Diseases

  • Foliar spraying with Molasses  Some nurseries are finding that weekly foliar spraying with molasses mixed 1:1000 or stronger helps prevent pests/disease.
     
  • Anthracnose in Mango  
    Anthracnose is one of the most serious diseases of mangoes in many areas where the crop is grown. The most devastating effects of anthracnose occur in areas where it rains during the mango flowering and fruit set stages. Although it appears to be less of a problem in the NT because flowering and fruit set  occur during the dry season, anthracnose can cause problems  here under certain conditions.  Mango anthracnose is caused by the fungus Colletotrichum  gloeosporioides var minor (also known by the name of its  perfect stage Glomerella cingulata var minor). Spore production by this fungus is favoured by wet or humid weather. The dispersal of these spores is particularly favoured by rain and wind. This enables spread of the disease over relatively short distances.  In areas where rain is prevalent during flowering and fruit set, anthracnose can cause destruction of the inflorescences and infection and drop of young fruit. This can obviously lead to serious losses.  Under NT conditions anthracnose tends to manifest itself later in the season. It can occur either as leaf spots or as fruit anthracnose. Occasionally anthracnose lesions are seen in young green fruit, more commonly in larger green fruit but most commonly in ripening fruit. The anthracnose fungus has the ability to produce what are known as latent infections. This means that the fungus has the ability to penetrate green fruit where it may go into a dormant state until the fruit ripens. Then the anthracnose fungus can be re-activated in response to physiological changes associated with ripening, resulting in the development of lesions with subsequent spoilage of the fruit. 

    SYMPTOMS  On leaves, spots form commonly towards the margins. They are tan to dark brown in colour, often with a darker border. Infection of young leaf flushes may occur when their emergence coincides with rainy weather. These infections often show up as lesions along the margins of the young bronze or pale green leaves, in which case  they are semi-circular in shape.  In very humid weather new twigs may show a dark affected area from the tip backwards, sometimes with defoliation of the young shoots.  © Northern Territory

    Government, 2007 Page 2 of 2  When newly formed fruit are affected the anthracnose shows as large, sunken, black lesions and the fruits so  affected drop off. Medium to large green immature fruit affected with pre-harvest anthracnose show large lesions which are glossy, black and sunken. With these fruit, splits and oozing often occurs.  The most common fruit anthracnose results from latent infections (see above) and is seen as slightly depressed grey-black areas in the skin on ripening fruit. In time the typical pink to orange spore masses (acervuli) form on this tissue. 

    CONTROL  Regular spraying of trees from flowering time onwards with mancozeb (at recommended label rates every 14  days) is useful to reduce the level of infection in the developing fruit. Do not use mancozeb within 14 days of harvest. If anthracnose becomes serious in green immature fruit it would be useful to give a couple of judicious sprays of prochloraz. It is important however not to overuse prochloraz as this may lead to development of resistant anthracnose strains. Copper sprays recommended for the control of mango scab will also control anthracnose with only a one day withholding period.  Post-harvest treatments are available for control of anthracnose in mango fruit. Prochloraz is used as a cold nonrecirculating  spray. Hot water dips used to control fruit flies will also control anthracnose and stem end rots. Hot benomyl dips will control anthracnose and are useful where stem end rots are a problem. 

    Controlling Anthracnose in Mango   by Tony Rola
    Control of Anthracnose must start when you have young flushes (new leaves). Spray the young leaves with 300 grams Copper Oxychloride combined with 2 kilos Muriate of Potash (0-0-60) dissolved in 200 litres of water. Spray at bud break and repeated 3 times at 2 weeks interval.
    During fruit production, include fungicide in the spray solution.
    After harvest, use hot water dip.
     

