Invasive alien species threaten Kenya

Anoplolepis gracilipes (yellow crazy ant) ​​adults – just one species the scientists say should be monitored. Credit: John Tann / via wikipedia – CC BY 2.0

CABI has led research prioritizing 120 potential invasive alien species (IAS) that could pose a threat to agriculture and biodiversity in Kenya.

From the first review, the study, published in the journal Biological invasionscompiled a list of 21 arthropods, nine nematodes and 20 pathogenetic species that the scientists say should be assessed and monitored to minimize their impact on key crops.

The scientists ranked the IAS in order of likelihood of entry, magnitude of socio-economic impact, and impact on biodiversity.

In the last decade, Kenya has been particularly affected by new introductions of invasive plant pests that damage crops. For example, in 2011, a new maize disease – later identified as Maize Lethal Necrosis Disease (MLND) – was reported in the Bomet and Naivasha counties of the country.

Other destructive invasive plant pests include the tomato leafminer (Pthorimaea absoluta), potato cyst nematodes, the autumn armyworm (Spodoptera frugiperda), and papaya mealybug (Paracoccus marginatus).

For example, de Groote et al. (2020) showed that fall armyworm caused a loss of about a third of Kenya’s annual maize production.

Invasive ants are also considered to have a serious impact on biodiversity worldwide. Two ants in the review scored high for their potential impact on biodiversity, yellow mad ant (Anoplolepis gracilipes) and Argentine ant (Linepithema humile).

The study, which took advantage of the premium version of the horizon scan tool included in CABI’s Crop Protection Compendium (CPC), suggests the IAS will likely arrive in several ways.

This includes natural dispersal, especially for many arthropods, arrival on a product in the case of seed-borne pests, with vectors that can spread naturally in the case of viruses and viroids, and as hitchhikers in the case of soil-borne pests that can be spread intentionally or unintentionally introduced with soil.

Regarding the three main arthropods, the scientists say that silver-leaved whitefly (Bemisia tabaci (MEAM1)), peace fruit fly (Bactrocera zonata) and the yellow mad ant pose the greatest risk and require further mitigation measures. This includes further molecular analysis for B. tabaci, a full pest risk assessment and monitoring for B. zonata, and a prevention and early detection program for A. gracilipes.

In terms of nematode species, groundnut testa nematode (Aphelenchoides arachidis), peanut pod nematode (Ditylenchus africanus) and potato tuber nematode (Ditylenchus destructor) represent the greatest threat and a full pest risk assessment and monitoring is recommended in all cases.

Finally, in terms of pathogenic species, citrus canker (Xanthomonas citri), Ceratocystis disease (Ceratocystis fimbriata) and bacterial stem rot of maize (Dickeya zeae) are the three main risks requiring either an investigation and/or a full pest risk assessment.

dr. Joseph Mulema, Senior Scientist, Research, based at CABI’s Regional Center for Africa, is lead author of the study. He said: “Kenya has prioritized a number of value chains under the Agriculture Sector Transformation and Growth Strategy 2019-2029 as key to improving livelihoods and supporting economic growth.

“Therefore, species that can affect the prioritized value chains are suitable targets for conducting a full pest risk analysis. The outcome of the analysis will advise the implementation of import controls and the preparation of contingency plans.

“By prioritizing risk, horizon scanning directs resource allocation to interventions most likely to reduce risk and is very helpful to national plant protection organizations and other relevant stakeholders.”

Since the study was conducted in 2018, four pest species have been found in Kenya. These include two arthropods (red gum lerp psyllid and the spotted wing drosophila) and two pathogenic organisms (the bacterial species, P. parmentieri and the viroid, potato spindle tuber viroid).

The scientists say that the results of their latest research should therefore be regularly reviewed in the light of new information that may arise. They suggest that part of the outcome of a horizon scanning process could be systematically monitoring information sources to detect potential risk changes, which can be recorded in a phytosanitary risk register.

“Given the practicality of the approach and the widespread lack of prioritization of pests in SSA, we propose that the approach reported here could benefit many other countries on the continent, if adopted,” added Dr. Mule to it.

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More information:
Joseph Mulema et al, Prioritizing invasive alien species with the potential to threaten agriculture and biodiversity in Kenya through horizon scanning, Biological invasions (2022). DOI: 10.1007/s10530-022-02824-4

Provided by CAB

Quote: Invasive alien species threat to Kenya (2022, June 16) retrieved August 23, 2022 from

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