 Potato Crop Management
Invader® is long lasting in the plant, allowing protection to be built up as the canopy grows.
- Effective at all infective stages of the blight life cycle.
- Its excellent activity makes it the most versatile product for protection against stem, foliar and tuber blight.
- Invader® offers persistence, so keeps working when the weather could prevent timely spray applications.
- It has a kick-back effect on mycellium if disease is already present.
- Dimethomorph is capable of penetrating and moving up the stem within one hour of application therefore protecting new growth.
Dimethomorph, one of the active ingredients of Invader®, is active at the key stages of the disease development and has preventative, kick-back and antisporulant activity. It is locally systemicity is also very valuable in helping to control infections on young growth and on stems. Invader® has significant activity on oospores. In-vitro tests have demonstrated that Invader reduced the number of oosproes to 0.4/cm2 on leaf area. AGRONOMY ADVICE MAY 2008 Last season the extreme blight pressure forced some growers to apply blight sprays at 5-day intervals. But the key to this working is to select active ingredients to overcome any phenylamide resistance that may have built up. Appropriate fungicide choice can also help to manage the more aggressive strains of blight that are becoming more common. This year more than ever before, it is essential to think about product choice for blight prevention, in light of an increase in the aggressiveness and fitness of the new A2 strains of blight. What this means in practice is that the disease has the potential to cycle more quickly and may flourish in less than ideal climatic conditions and there is also the potential for the development of oospores. Therefore, it is vital that spray coverage reaches the lower leaves, spraying is started earlier and that the appropriate product choice is made to control sporulation. Use a product which is active on oospore formation and germination because it will reduce the possibility of these survival bodies being created and acting as a possible cause of infections at the beginning of the season. The key to mastering blight control is to use more than 2/3 applications of Invader, keeping the intervals tight, two consecutive applications of Invader allow layers of protection to be built up early on. Potatoes are vulnerable to blight right from the start of the season, whether from seed infection (see picture below) or from spores blown in from dumps or volunteers. Early blight infections are the most damaging. 
The features and benefits of dimethomorph listed below illustrate why Invader is the best choice of product for this timing.
FEATURE | BENEFIT |
|---|
| Locally systemic. Movement within the transpiration stream with distribution via the xylem. |
Dimethomorph can move to unprotected new leaves and shoots as well as within the stem. |
| Translaminar with retention on contact surface. |
Dimethomorph can move to the underside of the leaf ensuring both surfaces are protected. |
| Anti sporulant activity. |
The production of new spores is limited. Secondary infections are checked stopping continued redistribution of the fungus within the plant and field. |
Long residual activity with a 10-14 day half life. (compare with half life of cymoxanil of 3-4 days)
Fungicidal activity down to low concentrations (1-2 ppm)
Dimethomorph moves into the plant within one hour. |
Dimethomorph remains fungicidally active for longer.
If spray intervals are stretched due to adverse weather, remaining levels of fungicide are still active.
Cymoxanil does not offer the same level of protection in the event of stretched intervals. | Dimethomorph has one of the widest spectra of activity on the lifecycle of potato blight of any potato fungicide. 
FEATURE | BENEFIT |
|---|
| Dimethomorph disrupts fungus cell wall formation causing lysis and death. It is active against most stages of the life cycle including oospores (the product of the A1 and A2 mating strains). |
In the field, blight is present at all stages. Use of Invader gives the greatest opportunity to control the fungus. Oospores are a potential source of new infection. |
| Dimethomorph is effective on all strains of blight including both A1 and A2 mating strains. |
All strains are controlled equally. In 2004 the A2 strain was recorded in greater abundance than in 2003. |
| Dimethomorph is effective against metalaxyl resistant strains. |
There will be no selection in favour of particular resistant strains. All strains are controlled equally effectively. | The object of early season use of Invader is to protect new growth, to build up longer lasting layers of protection lower in the canopy which will be more difficult to access later in the year. Dimethomorph movement within the stem will help control stem blight. Lesions on the stem produce more spores and are more weather resistant than leaf blight and they are more often closely associated with outbreaks of tuber blight. These properties make Invader the product of choice for this timing. The graph below illustrates that Invader (as it was performing in 2003 prior to the appearance of the new A2, blue 13 strain) was as effective as metalaxyl-m + mancozeb for the sprays during rapid canopy providing tight spray intervals are maintained.
The radio-graphs below illustrate the local systemicity of C14 dimethomorph distribution after application onto the stem of a potato plant, confirming its movement within the xylem of the haulm.
Source Albert,G. and Heinen, H. (1996). How does dimethomorph kill fungal cells? – A time-lapse video study with Phytophthora infestans. 11th International Symposium Modern Fungicides and Antifungal Compounds. Eds Lyr,H.; Russel, P.E.; Sisler,H.D.; Intercept Andover. 141-146 Fungazil 100 SL
 |
Silver Scurf
Helminthosporium solani
(and when applied prior to planting of the progeny crop) |
 |
Skin Spot
Polyscytalum pustulans |
 |
Gangrene
Phoma exigua |
 |
Dry Rot
Fusarium spp
| The key to obtaining the best result with Fungazil 100 SL is accurate application to the potato tuber. The product requires good coverage of the tuber for successful disease control. Fungazil 100 SL reduces the following diseases of potatoes when applied during storage and/or prior to planting of seed potatoes as a protective treatment: There are some key factors that pre-dispose the onset and establishment of storage diseases in potato tubers. BASF have produced a guide to help growers and store managers identify and address high risk situations before they affect marketable quality of both seed and ware potatoes whilst ensuring a good stewardship practice is adopted. There is also a Potato Seed Treatment Decision Tree folder produced by SAC and sponsored by BASF which has been designed to help growers and advisors make pro-active decisions for into-store and/or grading fungicide treatment of potato tubers. By ticking the boxes in the check lists, this enables you to identify and record at-risk situations where storage diseases are likely to be a problem based on current knowledge and experience. These decision trees are designed to support a responsible and rationale approach to the use of fungicide tuber treatments for the production of quality produce. You can view/download the guide from the connection below. To obtain copies of the Potato Seed Treatment Decision Trees folder e-mail: agri-info@basf.com Click here for the Fugazil 100 SL Stewardship Guidelines PRODUCTS RECOMMENDED FOR USE IN POTATO CROPS
HERBICIDE | Fungicide | Seed Treatment |
|---|
Basagran SG
Claymore
Laser
PDM 330 EC
Stomp 400 SC |
Fungazil 100 SL
Invader |
Fungazil 100 SL | Refer to product labels for full details. Information on SOLAs (Specific Off Label Approvals) is available to view and download from the Chemicals Regulation Directorate (CRD) website: https://secure.pesticides.gov.uk/offlabels/search.asp LINKS: Potato Council: http://www.britishpotatoes.co.uk Potato Review: http://www.potatoreview.com Mccain (Potato Story) http://www.mccain.co.uk/the-potato-story/ SAC (Scottish Agricultural College http://www.sac.ac.uk/knowledge/crops/examples/potatoesinpractice/ | 
