Acari
Astigmata
1
ASTIGMATA
ASTIGMATA
Size: 0.2-1.2 mm.
Shape: globose, oval, elongated, soft and usually smooth cuticle;
from white pearly to yellow-brown, sometimes pigmented;
opisthosoma generally oval.
ASTIGMATA
Chelicerae (ch) generally chelate and proviced with tooth.
Palps (p) 2-segmented, appressed to the chelicerae.
ch
p
Stigmata and tracheae absent; respiration by
means of the integument (high relative humidity is
required).
ASTIGMATA
Ontogenetic development: L, Pn, Dn (hypopus), Tn,
Ad.
Mainly in soils rich in decaying organic matter
(litter, organic fertilizer, dungs, nests, etc.), on fungi
and storehouses.
(from Hoy, 2011)
ASTIGMATA
Habitus:
- phytophagous,
- zoophagous (scabies, Hemisarcoptes predator of mealy
bugs, allergenic agents, etc.),
- mycophagous,
- saprophagous.
phytophagous
Acarus siro
zoophagous
Sarcoptes scabiei
Demodex
ACARIDAE
Size: 0.5-1 mm.
Economic importance is, however,
related mainly to the stored food.
Trophic behaviour: phytophagous (flower
bulbs some plants), mycophagous,
saprophagous, on stored food (grain, dried
fruit, nut, cheese, spices, cereals, pet food).
Favourable environmental conditions: they
require high relative humidity (>60%, 8090%) and protection from the direct
lightening.
Acarus ♂
ACARIDAE
Mainly oviparous.
Dn absent or as obligatory or facultative
hypopus.
They cause:
- damages to the stored food (flours,
pastas, cheeses, biscuits, sugar, dried
fruits) which become dusty and
unmarketable,
- dermatitis, allergic reactions, asthma.
Guanine in faecis stimulates the
development of microrganisms which
provoke a notable and further
deterioration of the stored food.
Fungal symbiosis.
ACARIDAE: control
Preventive means:
- respect of hygienic rules and cleaning of storehouse habitat;
- reduction of the relative humidity at values inferior to 60%;
- storing of seeds with a content of water inferior to 13%;
- application of controlled atmosphere.
Curative means:
- fumigation of the storehouses (laborious operation, specialised
operator requirements, operator risks, etc.)
- damaged materials must be taken away;
- sanification of the storehouses by means of pyrethroids;
- physical treatments by means of heat: immersion in water at 5060°C per 1-2 minutes or by high radio frequency.
ACARIDAE: identification
ACARIDAE
Acarus siro: on flours and grain (that have
absorbed moisture); frequently associated to
Aspergillus, Penicillium and Eurotium.
Thermic thresholds: 3-30°C
Good resistance to scarce availability of
oxygen.
Tyrophagus putrescentiae: prefers products at
high content of fats and proteins (salami,
cheeses, moulds on the surfaces of these
products). It lives also in mushroom tunnels
and damages were observed on cucumber and
melon.
It can carry viable spores in its digestive tract
as well as on the outside of the body.
ACARIDAE
Tyrophagus similis: omnivorous (organic
substrates, fungi included). Found on
cucumber, melon, spinach, etc.
It is well-adapted on fresh plant tissues rich of
proteins as cotyledon leaves or apical leaves;
common in the soil.
Tyrophagus similis pest of spinach
Tyrophagus similis
Damages on spinach
ACARIDAE: Rhyzoglyphus robini
Body size: 0.3-0.6 mm.
ACARIDAE: Rhyzoglyphus robini
Males and females mate several times a
day. Males may remain in copula for
20 minutes to 6 hours.
ACARIDAE: Rhyzoglyphus robini
A generation: 7-27 days at 26-13°C – facultative hypopus.
ACARIDAE: Rhyzoglyphus robini
It infests bulbous (onion, garlic, etc.) and
florals plants (Amaryllis, hyacinth,
narcisus, gladiolus, lily, freesia, etc.),
potatoes, grains; root of vegetables, vines,
wheat, oats and other crops; decaying
vegetable (e.g. fallen fruits) and animal
matter.
It prefers damaged bulbs.
It deeps gradually among the bulb scales.
Spread bacteria and
Pseudomonas, etc.).
fungi
(Fusarium,
ACARIDAE: Rhyzoglyphus robini
Monitoring:
- direct observation of symptoms (rot and
distortion appearance)
- sampling of plants or their parts (bulbs) and
direct observation under a dissecting
microscope.
ACARIDAE: Rhyzoglyphus robini
Agronomic control:
- solarization of the soil used for bulb production.
Physical control:
- bulb treatment by water at 37-41°C per 2-3 hours
- Bulb storing at -2°C.
Chemical control:
- Resistance to OPs.
Biological control:
- release of Hypoaspis aculeifer (10 predators per 100 bulbs, after
heat treatment; 100-500 predators per m2).