How Do You Control Greenhouse Kratky Pests Like Aphids and Whitefly?
Catch them early and remove them by hand. The most common greenhouse Kratky pests, aphids and whitefly, are easiest to control when you check the undersides of leaves every few days, wipe or rinse off small colonies, and use yellow sticky traps to watch numbers.
A greenhouse is warm and sheltered, which is good for plants and just as good for insects. With no wind, rain or many predators to knock them back, a few insects can become a colony in a week or two.
How to Spot Them
- Aphids: small, soft insects, green, black or gray, clustered on new shoots and under leaves. Leaves may curl, and you may see a sticky film.
- Whitefly: tiny white flying insects that rise in a cloud when you brush the plant. Look for them under the leaves of tomatoes, cucumbers and peppers.
- Both: leave sticky honeydew, which can grow a black sooty mold on leaves.
Check Often
- Every few days, turn over leaves near the top and middle of each plant.
- Hang yellow sticky traps just above the plants. A sudden rise in insects on the cards is an early warning.
- Check new plants before they go into the greenhouse. Pests often arrive on a gift or a nursery plant.
Removing Them
- Wipe small colonies off with your fingers or a damp cloth.
- Rinse aphids off with a gentle spray of water, holding the plant so the net cup doesn’t lift.
- Cut off a badly infested leaf or shoot and bag it.
- For bigger outbreaks, an insecticidal soap labeled for edible plants can help. Follow the label, and spray in the cool part of the day.
Keep Sprays Out of the Solution
Whatever you spray, keep it out of the nutrient solution. Cover the top of the container and the net cup with a cloth or a plastic bag before spraying, and let the leaves dry before you uncover it. Soap or oil in the solution can coat the roots.
Natural Predators
In a greenhouse, beneficial insects can do much of the work. Ladybugs and lacewing larvae eat aphids, and a tiny wasp called Encarsia formosa is sold to control whitefly. They work best released early, before numbers are high, and with doors and vents screened so they stay inside.
Prevention
- Space plants so air moves between them.
- Seal gaps around net cups so insects can’t reach the solution.
- Remove yellowing and dead leaves, which shelter pests.
- Clean the greenhouse at the end of each season.
Common Mistakes
- Only looking at the tops of leaves.
- Spraying straight over an open container.
- Bringing an infested plant into the greenhouse without checking it.
Common Questions
Do yellow sticky traps get rid of whitefly?
They catch some, but their main use is showing you when numbers rise. Combine them with removing insects and, if needed, predators or soap.
Is insecticidal soap safe for Kratky?
On the leaves, if it is labeled for edible plants and used as directed. Keep it out of the nutrient solution by covering the container first.
Why are pests worse in a greenhouse?
It is warm and sheltered, with no rain or wind and few predators, so insect numbers build up quickly.
Related guide: growing Kratky in a greenhouse.
Related article: What Is the Best Bench or Shelving for Kratky in a Small Greenhouse?