We received a question from a reader who has many little creepy-crawlies on his concrete in his yard. He says that some of his neighbors have a few, but that he has an absolute infestation. What are these little creatures, he wants to know, and wonders if they are related to his olive trees.
First, let’s look at his pictures. We see that there are, indeed, quite a few of these guys on his concrete. Our reader has also caught several of these in a jar, and has helpfully included a picture with a tape measure so we can get a sense of scale (thank you!).
From the pictures, it doesn’t look as though these are worms, but rather larvae. Therefore, first we’ll explore what larvae live near olive trees. The larvae of the Olive Fruit Fly (Bactrocera oleae, Dacus oleae) seem like a likely culprit. However, these larvae grow to be about ¼” in length and are light in color, and the reader’s creatures are much larger and dark, so we can eliminate those as an option.
However, the olive trees do give us useful information, because we know that the reader lives in a place where olive trees grow. In the US, we can expect to find olive trees in California, Hawaii, Florida, and Texas. With the photographs and the information we have we cannot make a positive identification, but one possibility comes to mind: the armyworm.
Armyworms are the larval form of the Mythimna unipuncta. Their larva can grow to be over 1” long, and like to eat grasses and grains. Armyworms get their name from the fact that, once they have eaten all of the food in one location, they travel en masse (like an army) to the next source of food. It is not uncommon to have infestations like the one the reader described.
If these are armyworms, then the reader may have some issues with his garden. Mythimna unipuncta can be quite a pest and can have an impact on lawns and gardens. However, they may just be moving through as they travel to their next destination. If their presence is annoying on the concrete surfaces in his yard then he can sweep them away with a broom.
If the reader is having issues with his yard, we recommend contacting a local pest-control expert for advice on how to deal with them. They can help positively identify the creature and know the best way to control them.