Aphid control
Aphel-line ab.
Aphelinus abdominalis
Aphelinus abdominalis
Aphel-line ab is a proprietary product containing the aphid parasitoid Aphelinus abdominalis. (Dalman), Aphelinidae, Hymenoptera.
The product is supplied to growers as a mixture of pure mummies and freshly emerged adults in 30 cm³ vials. A source of food is provided to ensure that emerged adults arrive in the best possible condition. A minimum of 250 viable adults are supplied per unit.
The mummies are removed from the leaves and all aphids and debris are removed before packaging.
Aphelinus abdominalis is a specialised parasitoid of aphids.
Female Aphelinus select aphids by palpating them with their antennae. Having located a host aphid of an appropriate size and species, they turn away, thenand then reverse towards the aphid with the ovipositor extended. The tip of the ovipositor is inserted into the ventral surface of the aphid and an egg is laid.
The egg hatches within the aphid and the resulting larva consumes the body contents, finally feeding on vital organs when nearly fully grown. The aphid host continues to feed and grow during this process and may initially produce some offspring. As the development of the parasite larva proceeds this ceases. When the parasite larva is fully grown the host dies and a distinctive black mummy is formed. At 20°C this occurs 7 days after parasitism. The mummy then takes a further 14 days to develop before an adult wasp emerges.
In one of the principal hosts, Macrosiphum euphorbiae, Aphelinus prefers to parasitise second and third instar aphids. Larger aphids are less frequently attacked, while first and small, second instars are used as a source of food by the adults. This host feeding is an important source of mortality in the aphids, with each female Aphelinus abdominalis killing approximately 2 aphids per day. By host feeding, the parasite obtains a source of proteins, which allows it to continue development of eggs and so increase the total number of offspring it produces.
In laboratory studies, each female is capable of producing an average of 250 or more offspring over a period of 3 weeks, with an average daily production of 14. Egg laying continues throughout the life of the female. This is in contrast to Aphidius, which produces a similar total number of offspring but does it over a much shorter period. It is unlikely that either Aphelinus or Aphidius will produce this number of offspring in a field situation.
Aphelinus is sometimes criticised on the basis that it tends to walk over the crop rather than fly and does not therefore find hosts well. This can also be interpreted as meaning that it remains on the crop and does not leave the glasshouse as readily as parasites that fly more readily. The fact remains that Aphelinus is a widespread, common and successful parasite, and as such it is obviously well adapted to finding suitable hosts.
Aphelinus abdominalis has been recorded as parasitising a wide range of aphid species. It can be used in any crop where the aphid pests Macrosiphum euphorbiae and Aulacorthum solani occur. It is also reported in the literature to parasitise Myzus persicae, but more recent reports show that it does not do so, and the parasite Aphidius colemani is better suited to this task.
(Aphelinus abdominalis)
Aphel-line ab is supplied as mummies with emerging adults in vials. There is no carrier material.
Instructions for Use
On receipt place the vials in a cool shaded area until ready to use. DO NOT EXPOSE TO DIRECT SUNLIGHT.
When ready to apply, open each vial carefully amongst the plants in the greenhouse.
For preventive use:
Release emerged adults by gently tapping the vial whilst walking among the plants.
Place the vial with remaining unhatched mummies in a shaded place amongst the foliage.
For corrective use:
Release emerged adults directly onto identified aphid colonies in the late evening or early morning.
Re-cap the bottle, and store at greenhouse temperature until more adults have hatched. Repeat the distribution daily for 2-4 days untilmostuntil most adults have emerged from the bottle. Finish by placing the open bottle next to a plant in case more hatch.Fasten the vial with the remaining unhatched mummies onto the plant beneath the colony, or place it on the bench or ground amongst infested plants in pots. Out of doors, or where there is overhead irrigation, place the vial horizontally to prevent it filling with water.
Storage.
Use within 18 hours of receipt.
Keep out of direct sunlight.
Keep in a cool dark place until use.
Best results with this product, as with any aphid parasitoid, are obtained by making low rate preventive releases when there is a risk of aphids invading the crop. These will spread throughout the crop and find low level infestations before they become damaging and often before they would be detected by routine monitoring. Colonies that do establish will grow more slowly than they would without the presence of the parasite and allow more time for other action to be taken. Once larger outbreaks of aphids are detected, higher release rates may be made immediately beneath colonies.
To apply the parasites preventively, use a release rate of between 0.2/m² and 0.5/m² each week. Holding the vial or bottle horizontal, carefully remove the lid in the crop to be treated and walk along the rows, gently tapping the vial to distribute the adult parasites. Do not tip mummies from the tube: this will reduce their emergence. Re-cap the tube and store at greenhouse temperature until more adults have hatched. Repeat the distribution of adults for 2-4 days until most adults have emerged from the bottle. Instead, pPlace the open tube with any remaining mummies amongst foliage in the glasshouse and leave it there for a week or longer until all the mummies have emerged.
For a corrective release, open the bottle or vial immediately adjacent to the aphid outbreak and rest it at the base of the affected plant. Repeat this as necessary.
Do not use Aphelinus abdominalis when the principal aphid pest is Aphis gossypii, Myzus persicae or Myzus nicotianae. Do not use when aphid numbers are very high. In this case make a corrective spot application of a compatible insecticide, such as pymetrozine, to reduce aphid populations before releasing Aphelinus.
Aphel-line ab. will help to prevent outbreaks of the aphids Macrosiphum euphorbiae and Aulacorthum solani when used preventively as recommended. It may even entirely prevent colonies developing if used at the beginning of the risk period. It may also be used at higher rates to bring moderate infestations under control, but should be used in conjunction with other control measures in this situation.
Aphel-line ab will not immediately control larger infestations of aphids. It may fail to control some species not mentioned here, so careful identification or monitoring of parasitism is important to ensure success.
Where the principal aphids present are Aphis gossipii, Myzus persicae or Myzus nicotianae, use the parasitoid Aphidius colemani.
For heavy outbreaks of Macrosiphum and Aulacorthum, it is preferable to reduce populations before releasing parasitoids. Some growers favour the use of lacewing larvae (Chrysoperla carnea) or Coccinellid beetles (Adalia bipunctata) as localised treatments.
Several compatible aphicides are available, such as pirimicarb and pymetrozine.