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Bromeliad Root and Heart Rot

 A talk given in August to the Queensland Bromeliad Society meeting.

 At the September and October meetings in Auckland members asked questions regarding their bromeliad plants rotting in the centre cup and also in and around the basal leaves. This article from Peter Paroz in Australia will help us all. ED.

Bromeliads are not subject to many pests and diseases, but heart rot and root rot can cause considerable losses. These two conditions can be caused by the same organism Phytophthera cinnamomi depending on the origin of the attack. This organism is a fungus with swimming spores which thrive in oxygen deficient conditions. The spores have a long time resting stage estimated at 12-15 years!!. It is highly invasive particularly when some form of mechanical damage has occurred. The mode of dispersal is not known but contaminated surface water is a possibility and rain water is suspected.

The organism is widely spread in soils where it has caused appreciable losses in avocado plantations attacking the roots. It is also reported as a problem in durian, oak and cacao trees and numerous ornamental shrubs in other parts of the world, and is a problem in Queensland pineapple fields. I have a copy of a newspaper article from the 1890’s which describes in recognizable detail crown rot in pineapples in Nundah. The organism gets its specific name from the cinnamon tree. The organism, previously unnamed, was identified as the cause of substantial losses in cinnamon tree plantation in Java about 1915.

The pineapple industry has developed a simple ‘baiting test’ for detecting phytophthera in soil, potting mixture or water. The procedure depends on the ready attack by the organism on the basal white tissue at the base of a bromeliad leaf. The original test used leaves from a pineapple top, but any young bromeliad leaf with white tissue is satisfactory.

Fill a glass jar to about 100mm with the water to be tested and place the test leaf in the water so that about 25mm of the leaf is submerged, Use a thin skewer to pin the leaf at the required depth. Allow to incubate for 8 to 10 days. Phytophthera is indicated by attack on the white tissue usually with a blue/black line and a foul smell. A less invasive organism pythium is indicated by cotton wool like growth around the leaf.

For soil or potting mix, boil and cool some water. Place 3 or 4 teaspoons of the soil or mixture in the bottom of the glass jar and gently pour in the boiled and cooled water, and set the leaf as above.

The recommended fungicide for the local pineapple industry is Ridomil (Fongarid). Aliette is a recommendation from the WWW. Another local recommendation is Phosforpine which is a phosphorous acid preparation neutralized to ph 5.7. This compound appears to act by inhibiting germination of the spores.

Bromeliad plants which are infested can sometimes be saved if the invasion is not too advanced. The best procedure is to remove as much of the affected tissue as possible back to white tissue. Treat with fungicide and allow the damaged tissue to dry and callous over. A serviceable fungicide for this purpose can be made from two parts slaked lime (calcium hydroxide not agricultural lime) and one part sulphur.

The recent heart rot problems that I am aware of seem to be associated with the use of chemical sprays; one for mosquitoes and the other for scale control. A possible reason is that the chemical was too strong and caused damage to the growing point of the plant allowing invasion by the fungus.?

ED: I have used Yates Bravo with considerable success, but we have asked our member Alan Cliffe, Development Manager of Nufram NZ, to advise on some NZ equivalents that can be purchased from your local plant shops or merchants.

Alan Cliffe comments…
‘The products listed above are all systemic ( absorbed by the foliage and translocated within the plant) fungicides with specific activity against phytophthora. The products that are available in New Zealand are similar to Australia. The first mentioned is Ridomil. Ridomil used to be available in NZ containing only the active ingredient metalaxyl. Now there is a new product available as Ridomil Gold MZ. It contains two active ingredients: metalaxyl-M plus mancozeb.Unless anyone has direct experience of the safety of mancozeb to bromeliads, I would be cautious because mancozeb contains a complex of manganese with zinc.
A similar product, Fongarid 25WP, containing the active ingredient furalaxyl, is available from Yates, in 500g packs. This is probably the best option as it is formulated as a powder, which is typically safer than the emulsifiable concentrate formulations. Phosphorous acid formulations are available as Foli-R-Fos ( from Key Industries , available as 1litre), or Foscheck ( available from Taranaki Nuchem in 1litre bottles).
The other type of product which will give some protection is Bravo. This contains the active chlorothalonil. There are many brands on the market, of different strengths, some in packs as small as 1litre. This is a broad spectrum protectant fungicide (does not get into the foliage but stops disease establishing on the surface), which has activity against a wide range of diseases.’?

ex November 2002 journal

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