Whitefly made simple: what they are and what to do about them

Whitefly

1. There are many species of whitefly 
2. Whitely will be found on the underside of leaves 
3. Whitefly are tiny
4. Whitefly suck on leaves
5. Whitefly is a vector, which is an insect that transmits disease from one plant to another
6. Whitefly can vector many diseases to many plants
7. Whitefly "poop" is called honeydew
8. Ants love honeydew
9. Honeydew drops from sucking insects and lands on the TOPS of the leaves below 
10. Fungi grows on honeydew turning the leaf top black, this is called sooty mold
11. Sooty mold can be washed off, disease cannot
12. Feeding whitefly nymph (immature, non-flying) can cause irregular ripening of fruit
13. A cold winter knocks down (reduces) whitefly and a mild winter allows them to feast and multiply

What to do when you have whitefly

1. Remove ALL non-producing plants in your garden ASAP
2. Check on your plants at least once a week (I lightly brush DRY plants and if they have dandruff, I spray)
3. Destroy plants infested with whitefly by putting in a trash bag and placing in trash, DO NOT compost
4. If you had a whitefly infestation, allow a long time break (at least a month) before replanting so whitefly children do not repopulate your next crop
5. Whitefly can be controlled with a non-organic systemic (ground applied herbicide) such as Bayer Advanced vegetable
6. Whitefly can be managed organically with sprays of dish soap (Dawn is too strong) and neem oil (separately, using one then the next day using the other). TEST small area first and wait 24 hours: up to 3 tablespoons of dish soap to a gallon of water. TEST and follow the directions on neem oil and never spray when the sun is high.
7. If it rains hard, respray your plants
8. Using a reflective mulch disorients flying insects and they won't land on your plants because they can't get their bearings. This only works while the plant is small though and is difficult to irrigate without drip irrigation.
9. I have NOT found sticky traps to work for whitefly outdoors

Considerations to save money

Start with disease resistant varieties.

Check plants often. 

Cooking oil can be used instead of horticultural oil, however cooking oil will clog up your sprayer and will ultimately cost more in sprayer replacements. Spend the extra few dollars and purchase a quality horticultural oil.

Purchasing a sprayer with a wand that has an bend at the end allows you to get under the leaves without having to stoop to get underside leaves. One-gallon sprayers with this sort of wand have been sited at Walmart for as low as $5 during the winter.

What I do for whitefly

Check on plants at least once a week by lightly brushing DRY plants.  If they have dandruff, I spray. 

As soon as the dew has dried, I use 3 tablespoons of the cheapest dish soap I can find mixed with one gallon of water and thoroughly soak the plant's underside of leaves. The next day as soon as the dew has dried, I use one tablespoon of Parafine horticultural oil to one gallon of water and also thoroughly soak the plant's underside of leaves. Never spray soap or oil when the sun can burn your plants. Continue this daily until whitefly is under control.

Photo credit: By Rasbak at Dutch Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3260096