Adriano Thibes Hoshino

Aphidophagous Parasitoids Can Forage Wheat Crops Before Aphid Infestation, Parana State, Brazil

ABSTRACT. Aphid parasitoids are common in Brazilian wheat fields, and parasitize aphids at the wheat tillering stage. However, there is little information available about when this natural enemy occurs in wheat crops. This study investigated the initial occurrence of aphid parasitoids in four commercial wheat crops in northern Paraná during the 2009 crop season. We installed two Malaise traps at each wheat farm, and 400 tillers were assessed weekly in each field for aphid abundance. During this study, we captured 4,355 aphid parasitoids and 197 aphids. Three species of braconid parasitoids were identified, including Aphidius colemani (Viereck 1912), Lysiphlebus testaceipes (Cresson 1880), and Diaeretiella rapae (McIntosh 1855). The aphids species identified were Rhopalosiphum padi (Linnaeus 1758) and Sitobion avenae (Fabricius 1775). This study showed that aphid parasitoids are present in wheat crops even when aphid densities are low, and in one farm, occurred before the aphids colonization. These reports can justified the high efficiency of these natural enemies against aphids in wheat fields.Aphid parasitoids are common in Brazilian wheat fields, and parasitize aphids at the wheat tillering stage. However, there is little information available about when this natural enemy occurs in wheat crops. This study investigated the initial occurrence of aphid parasitoids in four commercial wheat crops in northern Paraná during the 2009 crop season. We installed two Malaise traps at each wheat farm, and 400 tillers were assessed weekly in each field for aphid abundance. During this study, we captured 4,355 aphid parasitoids and 197 aphids. Three species of braconid parasitoids were identified, including Aphidius colemani (Viereck 1912), Lysiphlebus testaceipes (Cresson 1880), and Diaeretiella rapae (McIntosh 1855). The aphids species identified were Rhopalosiphum padi (Linnaeus 1758) and Sitobion avenae (Fabricius 1775). This study showed that aphid parasitoids are present in wheat crops even when aphid densities are low, and in one farm, occurred before the aphids colonization. These reports can justified the high efficiency of these natural enemies against aphids in wheat fields.

First Record of Heliothis virescens (Lepidoptera: Noctuidae) Damaging Table Grape Bunches

Summary Heliothis virescens (F.) was observed damaging table grape bunches (18 d after onset of the flowering period), in Marialva County, Paraná State, Brazil. The pest fully ruined the bunches for the fresh market, and the damage was characterized as quite different from that of other lepidopteran larvae on grapes. Proximity to soybean (Glycine max L. Merrill) fields in which H. virescens developed was the probable cause of its occurrence on grapes.

Abundância de inimigos naturais de pulgões do trigo em diferentes distâncias da borda da mata

The objective of this work was to assess the abundance of natural enemies of wheat (Triticum aestivum) aphids at different distances from the edge of the forest (2.0 to 200 m), in the municipalities of Londrina and Ibipora, in the state of Parana, Brazil, in the 2008 crop season. A total of 11,316 aphids, 682 mummies, 487 parasitoids, and 20,366 predators were quantified. The effect of the distance from the edge of the forest on aphids and parasitoids was not consistent. Among predators, the Dolichopodidae family was the most abundant (87.74 and 98.55% in Ibipora and Londrina, respectively) and showed a higher population near the edge of the forest, indicating that this refuge area favors that predator.

Root system and yield of sugarcane cultivated under different amounts of straw in southern Brazil.

The amount of straw of sugarcane needed to remain in field for sustainability of the production system and quantity that could be used in sectors such as cogeneration and production of bioethanol for optimization of power generation by the sector are unclear issues. The aim of this study was to evaluate the effect of different amounts of straw on the development of the sugarcane root system and yield using the variety SP 801816 in a Rhodic Eutrudox in southern Brazil. Six treatments were evaluated: 0 (no straw), 25, 50, 75 and 100% (20 Mg ha -1 ) of straw and straw burned at 60, 180 and 270 days after planting in 150 m 2 plots. Root samples were collected at 0.45 and 0.75 m from the planting line at depths of 0-0.10, 0.10-0.20, 0.20-0.40 and 0.40 to 0.60 m at harvest, and the stems of the plots were weighed to measure yield. In water stress period, the 50, 75 and 100% straw treatments promoted a greater root mass to 0.20 m deep, which was also reflected in the yield. The 50 and 75% straw treatments resulted in 25% greater yield than the 0 and 25% straw and straw burned, resulting in 28 Mg ha -1 more. The amount, 50% straw retention in the field is sufficient to increase the mass of the roots and, in turn, productivity, which is possible to remove the 50% surplus from the field for industrial processes for the production of energy, without the occurrence of damage to the crop.

