Soursop is central to Grenada’s agricultural exports and the island is the only country in the Caribbean authorised to send fresh soursop to the United States. The UN Food and Agriculture Organization values soursop as Grenada’s largest source of foreign agricultural earnings at US$ 2.6 million, which explains why farmers and scientists are working closely to protect the crop.
The croton scale, a sucking insect first reported in Florida in 2008, was confirmed in Grenada in May 2020 after samples were sent to the Florida Department of Agriculture. The pest mainly attacks croton but also infests shoots, leaves and fruits of mango, guava, plums and soursop. Females can live about 60 days and lay up to 400 eggs; they produce honeydew that encourages sooty mold and lowers fruit quality. Farmers reported damaged trees and lost sales, with one farmer seeing sales fall from 500 pounds to 300 pounds at times and an infestation reaching about 500 of 1,200 trees on a single farm.
Initial responses by the Pest Management Unit used pesticides, neem seed oils, pruning and spraying, but younger pest stages caused recurrences and the unit had limited capacity. Given these limits, authorities turned to biological control, drawing on past experience with the pink hibiscus mealybug in the mid-1990s when 25,000 ladybird beetles and parasitic wasps were used successfully. Now technicians from CABI and the Ministry of Agriculture, supported by PlantwisePlus and the Sandals Foundation, help move natural enemies between fields and rear them in the lab for release. Training with microscopes helps farmers recognise tiny beneficial insects. CABI is seeking donor support for a Caribbean Invasive Species Trust Fund, and experts warn that weak biosecurity and limited surveillance mean ongoing monitoring and long-term management will be necessary.
- Natural enemies identified: ladybird beetles, parasitic wasps, a moth.
Difficult words
- authorise — given official permission to do somethingauthorised
- export — goods sold to other countriesexports
- earning — money a country gets from selling goodsearnings
- infest — to attack plants or animals and live on theminfests
- honeydew — sticky liquid secreted by some insects
- sooty mold — black fungus that grows on sugary residues
- biological control — use of living organisms to control pests
- parasitic wasp — small wasp that lives on or in another organismparasitic wasps
- surveillance — close observation to detect problems early
- biosecurity — measures to prevent harmful organisms spreading
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What are the possible benefits and risks of using biological control instead of pesticides for soursop farmers? Give reasons from the article.
- How might weak biosecurity and limited surveillance make long-term pest management more difficult on the island?
- What practical steps could Grenada take to protect soursop exports to the United States in the future?
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