Ambrosia Beetle, Sunblotch Viroid, and Persea Mites call for urgent action.
By Catherine Riungu / catherine@hortinews.co.ke
The avocado sector in Kenya is currently facing an unprecedented threat, with three major threats posing a significant risk to the industry: the Ambrosia Beetle, Avocado Sunblotch Viroid (ASBVd), and the Persea Mite. These threats have not only caused panic among farmers but have also prompted calls for urgent action from the National Horticulture Working Group, with technocrats calling for urgent action to safeguard the fast growing sector from the imminent challenges. This report delves into these issues, drawing parallels to the devastation seen in other avocado-growing regions, particularly the United States.
Outbreak of Ambrosia Beetle in the US
The Ambrosia Beetle, reported to be wreaking havoc in the US is raising the antennae in Kenya. These wood-boring insects are known for cultivating symbiotic fungi as their primary food source, and they specifically target stressed or dying trees. However, some species, such as the redbay ambrosia beetle (Xyleborus glabratus) and Euwallacea fornicatus, have been observed to attack healthy avocado trees, making them a particularly dangerous pest. These beetles spread devastating fungal pathogens like Raffaelea lauricola, which causes laurel wilt disease, and can cause rapid mortality in avocado trees.
In the US, the redbay ambrosia beetle is already damaging the avocado industry, spreading the disease throughout the southeastern states. More than 40 percent of avocado trees in the country have succumbed to the pest. Similarly, the polyphagous shot hole borer, part of the Euwallacea fornicatus complex, has targeted avocado orchards, disrupting nutrient transport and leading to tree dieback.
The threat in Kenya is real, should the pest find its way here. Although it is classified as a quarantine pest by the Kenya Plant Health Inspectorate Service, Dr Lusike Wasilwa, the Deputy Director at the Kenya Agricultural Research and Livestock Organization ( Karlo) says the National Plant Protection Organization should be on high alert. The situation is exacerbated by weak cross-border inspection in neighbouring East African countries risking the entry of the pest into Kenya, a country with strong inspection and restrictions of plant materials imports. Says Apollo Owuor, Regional Coordinator, Comesa – EAC Horticulture Accelerator, “ We have FAO Africa based in Addis Ababa, InterAftivan Phytosanitary Council, international organizations like CABI, national research institutions and the WTO National Plant Protection Organizations which monitor such pests therefore border surveillance is critical to contain outbreak and spread.
Originally native to Asia, ambrocian beetles have been transported through global trade. It wa sforst detected in the US in 2002, likely through infested wood packaging materials. It has since spread throughout the southern eastern US. The Euwallacea fornicates complex has also seen a global spread with detections in Israel, South Africa and parts of the US – California and Florida where the beetles have caused significant damage to avocado trees and other host plants.
Farmers and the general public have been advised to report any new pest or disease in their areas for urgent action.
Avocado Sunblotch Viroid (ASBVd): A submicroscopic killer
ASBVd is a submicroscopic pathogen that has been wreaking havoc on avocado crops worldwide, and it has now emerged as a significant concern in Kenya. This viroid, which is the smallest known plant pathogen, infects avocado trees and significantly reduces fruit yield and quality. ASBVd manifests in a variety of ways, from sunken, discoloured fruit to stunted tree growth and twisted branches, leaving avocado farmers with reduced production. One of the most concerning aspects of ASBVd is that trees can remain asymptomatic carriers, silently spreading the disease through propagation materials, mechanical means, and root-to-root grafts between trees.
The transmission of ASBVd is facilitated by infected budwood, cutting tools, and even pollen from infected trees. This makes controlling its spread incredibly difficult, as even healthy-looking trees can harbor the viroid and unknowingly infect others. In response to this, farmers must ensure that their propagation materials are free from infection, adopt rigorous sanitation practices, and remove infected trees promptly to limit the spread of the disease.
Persea Mites: a silent yet devastating threat
While not as widely known as the beetle or the viroid, Persea Mites have been spreading rapidly in avocado orchards across Kenya. These microscopic pests target the foliage of avocado trees, causing significant damage by feeding on plant sap. The result is leaf yellowing, deformation, and reduced photosynthesis, which weakens the tree over time and compromises fruit production. Their ability to spread quickly and silently has made them a growing concern for avocado farmers, who are already struggling to deal with other threats.
The Persea mite’s rapid spread across the country has prompted calls for increased surveillance and control measures. While mite infestations can be difficult to detect in the early stages, consistent monitoring and the application of miticides are essential to preventing damage. However, given their small size and the fact that they often go unnoticed until significant damage has occurred, managing Persea mites remains a challenge for Kenyan farmers.
Need for urgent action
With these three significant threats to the avocado sector, there is an urgent need for a PRA (Pest Risk Analysis) and an action plan that will address both the immediate and long-term risks to Kenya’s avocado industry. KEPHIS must be on high alert and work closely with scientists, farmers, and international experts to develop an integrated pest management system that includes:
• Early detection systems using traps and surveillance.
• Strict quarantine measures to prevent the spread of pests and diseases.
• Farmer education on the symptoms and management strategies for these threats.
• Support for research into effective fungicides, miticides, and control methods for the Ambrosia beetle and Persea mites.
• Coordination with international bodies to monitor and control the introduction of new pests from global trade.
The avocado industry in Kenya has grown rapidly in recent years and is an important export commodity. However, the threats posed by these new pests and diseases are a stark reminder that the industry must remain vigilant and proactive. Failure to act now could lead to significant economic losses, and Kenya’s avocado sector could face a crisis similar to what has been seen in other avocado-producing regions. The clock is ticking, and it is time for coordinated action to protect this valuable sector.
Catherine Riungu/ catherine@hortinews.co.ke / @catherineriungu
