Guy Frederick Sutton

Most biological control programmes against invasive alien plants (weeds) utilise agents collected from indigenous populations of the target weed that are thought to have a long coevolution history between the target weed and the agent. These biocontrol agents are referred to as old associations. There are, however, several examples of cactus weeds being successfully controlled by new associations, which are agents collected on other cactus species rather than the target weed itself and are thought to lack any significant coevolutionary history with the target weed. It is therefore unclear whether new or old associations are more effective biocontrol agents for invasive alien Cactaceae. This study aimed to evaluate whether old or new associations of Dactylopius tomentosus Lamarck (Hemiptera: Dactylopiidae) are more effective biocontrol agents for invasive Cylindropuntia (Cactaceae) species. Three lineages of D. tomentosus were tested on seven Cylindropuntia species. The fitness of each lineage was assessed using adult survival, female body mass, and a fitness index, with phylogenetic distance between the primary host plant and closely related species used as a predictor. The results showed a significant negative correlation between fitness and phylogenetic distance across all lineages, with the highest survival, body mass, and fitness index on the primary host and its closest relatives. These findings support the use of old associations as biocontrol agents for Cylindropuntia species, and for invasive alien plants in general.

Spathodea campanulata P. Beauv (Bignoniaceae) (African tulip tree) is indigenous in Central and West Africa but is now a widespread invasive species throughout the Pacific. It is considered one of ...

This research evaluated the effects of mixed betabaculovirus and alphabaculovirus infections for the biological control of false codling moth, Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae). The research involved testing single and mixed treatments of two baculoviruses: Cryptophlebia leucotreta granulovirus (CrleGV) and Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), against neonate T. leucotreta larvae via surface dose response assays. The data shows various treatments comprising different combinations of these viruses, each applied across a range of dosages, against 24 neonate larvae, with each treatment performed in triplicate. Dosages are provided in terms of OB/ml and OB/mm2.

This research evaluated the effects of mixed betabaculovirus and alphabaculovirus infections for the biological control of false codling moth, Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae). The research involved testing single and mixed treatments of two baculoviruses: Cryptophlebia leucotreta granulovirus (CrleGV) and Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), against neonate T. leucotreta larvae via surface dose response assays. The data shows various treatments comprising different combinations of these viruses, each applied across a range of dosages, against 24 neonate larvae, with each treatment performed in triplicate. Dosages are provided in terms of OB/ml and OB/mm2.

Cold treatments are widely used for disinfestation of commodities in international trade and mostly require an uninterrupted duration of exposure to temperatures that do not exceed a specified threshold. The effect of temporary interruptions on cold treatment efficacy was tested on second instar larvae of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in Valencia oranges. In a first series of experiments using one room, a cold treatment of 6 d at a target pulp temperature of 0.9 °C was used. When applied continuously, this constituted the uninterrupted treatment. Interruptions to this treatment were simulated by removing fruit from the cold room until pulp temperatures reached either 3.1 °C or 5.1 °C and as soon as these were reached, fruit were brought back. The timing (first or second half), intensity (3.1 °C or 5.1 °C) and frequency (single or double) of interruptions were investigated in this series. In a second series of experiments using 2 cold rooms at a target pulp temperature of 0.9 °C, interruptions were induced by switching off cooling in one of the cold rooms until pulp temperature reached 5.1 °C. Once the latter was reached, cooling was switched on again. The total interruption time was at least 33 h with a minimum of 16 h for pulp temperatures to reach 5.1 °C and a minimum of 17 h for return to target temperature. In experiments conducted for either 6 or 14 d, there were no significant differences in larval mortality between interrupted and uninterrupted treatments. This study demonstrated that cold treatment efficacy was not compromised by temporary temperature interruptions.

Pre-release efficacy assessments (PREA) can be used to prioritise the most damaging candidate agents for further studies in biological control programmes against invasive alien plants. This study assessed the efficacy of various potential enemies of Trichocereus spachianus (Riccob.) (Caryophyllales: Cactaceae), an invasive cactus in South Africa, in order to prioritise the most damaging candidates for further studies, including host specificity testing. T. spachianus is considered indigenous in Argentina and Bolivia, but the original description was based on a cultivated plant, and it is either very rare or absent in its indigenous range, with no verified records of natural populations. This necessitates the use of new associations collected off close relatives of the target plant as potential biocontrol agents. We evaluated eight potential biocontrol agents by deriving host suitability indices (HSI) and performing efficacy trials. The HSI analysis demonstrated that only one out of the eight candidate agents, a cochineal insect Dactylopius confertus De Lotto (Hemiptera: Dactylopiidae), had high fitness (high survival, fecundity and complete development) on T. spachianus . This helped us eliminate ineffective agents early on in the programme. The cochineal insect was prioritised for efficacy trials, which demonstrated its high potential efficacy, killing approximately 89% of T. spachianus plants over 60 weeks. Taken together, our results indicated that D. confertus is a highly promising potential agent for the biocontrol of T. spachianus in South Africa. By prioritising candidate biocontrol agents based on efficacy prior to host specificity testing, we ensured that the highest priority candidate agent was identified for detailed and resource-intensive host specificity testing.

