Preliminary Predictive Model of Termiticidal and Repellent Activities of Essential Oil Extracted from Ocotea quixos Leaves against Nasutitermes corniger (Isoptera: Termitidae) Using One-Factor Response Surface Methodology Design

Termites are one of the most challenging pests that agriculture and urban environments are faced with. They bring substantial losses in annual and perennial crops and damage wood components at construction sites. The development of natural products with biological activity for termite control is an ecological alternative in the search to replace conventional products. Hence, the aim of this research was to predict the termiticidal and repellent effects of the essential oil from Ocotea quixos leaves on Nasutitermes corniger using a one-factor response surface methodology design. The variable analysed was the concentration of essential oil in ethanol at an interval of 0.3–0.05% for anti-termite activity and between 0.12 and 0.01% for repellent action. A 100% mortality rate was found at concentrations higher than 0.12% and at the minimum concentration analysed, the effect was 22.2%. As for the repellent action, the concentration of 0.12% was able to repel 100% of the termites and at 0.01% it repelled 48.9%. The analysis of the essential oil from Ocotea quixos leaves by GC-MS resulted in the presence of 42 compounds, 39 of them elucidated. The main compounds were (E)-cinnamyl acetate (36.44%), (E)-cinnamaldehyde (27.03%), (E)-β-caryophyllene (5.21%) and (E)-methyl isoeugenol (4.18%).

Repellency of p-Anisaldehyde Against Musca domestica (Diptera: Muscidae) in the Laboratory

The house fly, Musca domestica L. (Diptera: Muscidae), is a nuisance pest often associated with livestock production, and it can also mechanically transmit the causal agents of human and veterinary diseases. We found that a 0.5% concentration of p-anisaldehyde, produced by many plants consumed by humans, repelled adult M. domestica in static air olfactometer tubes under laboratory conditions for ≥24 h, but by 48 h the repellent activity had worn off. Repellency, however, was not observed in response to 0.5% p-anisaldehyde that had been exposed to sunlight radiation lamps for 2 h. When p-anisaldehyde was aged in darkness for 48 h, it showed strong initial repellency for <1 h. The repellent action of 0.5% p-anisaldehyde was sufficient to keep adult M. domestica from landing on three different food sources when the botanical substance was misted onto the food sources, and when it was placed in proximity to, but not in contact with, the food sources. Extension of p-anisaldehyde’s repellent action using solvents other than acetone is discussed.

Evaluation of lethal and repellent action of aqueous vegetable extracts for the control of spittlebugs (Hemiptera: Cercopidae)

Spittlebugs (Hemiptera: Cercopidae) are species considered to be the main pests of forage grasses throughout Tropical America. In Brazil, Mahanarva spectabilis (Distant) is the main and most limiting pest associated with elephant grass (Pennisetum purpureum Schum.). These insects have the potential to generate great economic losses for the milk and meat production chain, harming producers. Among the spittlebugs control tactics, the use of resistant grasses, biological control and the application of synthetic insecticides in adults are the best known methods. The use of synthetic insecticides is economically viable only when combined with other spittlebugs control strategies, but they are environmentally unsafe products, so it is necessary to research tactics that are less aggressive to the environment, socially viable and of low cost for mainly small farmers. In this context, the insecticidal and repellent action that plant compounds have against different insect-pest species stands out. Thus, the objectives of this research were to evaluate whether aqueous extracts of the aromatic plants A. sativum, R. graveolens, C. verum, C. citratus, S. aromaticum, I. verum, E. globulus, N. tabacum and T. vulgaris have an insecticidal effect on spittlebug nymphs and the choice of spittlebugs adults can be altered for elephant grass, by attraction or non-attraction, in olfactometry tests. In the first stage of the research, the insecticidal effect of the extracts on nymphs of M. spectabilis was evaluated. The results indicated that the tobacco extract was the most effective among all nine tested. At a concentration of 20%, after 48 hours, it reached an efficiency of 76%. Then, bioassays were carried out comparing 5 concentrations of tobacco extract (5%, 10%, 15%, 20% and, 25%), where the extract in the concentration of 25% reached an efficiency greater than 92%. As for the extraction methods, the infusion and decoction methods were shown to be equivalent to the standard extraction method (UAE). Tobacco extract is recommended as a strategy to control M. spectabilis, at a concentration of 25%, with its extraction by infusion and decoction. In the second stage, olfactometry bioassays were performed. The combinations of aqueous extracts applied to the host plant were tested against fresh air and against the host plant without the extract. The aqueous vegetable extracts of tobacco, star anise and eucalyptus were not attractive for the M. spectabilis, and can be used as a management tactic in the case of elephant grass.