Abstract
The pink hibiscus mealybug Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) is an invasive pest of an enormous variety of crops and has become a concern in many parts of the world. Early attempts to control M. hirsutus with chemical insecticides and cultural methods have failed due to the cryptic habit of the insect. We assessed the entomopathogenic nematode Heterorhabditis amazonensis as a biological agent against different insect stages. Comparing different concentrations of the nematode, insect females were very susceptible, with more than 90% of the insects killed. In second and third nymphal stages mortality rates varied from 20 to 60% depending on the nematode concentration. The first nymphal stage as much less susceptible to nematodes due to their small size. The number of nematodes capable of invading the insect host did not vary between the different concentrations. However, the LC50 for females (35.2 IJ/insect), second and third nymphal stages (83.9 IJ/insect) demonstrated that H. amazonensis should be considered as a potential biocontrol agent of the pink hibiscus mealybug.
Highlights
The pink hibiscus mealybug (PHM), Maconellicoccus hirsutus Green (Hemiptera: Pseudococcidae), has become a serious pest in Venezuela since its detection in the 1990s
Some laboratories in Venezuela work actively on these organisms (SanBlas et al, 2015), which are currently available in small quantities for biological control programs (San-Blas, Luzardo, Larreal, Portillo and Bastidas, 2017, San-Blas, Luzardo, Portillo, Fuenmayor and Bastidas, 2017) and production of these biocontrol agents is expected to rise shortly (San-Blas et al, 2019)
The mortality rates showed significant variations when the nematode concentration was increased in all PHM instars except in ‘crawlers’ (Fig. 1)
Summary
The pink hibiscus mealybug (PHM), Maconellicoccus hirsutus Green (Hemiptera: Pseudococcidae), has become a serious pest in Venezuela since its detection in the 1990s. Initial measures to control the pest were done using chemical insecticides and cultural methods but their efficiency was low due to the cryptic zones of the plants where the insects hide and because their impermeable waxy cover complicates the penetration of insecticides (Sagarra and Peterkin, 1999; Kairo et al, 2000; Chong et al, 2015). For these reasons, biological control by means of parasitoid wasps has been gaining acceptance. As EPNs have shown potential to become biological control agents of the above mentioned hemipterans, the objective of this work was to evaluate the pathogenicity, virulence, and infection rates of Heterorhabditis amazonensis Andaló et al (Rhabditida: Heterorhabditidae) against different stages of PHM under laboratory conditions
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