Thaumatotibia leucotreta, an important citrus pest in southern Africa, is subject to phytosanitary regulations for certain export markets. A systems approach has been developed as an alternative to standalone postharvest disinfestation methods, integrating multiple risk mitigation steps, including preharvest infestation monitoring. This study aimed to validate an existing preharvest monitoring protocol based on fallen fruit collected under designated data trees and to develop a novel monitoring system based on sampling of sanitation fruit. Monitoring was conducted in seven Navel orange orchards (N = 7 each year) during the 2021 and 2022 seasons, representing high and low infestation levels, respectively. Infestation levels were assessed over 11–12 weeks by inspecting fruit beneath four sets of five trees and all sanitation fruit collected per orchard. The new system, which involves inspecting a 100-fruit sample per orchard, was compared with the previous method. While the five-tree protocol tended to overestimate infestation, it remained effective. The sanitation-fruit sampling approach accurately reflected orchard-level infestation, with a 100-fruit sample sufficient for orchards as large as 20 hectares. Although random sampling is recommended, it was not essential for effectiveness. These results support the use of the new monitoring procedure in the systems approach for citrus exports for T. leucotreta risk mitigation.

Although variation in effect sizes and predicted values among studies of similar phenomena is inevitable, such variation far exceeds what might be produced by sampling error alone. One possible explanation for variation among results is differences among researchers in the decisions they make regarding statistical analyses. A growing array of studies has explored this analytical variability in different fields and has found substantial variability among results despite analysts having the same data and research question. Many of these studies have been in the social sciences, but one small “many analyst” study found similar variability in ecology. We expanded the scope of this prior work by implementing a large-scale empirical exploration of the variation in effect sizes and model predictions generated by the analytical decisions of different researchers in ecology and evolutionary biology. We used two unpublished datasets, one from evolutionary ecology (blue tit, Cyanistes caeruleus, to compare sibling number and nestling growth) and one from conservation ecology (Eucalyptus, to compare grass cover and tree seedling recruitment). The project leaders recruited 174 analyst teams, comprising 246 analysts, to investigate the answers to prespecified research questions. Analyses conducted by these teams yielded 141 usable effects (compatible with our meta-analyses and with all necessary information provided) for the blue tit dataset, and 85 usable effects for the Eucalyptus dataset. We found substantial heterogeneity among results for both datasets, although the patterns of variation differed between them. For the blue tit analyses, the average effect was convincingly negative, with less growth for nestlings living with more siblings, but there was near continuous variation in effect size from large negative effects to effects near zero, and even effects crossing the traditional threshold of statistical significance in the opposite direction. In contrast, the average relationship between grass cover and Eucalyptus seedling number was only slightly negative and not convincingly different from zero, and most effects ranged from weakly negative to weakly positive, with about a third of effects crossing the traditional threshold of significance in one direction or the other. However, there were also several striking outliers in the Eucalyptus dataset, with effects far from zero. For both datasets, we found substantial variation in the variable selection and random effects structures among analyses, as well as in the ratings of the analytical methods by peer reviewers, but we found no strong relationship between any of these and deviation from the meta-analytic mean. In other words, analyses with results that were far from the mean were no more or less likely to have dissimilar variable sets, use random effects in their models, or receive poor peer reviews than those analyses that found results that were close to the mean. The existence of substantial variability among analysis outcomes raises important questions about how ecologists and evolutionary biologists should interpret published results, and how they should conduct analyses in the future.

The Asian Citrus Psyllid (ACP) (Diaphorina citri Kuwayama, 1908) (Hemiptera: Psyllidae) is a major citrus pest. The species has been introduced to West and East Africa, but has not yet spread to southern Africa, where it could have a devastating impact on citrus farming and livelihoods. A proactive response is key to mitigating the species’ impacts, particularly the ongoing monitoring of potential invasion routes and entry points into South Africa. Species distribution models (SDMs) were developed under current and future climates for ACP in Africa, and these models were used to (1) determine where the species likely poses a threat, (2) identify potential invasion routes into South Africa, and (3) assess how these factors will be affected under climate change. The SDMs indicated that there is an almost contiguous band of suitable climate along the east coast of Africa that joins the species’ current range in East Africa to South Africa, and under aggressive climate change a potential route of invasion through Namibia and Botswana. Much of South Africa is climatically suitable for the species, but under climate change, climatically suitable areas are likely to shift further inland. The spread of ACP into South Africa is unlikely to be prevented, but the outputs of the present models will inform monitoring activities and assist with preparations to respond to this predicted biological invasion.