Exploratory Survey of Spotted Lanternfly (Hemiptera: Fulgoridae) and Its Natural Enemies in China

An invasive population of spotted lanternfly (SLF), Lycorma delicatula White, was first noted in North America in Pennsylvania in 2014, and by September 2020 populations had spread to six additional states. To develop a biocontrol program to aid in the management of the pest, exploratory surveys for SLF natural enemies in its native range were carried out in 27 provinces and other administrative regions of China from 2015 to 2019. Naturally laid egg masses were collected and sentinel SLF egg masses were deployed to attract egg parasitoids, and yellow sticky traps were used to collect SLF nymphs to discover and determine the parasitism rates of nymphal parasitoids. Results show that SLF is widely distributed in China (22 provinces and regions) and that the population densities in northeast China are higher than in southern and western China. An egg parasitoid, Anastatus orientalis Yang (Hymenoptera: Eupelmidae), and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae), were collected. Anastatus orientalis was reared from SLF eggs in seven provinces in China with parasitoid emergence rates ranging from 4.0 to 15.5% (or 17.6 to 37.3% if including only egg masses that had at least some parasitism). There were significant differences in parasitoid emergence rates between sites associated with factors including habitat and host plants. Dryinus sinicus was discovered in eight cities across six provinces. The percentage of SLF nymphs parasitized by D. sinicus were 31.1, 23.3, and 0% in Tai’an, Shandong Province, Beijing City, and Yan’an, Shaanxi Province, respectively. These two parasitoids are promising natural enemies that are being considered as potential biocontrol agents of invasive populations of SLF.

Life History and Rearing of Anastatus orientalis (Hymenoptera: Eupelmidae), an Egg Parasitoid of the Spotted Lanternfly (Hemiptera: Fulgoridae)

To support efforts to manage and contain spotted lanternfly (SLF), Lycorma delicatula White (Hemiptera: Fulgoridae), research is being conducted to develop classical biological control methods. To date, two potential biocontrol agents from China have been identified: an egg parasitoid, Anastatus orientalis, and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae). The research detailed here focuses on investigating the biology and rearing of A. orientalis to assess its potential efficacy in a biocontrol program and optimize its rearing. Female wasps lived significantly longer than male wasps (68 and 23 d, respectively) and females produced an average of 94 total progeny that successfully emerged as adults, with most progeny produced between weeks one and four of the females’ lives. The sex ratio of the progeny, with no re-mating, was initially highly female-biased but became progressively more male-biased, likely due to sperm depletion. There was no evidence of additional mortality to SLF eggs from wasp host feeding, but the data were highly variable and the sample size was small. There was high parasitoid emergence when oviposition conditions mimicked mid-September Beijing temperature and photoperiod; however, there was little emergence under 25°C and long-day conditions because most progeny entered a diapause. Storage of parasitized eggs in 5°C chill lowered parasitoid emergence rates. Lastly, there was no evidence that storing field-collected SLF egg masses in 5°C for 10 mo prior to parasitization affected parasitism rates. These findings inform our rearing protocol for A. orientalis and facilitate our testing of this species as a potential biological control agent for SLF.

Variable Efficacy of the Purple Loosestrife (Lythrum salicaria) Biological Control Program in Ontario: Recommendations for Future Monitoring

Invasive species represent a major threat to global biodiversity and have multi‐million dollar impacts onagricultural productivity as well as the functioning of natural ecosystems. Biological control, theintroduction of the natural enemies of invading species, is a potentially cost‐effective and powerfulmanagement tool for controlling the spread and impact of exotic organisms. However, the monitoringcomponent of biocontrol initiatives is rarely adequate to determine their success, impeding theimprovement of biocontrol techniques. In order to determine the efficacy of the biocontrol beetlesintroduced to control purple loosestrife (Lythrum salicaria), an invasive wetland plant in Ontario, 52 L.salicaria populations were surveyed in eastern and central Ontario in August and September 2009. Threepopulation types were surveyed, those in which the release of Galerucella species biocontrol beetles hadanecdotally been effective, anecdotally ineffective, and those in which beetles had never beenpurposefully released. The level of herbivory damage inflicted by the biocontrol beetles was recorded, aswell as plant height, flower number, and measures of stand density. It was determined that thebiocontrol beetles have spread throughout Ontario, and are inflicting a moderate level of damage onpurple loosestrife populations. However, significant variation exists among populations in thesemeasures, and levels of damage were not significantly different between the three site types. Thisindicates that a variety of ecological factors influence the efficacy of biocontrol, and it is recommendedthat the purple loosestrife biocontrol program be more intensively monitored in future so that it mayinform subsequent initiatives in Canada.

Effect of Wolbachia on insecticide susceptibility in lines of Aedes aegypti

Two stable infections of Wolbachia pipientis, wMelPop and wMel, now established in Aedes aegypti, are being used in a biocontrol program to suppress the transmission of dengue. Any effects of Wolbachia infection on insecticide resistance of mosquitoes may undermine the success of this program. Bioassays of Ae. aegypti were conducted to test for differences in response to insecticides between Wolbachia infected (wMelPop, wMel) and uninfected lines. Insecticides screened were bifenthrin, the pyrethroid commonly used for adult knockdown, as well as larvicides: Bacillus thuringiensis var. israelensis, the organophosphate, temephos and the insect growth regulator, s-methoprene. While differences in response between lines were detected for some insecticides, no obvious or consistent effects related to presence of Wolbachia infection were observed. Spreading Wolbachia infections are, therefore, unlikely to affect the efficacy of traditional chemical control of mosquito outbreaks.

Selection of Antagonist Microorganisms Against Helminthosporium solani, Causal Agent of Potato Silver Scurf

Silver scurf, caused by the fungus Helminthosporium solani, is an important disease affecting potato tubers. Control of the disease has been hampered by the development of H. solani strains resistant to thiabendazole, the only fungicide used in postharvest treatment. As a result, alternative control strategies are needed. In this study, 100 selected soil samples from the province of Québec were tested for their effect on silver scurf development on potato tubers. The results showed that 10 soils were able to decrease silver scurf development on tubers incubated at 10, 15, or 24°C. Many microorganisms were isolated from these soils and tested for their individual ability to reduce H. solani development using a whole-tuber assay. Several of them, including Alcaligenes piechaudii, Aquaspirillum autotrophicum, Arcanobacterium haemolyticum, Arthrobacter oxydans, Bacillus mycoides, Kocuria rosea, Streptomyces griseus, and a fungus of the class Zygomycetes displayed an ability to reduce the development of silver scurf on potato tubers at 10, 15, or 24°C. These results can find useful applications toward a biocontrol program of potato silver scurf as postharvest or seed tuber treatment.