Tag Archives: Downey Mildew

The 6 main pest and diseases of rose & how to treat them.

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Pest  and  Disease  Control  of  Roses  

Introduction  – What  is  IPC  and  its  Methods

For  those  that  have  followed  My  blog on

general  pest  &  disease  control   Will   remember  that    I  use  the  IPC  method  on  all  plants  especially  roses. So  you    will  just  need  to  skip  this  paragraph   until  you  get  to  the  one  you  that  you  know. For  those  that  are new .  I  will  briefly  explain  what  IPC  is  before  going  on to  the  Pest  and  Disease  section .

Briefly  I  P C  stands  for  :-

  • Identify  –  By  Identifying  the  pest  or  disease  you can  then  isolate  it  and   treat  it  without  harming  any  other  insects  or  predators  that  are  beneficial  to  the  plant
  • Prevention  –

Prevention  is  better  than  cure

If  you  followed  the  guide  lines  that  i  told you. You are   less  more  than  likely  to  get    infected by  a  blight  or  pest  but   like  the  common  cold  no  matter  how  much  we  keep  healthy  we  still  get  it.  so  is  very  much  like plants

in  their  case  they  will  become  less  sickly  if  we  observed  their  requirement  from  the  off  set  as  I   have  pin  pointed  in  the  first  blog  

Control   or  Monitor   methods –   And  finally  Control    With  the  pest  or  Disease on  rose    isolated  we  can  begin  the  applying  the  safe  practise  of  control   whether its  Chemical  or  Organic  or  mechanical

The 6 main pest  &  Diseases 

& How  to  treat them

The  main  6   pest  &  Diseases  of  roses  are :-

  1. Aphids  
  2. Black Fly
  3. White  Fly
  4. Mildew
  5. Rust
  6. Black Spot

There  are  others  pest  like  the  leaf  cutting  bee   thrips &saw flies   but  those  are  the  main  six

Saw  Flies

These are caterpillar-like larvae, which feed on the leaves of your roses in the spring. They are about 1 ¼ inch long and are light green, some with black spots. If you get on top of this pest right away, you should be able to control them by simply hand-picking them. Look for them on the undersides of the leaves.

Saw  Fly  symptoms

Saw fly larvae symptoms

These  you  just  simply  remove  and  incinerate as  the  caterpillar is  well  protected

 

 

 

Leaf  Cutting  bees

leaf  cutting  bee

Tel tail of leaf cutting bees

 

 

 

 

 

Thrips

Thrips are tiny, slender, dark brown or black, sucking insects that damage and destroy opening rose buds turning them brown and leaving them only partially opened. They also feed on the upper surface of the leaf. They can be difficult to see outdoors. If you think that your rose may have thrips, take a cutting inside and shake it over white paper to see if any fall out. Look for a brownish black insect with a narrow body up to 1/16 inch long. They thrive in hot, dry conditions. Regularly watering your roses and spraying with an insecticide or simply cutting off the affected rose or leaf should do the job

thrips

Thrips

 

 

 

 

  1. I have   already  been  mentioned  in detail along  with  white  fly  in  the  following  blog
  2. BlackFly  

Identification

Black  Fly

Black Fly

As  you  can  see  from  this  picture  these  pest  can  be  easily  Identified &  tend  to  swarm  in  colonies  attacking  anything  that  is  green  and  sappy  whether  it  your  green  beans or  bedding  plants  to  roses  that  have  been  over  feed  with  high  nitrogen  fertilizer  to  produce  sappy  growth .

Prevention

The  best  way  to  prevent  your  roses  being  attacked  by  these  pest  is  to  carefully  check  your  feeding  of  roses.

As  I  said  above  these  and  other  pest  like  aphids  like  green  sappy  growth  for  their  piecing and  sucking  mouth  parts

Feeding this way causes problems for the plant: aphids can transmit plant viruses, and the sticky honeydew they exude can attract sooty moulds to grow

As  in the  case of  lime  trees  every    where

Good  hygiene  too   don’t  compost  any  infected  plants  in  winter  as  the  females  lays  its  eggs  in  the  autumn on  plants  to  feed  its  nurseries and  ounce  the  eggs  has  hatched  in  spring  they  fly  off   on to  much  better  food  supply  and the  circle  begins.

