Tarcísio Visintin da Silva Galdino

Bioassay method for toxicity studies of insecticide formulations to Tuta absoluta (meyrick, 1917)

O principal metodo utilizado no controle da traca-do-tomateiro Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) e a aplicacao de inseticidas. As tecnicas atuais de avaliacao da toxicidade de inseticidas sobre essa praga nao simulam a situacao de campo e nao possibilitam a verificacao se as doses usadas no campo sao eficientes no seu controle. Assim, neste trabalho, objetivou-se desenvolver uma metodologia que represente as condicoes de campo para inseticidas de acao rapida (neurotoxicos e inibidores respiratorios) e de acao lenta (Bacillus thuringiensis e reguladores de crescimento. A metodologia mais eficiente para estudos de toxicidade de formulacoes comerciais a T. absoluta foi a imersao de folhas em calda inseticida. Para os bioensaios de inseticidas de acao rapida, sugere-se que estes sejam realizados em placas de Petri, contendo foliolos de tomate da 4a folha a partir do apice da planta, infestados com 10 larvas de 3o instar e eles podem durar 48 horas. Quanto aos bioensaios de toxicidade de inseticidas de acao lenta, sugere-se que sejam realizados em garrafas PET transparentes, de dois litros, contendo a 4a folha de tomate a partir do apice da planta infestada com 10 larvas de 2o instar e seu peciolo inserido em vidro de 120 mL contendo agua. Nesse caso, o bioensaio pode durar sete dias sem prejuizo na eficiencia.

Mapping Global Potential Risk of Mango Sudden Decline Disease Caused by Ceratocystis fimbriata.

The Mango Sudden Decline (MSD), also referred to as Mango Wilt, is an important disease of mango in Brazil, Oman and Pakistan. This fungus is mainly disseminated by the mango bark beetle, Hypocryphalus mangiferae (Stebbing), by infected plant material, and the infested soils where it is able to survive for long periods. The best way to avoid losses due to MSD is to prevent its establishment in mango production areas. Our objectives in this study were to: (1) predict the global potential distribution of MSD, (2) identify the mango growing areas that are under potential risk of MSD establishment, and (3) identify climatic factors associated with MSD distribution. Occurrence records were collected from Brazil, Oman and Pakistan where the disease is currently known to occur in mango. We used the correlative maximum entropy based model (MaxEnt) algorithm to assess the global potential distribution of MSD. The MaxEnt model predicted suitable areas in countries where the disease does not already occur in mango, but where mango is grown. Among these areas are the largest mango producers in the world including India, China, Thailand, Indonesia, and Mexico. The mean annual temperature, precipitation of coldest quarter, precipitation seasonality, and precipitation of driest month variables contributed most to the potential distribution of MSD disease. The mango bark beetle vector is known to occur beyond the locations where MSD currently exists and where the model predicted suitable areas, thus showing a high likelihood for disease establishment in areas predicted by our model. Our study is the first to map the potential risk of MSD establishment on a global scale. This information can be used in designing strategies to prevent introduction and establishment of MSD disease, and in preparation of efficient pest risk assessments and monitoring programs.

Is the Performance of a Specialist Herbivore Affected by Female Choices and the Adaptability of the Offspring

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.

Standardized Sampling Plan for the Thrips Frankliniella schultzei (Thysanoptera: Thripidae) on Watermelon Crops

Sampling plans are essential components of integrated pest management programs. The thrips Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae) is an important pest of watermelon crops. Despite the importance of sampling plans and of F. schultzei as a pest of watermelon crops, no research has been previously conducted on this subject for this crop. The objective of this work was to create a standardized sampling plan for F. schultzei in watermelon crops. Over two consecutive years, weekly samplings were performed in commercial watermelon crops. The aim of these assessments was to select the best sampling unit and the best sampling technique for F. schultzei assessment and to determine the number of samples necessary for a standardized sampling plan for this pest. In watermelon crops in the vegetative, flowering, and fruiting stages, the ideal location for sampling F. schultzei was the most apical leaf of the branches. The best sampling technique was a direct count of F. schultzei individuals. The F. schultzei sampling plan involved the evaluation of 69 samples per plot. The execution duration of this sampling plan in 1- to 15-ha plots was <1 h and was inexpensive (Abstract Sampling plans are essential components of integrated pest management programs. The thrips Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae) is an important pest of watermelon crops. Despite the importance of sampling plans and of F. schultzei as a pest of watermelon crops, no research has been previously conducted on this subject for this crop. The objective of this work was to create a standardized sampling plan for F. schultzei in watermelon crops. Over two consecutive years, weekly samplings were performed in commercial watermelon crops. The aim of these assessments was to select the best sampling unit and the best sampling technique for F. schultzei assessment and to determine the number of samples necessary for a standardized sampling plan for this pest. In watermelon crops in the vegetative, flowering, and fruiting stages, the ideal location for sampling F. schultzei was the most apical leaf of the branches. The best sampling technique was a direct count of F. schultzei individuals. The F. schultzei sampling plan involved the evaluation of 69 samples per plot. The execution duration of this sampling plan in 1- to 15-ha plots was <1 h and was inexpensive (

