Why do my feijoas have worms?

There is nothing quite as heartbreaking in the garden as anticipating that first, tart-sweet bite of a feijoa, only to slice it open and find it wriggling with life. If you are reading this, you have probably just experienced the sinking feeling of discovering larvae in your prize harvest. I have been farming here in San Diego’s coastal zone for years, and I can tell you that few things ruin a day faster than realizing you are sharing your crop with the local insect population.

We need to get straight to the bottom of this. You likely have an infestation of fruit fly larvae targeting your Acca sellowiana—commonly known as Pineapple Guava, Guavasteen, or simply Feijoa. In Southern California, the culprit is often the Mediterranean Fruit Fly (Medfly) or occasionally the Oriental Fruit Fly. They see your ripening fruit not as a snack, but as a nursery.

If you see a small, brown soft spot on the skin of your fruit that looks like a bruise but has a tiny pinprick hole in the center, do not eat it. That is the entry point where the female fly injected her eggs.

Understanding the Enemy: It Is Not Just “Bad Luck”

New growers often ask me if the worms come from the soil or the inside of the tree. The answer is an external invasion. The female fruit fly lands on the skin of the fruit just as it begins to release that intoxicating, perfumed aroma. She pierces the skin and lays a clutch of eggs just beneath the surface. Within 2-3 days in our 75°F San Diego weather, those eggs hatch into maggots.

Ever wonder why the prettiest, softest fruit usually hides the nastiest surprise? It is because pests are evolutionarily programmed to target the fruit with the highest sugar content for their offspring.

I once ruined an entire batch by assuming the soft spots were just from the fruit falling on the mulch. I processed about 20 pounds of feijoa into jam, only to see tiny white specks floating to the top of the boiling pot. I had to dump $50 worth of sugar and hours of labor into the compost pile. That was the day I stopped guessing and started inspecting. Here at Exotic Fruits and Vegetables, we’ve found that early detection is the only way to save the harvest once the season begins.

The Life Cycle Loop

To stop the worms, you have to understand how they use your garden. If you ignore the biology, you will waste money on sprays that do not work.

1. The Sting: The fly lays eggs in the fruit while it is still hanging or just fallen.
2. The Feed: Larvae hatch and tunnel through the flesh, causing rot (oxidation) and turning the inside brown.
3. The Drop: The fruit falls to the ground.
4. The Escape: The larvae crawl out of the fruit and burrow 1-3 inches into your soil.
5. The Pupation: They transform into flies in the soil, emerge, and start the cycle again.

Breaking this cycle at the “Drop” stage is the single most effective intervention you can make. If you leave rotting fruit on the ground, you are essentially breeding the next generation of pests that will attack your late-season crop.

How to Distinguish Damage Types

It helps to know what you are looking at. Many people mistake simple bruising for infestation. Here is a breakdown of what damage looks like compared to a healthy fruit.

Strategic Defenses: Physical Exclusion

Chemical sprays are rarely effective on feijoas because the larvae are protected inside the fruit, and you do not want to spray poison on something you eat skin-on. The absolute best way to ensure worm-free fruit is to create a physical barrier using organza bags. Think of it like installing a security system rather than hiring a guard to chase burglars after they are already inside.

Use organza mesh bags (4×6 inches) to cover individual fruits. I buy these in bulk for about $0.10 each. You slip them over the fruit when it is about the size of a large olive and pull the drawstring tight against the stem.

Does it look ridiculous to have a tree covered in little white wedding favor bags? Absolutely. Does it guarantee 100% clean fruit? Yes. Our experience at Exotic Fruits and Vegetables has shown that this method also protects the fruit from birds and squirrels, who are just as annoying as the worms.

