Contents: Packed as pupae inside parasitized aphid cases. Some adults may emerge in transit. Parasites are available in containers of 250 count or in mixes with A. ervi or A. abdominalis.

General appearance and lifecycle: Adults are tiny black wasps 4 -5 mm in length with other stages developing unseen inside hosts. Parasitized aphids will swell and harden into a leathery, gray or brown colored mummy-like casings, after which the adult wasp parasite emerges through a round hole made at the rear of the mummy. The first aphid mummies can be seen in the crop approximately 2 weeks after the first introduction of A.ervi. The life cycle of Aphidius ervi is longer than that of Aphidius colemani at the same temperatures, and the parasite is larger and selects larger hosts. Where A. colemani reaches adulthood within 14 days at 70º F (21º C), A. ervi takes nearly 19 days at the same temperature. At 60º F (15º C), the duration of the cycle is approximately 20 days for Aphidius colemani, while it is nearly 29 days for A. ervi.

Hosts: In particular the potato aphid Macrosiphum euphorbiae and the greenhouse potato aphid Aulacorthum solani. A. ervi is also commonly recovered from the Pea Aphid Acyrthosiphon pisum. Some research has been done on both Pea and the Green Peach Aphid, Myzus persicae. Other aphid species are also attacked, but less information is available about these species

Crops: Commercial greenhouses, ornamentals, shrubs, and outdoor crops

Environment: Tolerates 53º - 86º F (12º - 30º C) with optimum conditions at 65º - 80º F (18º - 26º C) and 60%-80% RH. Reduced efficiency above 86º F (30º C)

Application rates:

Infestation

Rate

unit covers

Frequency & Interval

preventive

0.15/10 ft2

16,500 ft2

every week

curative light

0.5/10 ft2

5,000 ft2

3 weekly introductions

curative heavy

0.5/10 ft2

5,000 ft2

6 times with 3 days between applications

Release: Use Aphidius ervi when aphid infestations are low. Release emerged adults as soon as possible upon receipt, preferably in cool morning or evening temperatures and under low light levels, by gently tapping open containers while walking through the crop. Containers with remaining pupae may be left open, in a shaded location, under existing aphid colonies and away from direct irrigation.

Important:

Apply as a preventative or at the earliest sign of aphid infestation. Aphid populations can increase up to 20 times in one week. Do not release immediately before or after pesticide applications. Check compatibility charts before pesticide use and be sure to properly identify your aphid species.

Storage

Use as soon as possible. Storage after receipt: 1-2 days at 47º - 50º F (8º -10º C) in the dark.

Aphidius ervi (parasitic wasp) Aphid Parasite

How does it work?

Aphidius ervi females seek out and parasitise aphids. The main target for this parasitoid in commercial crops is the potato aphid Macrosiphum euphorbiae. Other targets are the Pea Aphid, Acyrthosiphon pisum, and the Green Peach Aphid, Myzus persicae. Other aphid species are also attacked, but less information is available about these,

Once a female finds an individual aphid or aphid colony, she will palpate the aphids with her antennae. If the aphid she is examining is of the correct size, and has not already been parasitized, she rapidly curls her abdomen under her body and stabs the aphid with her ovipositor. This takes less than one second, but in this time the female checks the identity of the aphid with her ovipositor, and lays an egg into it if she is satisfied.

The egg soon hatches, and the resulting larva begins to feed within the aphid. Initially it will not kill the host, but as it grows it begins to feed on the vital organs so that the aphid dies. When fully grown, the Aphidius larva cuts a slit in the hollowed out shell of its host, and attaches the carcass to the substrate with silk. As it spins more silk within the host skin, this gradually takes on a golden color and forms the characteristic ‘aphid mummy’. Within the mummy, the larva pupates, and after five to ten days an adult is ready to emerge. The adult Cuts a circular trap door in the mummy, always on the upper surface at the back, and escapes through this to seek out new hosts.

When and where should you use it?

Aphi-line e can be used in any crop where Macrosiphum euphorbiae is the principal pest aphid occurring. Although it is a vigorous parasite which can attack many individual aphids, it will work best when used prophylactically during periods when aphids are expected to arrive in the crop. This will ensure that at least some of the initial aphids colonizing the crop will be found and parasitized, so that colonies may grow slowly or be stopped entirely before they reach damaging levels. There will then be fewer large colonies, and fewer aphids will develop as winged individuals and spread through the crop to form new foci of infestation.

This prophylactic approach can be achieved using either regular low rate releases of between 0.25/10 ft2 and 0.5/10 ft2/week, or by using cereal plants infested with an alternative aphid host which will not attack the principal crop. These 'banker' plants’ are popular with many growers, but they require horticultural care, and may need repeated releases of cereal aphids to function.

This prophylactic approach may entirely avoid aphid outbreaks, but if not it will slow the development of colonies of aphids and allow the grower extra time in which to act. Aphidius ervi can also be released correctively directly onto existing colonies, but the rapid reproductive rate of aphids and the lag between parasitism by Aphidius spp. and death of the host may allow the population to grow beyond the level at which economic damage is caused. It may therefore be necessary to use another biological agent or a compatible chemical agent to reduce localized outbreaks to a manageable level before releasing Aphidius.

How should I use it?

Adults must be released into the crop as soon as possible after receipt, ideally in cool temperatures and low light levels to avoid the risk that they will fly immediately to the roof of the greenhouse. If this is not possible, they should be kept below 10 C in darkness until release. Mortality will occur during any period of storage.

Aphidius ervi is originally a European species, but it has been widely introduced into North and South America, Australia and other regions in recent years as part of biological control programs for aphids on a variety of crops.

* Rincon-Vitova Insectaries, Inc. 2006. <http://rinconvitova.com/>; Applied Bio-nomics Ltd.  2008. < http://www.appliedbio-nomics.com/index.html>; Malias and Ravensburg Knowing and Recognizing (Netherlands: Koppert, 2003) 161