CABI News

CABI’s PlantwisePlus programme is working with Grenada’s Ministry of Agriculture and the Sandals Foundation to sustainably manage invasive Croton scale which can devastate the Caribbean country’s mango, guava, plums, and soursop crops.

Soursop, for instance, is a valued crop in Grenada, a Member Country of CABI, which is used to produce ice cream as well as cakes, juices, smoothies and even tea and margaritas.

As part of an Integrated Pest Management (IPM) plan for Croton scale (Phalacrococcus howertoni), CABI has updated its partners on progress made on a range of biological control agents to control the pest which, if left to feed on crops, can lead to leaf yellowing, wilting, and premature leaf drop.

The Croton scale can also produce honeydew, a sticky sugary substance, which can contaminate fruits, leaves, and other parts of the plant, and supports the growth of sooty mold. Sooty mold can further reduce plant health by blocking photosynthesis.

Investigating the efficacy of Biological Control agents

However, CABI – working with the Ministry of Agriculture and Sandals Foundation – is fighting back by investigating the efficacy of micro-parasitoids such as Metaphycus sp., Chartocerus sp., and predatory insects such as ladybugs (Coccinellidae) and lacewings (Chrysopidae) which are natural predators of scale insects.

In the case of the predatory insects, these beneficials natural enemies feed on the scale insects, reducing their population without harming the plant.

The micro-parasitoids are very specific and regulate the population of the pest parasitizing the scale insects by laying eggs inside them, eventually killing the hosts. They are often used in greenhouses and can be effective in outdoor environments with proper timing.

Evaluation of the Croton scale population at the field level during the technical visit (Credit: Natalia Corniani).

Scientists are also investigating fungal pathogens for the control of Croton scale. These include entomopathogenic fungi like Beauveria bassiana which can infect and kill scale insects. They are typically applied as sprays and are more effective in humid conditions.

Dr Yelitza Colmenarez, CABI’s Centre Director, Brazil, and Dr Natalia Corniani, Integrated Crop Management Advisor, met with colleagues from the Ministry of Agriculture and the Sandals Foundation to update them on progress being made.

The first technical meeting included Heidi Clark, Executive Director, while the second meeting also included and Georgia Scarlett, Environmental Manager, from the Sandals Foundation, the Minister of Agriculture, Lennox John Andrews, the Permanent Secretary, Isaac Bhagwa, the Chief Agricultural Officer, Thaddeus Peters, and the Plant Quarantine Officer, Francis Noel.

Embraced this sustainable method of control

Noreen Francine is a farmer benefiting from CABI’s research in partnership (Credit: Noah Friedman-Rudovsky/CABI).

Dr Colmenarez said, “When the study of the natural enemies started at the end of 2023 most of the plantations visited and evaluated in Grenada were suffering with the impact of the Croton scale in their tropical fruits production.

“One of the major challenges was the fact that the pest attacks the final product directly, making them not marketable. After introducing farmers to the use of the biocontrol agents, they embraced this sustainable method of control, which is an effective way to control the pest without leaving any pesticide residue in the final product, which happens when using chemical control.”

She added that capacity building was a key factor in the success of the work so far.

To ensure that the biological control agents could be recognize at the field level, remote and face-to-face training sessions were organized with the technical staff of the Ministry of Agriculture and campaigns with farmers were organized, in groups and during the weekly field visits that the extension officers are conducting.

The project has involved farmers as part of the field work and their involvement and capacity building on biological control has been an important factor to increase the familiarity with the biological control agents present at the field level and their use.

Dr Corniani said, “This project is contributing to establish a sustainable management of this invasive species and reinforcing food security and safety at the national level. The results obtained can be transferred to other Caribbean islands which could be facing similar challenges due to the impact of this pest.”

At the technical visit, His Excellency, Minister of Agriculture, St. Hon. Mi. Lennox Andrews, the Permanent Secretary, Mr Isaac Bhagwa, the Chief Agricultural Officer, Mr Thaddeus Peters, Mr Francis Noel, Plant Quarantine Officer, Mrs Georgia Scarlett (Sandals Foundation) and Dr Yelitza Colmenarez (CABI) – picture Natalia Corniani.

Additional information

Main image: Croton scale on soursop fruit in Grenada (Credit: Natalia Corniani).

Relevant story and blog

See also the story ‘Imported ladybirds save Grenada’s ice cream fruit’ published by SciDev.Net.

Read the PlantwisePlus blog ‘Advancing pest management in Grenada through PlantwisePlus biological control training.’

The Sandals Foundation

The Sandals Foundation is a non-profit organization launched in March 2009 to help Sandals Resorts International continue to make a difference in the lives of people in the Caribbean.

PlantwisePlus

PlantwisePlus gratefully acknowledges the financial support of the Directorate-General for International Cooperation (DGIS), Netherlands; European Commission Directorate General for International Partnerships (INTPA, EU); the Foreign, Commonwealth & Development Office (FCDO), United Kingdom; and the Swiss Agency for Development and Cooperation (SDC).