Biocontrol introduction
Target pest: Solanum mauritianum (Solanales: Solanaceae) = S. auriculatum, woolly nightshade
Agent introduced: Gargaphia decoris (Hemiptera: Tingidae), woolly nightshade lace bug
Imported:
2010
Import source:
Brazil via South Africa
Import notes:
Winks (2014) - Gargaphia decoris is native to South America. The first importation into New Zealand, of Brazilian provenance, was in 2010 from South Africa, where it had been released a decade earlier as a biocontrol agent.
Falla et al. (2021) - released individuals were sourced from Brazilian stocks that were established in South Africa after field thermal assessments revealed that they are able to tolerate colder temperatures than the Argentinian stock [that was originally released in South Africa (Cowie et al. 2018)]. [Note that subsequent assessments dismissed this idea, finding that both the original Argentinean and subsequent high-altitude Brazilian stocks could tolerate the low temperatures of South African winters (Cowie et al. 2018).]
Released:
2010
Release details:
Landcare Research (2011) - the first release was made in a forestry block at Tauranga (Bay of Plenty) in 2010. Since then releases have been made in Waikato, Taranaki, Northland and Manawatu-Whanganui.
Landcare Research (2014b) - since first release in 2010, released widely throughout New Zealand.
Landcare Research (2015j) - released at nine sites in the year Sep 2014 - Aug 2015.
Establishment:
Landcare Research (2014b) - established readily at many sites, but predation may limit its potential.
Paynter et al. (2018) - during surveys Sejanus albisignatus [a native mirid bug] observed eating a nymph but predation appears to be relatively trivial.
Falla et al. (2021) - G. decoris has established in the Northland, Auckland, Waikato and the Bay of Plenty regions of the North Island.
Impacts on target:
Landcare Research (2014b) - June 2014 reports of heavy damage to total defoliation under pines in 15-ha area in Ngapeke Forest Block, Bay of Plenty. Evidence here and in South Africa suggests G. decoris does best in partial shade.
Landcare Research (2015i) - some damaging outbreaks are beginning to occur.
Landcare Research (2017g) - beginning to cause significant damage at many sites.
Paynter et al. (2018) - major impacts have been observed on plants in shade or partial shade.
Paynter (2021b) - outbreaks of G. decoris have been largely confined to sheltered, shaded or partially shaded habitats. A recent New Zealand study showed that S. mauritianum trichomes [leaf hairs] are thicker and denser on plants in full sun, which may explain why G. decoris prefers shade.
Falla et al. (2021) - the overall damage inflicted to S. mauritianum has been deemed as ‘trivial’, both in New Zealand and South Africa (where G. decoris has also been released against S. mauritianum), except during sporadic outbreaks. Cowie et al. (2018) attributed the low performance of G. decoris in South Africa to sporadic fluctuations of its population density due to the effect of abiotic and biotic factors such as climate and predation.
Falla et al. (2023) - from glasshouse trials investigating why G. decoris more commonly infests plants growing in shaded locations rather than in full sunlight conditions, it was concluded that light intensity affected physical (such as leaf thickness and trichome density) and chemical (including glycoalkaloid concentrations) traits of S. mauritianum plants and that some of these effects influenced G. decoris performance. On young plants, G. decoris showed no discrimination between high-shade and low-shade leaves for oviposition or feeding. However, as the host plants grew older, second generation G. decoris females failed to oviposit on low shade plants and displayed smaller bodies compared to the females that developed feeding on high shade plants. Although the key factor behind the differential performance of G. decoris under contrasting light conditions remains unclear, it is believed that plant glycoalkaloid concentrations contribute to host plant selection. Trichome density was not considered a factor that would affect the performance and establishment of G. decoris because it had no problem ovipositing on leaves with high trichome density.
Landcare Research (2023g) - Gargaphia decoris only reaches high and damaging densities at shaded sites.
Paynter (2024) - factors influencing the success of weed biocontrol agents released and established in New Zealand were investigated. Each agent’s impact on the target weed in New Zealand was assessed as ‘heavy’, ‘medium’, ‘variable’, ‘slight’ or ‘none’, where a ‘heavy’, ‘medium’ or ‘variable’ impact have all been observed to reduce populations or percentage cover of their target weed in all or part of their respective target weed ranges in New Zealand. Results showed that: (i) agents that are highly damaging in their native range were almost invariably highly damaging in New Zealand; (ii) invertebrate agents with a closely related ‘native analogue’ species are susceptible to parasitism by the parasitoids that attack their native analogues and failed to have an impact on the target weed, and (iii) agent feeding guild helped predict agent impact - in particular, agents that only attack reproductive parts of the plant (e.g., seed and flower-feeders) are unlikely to reduce weed populations. Damaging impacts of G. decoris, a piercing/sucking insect, have not been reported in its native range, it does not have a New Zealand native ecological analogue and its impact in New Zealand is assessed as ‘variable’. Although G. decoris can impact S. mauritianum in New Zealand, despite not being reported having damaging impacts in its native range, it does so only at sheltered, shaded sites. As many S. mauritianum infestations occur in full sun, G. decoris does not provide adequate control in New Zealand, so the observations regarding its impacts in the native range are not particularly misleading with respect to predicting its performance in New Zealand.
