Why are my tomato leaves going yellow?
Are the leaves on your tomato plants going yellow? You can still see green veins, but the leaves are going yellow and curling?
Tomato yellow leaf curl virus is popping up in backyard veggie patches across the Wide Bay, and has been since it was first recorded in 2006.
The virus is spread by the silverleaf whitefly, and the Department of Agriculture, Fisheries and Forestry have the insect listed as a serious pest in tomatoes and other vegetable crops in Queensland.
David Gillespie is a former experimentalist for the Department of Primary Industries, and he says the whitefly is a insect you need to be well informed on in order to tackle it effectively.
"Whiteflies can become very resistant to insecticides and quite quickly so they're very destructive," he said.
"Growers will be noticing their plants that have green veins and yellow in between on the leaves. They are perhaps slightly cupped, bumpy, and sometimes they won't even set a fruit.
"Because it's a virus disease, once it's got into the plant there is not a lot you can do about it but what you have to do is mange silverleaf whitefly."
The whitefly will often feed off other vegetable crops.
Whilst most plants are immune to the disease, the feeding of the fly causes the leaves to have a mottled silver colour.
This cuts down on the amount of photosynthesis in the plant, meaning often less yield.
How do I get rid of silverleaf whitefly?
- Step 1 - Attract the whitefly's natural enemies; lacewings or lady-beetles.
"The larva of these insects will eat the eggs and nymphs of whiteflys," David said.
"Attracting the natural enemies is the first big step because they will help keep the numbers down."
- Step 2 - Monitor the insect activity in the garden and spray with white oil.
David recommends getting insect traps from your local hardware shop to keep an eye on the insect population in the veggie patch.
"Once you see the numbers start to build up you should spray with white oil, particularly focusing on spraying on the underside of the leaves," David said.
"The insect hides mainly on the underside of leaves... that can be bought in most hardware stores and home garden centres, that sort of thing.
"White oil is different to other insecticides in that it's a physical way of eliminating the insect. It basically suffocates the insect by blocking up its mouth parts.
"Growers use systemic insecticides, but they rotate them, but I'm not going to suggest that home growers do that."
When the silverleaf whitefly feeds, the plant can often exudate sugars which can lead to sooty mould appearing on the plants and fruit. David says the white oil will help cure that as well.