Mites - Pests of Ornamental Trees, Shrubs and Flowers - page 425

Family ACARIDAE

DAMAGE
General: infestations of this secondary pest may lead to
the complete breakdown and destruction of bulbs,
corms or tubers, the internal tissue turning blackish and
powdery. Freesia and gladiolus: attacked roots develop
dark brown streaks, and are often mined internally.
Also, if healthy corms are planted into heavily infested
soil, growing points and leaves are affected; these
become distorted and the leaves develop ragged or saw-
toothed edges.

Rhizoglyphus callae Oudemans ( 1138 )
A bulb mite
An often common, usually secondary pest of bulbs,
corms and tubers, including Freesia, Gladiolus ,
hyacinth ( Hyacinthus orientalis ), lily ( Lilium ),
Narcissus and tulip ( Tulipa ). Present throughout
Europe; also found in North America.

DESCRIPTION
Adult: 0.7 mm long; body oval, smooth, whitish and
very shiny, with discrete internal brownish patches and
several long hairs projecting back beyond the tip of the
hysterosoma; legs reddish brown and stout. Egg: 0.2 ×
0.1 mm; hyaline to whitish, smooth and shiny. Larva:
whitish and shiny; 6-legged. Nymph: similar to adult
but smaller. Hypopus: 0.3 mm long; dark brown; legs
short, very stout and with large claws.

Rhizoglyphus robini Claparède
A bulb mite
This species also infests bulbs and tubers but appears to
find diseased hosts less favourable than relatively
healthy ones. The mites are very similar in appearance
to Rhizoglyphus callae . However, R. robini is slightly
larger, and has noticeably shorter body hairs and very
short dorsal idiosomal setae. Over the years, both
species have been cited under the name R. echinopus .

LIFE HISTORY
Mites occur in large numbers within diseased and
otherwise unhealthy bulbs, corms or tubers. They breed
continuously under suitable conditions, passing through
egg, larval and two nymphal stages. Completion of the
lifecycle takes 1-4 weeks depending upon temperature.
A phoretic hypopal stage appears in some populations;
these hypopi attach themselves to passing insects,
such as small narcissus flies ( Eumerus spp.), and are
then transported to other hosts, thereby spreading
infestations.

1138

1138 Bulb mite ( Rhizoglyphus sp.) damage to bulb of Tulipa .