You open a carton of dates stored since harvest, and the fruit looks perfectly sound in color and texture. Then you break the first date and find a narrow tunnel packed with brown frass and fine silk threads, and perhaps a small pink larva wriggling inside. The second and third dates tell the same story, and you realize the infestation began months before you closed the carton.
This is the signature of the date moth (Ectomyelois ceratoniae), also known as the carob moth. It is one of the costliest date pests because it works in secret: it starts in the bunch on the palm, then follows the fruit into the store and the cold store. In this article we explain how to recognize it, where the infestation really comes from, and what stops it before and after harvest.
The sign: a narrow tunnel packed with brown frass and silk threads inside a fruit that looks sound from the outside.
The source: infestation usually begins in the bunch before harvest and travels into the store with the infested fruit.
The cycle: the moth's life cycle repeats in the store if infested dates remain, so the carton loses season after season.
The common mistake: spraying the store after infestation without removing the infested fruit, when the source is inside the fruit itself.
The rule: sorting, tight packing, proper cooling and a clean store before storage beat any treatment applied after the moth appears.
How do you know the dates are infested?
External signs are faint at first, because the larva enters the fruit through the calyx end or a small crack and feeds from the inside. That is why we rely on a systematic inspection rather than a casual glance:
- A tiny hole and frass: a fine opening near the calyx or on the side of the fruit, with brown dust or silk threads that glue the fruit together.
- A pink or white larva: up to about 15 mm long when fully grown, starting yellowish white and turning pink or red.
- A small gray moth: about 10 mm long with a wingspan of 22 to 24 mm, appearing at dusk near sacks and cartons and on the store walls.
- Silk cocoons: formed in cracks, between fruit and along the edges of crates, where the pupa stays for 7 to 10 days.
- Fruit dropping early: on the palm, infested fruit may fall or dry out inside the bunch.
Where does the infestation come from?
The usual question from growers is whether the worm came from the store or from the farm. The short answer is both, which is why treating only one place is not enough.
- Leftovers from the previous season: dates left on the palm or fallen beneath it are the first source of infestation in the following season, and the larvae overwinter in them.
- The heart of the palm and the leaf bases: larvae spend the winter inside the crown and between the frond bases for about four months before becoming active again.
- The store itself: cracks, leftover old packaging and heaps of fallen dates. An Algerian study of Deglet Nour stores found an average infestation of about 64%, rising the longer the dates were kept.
- Neighboring fruit: ripe pomegranates, figs, almonds, walnuts and citrus are hosts of the same insect, so having them near the store prolongs the pest's life.
Its life cycle: why does it renew every few weeks?
The adult moth does not feed and does not live long, only 3 to 5 days. But those few days are enough for a female to lay 60 to 120 eggs, and that is where the danger lies.
From egg to larva
The female lays eggs near the calyx or in cracks in the fruit, and they hatch within 3 to 7 days. The larva feeds for about four weeks in warm generations, eating the flesh of the fruit and leaving its frass inside.
The pupa and the next generation
The larva pupates inside a silk cocoon for 7 to 10 days, and then the moth emerges. References estimate three to four generations per year, the last of which overwinters as larvae inside the palm. That is why efforts are wasted when we only treat the store in autumn.
What does the farm and the warehouse lose?
The damage is not limited to the punctured fruit. It is the reputation of the whole batch when a buyer finds a single larva.
- Lost weight and value: Tunisian studies estimate that the moth infests about 20% of the harvestable crop every year, and infested dates lose their market price.
- Rejected shipments: some countries list the insect as a quarantine pest, so a small infestation is enough to have a whole container rejected.
- A preference for dry dates: the moth prefers dry fruit, so long-stored dates are more exposed than fresh rutab.
- Companion pests: studies have recorded dried fruit beetles and the almond moth (Cadra cautella) alongside it, all living on the same dates.
Prevention in the farm before it reaches the store
The best place to break the life cycle is the palm itself. We always start with sanitation before any pesticide, because it removes the winter shelter from which the first generation emerges.
- Collect the season's leftovers: right after harvest, remove abandoned bunches and fallen dates beneath the palm, and destroy them by burning or deep burial.
- Clean the heart of the palm: prune dry fronds and remove the fiber that builds up around the crown, where larvae hide.
- Cover the bunches early: place a mesh bag on the bunch when the fruit starts to color. It keeps out moths, birds and dust, and any larvae already present die because they eat each other inside the bag.
- Harvest on time: leaving dates to dry on the palm after ripening gives the moth extra time to lay its eggs.
- Track the moths: hang a sticky strip near the palms during the ripening season. Moths appearing on it are an early signal to start protection.
