Improving photoprotection ofBeauveria bassianaconidia for biological control of the cactus pestDactylopius opuntiaein the semiarid region northeast of Brazil

Abstract

A technical grade conidial preparation of the entomopathogenic fungus Beauveria bassiana isolate LCB63 was exposed to ultraviolet light (UV) from artificial and natural sources in the presence of various photoprotectants to develop a viable formulation to control Dactylopius opuntiae, a limiting pest of forage cacti in the Brazilian semiarid region. In the first experiment, Conidial viability was assessed in preparations containing water and liposoluble photoprotectants at a concentration of 1% and exposed to solar radiation for 0, 60, and 120 min. In another experiment, preparations containing different concentrations of the selected photoprotectants were exposed to natural and artificial UV radiation for 120 and 5 min, respectively. Insecticide activity of technical grade conidial preparations containing selected photoprotectants were evaluated against first instar nymphs of D. opuntiae. In general, no evaluated compounds showed deleterious effects on conidial germination, and they provided a strong degree of protection over a short period of time. One-percent concentrations of starch and skim milk resulted in low photoprotection over a longer irradiation period, while 1% Neo Heliopan AV, Neo Heliopan E1000 and Oxybenzone provided a moderate degree of protection. Increasing the concentration of Oxybenzone increased germination rate to 70%, while treatment with 1% Neo Heliopan E1000 maintained germination at 50%. A technical grade conidial preparation containing 1% Oxybenzone was effective in promoting D. opuntiae nymph mortality. These results suggested that addition of liposoluble photoprotectants could provide better photoprotection for B. bassiana LCB63 conidia in bioinsecticide formulations.

Efectividad de hongos entomopatógenos sobre la mortalidad de Dactylopius opuntiae (Hemiptera: Dactylopiidae) en condiciones de laboratorio

“…En bioensayos realizados sobre escamas Phoenicococcus marlatti, se observó que el hongo B. bassiana no logró parasitar el insecto (Asensio et al, 2005). A pesar de que en este estudio los valores de mortalidad registrados resultaron los más bajos Bb1 (16.5%) y GHA (22.9%, Santos et al (2011) al evaluar el efecto del hongo B. bassiana mezclado con agentes protectores sobre ninfas de primer instar de D. opuntiae, detectaron que al incluir un protector solar (Oxybenzone ® ) en la formulación del hongo, se alcanzaron valores de mortalidad de 46.5%. Dicho valor es más alto que los registrados en el presente estudio, donde B. bassiana (GHA) obtuvo una mortalidad máxima de 22.6%.…”

“…El empleo de biopesticidas, incluyendo aquellos formulados a base de hongos entomopatógenos, están tomando importancia como una alternativa al empleo de insecticidas. En este aspecto Brasil, ha destacado al realizar estudios con B. bassiana para el control de D. opuntiae (Santos et al, 2011) y Fusarium incarnatum-equiseti (Da Silva et al, 2016) pero no existen, de acuerdo a nuestro conocimiento, estudios en México donde se aborde el empleo de diferentes cepas de hongos para su control. Por lo anterior, se pretende evaluar la patogenicidad y virulencia de tres especies de hongos entomopatógenos (Metarhizium anisopliae, Beauveria bassiana y Lecanicillium lecanii) sobre la mortalidad de ninfas de segundo instar de la cochinilla D. opuntiae.…”

Compatibility of Metarhizium anisopliae with liposoluble photoprotectants and protective effect evaluation against solar radiation

“…After 7 hours of exposure, germination of the conidia remained high, at 98.82, 99.32 and 98.87%, in concentrations of 0.5, 1 and 2%, respectively. B. bassiana conidia exposed for 2 hours to natural solar radiation in the region of Petrolina, in the Brazilian semi-arid region, under the effects of Neo Heliopan ® AV, showed germination of 41% (SANTOS et al, 2011). The Neo Heliopan ® BB photoprotectant also showed efficient conidia protection, especially at concentrations of 1 and 2%.…”

“…Some authors used conidia germination (HEDIMBI et al, 2008;SANTOS et al, 2011) or colony forming units analysis (INGLIS et al, 1995) to evaluate the compatibility of M. anisopliae with liposoluble photoprotectants. They found that the photoprotectants have little or no effect on the fungus, a fact that was also observed for germination of the M. anisopliae JAB 68 isolate.…”

Selection of anti-wetting agents and photoprotectants compatible with a soybean weed control bioagent

“…BI: Biological index; CV: coefficient of variation; C: compatible; MT: moderately toxic; T: toxic. compatible with the fungus (Santos et al, 2011). However, this assessment did not consider the BI model, which includes data on vegetative growth and sporulation.…”