The following paper suggests spraying regimes for a commercial cut flower crop, outdoor grown. We have also posted elsewhere some photos of common problems and suggestions for remedies. This programme is designed to deliver a perfectly pest and disease free cut flower crop. If you are not worried about some powdery mildew and your cut flowers do not have to be absolutely pest free you can get by with very little spray usage. Our delphiniums are selected for thier relative resistance to powdery mildew.
Pest, weed and disease control in delphinium elatum as a cut flower crop.
The following is a list of measures that have worked for us. You may wish to try them but do so at your own risk.
Control falls into two categories: prevention and cure, and is achieved by both cultural and chemical methods.
The principle of an ounce of prevention being worth a pound of cure is a gross understatement. A milligram of prevention is worth a tonne of cure (in metrics too!!)
Dates refer to Southern Hemisphere 40-60 degrees South
Cultural - Prevention
- Soil preparation should ensure that all the necessary food elements are present in the right quantities and balance. Failure to provide an adequate balanced diet results in unhealthy plants susceptible to pest and disease attack.
- The soil should be able to hold moisture well without becoming waterlogged in times of continued wet weather. Good drainage is very important, especially between September and April when the plants are growing vigorously. Poorly drained soil encourages root rots.
- Weed control: Weeds must be kept at a minimum to prevent the build up of pests and diseases and allow adequate air flow between plants.
- Pest and Disease Control: Remove infected material
Chemical - Prevention and Cure
Even with the very best cultural practices chemical protection will still be needed. Chemicals should however be regarded as a tool - not as a bandage.
The major pests and diseases of delphinium in New Zealand and their possible chemical remedies, are as follows:
|PESTS||Slugs and snails||Mesurol|
|Caterpillars etc||Mavrik Aquaflow|
|Cyclamen mite||Vydate# or
Kelthane (Dicofol) /Thiodan
(damping off of seedlings)
|Black spot (bacterial)||Kocide 101 (copper) together with: Mancozeb
Super Six (sulphur)
|Virus Attack||no chemical control|
Your spray programme will vary from season to season and during the season according to stage of growth and pressure and type of diseases.
- these chemicals are very dangerous and should only be used when absolutely necessary and with extreme care.
- these chemicals are systemic and curatives and should be used sparingly or resistance may develop.
It is very important to apply a Kocide/Mancozeb spray and a SuperSix (sulphur) spray to new growth (when just emerged and up to 10 cm height). Both these sprays are excellent preventatives, the first against Blackspot, the SuperSix against powdery mildew.
Blackspot usually becomes difficult to control as the weather warms up in November. At this time include Agrimycin with the Kocide/Mancozeb and SuperSix spray every week for three weeks. Keep an eye out for it recurring.
Powdery Mildew will appear sometime in December (if not earlier) and is a product of warm humid conditions. Nimrod should then be mixed with SuperSix for three consecutive weeks and an eye kept out for further flare-ups. If Nimrod is not effective then Calixen should work but extreme care must be used as slightly too much will ‘yellow’ the plants and set them back.
Insects are not usually a problem with delphinium in New Zealand but if exporting the crop then Mavrik should be applied at weekly intervals.
A possible spray programme may be:
First spray of the season - late August or Early September: Kocide/Mancozeb - mix and leave overnight - spray in the morning.
The following week: SuperSix (Sulphur)
Thereafter alternate these sprays every week unless the occurrence of a disease dictates otherwise. Maybe use a Thiram/Phaltan for the odd time for a change.
Early November: Introduce Mavrik into the spray programme, viz Kocide/Mancozeb/Mavrik or Sulphur/Mavrik. Keep a good look-out for Blackspot and Powdery Mildew.
If Blackspot occurs introduce Agrimycin
If Powdery Mildew occurs introduce Nimrod
Do not combine Kocide 101 or Copper Oxycholoride with SuperSix (sulphur). I have used most other combinations without problems but check with me before using something new.
It is alright to use Sulphur/Nimrod/Agrimycin/Mavrik together when Blackspot/Powdery Mildew and caterpillars are a problem.
Spreaders and Stickers
Citowet at 25 mls per 100 litre is a good spreader and should be used at all times.
Rainguard is an excellent sticker and should be used when rain is likely or when you want to overhead irrigate shortly after spraying. It is a good idea to irrigate the evening after picking and before spraying.
Both these ingredients can be mixed with your sprays.
Make beds up as soon as possible to give yourself 4-6 weeks time to kill off weeds before planting.
When weeds have germinated to 2-3 cm in height spray off with Roundup
A week or two prior to planting spray with either Roundup or Paraquat.
One week before planting spray with:
- Foresite or;
- Lasso (Alachlor) or;
These are selective pre-emergence week killers. Foresite kills on emergence at the surface, Lasso and Dacthal kill on germination. All act differently and should be look up in the Agrichem Manual and understood, before applying.
Lasso and Dacthal may be applied over the delphinium crop. Foresite may not.
For best result apply either Lasso or Dacthal regularly according to the instructions on the label, after an initial application of Foresite.
No selective pre-emergence weedkiller will kill all weeds. There are many to choose from and they should be selected according to your weed problem.
No matter what you use there will always be some hand weeding to do.
General Spraying Considerations
- Do not spray in the heat of the day. Try to spray in the early morning or evenings.
- Always wear the proper spray clothing
- Make sure that application rates are working out OK. Check against the label
- ALWAYS READ THE INSTRUCTION ON THE LABEL. (They may change with your next purchase).
- Read the Agrichem Manual
- NEVER use more chemical than recommended.
I have found the measures I have outlined to be successful on my own property but cannot in any way guarantee their effectiveness elsewhere due to differing soil types, weather conditions and methods of application. Particularly, I cannot be responsible for any spray damage which may occur to any plants whatsoever. If you have not previously used a particular chemical combination try it on a few plants first - notwithstanding my recommendations.