Impacts on non-targets:
Hill (2009) - host range testing conducted in South Africa before lace bug was released there in 1999 showed that G. decoris could not survive or reproduce on plants outside the genus Solanum and showed very strong feeding and oviposition preferences for S. mauritianum. Analysis indicated that, with the possible exception of S. melongena (eggplant), no non-target species were likely to suffer more than incidental damage in the field. New Zealand has three native species of Solanum. Tests conducted in South Africa with these species provided strong evidence that they are not hosts for G. decoris.
Winks (2014) - Solanum mauritianum is the only species likely to be attacked. Host testing showed minor damage to eggplant (Solanum melongena) is possible but has never been reported in the lace bug's native range in South America or introduced range in South Africa.
Paynter et al. (2015) - surveys of potential non-target host Solanum melongena (eggplant) report no feeding.
EPA Applications:
EPA (2009b) - 15 Apr 2009: application by Environment Bay of Plenty to import and release from containment the lace bug Gargaphia decoris (Hemiptera, Tingidae) as a biological control agent for the weed woolly nightshade. EPA application # NOR08003, approved without controls 16 Sep 2009.
References
Cowie BW, Venter N, Witkowski ETF, Byrne MJ, Olckers T. (2018). A review of Solanum mauritianum biocontrol: prospects, promise and problems: a way forward for South Africa and globally. BioControl 63: 475–491 https://doi.org/10.1007/s10526-017-9858-0
EPA (2009b). EPA application NOR08003 to import and release from containment the lace bug Gargaphia decoris (Hemiptera, Tingidae) as a biological control agent for the weed woolly nightshade. Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/NOR08003
Falla C, Minor M, Harrington K, Paynter Q, Cordiner S, Najar-Rodriguez A (2023). Effects of light intensity on Solanum mauritianum (Solanaceae) morphological and chemical traits and the performance of its biological control agent Gargaphia decoris (Hemiptera: Tingidae). Biological Control 181, June 2023, 105218 https://doi.org/10.1016/j.biocontrol.2023.105218
Falla CM, Avila GA, McColl ST, Minor M, Najar-Rodríguez AJ. (2021). The current and future potential distribution of Gargaphia decoris: A biological control agent for Solanum mauritianum (Solanaceae). Biological Control, Volume 160, Sept 2021 https://doi.org/10.1016/j.biocontrol.2021.104637
Hill R. (2009). Application to EPA (NOR08003) to import and release from containment the lace bug Gargaphia decoris (Hemiptera, Tingidae) as a biological control agent for the weed woolly nightshade. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/NOR08003/8bf11bca4d/NOR08003-NOR08003-Final-decision.pdf
Landcare Research (2011). First woolly nightshade bug release. What's new in biological control of weeds 55: 3 http://www.landcareresearch.co.nz/__data/assets/pdf_file/0003/20649/wtsnew55.pdf
Landcare Research (2014b). Lace bug does best in shade. What's new in biological control of weeds? 69: 2 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-69
Landcare Research (2015i). Who's who in biological control of weeds? Weed Biocontrol: What's New? 73: 10-11 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-73
Landcare Research (2015j). Biocontrol agents released in 2014/15. Weed Biocontrol: What's New? 73: 2 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-73
Landcare Research (2017g). Who's who in biological control of weeds? Weed Biocontrol: What's New? 81: 10-11 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-81
Landcare Research (2023g). Who's who in the biological control of weeds. Weed Biocontrol: What's New? 105, August 2023 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/whos-who/
Paynter Q (2021b). Woolly nightshade lace bug: Gargaphia decoris. The Biological Control of Weeds Book - Te Whakapau Taru: A New Zealand Guide (Landcare Research) [Update of Winks (2014)] https://www.landcareresearch.co.nz/discover-our-research/biodiversity-biosecurity/weed-biocontrol/projects-agents/biocontrol-agents/woolly-nightshade-lace-bug/
Paynter Q (2024). Prioritizing candidate agents for the biological control of weeds. Biological Control, Volume 188, January 2024, Article Number 105396 https://doi.org/10.1016/j.biocontrol.2023.105396
Paynter Q, Fowler SV, Groenteman R. (2018). Making weed biological control predictable, safer and more effective: perspectives from New Zealand. BioControl 63: 427–436 (first published online 8 Aug 2017) https://doi.org/10.1007/s10526-017-9837-5 https://link.springer.com/article/10.1007/s10526-017-9837-5
Paynter QE, Fowler SV, Gourlay AH, Peterson PG, Smith LA and Winks CJ (2015). Relative performance on test and target plants in laboratory tests predicts the risk of non-target attack in the field for arthropod weed biocontrol agents. Biological Control 80: 133-142 https://doi.org/10.1016/j.biocontrol.2014.10.007
Winks C (2014). Woolly nightshade lace bug: Gargaphia decoris. The Biological Control of Weeds Book - Te Whakapau Taru: A New Zealand Guide (Landcare Research) [Updated 2021 - see Paynter (2021b)] https://www.landcareresearch.co.nz/discover-our-research/biodiversity-biosecurity/weed-biocontrol/projects-agents/biocontrol-agents/woolly-nightshade-lace-bug/
