ABSTRACT
Leucoptera coffeella (Lepidoptera: Lyonetiidae) is one of the main pests in coffee crops. The economic injury level (EIL) is the lowest density of the pest at which economic damages match the costs of control measures. The economic threshold (ET) is the density of the pest at which control measures must be taken so that this population does not reach the EIL. These are the main indices used for pest control decision-making. Control of L. coffeella is carried out by manual, tractor, airplane or drone applications. This work aimed to determine EILs and ETs for L. coffeella as a function of insecticide application technology in conventional and organic Coffea arabica crops. Data were collected over five years in commercial C. arabica crops on seven 100 ha central pivots. The cost of control in organic crops was 16.98% higher than conventional. The decreasing order of control cost was manual > drone > airplane > tractor application. Coffee plants were tolerant to low densities (up to 15% mined leaves) of the pest that caused losses of up to 6.56%. At high pest densities (54.20% mined leaves), losses were high (85.62%). In organic and conventional crops and with the use of different insecticide application technologies, EIL and ET were similar. The EIL and ET were 14% and 11% of mined leaves, respectively. Therefore, these indices can be incorporated in integrated pest management programs in C. arabica crops. The indices determined as a function of insecticide application technology in organic and conventional coffee are important as they serve producers with different technological levels. Additionally, EILs and ETs can contribute to more sustainable production, as control methods will only be employed when the pest density reaches these indices.
ABSTRACT
The intrinsic rate of natural increase of a population (rm) has been in focus as a key parameter in entomology and acarology. It is considered especially important in studies of predators that are potential biological control agents of fast-growing pests such as mites, whiteflies and thrips. Life-table experiments under controlled laboratory conditions are standard procedures to estimate rm. However, such experiments are often time consuming and may critically depend on the precise assessment of the developmental time and the fecundity rate early in the reproductive phase. Using selected studies of predatory mites with suitable life-table data, we investigated whether and how measurements of growth rates can be simplified. We propose a new method for estimating rm from partial life tables, in which the researcher can choose a level of precision based on a stand-in measure of relative error. Based on this choice, the procedure helps the researcher to decide when a life-table experiment can be terminated. Depending on the chosen precision, significant amounts of experimental time can be saved without seriously compromising the reliability of the estimated growth parameter.
Subject(s)
Arthropods , Mites , Animals , Life Tables , Pest Control, Biological/methods , Predatory Behavior , Reproducibility of ResultsABSTRACT
Essential oils have aroused interest in the industrial sector due to the multitude of potential applications, especially with respect their antimicrobial and antioxidant properties, among others. The objective of this study was to determine the chemical composition of the essential oil from the leaves of Myrcia oblongata DC by gas chromatography coupled to mass spectrometry (GC-MS). To evaluate the antioxidant potential of the oil by using the free radical capture method with 2,2-diphenyl-1-picryl hydrazyl (DPPH); to test the oil antimicrobial activity using the broth microdilution method; and to evaluate the repellency and fumigant potential of the oil on Dermanyssus gallinae (Degeer, 1778). The GC-MS analysis resulted in the identification of 30 oil constituents, with the bulk of the composition identified as caryophyllene oxide (22.03%) and trans-verbenol (11.94%). The oil presented moderate antioxidant activity compared to the synthetic antioxidant 2,6-di-tert-butyl-4-hydroxytoluene (BHT). Antimicrobial activity of the essential oil showed an inhibitory activity on Gram-positive bacteria, Enterococcus faecalis, Staphylococcus aureus, Bacillus subtilis and Staphylococcus epidermidis and for the yeast Candida albicans, and showed no activity against Gram-negative bacteria. All concentrations of the essential oil used in the fumigation test on D. gallinae resulted in mortality below 20%. For the repellency test, significant potential was observed for the concentration of 10%.
Os óleos essenciais tem despertado interesse no setor industrial por apresentarem multiplicidade de aplicações, destacando-se por suas propriedades antimicrobianas, antioxidantes dentre outras. Diante disto, o objetivo deste estudo foi determinar a composição química do óleo essencial das folhas de Myrcia oblongata DC pelo método de cromatografia gasosa acoplada à espectrometria de massas (CG-EM), avaliar o potencial antioxidante do óleo pelo método de captura do radical livre 2,2- difenil-1-picril hidrazil (DPPH), testar a atividade antimicrobiana pelo método de microdiluição em caldo, bem como avaliar a repelência e potencial fumigante deste óleo sobre Dermanyssus gallinae (Degeer, 1778). As análises de CG-EM resultaram na identificação de 30 constituintes, sendo majoritários o óxido de cariofileno (22.03%) e o trans-verbenol (11.94%). O óleo apresentou atividade antioxidante moderada quando comparada ao antioxidante sintético 2,6-di-tert-butil-4-hidroxitolueno (BHT). Em relação à atividade antimicrobiana, o óleo essencial demonstrou atividade inibitória para as bactérias Gram-positivas, Enterococcus faecalis, Staphylococcus aureus, Bacillus subtilis e Staphylococcus epidermidis, e para levedura Candida albicans e não apresentou atividade para bactérias Gram negativas. Todas as concentrações do óleo essencial testadas no teste de fumigação sobre D. gallinae apresentaram mortalidade inferior a 20%. Para o teste de repelência, observou-se um potencial significativo para a concentração de 10%.
