How to control aphids on leafy greens
I have had some issues with aphids on my spinach and arugula that are in the greenhouse. They haven’t infested my lettuce yet, but I bet they will. I do not spray insecticides on my annual crops, so I decided to explore other options. Aphids are susceptible to predators. However in the greenhouse they are protected. I decided to take out the spinach, as this is the most affected crop, and place outside. It is plenty warm enough, and maybe some predators will show up. Also, I want to quarantine these plants away from the others. Furthermore, aphids typically stay on the low leaves and lower stems, so upon harvesting most of these will not come along. The rest can simply be washed off.
***Update 3-24-2012 , I thought about putting all the spinach back in the greenhouse, sealing up the greenhouse, and doing a ladybug release to control the aphids. Ladybugs are voracious aphid eaters. You can buy ladybugs, and have them delivered through the mail. They come in different quantities depending on how much you need. The best way to release them is to immediately put them in the refrigerator upon arrival, then release a little at a time in the infested area. It is best to release them at night when they are less flighty, and have the evening to settle into their new home and find food. It is also important to water the plants before releasing them, as the ladybugs will be thirsty after their long journey.
The cheapest batch of ladybugs I could find was about $10, but the shipping was another $20. Ultimately, I decided it was not a good investment to protect about $40 worth of lettuce. So, my original plan of just putting the lettuce outside, and washing the aphids off when I harvest, will be good enough for me. If I could have gotten the ladybugs locally for $10, and no shipping, I would have given it a shot.
***Update 3-28-2012 Predators did finally show up to rescue my greens. All of my greens and even my cauliflower have been affected. The little aphid predators that showed up are actually called “Aphid Predators.” They are small slender black bodied winged insects that lay their eggs inside of the aphid adult. After that, the aphid predator larvae emerges from the aphid bursting through the body of the aphid killing it. The larvae then go on to eat 5-40 aphids per day depending on how many aphids are present. The entire cycle takes about 3 weeks. In the meantime, I am still harvesting greens, but it is a pain to shake off the aphids before bringing the greens in to eat, and the plants aren’t quite as vigorous as they were.
Aphid predators laying eggs in the aphids
***Update 4-27-2012 The aphid predator larvae did a good job of eating most of the aphids. My spinach crop recovered and I harvested some really nice spinach. The bad part was that the larvae were difficult to wash off the leaves. I had to literally wash and pick them off one by one. It wasn’t terrible, but I spent 15-20 minutes prepping my spinach for a meal.
Aphid predator larvae (They are oval shaped and brownish orange)