🌿 GHG Garden Detective Files #2
"Good gardeners don't just grow plants—they learn to read the stories those plants are telling."- The Grey-Haired Gardener.
I wasn't even in my own garden when this story unfolded.
Recently, I visited a friend who was excited to cut open a soursop she had harvested. From the outside, it looked reasonably healthy, although there were a few dark, sunken spots near the blossom end that raised our suspicions.
The outside of the soursop showed several dark, sunken lesions near the blossom end. At this stage, it was impossible to know exactly what had caused them.
Curious to see what was inside, we sliced it open.
Cutting open the fruit revealed areas of black rot beneath the external lesions, while much of the surrounding flesh remained white and apparently healthy.
The inside told a very different story.
A large, blackened area of decaying flesh had developed beneath the damaged portion of the fruit, while much of the remaining pulp still appeared healthy. The contrast was striking—and disappointing.
Neither of us could say with certainty what had caused the damage.
But one thing was obvious.
This wasn't an isolated problem.
If you've spent any time in Caribbean gardening groups, you've probably seen photos very similar to these.
One gardener blames seed borers.
Another says anthracnose.
Someone else insists it's fruit flies.
So...which is it?
That question sent me looking for answers.
Looking Beyond Social Media
Because this issue appears so frequently in gardening groups and among both home gardeners and commercial growers, I wanted to go beyond the opinions shared online and seek advice from someone who works with these problems professionally.
I recently spoke with Dr. Augustus Thomas, Assistant Lecturer (Plant Pathology) and AES Coordinator, Department of Food Production of The University of the West Indies, who generously shared his knowledge and practical recommendations.
The information presented in this article has been shared with Dr. Thomas for review prior to publication to ensure that I have represented his recommendations accurately.
It's Not Just One Problem
One
of the biggest things I learned from our conversation is that gardeners are
often looking at two problems working together.
According
to Dr. Thomas, several insect pests—including seed borer moths, scales
and mealybugs—cause injury to developing soursop fruits when they feed.
These
injuries allow for easy entry of fungal pathogens.
The
fungi are then responsible for the black rot that gardeners discover when the
fruit is finally cut open.
In other words...
The insects start the problem. The fungi finish it.
That explains why the symptoms can look so dramatic by harvest time.
Understanding the Life Cycle
Dr. Thomas explained that adult seed borer moths lay their eggs on developing fruits.
The larvae feed within the fruit, causing damage that opens the door for fungal pathogens.
Once they complete their development, they leave the fruit and pupate in the soil, later emerging as adults to repeat the cycle.
Understanding this life cycle helps explain why removing damaged fruit alone may not completely solve the problem.
Why Is It So Difficult to Control?
Unfortunately, once these pests become established, management becomes much more challenging.
Dr. Thomas explained that non-chemical methods alone are often not enough once an infestation is well established, particularly in larger trees.
Another challenge is ensuring that treatments actually reach the developing fruits.
Soursop trees can become quite tall and dense, making it difficult for sprays to penetrate the canopy effectively.
Dr. Thomas' Recommendations
Based on his experience, Dr. Thomas recommends an integrated pest management approach.
1. Reduce Existing Pest Populations
An appropriate insecticide may be necessary to reduce pest numbers.
Farmers also use a fine mesh around the fruits to deter pests.
The aim is to interrupt the pest's life cycle before more fruits become infested.
2. Protect Against Fruit Rot
Because fungal pathogens are responsible for much of the visible decay, a suitable fungicide should also be used to protect developing fruits.
3. Achieve Better Spray Coverage
One recommendation that stood out to me was the importance of good spray coverage.
Rather than relying solely on a knapsack or hand-held sprayer, Dr. Thomas recommends using a motorized mist blower whenever possible.
The fine mist penetrates the tree canopy much more effectively, allowing treatments to reach developing fruits hidden throughout the tree.
4. Apply Both Products Together
For efficiency, the insecticide and fungicide can be prepared separately according to label directions and then added to the sprayer for a single application, provided the products are compatible and their labels allow tank mixing.
5. Follow Up With Botanicals and Biologicals
Botanicals like neem may not eliminate an established pest infestation, but if used prior to pests being established it can help to deter their establishment and forms part of a longer-term management programme.
Biologicals like Biophyt 1.0 can also help to reduce disease severity and integrating them into an Integrated Pest Management (IPM) strategy will significantly reduce the reliance on chemicals and make the fruit healthier and safer for consumption.
Don't Forget Good Garden Hygiene
Chemical control alone isn't enough.
Good sanitation remains one of the gardener's best tools.
Remember to:
- Remove and destroy badly infected fruits.
- Pick up fallen fruits beneath the tree.
- Prune overcrowded branches to improve airflow.
- Monitor young fruits regularly for signs of damage.
These simple practices help reduce both pest populations and disease pressure.
My Take
When we first cut open my friend's soursop, it would have been easy to point the finger at a single culprit.
Instead, I discovered that the answer is often more complex.
The black rot that so many gardeners are seeing may actually be the result of insect pests and fungal pathogens working together.
That conversation with Dr. Thomas reminded me of something every gardener eventually learns:
Nature rarely reads the textbook.
Sometimes one problem opens the door for another and understanding that relationship is the first step toward finding an effective solution.
As gardeners, we don't have to know everything.
But we should never stop asking questions.
"Every garden mystery has a story. The patient gardener learns by observing first, asking questions second, and drawing conclusions last."
Have You Seen This in Your Garden?
Have you cut open a soursop only to find blackened flesh like this?
What methods have worked for you?
Have you tried fruit bagging, pruning, sanitation, neem, or other management techniques?
I'd love to hear about your experiences.
Leave a comment below. Your story might be the clue that helps another gardener solve the next garden mystery.
🕵️ GHG Garden Detective Files
Real garden mysteries. Real investigations. Practical solutions.
Grey hair, green thumb, proud of my roots
thegreyhairedgardener.blogspot.com
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ReplyDeleteNot surprising at all. The soursop is anticarcinogenic and abundantly found in nature particularly the tropics. Bio economic sabotage!! I won't doubt that certain pests and diseases that are affecting crops were bio engineered. Just like the beatles affecting the copra industry and red ring so that they can push their corn oil, soya, canola etc by these TNCs. Conspiracy theorist!! I doubt there could be correlations with tropical pests and diseases affecting the crops on all fronts. More diseases and pests mean more chemicals! A multi billion dollars industry. But until we find the root cause we live to fight another day!! Survival of the fittest 😀
ReplyDeleteThanks Louie, for sharing your thoughts — it’s clear you care deeply about the bigger picture. My post is centered on the local issue of black rot in soursops and what we can do as gardeners to manage it, but I appreciate hearing different perspectives on how plant health connects to wider systems.
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