So by  either  bagging  up  infected  plants  or  burning  them  you  are  at  least  cutting  down  on  the  numbers  in  your  garden . But  since  they  can  fly  doesn’t  really  guarantee  you  that  you  are  free  them

So  we  go  to  the  next  Section

Control  or  Management 

There  are   3   methods  of  control

  1. Cultural  

By  this  mean   good  hygiene  and  feeding  regime  as  I  said  above  also  to  encourage  their  natural  predators  into  the  garden   like  Ladybirds lacewings   even  small  birds  feed  on  the  insects  now  and  again

Click to tweet   how   you  can  attract  more  predators into  your  garden  

Spraying  with  tar  oil  or  winter  washes   tends  to  work  well in  winter    when  the  female  lays  it  eggs

Natural  Predators

2. Biological  Control  

is comparatively expensive, but effective – if you can create the right conditions. The main problem being that there will be a time lag between being able to source the biological control of Blackfly. Together with this, there will need to be enough Blackfly for the biological predators to act upon.

However  ongoing  research according  to  this  article  here  published  in  2005

This discovery has applications for pest management – the aphid sucrase enzyme could be a suitable target for specific inhibitors that would abolish its dual role in osmoregulation and carbon nutrition of the aphid.

that  these  pest  can  be  controlled  by  spraying  or  other  methods  not  yet  mentioned,

Current research is focussing on determining the mechanism – it’s possible that an anti-microbial with the symbiotic bacteria as the primary target may have evolved in certain plants.

As  I  already  have  gone  into  detail  about  the  use  of  chemical  as  a  method  of  culture  I  wont  go  into  detail  here  but  only  to  stress  the  dangers 

Mildew  

Mildrew

The effect of Mildrew on roses

As you  can  see  from  the  picture  that  Mildew  can  be  easily  recognised  by  its  powdery  white  effect  on  leafs  and  stems .                        In  fact  Mildews  a  fungal  Disease  rather  like BlackSpot  but  cause  its  feeds  on  moisture  on  the  plant  leaves   it  easily  remedied  by  following  the  procedure

Prevention 

Cultural  control

If you  seen  any signs  on   your  roses  whether  on the  leaves  or  buds  its  best  to   prune  them  out  to  avoid  the  spores  from  spreading  any  further.

Good  hygiene  again  is  important  –  keep  the  center  clear  of  branches  in  the  spring  to  allow  air  flow  through  and  around  the  plant

Try  avoid  watering  from  above  or  in  between  the    branches  water  from  the  bellow ,

Avoid  watering  in  them  evening   go  for   in  the  morning    where  if  you  have  splashed  the  leaves  the  water  has  a  chance  to  dry  off

Plant  rose  far  enough  part  so  they  can  spread  out

Control  

 

Rose Rust

Identification

As  you  can  see  from  these  two  examples  that  rose  rust  can  be  easily  recognised  by  its  orange  flex on leaves  and buds

Rose  Rust

Rose Rust on buds

Rose  Rust

Rose Rust on leaves

 

 

 

 

 

And  like  Powdery  Mildew  its  a  fungal  disease  on  the  roses  but  less  severe. That  occurs  from  the  beginning  of  spring  right  up  to  summer  should  the  environmental conditions  be  right  for  the  spores  to  spread

