Entomologist: Food moths eat everything

PAP: I just cleaned out my pantry, throwing out all my flour, groats, pasta, etc. It's all because of those pesky food moths. In Poland, there used to be standards for the number of eggs and larvae in grain products, and now they're gone, but in the United States, they still apply. Why?

Prof. Stanisław Ignatowicz : We have joined the European Union and are bound by EU regulations. According to these regulations, a food product is considered unfit for consumption if it contains pests. The number of pests is not specified; the mere fact that a pest is found eliminates the product.

Another issue is how often food products such as groats or pasta are checked for pests.

Food production facilities use the HACCP (Hazard Analysis and Critical Control Points) system, which aims to prevent microbiological, chemical, and physical hazards at all stages of food production and distribution. It is intended to ensure food safety.

I remember from my youth, when buying beer in the countryside, the saleswoman would hold the bottle up to the light and check for any floating objects, like mice, insects, or other foreign bodies. Only after checking would she serve it. So, the inspection was done just before sale. Now, the quality of the raw material is monitored very rigorously during production – even the presence of a single insect in food eliminates it for further production.

PAP: So where did these moths come from in my pantry? In bags of groats or flour?

SI: Don't worry, the average person eats more than 1 kg of insects in their lifetime. And these food moths in cereal product packages come from the fact that even if their production was perfectly controlled, if they weren't packaged very tightly, they end up in warehouses, various wholesalers, where they linger for months or even longer. And it's possible that goods from a sleazy manufacturer end up in the same place, infected with pests that breed there. That's the whole secret.

PAP: And no one controls the stores in this respect?

SI: It's difficult to combat insects there. Have you ever seen a chemical treatment performed in a grocery store? It's practically impossible, if only because the products there are unpackaged, providing the pests with ideal conditions to thrive. Especially since customers help them, for example, by damaging the packaging to see what's inside.

PAP: It's hard for me to imagine someone opening a box of pasta...

SI: Let me give you another example explaining why food moths are colonizing stores. Customers love chocolate candies and readily buy them by the pound. The candies are displayed for sale in large cardboard boxes, the contents of which are replenished daily. This means that new candies are added to the old, increasingly stale ones. These old candies can even be many months old. And you should know that food moths are very greedy, devouring everything, not just grain products, but also herbs, tea, dried fruit, and if the candies contain nuts, they simply go crazy with joy. And we bring these delicacies home, which is why food moths are uninvited guests in over 90 percent of kitchens and pantries.

PAP: One such small insect and so much trouble.

SI: Oh, there are several species. For example, the flour moth (Ephestia kuehniella) and the granary borer (Plodia interpunctella) – both species readily feed on bulk foods such as flour, groats, rice, breakfast cereals, pasta, nuts, and dried fruit.

The flour borer has outnumbered the flour moth, which develops in flour.

Then there is the date moth, which likes not only dates, but also oil seeds, dried fruit, nuts...

And then there's the caries beetle, the smallest of them all, inconspicuous—it, in turn, prefers products like herbs, tea, and generally dried plants, including tobacco products. It's this caries beetle that can make a pack of cigarettes so disgusting that they're impossible to smoke. This caries beetle, along with the cigar beetle, is the number one enemy of tobacco companies, which combat it with all their might.

PAP: And they cannot fight it...

SI: These moths vary in size, coloration, and somewhat in their habits, but we can suspect that they evolved from a single species. Why? Because females produce a sex pheromone that males of all species respond to. For example, a female granary borer releases a scent that male caries moths pick up and race towards. The same is true for male food moths of other species.

But interspecies crossbreeding doesn't occur. Males of different species have different courtship dances, and females only like the way a male of their own species dances; they won't allow any other male to dance.

PAP: Overall, female food moths have a sad and very short life.

SI: Unfortunately, because they don't eat anything, they only drink. If they had a choice, they would drink honey water, which is like an energy drink for them. Generally, females survive on the energy stored by the caterpillar they once were. That's why caterpillars are the most harmful: they feed intensely, become fat, and only then pupate. Males don't live long either—two or three weeks at most.

For this reason, their pheromones are so powerful that if a female encounters a male, he fertilizes her, and she lays 200-400 eggs. She may then die.

PAP: Can we do anything to prevent these butterflies we don't like from living in our homes?

SI: Well, that's the biggest problem, because we usually detect these pests too late – either when adults are sitting on the walls or when product packaging is covered in the yarn they produce.

The easiest way is to buy tightly sealed containers. Very tightly, because even a hole the size of a Roman Times 12 dot is a gateway for an enterprising and desperate larva. And once it gets in, eats, and grows fat, it will chew its way out of the packaging, leaving its droppings and yarn inside.

This yarn plays a big role in the lives of moths - they can feed safely under its cover, it also protects them from their enemies, such as the Habrobracon wasps or Venturia canescens, and then they make a cocoon from this yarn in which they pupate.

PAP: Food moths not only irritate us by invading our grocery cupboards, but they also cause real damage to global economies. Approximately 60% of companies report revenue losses ranging from 1% to 9% of their annual income due to such contamination.

SI: We've already mentioned that these insects love nuts. So let's imagine factories producing chocolate products that contain nuts. If someone finds caterpillars in these candies or bars, all they have to do is post a photo on social media – then the manufacturer suffers huge losses. The manufacturer, not the wholesalers or stores. There have been countless such cases; one leading confectionery company, which was hit by this in the pre-Christmas period, lost a quarter of its annual sales. I also remember the case of a factory near Warsaw that produced chocolate for blood donation centers. It didn't survive the apple borer larvae scandal and went bankrupt.

PAP: So I'll ask again whether these food moths do anything good in the ecosphere?

SI: My theory is that every animal plays a role in nature. When we were gone, these moths already existed and served as some of the first animals to decompose the organic matter found in old fruit, seeds, and nuts that hadn't germinated. And as we began to store these as supplies, moths appeared to help us sort them out.

Interviewed by: Mira Suchodolska (PAP)

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