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I really enjoyed
Phil Dudman’s Citrus Care Guide in the August issue; however, there was nothing about citrus leaf miner. Are there any advancements in treatment for this problem? Bruce Adams, Narangba, Qld
PHIL DUDMAN SAYS Leaf miner makes its presence felt in the summer months, when the pest is most active, but you may also see some damage in spring. The adults lay their eggs on new leaves, just beneath the surface. When they hatch, larvae ‘mine’ the leaf as they feed, creating their familiar silvery trail.
When they’ve had their fill (after about six days), the larvae head to the edge of the leaf to pupate, which causes the leaf to curl. The standard control method is to apply an oil-based spray to new growth. The adults dislike the oily surface and go elsewhere. For maximum effect, you need to maintain an oily coverage on the leaves by spraying weekly. If you’re not up for that commitment, rest assured established plants tolerate leaf miner damage and will still flower and fruit well – it just looks ugly. I sometimes prune out and pick off the worst-affected foliage if I can’t stand the shabbiness. If you’re onto it as soon as you notice the damage, it will help reduce their numbers, which means less damage in future. Also keep in mind that the spring flush of new growth is mostly unaffected by the pest and will make even the worst-damaged tree look pretty again.
Leaf miner pheromone traps are a recent development worth trying. These attract and trap the males, which means fewer pregnant females, and provide a good indicator of when the pest is active.
QI’ve had these black bat plants (Tacca chantrieri) for many years. They all grew from one plant, which I divided. They have become very leggy and stopped sending up suckers. Should I re-pot them lower in the pot? Gabrielle Vaccaro, Sunnybank, Qld
AB BISHOP SAYS Bat plants don’t like to be pot-bound. Your pot looks small for the size of the plants, which is probably why growth has slowed. Divide rhizomes with a sharp knife and plant each into individual pots. Use a premium potting mix and ensure that the entire rhizome is submerged, with only the foliage above. Place the large rhizome (below) horizontally; it should send up new shoots from the nodes.