- Sort at picking: remove any punctured or soiled fruit before packing, and never mix it with sound fruit so that it does not spread the infestation.
In the store and the cold store
If the dates reach the store sound, the job now is to keep a new moth from entering and to leave nothing in the store that feeds it. These are our rules for small and medium warehouses:
- A closed, sealed store: doors with cracks sealed and fine mesh over openings, because the moth flies at night toward the smell of dates.
- Cooling or freezing: low temperature stops larval development, and freezing for several days before long storage is a well-known way to eliminate hidden eggs and larvae.
- Sticky traps for monitoring: we hang sticky strips near doors and between shelves, so that if moths appear we know an infestation exists before it spreads.
- Stock rotation: take out the older batches first, and do not leave forgotten cartons behind the shelves.
- Wash and dry reused crates: used crates carry eggs and cocoons in their corners.
Large warehouses use phosphine fumigation, but that is specialist work carried out by a licensed operator and is not suitable for household stores. Research is also testing alternatives such as diatomaceous earth and volatile camphor oils, and spinosad killed about 85% of eggs in a laboratory trial, but these are still under study and do not replace sanitation.
A field example: a small farm harvested its dates well but stored them in a room next to a heap of fallen dates and old cartons. Two months later larvae appeared across the whole batch, even though the fruit was sound when picked. The mistake was not in the dates but in the surroundings: the room itself was the source of infestation. That is why every consultation we do starts with a question about the state of the store, before any question about pesticides.
The products we recommend for the date moth
At Orkida we arrange the solution from least to most intervention: physical protection of the bunch, then monitoring, then a targeted spray against young larvae when needed, then disinfection of the empty store.
- Date protection bags, 80 x 100 cm (25 bags): strong mesh that lets air through and keeps out moths, birds and dust. Fit them on the bunch after fruit set, before moth activity rises, and tie the opening at the top while leaving ventilation.
- Radiant 120 SC from Corteva: its active ingredient is spinetoram, from the spinosyn family. It acts by contact and ingestion on the larvae of moths and butterflies and is relatively gentle on natural enemies. We use it as a targeted spray on the bunches when moths and young larvae begin to appear, observing the pre-harvest interval.
- Catch Master sticky strips for flying insects: four non-toxic strips, 60 cm long, which we hang at store doors and above shelves to know when moths arrive. They are a monitoring tool before they are a treatment.
- Actellic 50 EC from Syngenta: pirimiphos-methyl, an organophosphate well known in grain stores. We use it on the walls, floors, shelves and cracks of the empty store before the storage season, and never spray it on dates that are ready to eat.
Stick to the dose written on the label and to the pre-harvest interval, because dates are eaten without cooking and there is no room to exceed the limits. For stores that also hold grain and pulses, see also Stored product pests and grain weevils.
The moth and its neighbors on the palm
Someone who sees damaged fruit in the bunch can easily mix up the causes. Date palms have other pests with their own signs, and telling them apart decides the timing and the treatment:
- Hamira (the lesser date moth): a different insect (Batrachedra amydraula) that attacks small fruit after pollination, eating the inside and leaving the skin, and the fruit turns red.
- Dubas: honeydew covers the fronds and the fruit. Read Dubas bug on date palms to learn its timing.
- Dust mite: dusty webbing around green fruit in summer, with details in Dust mites on date palms.
Frequently asked questions
Can we eat dates in which we found a larva?
It is best to discard fruit that is punctured or surrounded by threads and frass, because the infestation makes it contaminated and prone to rot. If the rest of the carton is sound, sort it date by date and put it in the freezer for several days before eating.
Does cooling kill the moth?
Cooling slows larval growth and limits reproduction, while freezing for several days kills the stages inside the fruit. We recommend it for dates meant for long storage at home.
When should I put bags on the bunches?
At the start of fruit coloring and before moth activity peaks, after making sure the bunch is clean and free of larvae. Putting them on late means you are sealing the larvae inside the bag.
Should I spray against the moth in the store while the dates are there?
No, we do not spray pesticides on dates that are ready to eat. We treat the store while it is empty and clean, before packing, and when dates are present we rely on sanitation, cooling and sticky traps.
What is the difference between the date moth and the almond moth?
The date moth usually begins the infestation in the field and enters the fruit while it is still on the palm, whereas the almond moth infests stored materials after they enter the warehouse. The two can occur in the same place, which is why we monitor both with sticky strips.
Can the moth move from pomegranates to dates?
Yes, since pomegranates, figs and almonds are also hosts. Avoid leaving fallen or rotting fruit near the palms, and keep it away from the store.
Image credit: Ren Y, Yang L, Wikimedia Commons (CC BY 3.0)