rd instar larvae were offered leaves and survival was monitored over a 7-day period. Results: All three B. bassiana isolates were virulent to T. absoluta, with approximately 90% mortality over 10 days when conidia had been applied to leaf surfaces. Various plant inoculation techniques were tested but only seedling inoculation was successful. LPP139 successfully colonized all of the plant tissues. High percentages of colonization were observed in roots, stems and leaves up to 30 days after inoculation, with no negative effects on plant growth. When T. absoluta larvae were exposed to B. bassiana colonized leaves, survival was reduced to zero over a 7-day period. Conclusions: The endophytic colonization of tomato plants with EPF is a promising method of controlling the South American tomato pinworm. The fungus was detectable for up to 30 days, longer than has been previously observed

In the present study, we evaluate the toxicity of six insecticides to Brevicoryne brassicae (L.) (Hemiptera: Sternorrhyncha: Aphididae), predatory coleopterans Cycloneda sanguinea (L.) (Coccinellidae) and Acanthinus sp. (Anthicidae), and the hymenopteran parasitoid Diaeretiella rapae (McIntosh) (Braconidae, Aphidiinae). Late-instar nymphs of B. brassicae and adults of C. sanguinea, Acanthinus sp. and D. rapae were exposed to nine concentrations of acephate, deltamethrin, dimethoate, methamidophos, methyl parathion and pirimicarb. Selectivity, toxicity, and tolerance ratios were calculated from LC 50 values to determine insecticide toxicity to B. brassicae and natural enemies as well as insecticide tolerance of the natural enemies. Pirimicarb was highly selective to Acanthinus sp., C. sanguinea, and D. rapae. Dimethoate, methamidophos and methyl parathion also showed selectivity to C. sanguinea and Acanthinus sp., but not to D. rapae. Methamidophos was the least potent insecticide against B. brassicae exhibiting the highest LC 50 amongst the products tested and was more toxic to the D. rapae relative to the aphid. Overall, the predators Acanthinus sp. and C. sanguinea were more tolerant to the insecticides than was the parasitoid D. rapae. The role of insecticides in IPM systems of brassica crops is discussed based on the toxicity to B. brassicae and selectivity to natural enemies.

The performance of herbivorous insects is related to the locations of defenses and nutrients found in the different plant organs on which they feed. In this context, the females of herbivorous insect species select certain parts of the plant where their offspring can develop well. In addition, their offspring can adapt to plant defenses. A system where these ecological relationships can be studied occurs in the specialist herbivore, Tuta absoluta, on tomato plants. In our experiments we evaluated: (i) the performance of the herbivore T. absoluta in relation to the tomato plant parts on which their offspring had fed, (ii) the spatial distribution of the insect stages on the plant canopy and (iii) the larval resistance to starvation and their walking speed at different instar stages. We found that the T. absoluta females preferred to lay their eggs in the tomato plant parts where their offspring had greater chances of success. We verified that the T. absoluta females laid their eggs on both sides of the leaves to better exploit resources. We also observed that the older larvae (3rd and 4th instars) moved to the most nutritious parts of the plant, thus increasing their performance. The T. absoluta females and offspring (larvae) were capable of identifying plant sites where their chances of better performance were higher. Additionally, their offspring (larvae) spread across the plant to better exploit the available plant nutrients. These behavioral strategies of T. absoluta facilitate improvement in their performance after acquiring better resources, which help reduce their mortality by preventing the stimulation of plant defense compounds and the action of natural enemies.

Spatial distribution studies of insect pests make it possible to determine their colonization and dispersal patterns. Watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai) is among the most frequently consumed fruits in the world, and the common blossom thrips, Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae), is one of the most important insect pests of this plant. The objective of this study was to determine the spatial distribution of F. schultzei in commercial watermelon crops using geostatistics. The studied F. schultzei populations presented an aggregated distribution. The colonization of thrips began at the borders of the crops, especially in the areas located in the opposite direction to that of the prevailing winds. The highest densities of thrips occurred in crops that had cucurbits in the surrounding areas. When monitoring for F. schultzei populations, greater attention should be given to sampling that part of the crop located in the opposite direction to that of the prevailing winds because this is where colonization begins. Even at low densities, the aggregation points of thrips in the crop should be located and controlled so that they do not cause damage. In sampling programs for F. schultzei, samples should be taken at distances greater than 9 m apart because this is the distance up to which densities of this species show spatial dependence. Planting watermelon crops close to other cucurbits should be avoided, as these alternate hosts may act as a source of infestation by this pest.