The dried-fruit beetle (Carpophilus hemipterus) is an insect belonging to the order Coleoptera, family Nitidulidae. It is also commonly known as the dried-fruit carpophilus and is a small beetle native to India, although it has a cosmopolitan distribution today, meaning it is found all over the world. In Italy, it is widespread in all regions, but especially in the southern regions and islands. Contrary to its name, which may suggest attacks and infestations concentrated only on stored foodstuffs (dried fruit), it is a pest that also damages fruit in the field, especially peaches and figs.
Let’s explore how to identify this beetle and how to protect orchards and stored dried fruit.
Description of the Dried-Fruit Beetle
The Carpophilus hemipterus measures 2-4 mm in length. The body of the adult is sub-oval, convex, and brown in color. It has a densely and finely punctuated pronotum. The elytra (wings) are dark brown, each with a large yellowish spot.
Eggs and Larvae
The egg of the dried-fruit beetle measures 0.9 x 0.3 mm, has an elongated shape, and is cream-colored. The larvae are whitish and measure 4-5 mm in length.
Damage Caused by the Beetle in the Field
In orchards, beetle infestations mainly target late-ripening peaches and figs, especially during late summer. Occasional attacks have also been reported on kiwis and oranges. Adults can penetrate ripe fruit on trees, causing primary attacks in the peduncle area or by exploiting holes already made by other pests such as vine eulia (Argyrotaenia ljungiana), oriental peach moth (Cydia molesta), and earwigs (Forficula auricularia). Carpophilus hemipterus is commonly found on decaying fruit fallen to the ground or mummified on the plant.
Damage to Stored Fruit
Damage due to the trophic activity of the beetle can also occur on harvested fruit stored in warehouses, especially in rooms at room temperature. The erosions created become entryways for fungal pathogens such as botrytis and monilinia, yeasts, and bacteria. This results in the rapid development of rotting spots that quickly spread throughout the fruit.
Damage to Dried Fruit in Pantries
Naturally, dried fruit stored in pantries and other substrates are also subject to attacks by the beetle. Common examples include dried figs, dates, prunes, almonds, walnuts, hazelnuts, carob beans, cornmeal, peanuts, cassava flour, flaxseed, dried potatoes, loose rice, spices, sugar, and more.
Life Cycle of Carpophilus hemipterus
In open fields, Carpophilus hemipterus overwinters as an adult or pupa hidden in the top few centimeters of soil. It can also overwinter as a larva on stored foodstuffs.
Adults undergo 5-6 generations per year, with the highest populations occurring in mid-summer.
Females can lay up to a thousand eggs, which are deposited on ripe fruit on trees, fallen fruit on the ground, and other substrates in storage.
Larvae complete their development in 2-3 weeks, then exit the fruit and pupate in the soil or among infested stored food. After another 2 weeks, new adults emerge.
Preventing the Dried-Fruit Beetle
To eliminate the dried-fruit beetle present in orchards, agronomic prevention is of fundamental importance.
It is essential to remove fallen fruit on the ground, which represents the ideal development substrate for the insect.
After removing the fruit, at the end of the season, it is also useful to cultivate the soil with a tractor plow, rototiller, or power cultivator.
Biological Defense Against the Dried-Fruit Beetle
Another solution for field infestations is mass trapping with pheromone traps. In orchards heavily infested by the pest, it is recommended to use at least 20 traps per hectare. The effective pheromone against Carpophilus hemipterus is only available in highly specialized stores.
Some studies are also testing the effectiveness of rosemary essential oil against the pest.
Defense of Dried Fruit in Storage Facilities
Preventing infestations of foodstuffs is done somewhat similarly to how we’ve seen for other pests of this type, such as the tobacco beetle, the bean weevil, the Indian mealmoth, the mealworm, the grain weevil, and the biscuit beetle. Specifically, it is essential to periodically inspect storage areas, being attentive to signs of infestation by pests (bites, rotting fruit, larvae, etc.). If damaged food is found during the inspection, it must be immediately removed, and the storage areas or shelves should be thoroughly cleaned. An excellent repellent product, entirely safe for humans and effective at keeping the dried-fruit beetle out of storage areas, is diatomaceous earth or fossilized flour, which should be strategically spread at potential entry and transit points in the warehouse.