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Ministry of Agriculture, Food and Rural Affairs

Viruses

Beginner

Scientific Names
Various viruses including Asparagus Virus 1 (AV1), Asparagus Virus 2 (AV2) and Cucumber Mosaic Virus (CMV)

Identification

  • Difficult to identify
  • Slight reductions in vigour and yield
  • Symptoms are more pronounced if both AV1 and AV2 are present in the plants.
  • May impact the longevity of the plantation
  • Infected plants are more susceptible to fusarium

Period of Activity
Viruses can be present at any time, although they are most common following periods of heavy aphid infestations. Viruses may be present and undetected in the crop for a long period of time.

Scouting Notes
When scouting, take note of asparagus aphid activity, or any other types of aphids present in the field. Be aware of unexplained changes in plant vigour or increased levels of fusarium.

Thresholds
None established.

Advanced

Scientific Names
Various viruses including Asparagus Virus 1 (AV1), Asparagus Virus 2 (AV2) and Cucumber Mosaic Virus (CMV)

Identification
Viruses in asparagus crops are difficult to identify. An individual virus may result in slight reductions in vigour and the number of spears. These symptoms are more pronounced if both AV1 and AV2 are present in the plants.

The presence of viruses in the crop may impact the longevity of the plantation. Infected plants are more susceptible to fusarium and other root pathogens.

Biology
Many viral diseases can be spread by aphids and/or other leaf-feeding insects, such as thrips. Insects can carry and transmit a virus for their entire life (persistent transmission) or they can acquire a virus during feeding (non-persistent transmission).

In persistent transmission, an insect can become infected after feeding on an infected plant for an extended period of time (at least several minutes to 1 hour). After an incubation period (sometimes several days or weeks), the insect is able to spread the virus for the rest of its life.

Non-persistent transmission occurs when an insect lands on and samples plant tissues from many different plants. The insect picks up the virus from an infected plant and transfers it to the next plant. As the insect feeds, it clears the virus from its mouthparts and is no longer able to transmit the disease to additional plants. Soybean aphids are a common vector of many non-persistent viruses. AV1 and CMV are both non-persistent viruses. Because the virus does not persist within the aphid, chemical control of aphid populations will not necessarily prevent the transmission of these viruses.

AV2 is transmitted mechanically, in pollen or on infested seed. Cutting knives are a common method of mechanical transmission.

Period of Activity
Viruses can be present at any time, although they are most common following periods of heavy aphid infestations. Viruses may be present and undetected in the crop for a long period of time.

Scouting Notes
When scouting, take note of asparagus aphid activity, or any other types of aphids present in the field. Be aware of unexplained changes in plant vigour or increased levels of fusarium.

Thresholds
None established.

Management Notes

  • Plant only virus-free seed, transplants and crowns.
  • Scout regularly for asparagus aphids.