The Role of the Beetle Hypocryphalus mangiferae (Coleoptera: Curculionidae) in the Spatiotemporal Dynamics of Mango Wilt

Abstract The knowledge of the spatiotemporal dynamics of pathogens and their vectors is an important step in determining the pathogen dispersion pattern and the role of vectors in disease dynamics. However, in the case of mango wilt little is known about its spatiotemporal dynamics and the relationship of its vector [the beetle Hypocryphalus mangiferae (Stebbing 1914)] to these dynamics. The aim of this work was to determine the spatial-seasonal dynamic of H. mangiferae attacks and mango wilt in mango orchards and to verify the importance of H. mangiferae in the spatiotemporal dynamics of the disease. Two mango orchards were monitored during a period of 3 yr. The plants in these orchards were georeferenced and inspected monthly to quantify the number of plants attacked by beetles and the fungus. In these orchards, the percentage of mango trees attacked by beetles was always higher than the percentage infected by the fungus. The colonization of mango trees by beetles and the fungus occurred by colonization of trees both distant and proximal to previously attacked trees. The new plants attacked by the fungus emerged in places where the beetles had previously begun their attack. This phenomenon led to a large overlap in sites of beetle and fungal occurrence, indicating that establishment by the beetle was followed by establishment by the fungus. This information can be used by farmers to predict disease infection, and to control bark beetle infestation in mango orchards.

Assessing the spatial distribution of Tuta absoluta (Lepidoptera: Gelechiidae) eggs in open‐field tomato cultivation through geostatistical analysis

BACKGROUND The spatial distribution of insects is due to the interaction between individuals and the environment. Knowledge about the within-field pattern of spatial distribution of a pest is critical to planning control tactics, developing efficient sampling plans, and predicting pest damage. The leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is the main pest of tomato crops in several regions of the world. Despite the importance of this pest, the pattern of spatial distribution of T. absoluta on open-field tomato cultivation remains unknown. Therefore, this study aimed to characterize the spatial distribution of T. absoluta in 22 commercial open-field tomato cultivations with plants at the three phenological development stages by using geostatistical analysis. RESULTS Geostatistical analysis revealed that there was strong evidence for spatially dependent (aggregated) T. absoluta eggs in 19 of the 22 sample tomato cultivations. The maps that were obtained demonstrated the aggregated structure of egg densities at the edges of the crops. Further, T. absoluta was found to accomplish egg dispersal along the rows more frequently than it does between rows. CONCLUSION Our results indicate that the greatest egg densities of T. absoluta occur at the edges of tomato crops. These results are discussed in relation to the behavior of T. absoluta distribution within fields and in terms of their implications for improved sampling guidelines and precision targeting control methods that are essential for effective pest monitoring and management.

Feasible sampling plan for Bemisia tabaci control decision-making in watermelon fields

BACKGROUND The silverleaf whitefly Bemisia tabaci is one of the most important pests of watermelon fields worldwide. Conventional sampling plans are the starting point for the generation of decision-making systems of integrated pest management programs. The aim of this study was to determine a conventional sampling plan for B. tabaci in watermelon fields. RESULTS The optimal leaf for B. tabaci adult sampling was the 6th most apical leaf. Direct counting was the best pest sampling technique. Crop pest densities fitted the negative binomial distribution and had a common aggregation parameter (Kcommon ). The sampling plan consisted of evaluating 103 samples per plot. This sampling plan was conducted for 56 min, costing US

Active insecticides for Diaphania hyalinata selective for the natural enemy Solenopsis saevissima

2.22 per sampling and with a 10% maximum evaluation error. CONCLUSIONS The sampling plan determined in this study can be adopted by farmers because it enables the adequate evaluation of B. tabaci populations in watermelon fields (10% maximum evaluation error) and is a low-cost (US

Spatial distribution and losses by grain destroying insects in transgenic corn expressing the toxin Cry1Ab

2.22 per sampling), fast (56 min per sampling) and feasible (because it may be used in a standardized way throughout the crop cycle) technique.

Effects of glyphosate on the non-target leaf beetle Cerotoma arcuata (Coleoptera: Chrysomelidae) in field and laboratory conditions

ABSTRACT The objective of this study was to determine the toxicity of the nine synthetic dienamides against the insect pest Diaphania hyalinata (melonworm) and the selectivity of these substances for the predator Solenopsis saevissima (fire ant). Four bioassays were conducted. To begin with, the dienamides that caused high mortality of D. hyalinata have been selected. In the second bioassay the dose-mortality curves of the selected dienamides have been constructed. In the third bioassay, the survival curves for D. hyalinata and the elapsed time to kill 50% of their population have been determined. In the fourth biological test, the selectivity of the substances to the predator S. saevissima has been evaluated. The most active (2E,4E)-N-butylhexa-2,4-dienamide 3d has killed 95% of the melonworm, D. hyalinata, and less than 10% of the natural enemy S. saevissima. The results presented by this compound are superior to the outcome displayed by the commercial insecticide Malathion®. Three of the dienamides prepared in this manuscript have proven to be selective in killing the pest, but not the beneficial insect.