  • Bacterial Black Spot  Copper sprays are used on mangoes to control bacterial black spot and in the case of copper hydroxide and copper sulphate these products are also approved to control anthracnose on leaf and fruit. I am sorry but there are no alternatives to copper that are registered for use on mangoes that give effective control. In avocado for example, where copper sprays have been reduced, deleted or replaced with other 'softer' products sooty blotch has appeared and anthracnose has not been well controlled. If you wish to speak to me on this subject please phone 02 6626 2435 John Dirou, District Horticulturist - NSW DPI.
     
  • Disease Management brochures:  https://www.soilwealth.com.au/resources/fact-sheets/pest-and-disease-man...
     
  • Banana Bunchy Top Disease   https://www.ctahr.hawaii.edu/oc/freepubs/pdf/CFS-BAN-4A.pdf 
  • Confidor for pest control   Our Flat Seedless Persimmon has just finished producing this year thanks to an early spray of Confidor just after fruit set to control the Fruit Spotting Bug so we had an excellent crop. I used nylon stockings to keep fruit fly and birds from them. The stocking leg was able to be wrapped over the fruit 3 or 4 layers thick. The bats still were able to suck/eat 3 of the fruit through the stockings but this was stopped by hanging wind chimes and tinsel strings in the tree. We still had landings after that but a step ladder left erect close to the tree seemed to keep them right away. Next year I’ll try motion sensor lights; they work well except windy days set them off.
     
  • Flying Fox  My favorite store, ALDI, had rechargeable spotlights on sale at $24; 55watt halogen searchlights, the bats were like stunned mullets and the toads become totally paralyzed. The trees look very different in its light and what was very noticeable was that fruit and flowers really stand out. It’s a great way to find those hard to see fruit. It was the first time I’ve been able to see how nimble bats are through the trees once they recover. If you’ve got a strong spotlight give it a go as you will be surprised how different it all looks.
     
  • Damping off  in seedlings This can happen if you try to grow certain seedlings too late in the summer and they are not mature enough in the autumn to fight off the fungals.  Fungicides labelled for damping off will help but air circulation around the plants and refraining from overhead watering later in the day, are very important in preventing it.
     
  • Having a problem with black spots on Pawpaw? 
    Small black spots = cold
    Large black spots = anthracnose
     
  • Dieback   Several custard apple orchards have recently reported cases of branch and tree dieback. Disease isolations carried out by the Department of Agriculture and Fisheries have identified two different pathogens with a possible third pathogen currently being identified. The pathogen Lasiodiplodia was identified to be causing branch dieback and trunk cankers in one orchard in Queensland in 2015. More recently Neofusicoccum parvum was identified in the Northern Rivers causing branch dieback in one orchard. Dark necrotic lesions were found under the bark surface. A clear definition of the lesion and healthy tissue can be seen.  Neofusicoccum parvum is a fungi in the Botryosphaeriaceae family. It has a wide host range that affects a range of horticultural crops and native vegetation. Neofusicoccum parvum is described as an opportunistic pathogen that often infects stressed or damaged trees. It also has the potential to spread through pruning cuts. Neofusicoccum parvum is a relatively weak pathogen that generally only becomes a problem when trees are under environmental stress. Fungicide sprays used to control other diseases in custard apple orchards will usually keep this disease under control. The spread of Neofusicoccum parvum can be limited by sterilising pruners that have come in contact with the diseased limbs while pruning and removing affected prunings from the orchard. In severe cases of Neofusicoccum parvum, or any other pathogens causing dieback, remove affected branches by cutting back the branch until clean wood can be seen. This is sometimes called “eradicative pruning” and can greatly reduce the potential spread of pathogens causing branch dieback. Healthy shoots should develop behind the pruning cut.  Ref:  George Allen
     
  • Dieback  On Quantum there was a segment on Phytophthora in rain forests in North Queensland and the conclusion was that the disease was present only in disturbed soil that became alkaline. Maybe by maintaining an acid soil we might be able to control it in our trees.
     