Prevention 

6  Cultural  Methods of  controlling  rust  

  • Good  Hygiene  as  always  –
  1.  remove  infected    leaves  and  incinerate  to  prevent  the  spores  from  spreading    like  Black Spot   spores lay  dormant  in  the  on  the  soil  surface  until  they  are  either  splashed  up  by  the  rain  or  watering  from  above   or  carried  up  by  insects  especially  ants . So  clearing  the  ground  of  debris  around  the  plant  is  a  must.
  2. Pruning –  By  leaving  the  center  clean  and  cutting  out  crossing  branches  improves  the  air  circulation  around  the  plant  thus  reducing  the  breeding  grounds  for  the  spores  to  live  by  drying  out  the  leaves  and  buds.
  3. Weeding  –  By  clearing  any  weeds  around  the  plant  esp  oxalis  that  get  infected  by  rust  you  are  reducing  the  risk  of  it  spreading  to  the  roses
  4. Improve  the  soil  structure  of  the  soil  by  forking  over  the  ground  in  spring  to  improve  drainage
  5. Avoid  watering    from  above   always  water  from  the  base  of  the  plant
  6. Avoid  working  on  rose  beds  when its  wet  as  you  can  spread  the  spores  by  simply  walking  around .

Control  

Chemical  Control  

When  you  see  the  first  signs  of  rust    spray   the  entire  rose  bush  with  a  copper formulated  compound   examples  can  be  found  here     until  the  bush  is  cleared  giving  it  a  good  drench.

Always    go  by  the  rules  i have mentioned   for  proper  chemical  Management

Organic  Control

There  are  many  new  ‘organic  formulations’  on  the  market  you  could  try if  you are  organically  minded  one  is  the

Disease  spray

Vitax organic spray for pest and disease

 

Vitax  2  in  1  pest  and  disease  control  spray    Yet I  haven’t  had  the chance  to test  it  out  yet.

But  Vitax  is  reputable  firm  that  specialize  in Rose  Care  products

 

 

 

 

 

 

Black Spot.

Identification

Black Spot  spores  on  roses

Black Spot spores on roses

Finally  I  come  to  most  dreaded  killer  of  all  roses,

Black Spot  –  as  You  can  see  by  this  image    this  too  easily  recognized  by  it  instinctive black splotches  that  are  actually   spores .  The  thin  white  threads  are  in  the  roses  stem. hence once  you  see it  its  pretty  much  that  there is  no  real  cure  for  it  except  to  either  live  with it  or  destroy  the  bush  all  together.

In  cases  of  My  many  Clients  they  rather  live  with  it  until  it  dies  completely

So  what  can  be  done  to prevent  it

Prevention

Cultural  Prevention

  • As  I  mentioned  at  the  very  start  of  the  Blogs  on  roses    That  when  planting  a  new  rows  always  make  sure  the  rose  gets  a  good  start
  • Mulching  around  the  roses  in  spring  with  sterilized compost  like  Cocopeat  or  peat based formulations     This  will  stop  any    fungal  spores  that  i  mentioned  above  from  splashing  up  and  infecting  younger  shoots
  • Pruning  out  any  dead  diseased  or  dying  branches  and  incinerating  it  (  Do  not  compost  them
  • Improve  the  air  circulation  around  &  inside  the  bush  by  cleaning  out  any  inward  pointing  branches
  • Don’t  plant  roses  close  together  as  one  rose  can  spread  the  disease  to  another  and  this  too  allows  air  to  circulate
  • Water  from  the  base  only

Chemical  Control  

Organic  Control

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Powdery Mildew

Identification and  damage

Image

Powdery Mildew on a Rosa species .

As you  can see Mildew  comes  in  a white powdery  mycelia and spore growth that forms on leaf surfaces and shoots and sometimes on flowers and fruits.These  are  the  fruiting of  the  fungus.

It  can  severely  effect  woody  plants  as  young  sapping which  would  dwarfed.

Cause

Downey Mildew  thrive  in  temperatures ranging  from  50 to  60  degrees  wuth  humidity  of  90%

It  can  be  recognized  by  only  being  specific  to  the  leaves  &  not  like  its  other  relation Powdery  Mildew  which  effect  the  stalks  as  well.

And  require  the  opposite it  needs  free  water  and  temperatures  ranging  from

60 -80  degrees  to  germinate.

