Potential use of Negramina (Siparuna guianensis Aubl.) essential oil to control wax moths and its selectivity in relation to honey bees

The utilization of synthetic insecticides is one of the most prevalent strategies used to control wax moth infestations, especially when the strength of bee colonies is weak. However, toxicity to bees and contamination of their products has been considered to be consequences of insecticide residues, increasing the risk of hazards to human health and to the environment. Here, we evaluated whether the application of Negramina, Siparuna guianensis Aubl., essential oil would be selective against the honey bees Apis mellifera L. without compromising the control of the wax moths Galleria mellonella L. and Achroia grisella F. The Negramina essential oil was chemically characterized and tested for insecticidal and repellent activities against A. mellifera as well as against both moth pests. The chemical composition of the essential oil revealed β-myrcene (79.7%) and 2-undecanone (14.6%) as the oil’s main constituents. While G. mellonella and A. grisella were similarly susceptible to Negramina oil, the forager bees were five- to 10-fold more tolerant to the actions of the essential oil. Furthermore, the Negramina oil (0.30 μg of essential oil/cm^2) did not repel honey bee foragers but did exhibit repellent activities (0.08 μg of essential oil/cm^2) against the larvae and adults of both wax moth species. By exhibiting desirable levels of selectivity against A. mellifera and providing relevant control levels against wax moths, the application of Negramina essential oil represents a desirable tool to replace the use of synthetic insecticides against wax moths in weak honey bee colonies as well as in stored honey bee combs

Severity of gummy stem blight on melon in relation to cultivars, use of fungicides and growing season

<div><p>ABSTRACT The authors aimed to evaluate the resistance to gummy stem blight and the agronomic traits of the melon crop in the Southern Region of the State of Tocantins, Brazil, in two growing seasons, submitted or not to treatment with fungicides. Two experiments were carried out: dry season (experiment I), and rainy season (experiment II), respectively, comprising the periods from July to October 2013 and from March to May 2014. Six melon cultivars were used in each season. In the dry season: Eldorado 300, Hibrix, Dourado Amarelo, Louro, Gaúcho Redondo and Canarian; and in the rainy season: Eldorado 300, Hibrix, HF-4439, Louro, Gaúcho Redondo and Canarian. Treatments consisted of each cultivar and split plot with (WA) or without fungicides application (NA). All cultivars were susceptible to disease, considering that Gaúcho Redondo was the least susceptible in the dry season. The fungicide application decreased disease severity in the dry season, however the productivity of the crop in treatments without fungicide application were not compromised, due to the late onset of the disease, and ranged from 19.2 t/ha for Eldorado 300 up to 41.9 t/ha for Canarian. The total soluble solids showed average values of 12°Brix, except for cultivar Gaúcho Redondo, which showed brix value lower than commercial standards. During the rainy season, fungicide application did not protect the plants, which did not complete the cycle, resulting in the absence of marketable fruit production. The climatic characteristics observed in the rainy season, with high humidity, leaf wetness and high temperatures are favorable for the development of gummy stem blight in melon plants. Thus, in Tocantins, the dry season is characterized as the best time of year for cultivation, between April and September.</p></div