  • An effective solution for fungal problems is to change the pH on the surface of the leaf. This is done by spraying one day with bi carb soda and the next with apple cider vinegar - diluted of course. This has the effect of changing the pH rapidly and fungus finds it hard to handle.
     
  • Mango Malformation Disease (MMD) Source: Biosecurity Queensland  <http://www.dpi.qld.gov.au/26_16002.htm
    Biosecurity Queensland is investigating a suspected case of Mango Malformation Disease (MMD), a slow moving fungal disease, identified on a single property at Caboolture. Biosecurity Queensland Mark Panitz said the property had been placed under quarantine. "The property is not a commercially-managed orchard but we are taking this seriously and moving quickly to protect Queensland's AUD 70 million [USD 62 million] mango industry," he said. "Biosecurity Queensland is already surveying nearby properties for any evidence of MMD. This is a critical 1st step to identify where the disease is." Mr Panitz said MMD could significantly reduce yields in mango orchards if left unmanaged. The Australian Mango Industry Association (AMIA) said MMD did not affect the quality of the fruit. Biosecurity Queensland is working closely with AMIA and the Federal Department of Agriculture, Fisheries and Forestry to ensure any potential impacts are minimised. This is a fungal disease caused by several species of Fusarium, some yet to be described. Mango is the only known host, and it is one of the most important diseases of this crop. The disease was 1st reported in India, but has subsequently been found in many other regions. However, fungal species contributing to MMD may possibly vary in different areas. Infected shoots are misshapen with shortened internodes and small stubby leaves. Inflorescences are shorter, thicker, have crowded branches and do not bear fruit. Shoot malformation is most severe on seedlings but can also seriously affect mature trees. Symptoms are thought to be a result of hormonal imbalances induced by the fungi. The epidemiology of MMD is poorly understood. It spreads very slowly, but if left unchecked, it can severely reduce yields. The main method of spread to new areas is through infected vegetative planting material; there is no evidence of spread with fruits or seeds. It is often associated with the bud mite Aceria mangiferae, but the mites have been shown to spread the disease only within a tree, not between trees. Disease management relies mainly on phytosanitary measures, removal/exclusion of inoculum, and the use of clean planting material. Australia was thought to be free of MMD until it was detected in a small number of trees on a research farm in the Northern Territory in 2008. The station was quarantined; extensive surveys in the area did not detect any additional trees with MMD symptoms, and affected trees were burnt. It remains to be clarified what the sources of both the NT and QLD infections may have been and if the 2 outbreaks are in any way connected.
     
  • Mango Spray Schedule   Bruce at Wamuran Co-Op says the spray schedule for Mango is: Copper Oxy and Mancozeb 25gm of each in 10 litres every 7 days in wet weather and 10-14 days in fine weather – stop spray a fortnight before harvest.
     
  • Mancozeb   A useful tip that came from one of our members was that spraying with Mancozeb after physical damage was effective in enabling the repair of plants and fruit. The use of copper sprays tends to accentuate the damage due to the restricting effect it puts on cell division. Funguses find it hard to multiply in the presence of copper at higher rates, but so do plant cells. Mancozeb on the other hand consists of Zinc and Manganese. Zinc is beneficial to reproduction and growth and Manganese is important in plant health. Mancozeb has been passed for use on a lot of crops in Queensland, so before using it, check if it has been passed for the plant and use as per instructions. Maybe Zinc Sulphate used as a trace element spray would also help in these circumstances. Should be a great Mango season with this dry weather, no anthracnose. If it does rain when the flowers are on don’t forget to spray. Mancozeb is good on flowers. If some of your mango trees flower very early, cold damage to the embryos will cause a lot of them to abort and fall off. Just remember that you will have to supply water and nutrient to fill the fruit from here on. If you get rain then a spray of copper-oxychloride will help defend against fungal problems, and still be reasonably environmentally friendly.
     
