Page 20 - EER-2-1

Explora: Environment
and Resource Data should determine biocontrol success

success of the plants before agent release. There is thus development in the galls of the agent U. morrisii released on
no data to compare to if such data are not collected A. saligna. When these trees occur next to citrus orchards,
before release. Second, the State of Invasive Species these galls provide an additional niche and potential source
Report identifies biocontrol of weeds as one of the best- for this pest. Similarly, galls of T. acaciaelongifoliae released
124
23
documented management actions in South Africa and on A. longifolia were found to contain, among several other
suggests more investment into biocontrol in South Africa. inquilines, the litchi moth (Cryptophlebia peltastica), which
However, as shown here for Acacia spp., the data does not is a known pest of several tree crops. These associations
125
support this assertion. Third, Australian Acacia biocontrol by species of the same families (e.g., Tortricidae) are also
agents have been released into other continents based found in the native Australian range, and it has been
125
on South African recommendations that biocontrol will proposed that investigating ecological interactions (e.g., by
be successful in reducing the impacts of these invasive representatively sampling developed, pre-emergence galls
species. The question arises whether the import of these and rearing out all occupants) before the release of galling
agents to other continents to initiate biocontrol programs agents will identify potentially problematic non-target
(e.g., A. longifolia in Portugal ) will potentially solve any associations.
121
of the invasive species-induced environmental problems D. dielsi released on A. cyclops in South Africa provides
faced if additional control methods (such as mechanical
clearing) are not implemented simultaneously. Recently, another case of an unintended consequence with one of
the European Food Safety Authority–Plant Health (EFSA- the gall-forming biocontrol agents released on Australian
PLH) (IOBC) approved the release of T. acaciaelongifoliae Acacia. Recently, it was found that this biocontrol agent’s
galls harbor the straw itch mite, and these mites were found
in Portugal, Jeger et al. 122,p.272 state that “Given that release of at coastal towns where “bite outbreaks” are periodically
the BCA would substantially reduce (1) the vegetative growth, experienced. Again by releasing the gall-forming
126
reproductive potential and population density of invasive
alien A. longifolia, (2) the negative impacts of the invasive biocontrol agent, a trophic connection has been made to
alien A. longifolia on biodiversity and ecosystems, and (3) the another organism, which would not be associated with the
negative impacts of current control measures for the invasive invasive plant species had the agent not be released.
alien A. longifolia, the consequences of the release of the wasp Carvalheiro et al. showed that high biomass
127
on the invasive alien plant A. longifolia were rated as massive.” biocontrol agents have the greatest potential for non-
This assessment by the EFSA-PLH has no empirical basis target interactions. Targeted Australian Acacia spp.
but was based on the qualitative claims in the South African are still abundant in South Africa, thus there is a large
literature and expert biocontrol practitioners. Surprisingly, biomass of various species of introduced gall-forming
seed banks of A. longifolia in Portugal pre-agent release biocontrol agents that can now interact with native species.
99
and South Africa are comparable, yet T. acaciaelongifoliae Overstating the benefit from a seed-reducing agent on the
13
has been present in South Africa for more than 30 years and one hand, and downplaying any future non-target impacts
is considered a highly successful seed-reducing agent. on the other hand (which under current global change
123
In fact, Strydom et al. 13-15 show the exact opposite of the may become even more difficult to anticipate, Bradley
assessment by the EFSA-PLH test case, which was based et al. ), biocontrol using galling agents is unfortunately
128
on expert opinion presented in the literature. This calls recommended without the necessary supporting data that
into question whether subjective assessments of control, 10,28 benefits outweigh potential costs.
by the biocontrol practitioners themselves, are sufficiently
scientifically rigorous on which to base policy decisions, 5. Conclusion
especially as it may involve in-between continent transfer Scientific advances are driven by posing questions and then
of non-indigenous species (i.e., the selected agents). Surely, collecting data to test the hypotheses, followed by peer-
there is a conflict of interest to ask biocontrol practitioners review to support the data interpretation and conclusions.
whether biological control is effective? In fact, the hypothesis, “has the release of a gall-forming
The last implication is that there are several non-native biocontrol agent significantly reduced the abundance of the
gall-forming species that have been released in South targeted host?” has not been asked, and consequently has
Africa and Portugal (and recently New Zealand) that can not been tested with empirical data. The only data that we
31
form trophic connections and have other non-intended are aware of are those from Strydom et al., 13-15 which provide
consequences compared to when the targeted host plants did seed bank, seed rain, and gall to seed pod abundance data that
not have any gall formers present. Seymour and Veldtman show that the amount of seed reduced by biocontrol agents
124
found that the false codling moth (Thaumatotibia leucotreta), on A. longifolia, A. pycnantha, and A. saligna is ecologically
a major pest of citrus crops, occurs and completes its irrelevant in terms of limiting these invasive plants. In other

Volume 2 Issue 1 (2025) 14 doi: 10.36922/eer.5876