Gadenin日本語Get the appFirst, work out whether it is a pest at all
Feijoa has remarkably few real pests and almost no serious diseases in most gardens. That means the majority of complaints about it trace back to growing conditions rather than to an organism, and reaching for a spray is usually the wrong first move. Before you look for a culprit, check three things: whether the flowers were pollinated, whether the plant dried out while the fruit was swelling, and whether the ground stays wet in winter.
The classic false alarm is fruit that swells to marble or walnut size and then drops in quantity. That is almost never a pest. It is water stress, poor pollination or a heavy nitrogen feed that pushed leaf growth at the expense of fruit. A deep weekly soak from flowering until the fruit reaches full size prevents most of it.
The second false alarm is a plant that collapses suddenly with wilting leaves that stay attached. That is root or collar rot from waterlogged soil or from a stem buried too deep at planting, and by the time it shows above ground it is usually too late. On heavy soil the prevention is mound planting and never watering into standing wet.
| Problem | First sign | When | Action |
|---|---|---|---|
| Fruit fly | Small sting mark; maggots in fallen fruit | As fruit approaches ripeness | Collect daily, bag and dispose; use traps where it is a known local pest |
| Scale insects | Brown or white bumps on stems, sooty mold, ants | Any time, worse in still air | Horticultural oil, prune out congested wood |
| Thrips | Silvered, stippled leaves; scarred fruit skin | Warm dry spells | Tolerate; oil or soap if severe |
| Wasps and ants | Hollowed fallen fruit, insects at the drop zone | Harvest weeks | Collect fruit twice daily; do not leave windfalls |
| Root or collar rot | Sudden wilt, leaves stay on, stem dark at base | Wet winters, heavy soil | Prevent by mound planting; usually fatal once seen |
| Birds and possums | Fruit gone, or bitten and dropped | Harvest weeks | Net the plant; keep it low enough to net |
| Leaf spot | Brown blotches on older leaves | Wet weather | Rake litter, open the center; rarely needs more |
Fruit fly and the ground rule
Where fruit fly is present, feijoa is a host, and the biology of this crop makes the problem worse than it needs to be. Because the fruit is gathered off the ground rather than picked, every fruit that lies uncollected is a breeding site: the female lays into the fallen fruit, the larvae develop inside it, and they drop into the soil to pupate directly under your plant. A week of not collecting can seed the next generation.
The single most effective control costs nothing. Collect every fallen fruit, every day, including the ones you would not eat, and dispose of the rejects properly. Do not throw them on the compost pile or into a hedge, which simply relocates the problem. Seal them in a bag in the sun for several days, or freeze them, or bury them deeply.
Where fruit fly is a declared local problem, add traps in the plant from the start of the season and check them, so you know whether the fly is present rather than guessing. In areas without fruit fly, none of this is necessary and daily collection is still worth doing for the sake of wasps, slugs and fruit quality.
Scale, thrips and sooty mold
Scale insects are the commonest true pest on feijoa and are easy to miss because they look like part of the bark: small brown, gray or waxy white bumps clustered along stems and on the undersides of leaves, often on a plant that has grown congested. They suck sap and excrete honeydew, which grows a black sooty mold on the leaves below and attracts ants marching up and down the stems. Ants on a feijoa are a reliable signal to go looking for scale.
The treatment is horticultural oil applied thoroughly to stems and both leaf surfaces, repeated after two or three weeks, combined with pruning out the most congested growth so air and light get in. Do not spray oil in strong sun or in high heat, which scorches the leaves. Controlling the ants helps, because ants defend scale from the predators that would otherwise deal with it.
Thrips rasp the leaf surface and leave it silvered and stippled, and can scar the skin of the fruit with silvery-brown patches. The damage is cosmetic on a fruit you scoop with a spoon, so tolerance is a reasonable policy on a garden plant. If an infestation is heavy enough to check growth, insecticidal soap or oil applied to the undersides of the leaves is the usual answer.
Both pests are worse on soft, sappy growth. If you are seeing them year after year, look at how much nitrogen the plant is getting: feijoa needs very little, and overfeeding produces exactly the tissue these insects prefer.
The drop zone is the disease control
Almost everything that goes wrong with feijoa fruit happens on the ground rather than on the plant. Fallen fruit left lying ferments, draws wasps and ants, feeds slugs and snails, breeds fruit fly and grows molds that then colonise sound fruit that lands beside it. A garden with a clean drop zone has few pest problems; a garden with a week of windfalls underneath has all of them at once.
- Clear and mow before the drop starts Cut the grass short under the plant and remove weeds and debris. You cannot collect what you cannot see, and green fruit in long grass is invisible.
- Collect twice a day in warm weather Once a day is the minimum, twice is better when it is warm. Take the damaged fruit as well as the sound; leaving rejects behind defeats the purpose.
- Dispose of rejects so nothing completes its life cycle Bag and seal, freeze, or bury deeply. An open potting mix heap near the plant recycles the pest rather than removing it.
- Net if birds or possums are taking fruit Keeping the plant pruned to six to eight feet (1.8-2.4 m) makes netting practical. Fix the net clear of the foliage and tie it in at the base so nothing gets under it.
- Rake and mulch at the end of the season Once the last fruit is down, clear all remaining fruit and leaf litter and refresh the mulch. This closes the year and removes the overwintering sites.
Keep a short note each season of what you saw and when: the date wasps first appeared, whether any fallen fruit held maggots, whether ants were running the stems. Feijoa problems are strongly seasonal, and a few years of notes tell you whether a bad year was the weather or a pest that is establishing itself in your garden.