  • Phosphorous Acid and Phosphoric Acid are two chemical products commonly used in horticulture but they have very different uses.
    Phosphorous Acid has some fungicidal activity and is commonly used to treat Phytophthora root rot in a range of crops.
    Phosphoric Acid is used as a Phosphorous (P) fertilizer especially in hydroponic and fertigation systems because it is very soluble in water. Each product has its specific use and these are not interchangeable. The table below summarizes the properties of each product.
    References:   Brunings, AM, Datnoff, LE and Simonne, EH
    Phosphorous acid and Phosphoric acid: when all sources are not equal. University of Florida.
     
  • Phytophthora   This is a solution to a wide spread infection of many plants that often cripples the growth and production of them and for some such as Avocados results in death. Australian state governments are recommending its use to save many species of trees from extinction; WA and SA are particularly hard hit. http://www.parkweb.vic.gov.au/resources05/05_2089.pdf
    I was very interested in the biodynamic farming practices at Philippe dufaud's place, particularly the drum of liquid compost being stirred. I was given a bottle of this compost tea from the barrel and this now forms the basis of a microbial/fungal tea mix I have brewing in a 65 litre bin. I did some research on the net & with what I thought I knew put together a compost tea brewing kit. A 65 litre bin, aquarium air pump, plastic tube & an aerator stone, this is now blowing bubbles through my tea. I’ve added composted cow manure, seaweed liquid, fish emulsion, compost & molasses plus some mulched Pitaya (which I had noticed was a good compost exhilarator) A witches brew that will be hard to check for bacterial & fungal action. On looking at the web again, I realized that this was big business & equipment could be very expensive & checks need to be carried out by a good laboratory. After much reading I suspect that given the right conditions your soils will be colonized naturally, a well composted, mineralized & mulched garden probably will over time end up with the right balance of flora & fauna - that’s if you don’t kill it by our normally heavy handedness, the use of pesticides, fungicides, chemical fertilizers that burn & digging & solarising the soil. I didn’t realize just how complex soils are; one author was saying there were 300 named species of earth worms in Australia & he believed there were at least twice that many. In a plot at Samford they found 23 species, the weight of bacteria in a hectare of soil is about the same as 2 cows, there are vast amounts of fungus & other living creatures that live in balance & it is they that we owe the fertility of the soil to, & also our own existence. Think twice about how you use your soil; it is the foundation to our life & much abused by our ignorance & arrogance.    Ref: George Allen 
     
  • Powdery Mildew in Mangoes  Signs to look for are when they completely lose their first flowering but put out a second flowering. You’ll usually see a white residue and the panicle flowers are brown and brittle. Some people spray neutral copper and a wetting agent when the panicles are almost ready to open and others swear by wettable sulphur and a wetting agent. Sulphur will give a good set.
    Copper seems to be best after the small fruit have formed and will avoid the black spots from anthracnose.
     
  • Powdery Mildew… Prior to spraying, the plant should have been watered for 2 days!
    Mix 1 full teaspoon of baking soda, 1 tablespoon of mineral oil, half a teaspoon of dishwashing soap or insecticidal soap, 4 litres of water.
     
  • Milk Spray Recipe for Mildew
    12 cups full cream milk to 1 cup water. You could add 1tsp bi-carb also to it.
     
  • Yates Pest Oil:  Do not use if shade temperatures exceed 32°C (35°C for citrus) or when soil is dry and plants are suffering from moisture stress. Do not pick edible fruits for 1 day after spraying. Do not spray on Glen Retreat mandarins. Do not apply for at least one month after spraying with Lime Sulphur or Sulphur.
     
  • White Oil recipe   Cup of oil, cup of water, a few lux flakes - mix in a vitamiser then dilute it 10:1 when you go to use it.
     
