Detailed responses to Barbara’s questions from the previous issue:
1: Leaf-Miner Caterpillar - A small insect lays its eggs on the underside of the leaves – broad-leafed species - eg: cucumbers, eggplant, are preferred, but any soft leaf will do. The hatched larva burrows into the leaf and devours it from within, hence the squiggly lines. Any stomach poison which is absorbed by the leaf will kill it, but it rarely seriously affects the plant.
Organic remedies are neem leaf insecticides (see previous articles available on this journal’s website), or ‘Derris Dust’ which is made from a locally-grown tuber which is simply called ’tuba root’. I have never seen this for sale locally. You could make an infusion of grated tuba root with boiling water if you can source a supply. Add a squeeze of dishwasher detergent to make it stick.
2: Powdery Mildew - This is common here as it likes warm, moist conditions, and is a fungal infection. Numerous chemicals are available for its control. Organically, a solution of 50/50 milk and water has some effect when sprayed over the plant, but expect to do it often as it has no carry-over capability.
3: Blossom-end Rot - This is most usually caused by over-watering; lime deficiency can also be a cause. A handful of garden lime per sq.m is usually enough to address this. Do not water over the foliage, rather allow the hose to gently water the soil beneath. A good soaking weekly is preferred by tomatoes, rather than frequent sprinklings.
White Oil – Now usually labeled ‘All-Season’s Oil’ these days and, as its name implies, may be used at any time. Do not spray in the middle of the day as it reacts with sunlight to cause a phyto-toxic burn. Late afternoon is the best time. Again, a recipe for easily made white oil (a soft soap/kerosene emulsion) has been published previously. (See B.A. website).
White Moths/Fluff – I doubt that your white moths are the Cabbage White Moth. As their name implies, they prefer all members of the cabbage family. Keep a sharp lookout for green caterpillars however, especially around any of the sawi hijau family: Treatment again as above, or in prior articles. ‘White fluff’ (as found in cushiony scale) would not be dislodged by shaking a tree. If the fluff is firmly attached to the plant, again refer to prior articles for treatment.
Ian, Singapore, writes: I have Heliconias in my planter box. I water them every alternate day. They have ample sunshine. Please advise the likely cause of the spots and dry edges on the leaves (photos attached). How to prevent it in future? They are not flowering anymore. What did I do or not do? I look forward to your answer.
I asked Ian for further information. The two Heliconias he grew were Heliconia psittacorum cv. Andromeda; Heliconia psittacorum x H. marginata. Both are near species/hybrids, which grow vigorously and flower more or less continuously.
They are hardy, easy to grow, and multiply rapidly; producing a dense root mass. Ian told me that he grew them in planter boxes 50cm deep, and used fertilizer pellets every six months. They flowered well for the first two months, but have not flowered since. He waters them every second day.
I consider the marks on the leaves to be sun scorch which has two possible causes: 1: Perhaps they get a little too much sun; remedy this by moving positioning them to get some shade in the middle of the day. 2: A more likely reason is that, after two years, the root mass is so compacted his watering simply runs down the sides of the container leaving the plants water-stressed and more apt to be affected by the sun.
Turn the plants out of their containers; divide into smaller clumps, trimming the roots severely; replant just half into new growing medium. Singapore garden centers all stock ’burnt earth’ which is an ideal base as a container medium. To this, add a generous amount of compost, plus some water-saving crystals (these absorb water and release it as the plants require). Re-potting is the best time to include slow-release, pelleted fertilizer, mixing it through the potting medium.
Given the vigor of these Heliconias, expect to need to do this on an annual basis. Once every two weeks, add some foliar fertilizer to the watering can and water over the leaves, as it is absorbed by the green parts of the plant.
There are a number of proprietary brands – look for one high in phosphorus, as it stimulates flowering. (Chemical ratios are usually on the label.) The best one I know is an English product named ‘Phostrogen’ though it may not be readily available. Usual dosage - one level teaspoon (some even include a measure) to nine liters of water.
Please send all your gardening questions to
E-mail: gardendoctor08@yahoo.com