Management  

Prevention  is  the  only  way  with  this  I’m  afraid  :-

  • Make  sure  that  the  air  is  well  circulated  either  out  doors  or  inside
  • water  the  plant  in  the  morning  and  in  the  evening  if  necessary.
  • apply  fungicide  at  the  first  sign  of  attack   and  remove  and  dispose of  infected  leaves
  • As  it  wind  blown  and  dependent  on  climate  make  sure  that  the  plant  is planted  in  the  right  environment &  that  there  isn’t  any  other  plant  that  is  infected  with  it  near  by .
  • Plant a  species  that  is  immune  to  it  if  possible for  example  Rosa  rogusa  or  aImage

    Image

    Rosa Rugosa alba

Cultural Practises

As  Mildew  seem  to  thrive  in  shady   moderate  temperatures ( esp Powdery Mildew)  place  plants  in a sunny  area  with  good  circulation

Avoid  over  feeding  the  plants  with  fertilizer  as  this  will  make  sappy  growth .giving  the  plant  an  over  head  watering  will  wash  of  the  spores  and   kill  them  in  the  soil

Fungicides  applications  

In  severe  cases  when  roses  and  other  woody  plants  are  infected  spraying  with  fungicide  will  be  the  only  alternative.

These  are  classified  as  :-

  • Preventive
  • Eradicator

Preventive

These  fungicides  are  applied  to  new  growth  before  mildew  has  a  chance  to  get  a  foot  hold.

These  include :-

  • Horticultural  oils  like  neem,jojoba (read  My  article  on  neem  oil  )
  • Powders  like  sulphur , potasium  bicarbonate
  • and  Biological    with  serenade

For Mild to  heavy  infestation  spray  with  the  plants  natural  product  ie  Neem  oil. Becareful  never  to  apply  a  oil   spray  within  2  weeks  of  sulphur  spray  or  it  will  burn  the  leaves.

Also  never  apply  oil  sprays  when  the  temperature  has  reached  90  degrees 

Sulphur

1832

An Organic Sulphur Spray

Copper fungicide

An H&S approved copper fungicide

Sulphur  sprays  have  been  used  for  centuries  and  rather  ironic   that  in  the  days  of  the  smug  plant  diseases   never  appeared  cause  the  sulphur  was  believed  to  keep  it  at  bay

The  best  sulphur  to  buy  are  the  wettable  kind  cause  the  dust  can  be  toxic  to  humans

Copper  Formulations

Although  copper  has  been  used  for ages  as  an  effective  fungicide  when  it  mixed  with  a  another  formulation  like lime it acts a bactericidal thus  killing  off leaf  spot  and  fireblight

Vitax-Catalogue-16-Aug-2012-058-624x780

Vitax Bordeaux Mixture
(Disolve in Water and use a spray)
Contains Tetra-copper Tricalcium Sulphate

Vitax Bordeaux Mixture should be mixed with water and then applied, without drenching, as a fine spray to both sides of affected foliage.  The actual dilution rates vary from plant to plant and full instructions are provided on the product label.

Bicarbonates

baking-soda

Contrary  to the  myth  Sodium  Bicarbonate    found  in  Baking  Soda  actually  restricts   fungus  growth  due  to  its  alkalinity &  there  fore  only  useful  as  a  preventive measure.

Also available to licensed applicators only is a fungicide containing potassium bicarbonate (e.g., Kaligreen).

Sprays of potassium bicarbonate can injure the plant, so use these products with caution.overuse should be avoided because of possible negative effects (sodium accumulation and alkaline pH) on the soil

Biological Fungicides

5878321_2 Biological fungicides (e.g., Serenade or UK  Myclobutanil ) are commercially available beneficial microorganisms formulated into a product that, when sprayed on the plant, destroys fungal pathogens. The active ingredient in Serenade is a bacterium, Bacillus subtilis, that helps prevent the powdery mildew from infecting the plant.

Myclobutanil is a triazole chemical used as a fungicide. It is a steroid demethylation inhibitor, specifically inhibiting ergosterol biosynthesis. Ergosterol is a critical component of fungal cell membranes.

These products have some effect in killing the powdery mildew organism but are not as effective as the oils or sulphur in controlling it.