Do They Eat Mealybugs?
By Devin Carroll
Updated November 2006
Observations on possible predators of grape mealybugs under grape bark in the San Joaquin Valley..
Mealybug destroyer, Cryptolaemus montrouzeri. Yes, well known. Cryptolaemus is rarely found unless it is released. Many observers suspect it does not tolerate San Joaquin Valley winters.
Another lady beetle, possibly a Scymus species, is endemic to the San Joaquin Valley. It preys on both grape mealybug and vine mealybug. It has an Encyrtidae parasite.
Encyrtidae parasites. Yes, well known.
Predaceous gall midge, Dicrodiplosis californica. Yes, well known. “Midge maggots”.
Lacewing, Chrysopidae. Yes, well known. I have several feeding observations. The mealybug wax or honeydew tends to gum up the mandibles on smaller lacewing larvae. Lacewing eggs are good ant food. We have poured thousands of lacewing eggs on a single grape vine, with ants present, and saw no discernable difference in the mealybugs, or more lacewings, for that matter. Still, I think lacewings are a significant mealybug predator.
European earwig, Forficula auricularia. Yes. I have one observation of a half-grown earwig eating mealybug eggs, on June 23, 2003 in Delano. Earwigs are common and could be a significant predator.
Carpet beetle, Dermestidae. Yes. The larvae are very slow feeders and it is hard to tell if they are eating something. They often have their nose in mealybug eggsacs, but they could be eating the silk or honeydew.
But on one occasion I found a Dermestid larvae in the middle of an egg mass, where it had obviously eaten out a circle in the middle. I did not directly observe feeding, but I am quite certain that the Dermestid had eaten many eggs.
Dermestid beetles have been reported feeding on eggs of corn rootworm beetles and gypsy moths.
Minute Pirate Bug, Dufouriellus ater. Maybe. This pirate bug is solid black and very flat. The nymphs and eggs are bright red. D. ater is often abundant under grape bark, under pomegranate bark, and in old almond stick-tight nuts. They are very shy and as soon as you pull back the bark, they look for some place to hide. I have made only one feeding observation in many years of trying. The victim was a psocid under grape bark. Psocids are very common in all three aforementioned habitats.
D. ater is often found in association with mealybugs, but so are psocids. Sometimes, it seems that mealybug populations markedly decline in the presence of these pirate bugs, where the more well-known predators and parasites are not very abundant. If anyone observes one of these guys feeding on a mealybug, I’ll give you a nickel.
Hajak & Dahlsten have observed D. ater as a significant predator of elm bark beetle in California.
Snakefly (Raphidiidae). Maybe. I observed a vineyard near Fowler with snakefly larvae abundant under the bark. These are large, snaky guys. They remind me of centipedes when they move. There was a heavy population of mealybugs that cleaned up that season. Other predators and parasites were present, including midge maggots and a few Cryptolaemus, but my impression was that the mealybugs cleaned up faster than expected from these others. I made no feeding observations of the snakefly larvae, but they looked like they could eat a lot of something.
Spiders. Yes. Trachelas, a brown and grey club-footed spider (Clubionidae) common under grape bark, is listed as eating mealybugs, in Spiders in San Joaquin Valley Grape Vineyards. I have not seen this, but this is a shy spider which hides in the daytime.
I have one observation of mealybugs wrapped up in a small spider web on grapes, my guess was Dictyna.
“Mealybug caterpillar”. Probably not. This caterpillar is always associated with mealybugs, as far as I have seen. It is usually under the bark, although I once saw possibly the same caterpillar feeding on some open grapes in a mealybug-infested bunch. The caterpillar looks roughly like a small navel orangeworm but more translucent. It appears to be feeding around the mealybug egg masses, I suspect on the honeydew or wax.
Some caterpillars are predaceous, but it’s pretty rare.
Raisin moth larvae are also commonly associated with mealybugs, both under the bark and in bunches.
Whirligig mite, Anystis. No. This large, fast, bright red predatory mite is known as a predator of leafhoppers and many other arthropods. In early spring, the juveniles often hunt on the tops of spurs, where mealybug nymphs are crawling around budbreak. On March 2, 2004, near Delano, I watched an Anystis juvenile catch and quickly reject a mealybug nymph. Although they apparently do not eat mealybugs, they might kill a fair number.