|
|
|
Aphidius
Aphid Parasitic Wasps by Applied BioNomics PO Box 1555, Ventura, CA 93002800-248-2847 *
805-643-5407 * fax 805-643-6267 question
e-mail bugnet@rinconvitova.com orders
orderdesk@rinconvitova.com www.rinconvitova.com |
|
|
Aphidius
(Aphidius
matricariae, Aphidius colemani, Aphidius ervi)
Target pests
Aphidius matricariae: Green peach aphid (Myzus
persicae); related aphids.
Aphidius colemani: Melon aphid (Aphis gossypii)
Aphidius
irvi Potato aphid (Macrosyphum euphorbiae)
Description
‘Aphidius’ species are a
group of native parasitic wasps, frequently found parasitizing aphids in
greenhouses and outdoor crops.
·
Adults are
tiny, dark coloured, non-stinging wasps, up to 2-3 mm (1/8 inch) long.
·
Larvae
develop entirely inside host aphids, which eventually become rigid mummies when
the larvae pupate.
Aphidius is a good
searcher, and can locate new aphid colonies even when aphid populations are
low.
Use in Biological Control
·
Aphidius matricariae parasitizes about 40 aphid species, including green peach
aphid and closely related species (for information on aphids, see Sheet 340).
·
Optimum
conditions are daytime temperatures of 18-25 ºC (64-77 ºF) and relative
humidity 60-80%.
·
Aphidius
is not effected by short-day induced diapause, so it can be used year-round.
·
Aphidius
alone will not provide control when aphid populations are high, but can be used
with Aphidoletes, green lacewing and ladybugs to provide control.
·
Effectiveness
may be reduced in late summer when Aphidius itself may be attacked by naturally
occurring parasitic wasps (called hyperparasites).
Monitoring Tips
Use a 10-15 X lens to
inspect aphid mummies for round holes in the hind end, which indicates the
adult parasites have emerged. A ragged emergence hole, in the top (mid-back) of
the mummy indicates a hyperparasite has emerged (see diagram).
Life Cycle
A complete life cycle takes
10 days at 25 ºC (77 ºF) and 2 weeks at 21 ºC (70ºF).
·
Sex ratio
in the population is about equal, although there may be slightly more females
than males (50-60% females).
·
Each
female lays about 100 eggs in aphids but may attack 200 to 300 aphids in the
process.
·
The larvae
develop entirely inside the aphids and do not kill their host until the wasp
larva is ready to pupate.
·
The larva
pupate inside the aphid’s body, which become a rigid, leathery, golden-brown
mummy.
·
Adults
emerge from the mummies by cutting an exit hole in the top. The empty mummy
remains on the leaf surface. The size of the adult parasite and the number of
eggs it can lay, depends on the size of the aphid it came from.
Product Information
Aphidius is shipped either
as parasitized aphid mummies (pupae) from which adults will emerge, or as newly
emerged adults. The advantage of shipping adults is that they usually arrive
pre-mated and the supplier can ensure they are sent without hyperparasites.
Adults should be released
immediately by walking along the rows, allowing them to fly out of the
container.
If necessary, parasitized
aphid mummies may be held at 4-10 ºC (39-50 ºF) for up to 3 days.
Introduction Rates
Aphidius is most effective
when aphid populations are low. Parasites can be introduced at low rates before
aphids are detected in greenhouses or when aphids are likely to move onto crops
outdoors. When aphids have been detected in a crop, higher release rates should
be used over a period of at least 3 weeks.
Because of the time it
takes for larvae to develop inside aphid mummies, use at least two releases one
week apart to establish overlapping generations of the parasite.
General
introduction rates
·
Before
aphids are detected — 1,000 Aphidius/ha
weekly (400/acre)
·
After
aphids are established — 5,000 Aphidius
/ ha (2000/acre) 2-3 times, one week apart.
Specific
crops
·
Greenhouse
peppers — Before aphids are detected: 1,000 Aphidius/ha
(400 Aphidius/acre) weekly. After aphids are established: 5000
Aphidius/ha (2000/acre), 2-3 times or until significant numbers of mummies
begin to develop.
·
Greenhouse
tomatoes — 1 Aphidius/10 plants, weekly for 2 weeks.
·
Greenhouse
cucumbers — 1 Aphidius/plant, weekly
until established.
·
Gerberas,
Lisianthus and stocks -- 0.5 Aphidus/ m2
(10 ft²), weekly for 3
successive weeks for prevention or every other week for Gerberas, 1-3 Aphidius/
m2 (10 ft²), weekly for at least 3 successive weeks
for cure.
·
Ornamentals and outdoors — 0.1-3 Aphidius/m2 (10 ft²) or 0.1-5 Aphidius/plant, weekly or
until control is evident.
Note: The yellow sticky traps used for monitoring pest also trap
Aphidius. If yellow traps are necessary for monitoring whitefly, do not release
Aphidius near the yellow traps and use no more than 1 yellow trap per 100
plants. Aphidius are not attracted to blue sticky traps, which can be used for
monitoring thrips where Aphidius is being released for aphid control.
For Best Results
·
During
spring and summer, aphid populations grow too fast to be controlled by the parasite
alone therefore it is advisable to introduce additional aphid predators such as
Aphidoletes
aphidimyza, green lacewing and/or ladybugs.
·
In
gardens, wash high populations of aphids from plants with a strong water spray
before introducing the aphid parasite. Note: Aphidius does not attack
many common aphid species, such as potato aphid.
Using Pesticides
Aphidius matricariae is likely to be sensitive to the same pesticides as Encarsia
formosa (see Sheet 180).
Growth regulators used in
crop production should not be harmful to Aphidius.
Spreader-stickers are
likely to be harmful to Aphidius on contact, but do not have residual effect.
Insecticidal soap and
pirimicarb (e.g., Pirliss®) can be used to reduce aphid numbers in
hot spots without harming the pupal stage of Aphidius.