Virulence and Pre-Lethal Reproductive Effects of Metarhizium anisopliae var. anisopliae on Pseudococcus viburni (Hemiptera: Pseudococcidae)

Abstract

Obscure mealybug, Pseudococcus viburni (Signoret), is a cosmopolitan pest that causes damage by suction of vascular juices and the production of honeydew, as well as for being a quarantine insect. Within control options, entomopathogenic fungi are a good alternative, nevertheless, more research is needed. In this research, the Metarhizium anisopliae var. anisopliae (Metschnikoff) isolate Qu-M984 was evaluated on P. viburni under laboratory conditions. Virulence was evaluated by lethal dose 50 (LD 50 ) and lethal time 50 (LT 50 ), for each of the four life stages of the female. The doses tested were 10 5 , 10 6 , 10 7 and 10 8 conidia mL -1 . Also fecundity, egg size, fertility, and longevity of adult females were evaluated at doses of 10 5 and 10 6 conidia mL -1 , the evaluations were made every 2 d throughout the insect life time. The LD 50 and LT 50 obtained were variable for each life stage, although without statistical differences among life stages (P > 0.05), ranging from LD 50 = 7.3 × 10 5 to 4.9 × 10 9 conidia mL -1 and LT 50 = 7.74 to 9.97 d at 10 8 conidia mL -1 . Significant differences (P ≤ 0.05) were observed on longevity at 10 6 conidia mL -1 . Longevity was 29% less compared to the control. This result on longevity at relatively low dose is relevant due to the fact that decrease possibilities to find live quarantine insects at the moment of harvest. Fertility, fecundity and egg size showed no differences (P > 0.05).

An Agricultural Detergent as Co-Adjuvant for Entomopathogenic Fungi and Chlorpyrifos to Control Pseudococcus viburni (Hemiptera: Pseudococcidae)

“…Amnuaykanjanasin et al (2013) indicated that strain BCC2660 of B. bassiana (different than the one in our study) required 6 to 7 d to cause complete mortality on the cassava mealybug Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) when sprayed at a 10 8 conidia per mL, greater than what we used herein. Spraying P. viburni females with the same strain of M. anisopliae used in our study, Pereira et al (2011) reported a LC 50 of 3.2 × 10 4 conidia per mL with a mean lethal time (LT 50 ) of 7.4 d on females (closer to our results) but at a lower application rate. Furthermore, Pereira et al (2011) found that the M. anisopliae strain we tested reached a LT 50 on P. viburni in 7.7 to 10.0 d at 7.3 × 10 5 to 4.9 × 10 9 conidia per mL, requiring longer time than our study.…”

“…Spraying P. viburni females with the same strain of M. anisopliae used in our study, Pereira et al (2011) reported a LC 50 of 3.2 × 10 4 conidia per mL with a mean lethal time (LT 50 ) of 7.4 d on females (closer to our results) but at a lower application rate. Furthermore, Pereira et al (2011) found that the M. anisopliae strain we tested reached a LT 50 on P. viburni in 7.7 to 10.0 d at 7.3 × 10 5 to 4.9 × 10 9 conidia per mL, requiring longer time than our study. Not surprisingly, we also found that chlorpyrifos was acutely more toxic than the fungal formulations to control female P. viburni.…”

Modification of reproductive schedule in response to pathogen exposure in a wild insect: Support for the terminal investment hypothesis

“…Few studies have examined changes in egg size in insects in response to pathogens, but an experiment with mealybugs and Metarhizium sp . also found no change (Pereira, Casals, Salazar, & Gerding, 2011). Interestingly, another study with beetles ( Tenebrio molitor ) did find a reduction in egg size when healthy females were mated with fungus‐infected males, which the authors suggest is due to infected males producing reduced resources or the females choosing to invest less (Reyes‐Ramirez et al 2019).…”

Effect of relative humidity on the efficacy of entomopathogen Beauveria bassiana-based mycopesticide against red spider mite Tetranychus macfarlanei

“…No infection is thus apparent when the conidial dose is lower than the threshold (Devi & Rao 2006). It has been reported that a certain amount of pathogen concentration is required for successful infection, such as 1×10 7 conidia/ml B. bassiana against Metarhizium anisopliae (Metschnikoff) Sorokin (Coleoptera: Meloidae) (Devi & Rao 2006), 1.6×10 8 conidia/m 2 of M. anisopliae (Ascomycota: Hypocreales) against Anopheles gambiae Giles and Culex quinquefasciatus Say (Diptera: Culicidae) (Scholte et al 2003), and 1×10 6 conidia/ml of M. anisopliae isolate Qu-M984 against Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae) (Pereira et al 2011). Moreover, higher concentrations of B. bassiana are known to infect Lygus hesperus Knight (Hemiptera: Miridae) even at lower humidity (Dunn & Mechalas 1963).…”