5 Organic Controls for Greenhouse Whitefly

, written by Benedict Vanheems gb flag

Greenhouse whitefly

It’s that time of year again, when wafts – nay, clouds – of whitefly lay siege to summer favorites like tomatoes and cabbage. They appear from seemingly nowhere and colonize plants fast – they’re certainly contenders for the most efficient-at-reproducing-and-spreading pest!

How to Identify Greenhouse Whitefly

For those unfamiliar with whitefly (lucky you!) here’s a quick description of what you’re looking for. Greenhouse (or glasshouse) whitefly are closely related to aphids but a touch smaller, at around 1-2mm (a twelfth of an inch) long. They have a triangular shape, like tiny, anaemic cheese wedges. The real clincher for quibble-free identification is their habit of swarming away when approached or disturbed.

Just like aphids they produce a sticky ‘honeydew’, which is in fact…their feces. Yes, it’s all very unpleasant stuff. And if that’s not enough, honeydew can attract diseases such as black sooty moulds on plants already weakened by the whiteflies’ persistent sap sucking.

Whiteflies are great at making more of themselves. Each adult lays hundreds of eggs which hatch out into larvae with an insatiable appetite for whatever plant they’re sat on. Severely affected plants can eventually turn yellow and wilt, producing lacklustre growth at best. As well as tomatoes and cabbage family crops, particular whitefly favorites include peppers, eggplant, strawberries, cucumbers, pumpkin, okra and sweet potato. They will attack plants growing outdoors as well as in the greenhouse.

Greenhouse whitefly are tiny but can seriously weaken plants

Greenhouse Whitefly Organic Controls

Whitefly can strike any time from the middle of summer. The first frost will put paid to their plans for crop-wide domination but, be warned, in mild areas or in warm greenhouses they can happily remain active throughout the winter. Needless to say, the first line of control is to take action as soon as they appear; the early gardener catches the whitefly, so to speak. Here are five tactical techniques to help you banish the bugs:

1. Blast off. Begin with a good, strong blast from the hose to knock the whitefly off your plants and onto the ground where they’ll perish. Blast all areas of the leaf, especially the undersides where they mostly congregate.

2. Organic insecticidal soap. With an initial assault complete, it’s now time to apply an organic insecticidal soap, again taking great care to cover all areas of the leaf including, crucially, those undersides. Spray at a cooler time of the day and follow up with one or two more sprays a few days later.

Recipes abound for homemade insecticidal soaps. For example, add a few drops of dish washing liquid and a squeeze of lemon juice into a spray bottle then top up with water, shake and spray. The trouble with homemade sprays is that their effectiveness varies dramatically, and they aren’t always as harmless as they seem, potentially knocking back whitefly predators too. They are perhaps best reserved for use within a closed environment such as a greenhouse, but be aware that results may disappoint and potentially could do more harm than good.

3. Vacuum. What, really? Yes, really! In a bad outbreak a handheld vacuum can be very effective at sucking up clouds of whitefly from disturbed leaves. Repeat over several days to begin to bring an infestation under some semblance of control.

Sticky traps help monitor greenhouse whitefly populations, and are easy to make at home

4. Sticky traps. You can buy sticky traps, or make your own. Simply paint or color in cards yellow, then smear with a concoction of petroleum jelly cut with a little dishwashing liquid. Hang up close to affected plants. Whitefly love the color yellow and will flock to the cards, only to get stuck and meet their end. Hanging up sticky traps is also a great way to monitor populations of whitefly early on in the season – act immediately when you spot them.

5. Parasites. Encarsia formosa may sound like the Latin name of a beautiful vine, but it’s actually a special type of parasitic wasp that lays its eggs inside whitefly larvae. Then, when the eggs hatch, the young Encarsia feed on the larvae from the inside out. If that all sounds a bit grim, it is.

And it gets worse. The whitefly larvae are still alive at this point and it’s only when the parasite is almost ready to hatch out as an adult that it then sets to work on its host’s vital organs. Once these are devoured, the whitefly turns black and just over a week later, adult Encarsia hatch out to go on a morbid hunt for their next victims.

Gross as it is, Encarsia formosa are formidable at controlling whitefly within a greenhouse. You can buy them on cards primed with ready-to-hatch pupae to hang up near infected plants. They need a relatively warm temperature of at least 21°C (70°F) and can really only be used within enclosed environments.

Flowers will help to draw hoverflies and other greenhouse whitefly predators to your garden

Other Greenhouse Whitefly Predators

If the Alien-like approach of Encarsia is too much, consider one of the whitefly’s many other natural enemies, including hoverflies and ladybirds. Flowers and flowering herbs such as calendula, thistles, oregano, fennel, parsley, poached egg plant and buckwheat are all easy to grow and will draw in whitefly-eating predators by the crowd. They’ll feast on aphids too.

Grow some of them next to the greenhouse door to tempt these beneficial bugs closer. A few pots of choice favourites placed inside will almost certainly seal the deal.

