The whitefly is probably the one insect that tomato plants suffer from the most. In the spring there is nothing to worry about, but in the second half of summer, a plague can develop explosively, especially when you’re growing tomato plants in a greenhouse.

Whiteflies are tiny white flies (hence their name)😃, only about 1 mm big. They suck sap from the leaf of the tomato plant and defecate sugars. It’s not a problem if you have a few whiteflies, but if you have hundreds, the contaminated plants become a dirty sticky mess.

The adult whitefly lives in the crown of the plant, where the leaves are tender and juicy. The larvae hide under the leaves halfway down and at the bottom of the plant. A female can deposit 400 to 600 eggs in her life. So if you kill one whitefly female, that will save you at least 400 offspring.

Hygiene is very important. At an average temperature of 20 degrees, it takes only 30 days after hatching for an adult specimen to lay eggs. That is quite long for a pest insect. If you start with a few whiteflies, it will take longer for the population to become large enough to cause damage and nuisance. At the end of the tomato season, remove all the plants from the greenhouse. And make sure to remove all the weeds too (the whitefly can overwinter well in weeds). The fewer green plants left in the greenhouse, the greater the chance that the whitefly will not survive the winter.

The moment you spot the first whiteflies in your tomato plants, it is wise to catch them straight away. But how do you catch flies only 1 mm in size?

You can buy sticky yellow sheets that work like fly traps. The whitefly is attracted to the yellow color, lands on the sticky sheet and gets stuck. This method catches lots of whiteflies and slows down the growth of the population. Hang these traps in the crown of each plant infected with whitefly. Replace the sheets when they get too dirty and no longer stick properly.

If the white fly population continues to increase despite the yellow fly traps, then spraying a mix of soft soap and white spirit is a good option. This is an old, well-known eco-friendly product and also works well against aphid and spider mites.

Make sure to use soft soap, not detergent! They are not the same. Note that soft soap is made from the potassium salts of fatty acids. A well-known brand available all over the Netherlands is called Driehoek groene zeep.

- 1 liter water

- 30 grams of soft soap

- 20 ml white spirit

Mix everything well and pour into a plant spray bottle. Spray the top half of the plant soaking wet, especially in the mornings. Repeat this every 5 to 7 days until the white fly decreases. Do not stop too soon. For at least 30 days larvae will be hatching out into adult whiteflies and moving into the crown. You have to kill them every time, otherwise the new whitefly will lay more eggs and there you go again.

Our potted tomatoes don’t get whitefly because we have already harvested them before the whitefly season begins.

In the past when my father and I grew vine tomatoes for a supermarket, whitefly was our number one enemy. Early in the year we would release a plant bug that loves to eat whitefly. This green, mobile little creature, only 4 mm in size, is called Macrolophus. The beauty of the Macrolophusbug is that it eats everything you can get on a tomato plants in terms of pests: whitefly, caterpillars, eggs, the tomato leafminer moth(Tuta absoluta) and spider mite. And if they don’t find a single pest to eat in your tomato plant, then population stays alive by drinking the sap of the plant. An ideal creature.Macrolophus is still the basis of biological control for the professional tomato gardener.

I also put Macrolophus in my own hobby greenhouse. Since I’ve been doing that I hardly ever suffer from pests. I hear you think, I also want to set Macrolophusonto my tomatoes. If you suffer from whitefly every year, I would recommend it. The perfect time to set them out in a cold greenhouse is in early June.[

- At the end of the season, remove as many plants as possible from the greenhouse.

- Hang yellow traps on spotting the first whitefly.

- If the whitefly problems gets worse, then every week sprayasolution of soft soap and white spirit.

- If whitefly is an annual problem, put Macrolophus in the greenhouse at the beginning of June.