What are the red brown spots on my pittosporum tenuifolium its spreading on the leaves
Row of 14 Screenmaster. 1 plant has many leaves developing red-brown spots (pic attached). Some of the other plants have some spots, but not as many (the closest to the worst seeming to have the next most, thus suspecting contagion). The most spotty plant also seems host to many black diamond-shaped bugs (with white spots, shown in pic). Is there any way to arrest the spread without wholesale prune-back?
What a shame the foliage of your pittosporum is looking so poorly. Pittosporums are susceptible to attack from a number of pests such as aphids and mites and both of these pests can carry viruses which result in leaf damage. You can certainly control the aphids and mites by spraying Yates Nature's Way Vegie & Herb Spray Concentrate but the damage has been done so I don't think there is any alternative but to prune off the infected foliage. Pittosporum can be infected with a leaf spot fungus but the spots don't appear to be consistent with the ones in the photo. It is not going to do any harm to prune back the infected foliage. Pruning will help to initiate new growth and at this time of year the plants will put on new growth in no time at all. It would be wise to monitor your plants for pests and take the appropriate action if any appear.
Answered: 6 Jan, 2014