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Show Comments


"In recent months, we have had swarms of white fly and aphids - uncontrollable. We tried everything! We have lost all of our crops of tomatoes, broccoli, eggplant, and cauliflower. I really do not know what more we can do to control this - we have tried all of the ideas as posted above. "
Maureen on Saturday 4 August 2018
" Hi Maureen. That sounds terrible! I am so sorry have lost all of those plants. I am at a loss also as to what to suggest having tried the above already. Hopefully someone else will post some other ideas that may have worked for them. "
Ben Vanheems on Sunday 5 August 2018
"Hi Maureen, Try attracting predator insects such as ladybirds or praying mantis. they will help to control the white fly and aphid populations. Research what type pf plants can be planted to attract these predators - alyssum may be useful here, and it makes a good companion plant for some vegetables. You could also make your own insecticide. My horticultural course recently made an organic insecticide using onions, chillis, garlic and a few drops of detergent, distilled over a few days. This works but is only effective for a couple of weeks. Regards, Spencer Rigby"
Spencer Rigby on Thursday 20 September 2018
"Great advice, thanks Spencer. We have a few articles/videos on this site on attracting beneficial insects, which should be a help too."
Ben Vanheems on Thursday 20 September 2018
"I'm a trainer at a local RTO running their horticulture program. Many of your articles have been very useful resources to enhance the training that I provide. I also utilise a lot of the public feedback, as these are the issues that my trainees often encounter when they start to work on their own gardens. Keep up the good work."
Spencer Rigby on Thursday 20 September 2018
"Many thanks Spencer - really pleased the articles are of use!"
Ben Vanheems on Thursday 20 September 2018
"Preying Mantis prey on hummningbirds and some good bugs, so be careful what you use. Lady bugs are a safe bet. I will be putting my cordless vacuum to good use!"
Sharon Aumani on Monday 22 July 2019
"Great stuff Sharon, thanks for posting."
Ben Vanheems on Wednesday 24 July 2019
"This morning went into garden as usual, saw my plum tree covered in whitefly ( 21st May 2020 ). Unfortunately when I planted my plum tree i did not realise my neighbours had a mature plum tree next door, it seems the infestation of whiteflies is due to the dewfall from overhanging branches on my plum tree. each morning i have to wash the leaves. "
Rashid Irshad on Thursday 21 May 2020
"That is a nuisance Rashid. "
Ben Vanheems on Thursday 21 May 2020
"Can you still eat the leaves after spraying with organic pesticide?"
Philip on Thursday 15 October 2020
"I would advise against that Philip. Sprays are usually reserved for the parts of the plant you wouldn't eat anyhow. That said, check the specific instructions on the sprays themselves, which will be able to advise more accurately. Usually there is a set time after which it's safe to eat any sprayed leaves. But I tend to err on the side of caution. But that's just me!"
Ben Vanheems on Thursday 15 October 2020
"Total, novice at this, wish to learn from disciplined teacher, can this group provide recommendation in or near Dallas, Tx, 75233. "
Ples Montgomery III on Friday 16 October 2020
"You might want to try contacting the Dallas County Master Gardeners for advice (search online). "
Ben Vanheems on Monday 19 October 2020
"My vegetable garden 1st harvest was plentiful and beautiful but by June I was constantly fighting a battle with white fly, that destroy my plants. I do have a Nursery on the other side of my back wall. And get different insects. But, next spring I will try a few of the suggestions that have been posted. "
Liz on Sunday 25 October 2020
"Hi Liz. I hope some of the suggestions work for you. Certainly working with nature where you can can be very effective."
Ben Vanheems on Thursday 29 October 2020
"I've still got whitefly on my kale even today 19 December in Yorkshire. They lurk in the crevices underneath the leaves. I thought they would have been killed off by now. Will a hard frost shift the little devils?"
Janet Young on Saturday 19 December 2020
"A hard frost should certainly help. We haven't had a REALLY hard frost yet, so it's perhaps no surprise they are still lurking. But a couple of nights of sustained hard frosts should get rid of them, or at least knock them right back."
Ben Vanheems on Monday 21 December 2020
"I know how you feel! WHITE FLY $^####^ In the middle of trying to save my Tomato and Zucchini crops. Have covered them with Neem Oil, to the point where my hands are soft and supple. And still, they come, then was blasting over and under with H2O, and still, they came, next was spraying with Alcohol, Mouth wash, and Neem oil, and still they come! Put up three Yellow Peanut butter caps covered in Neem oil a metre from the plant and start to see a difference, literally hundreds have got stuck in the oil in 24 hours. So much so that I've had to wash the oil off and reapply. Now I've put the yellow pot tops inside the Tomatoes cage to attach the most I can. I expect had I had the Yellow peanut butter caps when planing my Tom plants, I'd be much better protected at this time. Let's see how a few days go and re-evaluate the results."
AIM2XL on Sunday 7 March 2021
"Interesting results there - thanks for sharing. I hope you win the war in the end!"
Ben Vanheems on Monday 8 March 2021
"Ah yes - the dreaded whitefly. They are the zombie hoard of the insect world. When we get them the only thing to do is haul all our plants (ones in pots) outside and do the water blast and let the sun bake the flies. While that is going on, we are inside with a vacuum and then blast every surface with water and insecticidal soap and then hang new traps. If you don't clean the inside of the greenhouse surfaces, the ones that flew off while you are moving the plants will just wait you out. But it is a constant battle. "
Tina on Wednesday 23 June 2021
"It sounds like you're very determined Tina! As you say, it is indeed a constant battle!"
Ben Vanheems on Thursday 24 June 2021
"I see this my wardrobes and cloths.. it is spread inside the house.. how to control it inside the house.. it is there in all my cloths.. "
harishkumar on Thursday 5 August 2021
"I suspect you may be seeing tiny moths inside your wardrobe - some species of moths are attracted to clothing and can make holes in fabrics."
Ben Vanheems on Thursday 5 August 2021
"ive gave up on growing eggplants and zuccini all becouse of whiteflies.. but now my tomatos are suffering, and my tomatos are a red line. so its war!! ill be trying your methodes and do hope i win."
abdullah on Monday 18 April 2022

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