My Step-by-Step Protocol for Exclusion

• Thin the Fruit: In June, when fruit sets, remove clusters. Reduce to one or two fruits per terminus. This makes bagging easier and increases fruit size.
• Apply the Bag: When the fruit is roughly 1 inch long, slip the organza bag over it.
• Secure the Tie: Pull the drawstring tight. Ensure there are no gaps larger than 1mm around the stem.
• Monitor: As the fruit grows, the bag expands. When the fruit drops, it falls into the bag, staying clean off the ground.

Sanitation: The Boring but Critical Reality

If bagging 300 fruits sounds like a nightmare, you must rely on rigorous sanitation. You cannot be lazy with this. Leaving fruit on the ground acts like a beacon. The fermentation smell draws in fruit flies from miles away.

When I collect fallen fruit that I suspect is infected, I do not just toss it in the compost pile where the larvae can survive. I freeze the bad fruit for 48 hours to kill the larvae, or I seal it in a black plastic bag and leave it in the sun for a week to “solarize” it. You must pick up every single fallen fruit every single day during the harvest season.

Chickens are excellent allies in this war. If you have a coop, letting them run under the feijoa hedge cleans up the dropped larvae and breaks the pupation cycle in the soil.

Harvest Timing: Beating Them to the Punch

The biggest mistake I see San Diego growers make is waiting for the fruit to fall. While fallen fruit is traditionally considered the ripest, it is also the most vulnerable. What if I told you the best time to pick is actually before gravity does the work for you?

Touch-picking is a game changer. When the fruit changes color slightly from a deep glossy green to a duller, yellow-green, gently tilt it. If it snaps off the branch with zero resistance, it is ready.

I harvest every two days. I walk the rows and gently cup the fruit. If I have to pull, I leave it. If it falls into my hand, it comes inside. This reduces the window of opportunity for the flies to strike when the fruit is softest and most aromatic.

Soil Management and Trapping

While barriers and sanitation are primary, you can lower the population pressure using traps. I make a simple lure using apple cider vinegar and a drop of dish soap. The fermentation scent mimics rotting fruit, and the soap breaks the surface tension so the fly sinks and drowns.

Do not rely on traps alone. I once hung 20 traps and still lost 40% of my crop because I got lazy with picking up the drops. Traps reduce numbers; they do not eliminate the threat.

Think of your soil as a bunker where the enemy hides during winter. In our mild climate, pupae can survive in the top few inches of soil. Applying a thick layer of mulch—about 3 to 4 inches of wood chips—can make it difficult for the larvae to burrow down and for the adults to emerge.

We at Exotic Fruits and Vegetables believe in building healthy soil ecosystems. Beneficial nematodes (Steinernema feltiae) are microscopic warriors you can water into your soil. They actively hunt down fly larvae and kill them underground. I apply a pack of beneficial nematodes every spring just as the soil warms up to 60°F. It costs about $35 for a treatment, but it saves hundreds of dollars in lost fruit.

Avoid using broad-spectrum pesticides like malathion. Not only is it toxic, but it also kills the beneficial wasps that might naturally parasitize the fruit fly larvae.

Summary Checklist for a Worm-Free Harvest

If you are overwhelmed, just focus on these priority actions:

1. Bag your best fruit. You do not have to bag them all. Bag the 50 largest ones to guarantee a dessert harvest.

2. Sanitize daily. Never leave a fruit on the ground overnight.

3. Harvest early. Learn the “touch-pick” method to get fruit off the tree before it softens too much.

4. Solarize waste. Cook the bad fruit in sealed plastic bags for a week before composting to ensure all larvae are dead.

“The best fertilizer is the gardener’s shadow.” This old saying is doubly true for pest control. Your presence in the garden is the best deterrent.

Growing Acca sellowiana in the United States is a rewarding challenge. The flavor of a perfect, chilled feijoa—tasting of strawberry, pineapple, and mint—is worth the battle. Don’t let a few worms discourage you. Nature is resilient, but with a few organza bags and some vigilance, you can be smarter. What is the point of growing your own food if you cannot enjoy it? Take back your harvest this season. Get out there, inspect those skins, and enjoy the literal fruits of your labor.