  • Using the Leaves of the Horseradish Tree as a fungicide - Moringa oleifera  Choose leaves that are free from disease. Wash and clean the leaves, chop up finely and mix in water, 1kg leaf to 3 ltrs water; let it stand overnight, strain then spray early morning on infested plant parts. For Anthracnose, Early blight, Fruit rot, Leaf spot. Always test the plant extract formulation on a few infested plants first before going into large scale spraying. When adding soap as an emulsifier, use a potash-based one.  Wear protective clothing while applying the extract. Wash your hands after handling the plant extract. References  * Sangatan, P.; Sangatanan, R. (2000): Organic fungicide. How to process/prepare organic fungicides. Practical guide to organic pesticides.  Technology and Livelihood Series. Busy Book Distributors, Quezon City.
     
  • Smartphone App for growers of Grapes to recognise diseases and disorders.
    https://www.adelaide.edu.au/news/news100582.html
     
  • Integrated Approach to Pest Management using Saltbush  -   Gardening Australia
    Not very long ago, this thriving market garden in Virginia, north of Adelaide, had a real problem with disease. The tomato-spotted wilt virus that lived in the weeds surrounding the farm was ruining Dino Musolino's lettuce crops. "The virus came from the weeds - predominately the thistles - that have the virus. Then the Western Flower Thrip brought it in to the lettuces. We used to spray with chemicals. We would spray five to seven religiously through the summer months. Not only is it expensive, it's not a great way to present product. We'd like to minimise chemicals wherever possible," Dino explained. Five years ago, Dino got together with entomologist and botanist Glenys Wood, an expert in biological pest control. By planting some humble saltbush species around the farm in place of the weeds, both the disease and the pest that spreads it has now been all but eliminated. "There was a mix of seasonal weeds here, Sophie - weedy brassicas, thistles, mallows - that are favoured by the Western Flower Thrips. That's a problem in the crops and when the crops are cleared, the thrips and the other pests come out and they quite happily survive and reproduce in the weeds and then go back in the crop afterwards," said Glenys. "Previously, every time the weeds got to the stage that they were flowering and had broad enough leaves for chemicals to be effective, he'd have to spray them. It creates a bare earth buffer around your crop. It's expensive and certainly bad for biodiversity."
    Glenys thought that the need to spray weeds could be eliminated by planting a variety of saltbushes. "We chose saltbush because they're deep-rooted and they grow quickly, joining up and shading the soil to eclipse the weeds. That excludes or suppresses quite a few of the pests that are likely to come in. We think that perhaps the pests don't see the colour of the native plants. They don't like to lay their eggs in there and the plants themselves don't have the virus, so you're not keeping stocks of the virus that would have been in the weeds, near your plants," Glenys said. Glenys recommended Fragrant Saltbush (Rhagodia parabolic); Ruby Saltbush (Enchylaena tomentose); Coast Saltbush (Atriplex cinerea) and Seaberry Saltbush (Rhagodia candolleana). The plants also attract beneficial predators. "Ladybirds and lacewings, hoverflies and even predatory mites deal with the eggs of the pest mites on the crops," she explained. Glenys also gave Dino a present so he could check on the effectiveness of the salt bush plantings - a handheld microscope. Dino's found it useful: "We'd just look broadly at the damage before, but now we have these wonderful little tools here that allow us to have a good close look." "So you're becoming an entomologist too?" asked Sophie. "Well, I don't want to take anybody's work away, but I'm pretty good at it," said Dino. "I notice that you've also got plantings under the raised racks of lettuce," Sophie observed.
    "Well, once we found that there was a result, and a good result, we thought we would spread the plantings around the perimeter of this greenhouse and it's proven to be working, so we're looking to continue to plant," Dino said. Glenys wasn't sure if the scheme would work: "I wasn't sure how it would influence the lettuces on top of the table, but just a quick look shows that there's quite a few predatory spiders in there already, so it looks like it's working so far." The native planting project has been more successful than Dino thought possible: "We've reduced our spraying by about 95 percent. We've only come out on really rare occasions to apply that chemical because we have no need with the beneficial plants that are here. It's a saving of cost and labour - it puts a smile on my face," Dino finished.