Answer: The interesting thing about aphids is that their populations soar when weather conditions are warm, such as inside a greenhouse. Aphids are mostly female, and they bear live young which are capable of bearing live young almost immediately. Because of this, you can have three or more generations feeding on a single plant part within just a few days. In the fall months some males are born. They mate with the females, who then lay eggs that will overwinter. Then, when the weather warms and new plant growth begins, the eggs hatch into female aphids. This lifecycle is why they're so difficult to control. So, the obvious answer is that if your greenhouse is heated over the winter, the aphids will contine to produce offspring. If it's not heated, the eggs will survive, only to hatch in the spring. You can thoroughly wash all surfaces (and nooks and crannies) in your greenhouse to eliminate the eggs. You can use Insecticidal Soap against the first generation of aphids you find (to keep them from producing subsequent offspring), and you can place yellow sticky traps around in your greenhouse to attract and suppress the population of aphids. Make your own traps by smearing petroleum jelly or 'Tanglefoot' on bright yellow pieces of cardboard or heavy paper. The insects will be attracted to the color and will get stuck on the surface when they fly too close. Hope the above helps you control the pesky pests!
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