First report of Chrysodeixis includens (Walker, [1858]) (Lepidotera: Noctuidae) Injurious to Pineapple (Ananas comosus L.) (Bromeliaceae) in Brazil

aInstituto Agronômico do Paraná – IAPAR, Polo de Santa Tereza do Oeste, Rodovia BR 132, Km 188, CEP 85825-000, Santa Tereza do Oeste, PR, Brazil bInstituto Agronômico do Paraná – IAPAR, Rodovia Celso Garcia Cid, PR 445, Km 375, CEP 86047-902, Londrina, PR, Brazil cUniversidade Estadual de Londrina – UEL, Rodovia Celso Garcia Cid, PR 445, Km 380, Campus Universitário, CP 10.011, CEP 86057-970, Londrina, PR, Brazil

Non-crop habitats modulate alpha and beta diversity of flower flies (Diptera, Syrphidae) in Brazilian agricultural landscapes

Non-crop habitats play a key role in maintaining functional diversity and ecosystem services in farmland. However, the interplay between beneficial insects and landscape variables has rarely been investigated in Neotropical agroecosystems. We used flower flies as a model group to investigate the effects of landscape attributes on beneficial insects in agroecosystems across a gradient of landscape complexity. We specifically ask: (i) Do the abundance and species richness of flower flies in cereal crops increase with increasing landscape complexity? (ii) Do the effects of landscape variables on local flower fly communities differ between spatial scales? (iii) How do landscape complexity and local factors (crop size, altitude and insecticide applications) affect beta diversity? We sampled flower flies in 54 edges within 18 wheat crops in Paraná State, southern Brazil. The percentage of non-crop habitats, landscape diversity and edge density were the explanatory variables, which were calculated at multiple spatial scales for each landscape. We collected 8340 flower flies, distributed in 12 genera and 52 species. Species richness was positively associated with the percentage of non-crop habitats, but total abundance presented non-clear pattern. However, abundance without the dominant species was also positively associated with the percentage non-crop habitats. Similarly, beta diversity was related to non-crop habitats, suggesting that the reduction in non-crop habitats implies in species loss. We have provided the first insights into the importance of non-crop habitats on the conservation of beneficial insects within Neotropical farmlands. To guarantee high levels of biodiversity within agroecosystems we need to promote the conservation and restoration of non-crop habitats in the surrounding landscapes.

Mulching with Sugarcane Straw Reduces Weed Density in Sugarcane Field

Occurrence of weeds in sugarcane crop according to levels of straw over the soil was studied. Experiment was carried out during two annual cycles. Treatments were 0 % (no straw); 25, 50, 75 and 100% (i.e., 5, 10, 15 and 20 t/ha of straw, respectively); and straw burned over the soil. Floristic analysis of weed species was achieved. Percent area occupied by weeds was assessed visually and regression analysis between weeds and amount of straw mulch was performed. Floristic analysis characterized 19 weed species, from eight botanical families: Amaranthaceae, Asteraceae, Commelinaceae, Convolvulaceae, Euphorbiaceae, Poaceae, Portulacaceae and Solanaceae. Highest richness of species was observed for Asteraceae and Poaceae, with seven and four species, respectively. Higher frequency was found for Amaranthus hybridus, A. viridis and Physalis angulata (85% of samples) for first annual crop cycle; and A. hybridus, Bidens pilosa and Cenchrus echinatus predominated (83% of samples) in second cycle. A. hybridus was the most frequent species in both cycles. The highest density of weeds was observed in treatments with straw burned. Application of 75 and 100% straw showed highest suppression for low and high density of weeds, respectively. Increasing level of straw leads correspondent weed control. That information is vital to orientate decision which amount will deposit over the soil since in recent years the straw is also demanded for alternative sources of energy, as thermal or second generation bio-ethanol.