Plant Doctor Archive

Mite menace

SOME of the leaves on my brugmansias are crinkly and distorted. Another one nearby is growing well and flowering, no problem. Can you help?

THE MOST likely reason is damage to the emerging leaves, probably caused by mites. The two-spotted mite - sometimes referred to as spider mite - is a common pest on brugmansias, particularly in hot, dry sunny weather.

It's possible mites damaged the bud last season and you're only now seeing the effect as the leaves grow.

Two spotted mites are so small you can barely see them with the naked eye. They suck sap from the leaves and lay eggs on the undersides. With a heavy infestation, you'll sometimes see fine webbing on the shoot tips with mites crawling around on it, but this is more common in greenhouses than outdoors.

Mites can be difficult to control with sprays. My advice is to prune away the affected shoots and burn them or dispose in the rubbish. Fertilise the plant and water if necessary to encourage strong growth - a vigorous brugmansia will still grow and flower quite happily with some mites on it.

If you do decide to spray, use a product like Mite Killer or Guardall.

With some plants a thorough spray in winter with oil (such as Conqueror or Clear White Oil) is useful for killing eggs as well as any overwintering adults on your plants.

However, I suspect winter-oil sprays may just damage brugmansias so do a small trial first, on say just one branch, before going ahead and spraying the whole lot.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.