Download Do They Eat Mealybugs?

Do They Eat Mealybugs?
By Devin Carroll
Revised 2013
Observations on possible predators of grape mealybugs under grape bark.
Mealybug destroyer, Cryptolaemus montrouzeri. This well-known mealybug predator is not
very common in the San Joaquin Valley. Possibly it is limited by hot weather.
"Little Brown Mealybug Destroyer", Nephus sordidus. Much more common than Cryptolaemus
in the San Joaquin Valley. A key predator of both vine mealybug and grape mealybug. Works
mainly under bark.
Predaceous gall midge, Dicrodiplosis californica. “Midge maggots” are especially important on
grape mealybug, but also can control vine mealybug under bark.
Green lacewing, Chrysopidae. An important predator, but I would judge them second tier
compared to midge maggots and Nephus. I have 3 observations of larvae eating grape
mealybugs. The mealybug wax or honeydew tends to gum up the mandibles on smaller lacewing
larvae.
I also have 2 observations of larvae eating parasitized mummies of both grape and vine
mealybugs, so they can also be detrimental to biocontrol.
Lacewing eggs are good ant food. We have poured thousands of lacewing eggs on a single
grape vine, with ants present, and saw no discernible difference in the mealybugs, or more
lacewings, for that matter. But when the eggs are laid on their stalk, they are better able to
survive.
Brown lacewing, Hemerobiidae. Good mealybug predators. They are nocturnal, so it’s hard to
see how well they are working, compared to green lacewings.
European earwig, Forficula auricularia. 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. On one occasion I found a dermestid larva in the middle of a GMB
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.
Another time I saw a large larva that had eaten close to half of GMB adult, probably starting
with eggs which were all consumed.
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.
Dermestid beetles have been reported feeding on eggs of corn rootworm beetles and gypsy
moths.
The dermestid species common under grape bark may be Anthrenus verbasci or a related
species.
Minute Pirate Bug, Dufouriella ater. I suspect this bug eats mealybugs, but I have not had a
certain feeding observation. Adults are 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.
Hajak & Dahlsten have observed D. ater as a significant
predator of elm bark beetle in California. Gao reported they prey on Pine Bast Scale.
Snakefly. Negha meridionalis (Inocelliidae). I have seen many
vineyards with snakefly larvae abundant under the bark. These
are large, snaky guys. At first I thought they were carabid
beetles, but I was corrected after posting pictures on
Bugguide.net.
I have never seen them eating anything, but they are
predators so they must be eating something. In some cases I
have seen heavy populations of mealybugs clean up in presence
of snakefly larvae, but other predators and parasites were
usually present.
I have seen a small snakefly larva crawl over a mass of
grape mealybug eggs without reacting, but the snakefly was
looking for a place to hide. I have also seen a medium larva in a
hole together with a carpenter worm and vine mealybug
nymphs, with no evidence of predation.
Spiders.
I have seen the following spiders eat mealybugs, but not many:
Hololena nedra, Theridion sp., Xysticus. For discussion of these
species, see here.
Costello et al. list mealybugs as a prey of Trachelas, a
brown and grey club-footed spider. This spider is common under grape bark, where it could find
many mealybugs.
Whirligig mite, Anystis. No. This large, fast, bright red predatory mite is known as a predator
of leafhoppers and many other arthropods, but apparently does not like mealybugs. 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.
“Mealybug caterpillar”.
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.
I have not identified the species. The picture is of one I reared from a pupa. I need to take
some pictures of the larva.
Some caterpillars are predaceous, but it’s pretty rare.
Costello, M. J., M. A. Mayse, K. M. Daane, W. A. O'Keefe, and C. B. Sisk. 1996. Spiders in San
Joaquin Valley grape vineyards. University of California Division of Agriculture and Natural
Resources Leaflet #21530.
Hajek, Ann E. and Donald L. Dahlsten. 1985. Factors Influencing the Mortality of Scolytus
multistriatus (Coleoptera: Scolytidae) in Elm Branches in California. The Canadian
Entomologist, 117, pp 819-828.
Gao Wen-Gheng. The Anthocorid Dufouriella ater(Dufour)——A New Natural Enemy of
Japanese Pine Bast Scale Matsucoccus matsumura (Nuwana)[J]. Acta Entomologica Sinica,
1987, 30(3): 271-276.