Dried Fruit Beetle

A reader asked me about dried fruit beetles in their compost and worm bin, so let’s learn more about these pests to see if we can help him and prevent the same problem for ourselves.

Dried fruit  (or driedfruit) beetles, along with sap beetles, are members of the Carpophilus family. They have been California pests since the mid 1700’s. You can even read an excerpt on these pests that was written in 1758, and re-published by the Entomological Society of America in 1915!

Dried fruit beetle (Udo Schmidt) CC BY-SA 2.0

Dried fruit beetle description

These small black or brown beetles are only 1/10 to 1/5 of an inch long. They have clubbed antenna and some specimens have light yellow spots on their wing covers. The larva is a small white grub with a brownish head, three pairs of true legs, and two tiny horns at the back end. Larvae will try to hide when disturbed. The pupae look like tiny white packets.

​Dried fruit beetle lifecycle

Female dried fruit beetles (C. hemipterus) lay between 1,000 and 2,000 eggs in their lifetime, usually on ripe and rotting fruit. Eggs hatch rapidly, in as little as 1 to 5 days. The larva cause significant crop damage as they feed. When they have eaten their fill, they burrow into the soil (or compost) to pupate. As soon as they emerge, they mate and egg laying occurs within 1 to 8 days thereafter. These pests can have a new generation every three weeks! They can live for over a year, but most individuals live for 100 to 145 days.

Damage caused by dried fruit beetles

Dried fruit beetles enter ripening fruit through naturally occurring openings, such as the eye of a fig, or through entry points created by other insects or physical damage. If their presence wasn't bad enough, dried fruit beetles can also carry bacteria that make fruit rot or turn sour, which then attracts other pests, such as naval orangeworms and vinegar flies. Dried fruit beetles can be found in stored beans, bread, sugar, honey, cornmeal, nuts, and cereals. In the field, they attack a wide range of plants, including:

• apricot
• corn 
• cowpeas
• nutmeg
• oats
• pineapple 
• sorghum
• sunflowers
• tobacco

Preventing dried fruit beetle infestations

Prevention is key here (Sorry, David). Dried fruit beetle life cycles can be interrupted in the field by ensuring that fallen fruit is removed regularly. This is especially true for citrus fruit, since dried fruit beetles seem to prefer laying their eggs in fallen citrus fruit. Be sure to harvest ripe fruit right away. By eliminating the food supply, these pests can generally be kept under control.

Dried fruit beetle controls

Many gardeners have had success using funnel traps baited with fermenting fruit and water, or yeast, sugar, and water. High moisture levels are needed for these pests to thrive. Removing excess moisture can cut the dried fruit beetle lifespan in half, reducing the number of potential offspring. Low humidity significantly increases the time it takes for larva to develop. It also interferes with egg-laying (oviposition).

In commercial environments, severe infestations are treated with fumigation. Generally, these pests will not harm the worms in a worm bin, but they tend to indicate sanitation issues elsewhere on the property (or on nearby properties, since the adult beetles can fly).