DISEASES

DISEASES & PESTS

Crown rot and root rot
  • Asparagus is affected by two Fusarium species.
  • The first is Fusarium oxysporum pv. asparagi which causes crown rot; and the second one is Fusarium moniliforme which causes root rot.
  • The crown rot fungus is found in most soils but at very low levels.
  • If asparagus crowns are planted that have crown rot they will not produce spears for more than 4 to 7 years, and this is not profitable.
Control measures
  • Do not plant asparagus in soil in which asparagus has been grown in the last 5 years.
  • Do not purchase crowns grown in soil where asparagus was grown in the last 5 years.
  • Purchase only certified crowns, keep asparagus growing rapidly to reduce crown rot disease by following the recommended management practices.
  • The root rot pathogen may be spread through asparagus seed. Make sure to treat seeds for producing crown.
Cercospora blight : (Cercospora asparagi)
  • Symptoms include small, oval and grey to tan lesions (spots) with reddish brown borders on the needles and small branches.
  • It causes the needles to fall from the mature fern.
  • It can be identified by the browning of needles.
  • The disease occurs when the humidity and temperature are very high.
Control measures
  • An integrated approach of several cultural practices will help provide partial control.
  • Schedule overhead irrigations to allow thorough drying of the foliage before nightfall, or use drip or furrow irrigation to keep foliage dry.
  • Wider row spacing will increase the air movement to dry foliage and delay canopy closure.
  • Rows should also be planted in a north-south direction to take advantage of prevailing southerly winds in drying foliage burning.
  • Disposal of infested residue in the spring delays blight appearance by about one week.
  • There are no known asparagus varieties resistant to Cercospora blight.
     
Soft rot: ( Erwinia spp.)
  • Harvested asparagus is susceptible to bacterial soft rot.
Control measures
  • Management is based on avoiding injuries and immediately cooling harvested spears.
  • Wash water and water used for hydrocooling should contain chlorine.
Rust : ( Puccinia asparagi)
  • It is not a common disease.
  • Rust causes small brown rusty pustules on spears and fern branches.
Control measures
Asparagus beetle
  • Asparagus beetles and their larvae attack on spears and ferns.
Control measures
  • Spray carbaryl (0.1%) to control this insect.
Army worms
  • Army worms can be especially bad on young ferns.
Control measures
  • These can be controlled by deltamethrin (0.0025%) or carbaryl (0.1%).
European asparagus aphid
  • It can be a problem occasionally.
  • The blue-green aphid forms colonies in August or September.
  • When the aphid forms colonies, it causes "Christmas tree" or bonsai effect.
  • The new fern becomes shortened or stunted and new needles look like they are clustered.
  • The entire plant takes on a blue green colour.
Control measures
  • It can be controlled with a spray of malathion (0.05 %) or oxy-demeton methyl (0.025 %).

Last modified: Sunday, 17 June 2012, 5:39 AM