Tuesday, April 19, 2016

Plant Pests and their Predators: Aphids and Ladybugs

Most Plant Pests Have Natural Predators


Plant insect pests begin to appear in our gardens as the weather warms up. I'm an organic gardener who doesn't use pesticides, so I looked to nature to help me keep aphids under control when I spotted them on my calendula flowers last week. The infestation was severe. I knew nature's cure was the hungry ladybug. Ladybugs are one of the aphid's major predators to help get rid of these plant pests. 

That's why I was so happy to discover one on this infested plant. After I took the picture, I saw there were actually two of them. I did a little happy dance. Can you see them both? I told them to go invite their friends to the aphid feast. I apologize for the the bit of blur in these photos. It was windy and very hard to shoot from a squatting position.



The Pests: Aphids

I first noticed my aphid infestation on April 11. I've never had an aphid problem here before. So when I went out to pick a calendula flower to put in my salad, I wasn't happy to see most of my plants covered with aphids like this.



On that day I did not see any ladybugs. I began to pray they would arrive. In droves! Knowing, though, that it might take a few days before they discovered my aphid feast, I pulled out some of the most heavily infested plants and threw them away. Then I waited and watched.



The Predators: Ladybugs


Finally my watching was rewarded with a sighting. I might mention that ladybugs can be hard to see. Do you see the one in the photo below, hiding under that yellow calendula on the left side? You can also see the aphids. One adult ladybug can eat up to 50 or 60 aphids a day. The larvae are said to eat them even more voraciously.



Although I was able to use this diagram to identify my ladybugs, it took repeated trips to the garden to get it right. It's hard to count spots when they are moving, and the ladybugs seem to keep their heads down most of the time when they are eating. I didn't want to frighten them away during dinner, so I had to be very gentle when turning the leaves for a better look. I have finally concluded that they are seven-spotted ladybugs (or, technically ladybird beetles), scientifically named Coccinella septempunctata. 

Below is a photo of the seven-spotted ladybug larva on a catmint plant next to the infested calendula.



Below is the adult seven-spotted ladybug or Coccinella septempunctata.



I went back to the garden to try to better identify the ladybug I had captured earlier with my camera (below) and couldn't find it. But I did another happy dance when I saw at least four seven-spotted ladybugs in these same flowers. I thought maybe I had misidentified this one below, but I see now that its head shows more clearly in the photo than I had thought. It is a convergent ladybug (Hippodamia convergens). 





Now that the ladybug air force is landing, I believe my aphid problem will be gone soon. Already the stems and flowers of the plants that ladybugs and their larvae have settled on are looking cleaner than they did before the ladybugs landed on them. The ladybugs seem quite happy, since they haven't left the plants since I started photographing and trying to identify them this morning. Every time I go out to  count spots or take another photo, they are in almost the same place. I hope they lay eggs and hang around.

Organic Aphid Control 

If you have an aphid problem and no ladybugs, you can buy live ones at Amazon.  Green lacewings eat even more aphids than  ladybugs do, and you can also buy those if you need them. Amazon sells the eggs, the larvae, and packages of combined live ladybug and lacewing eggs. 

 Predalure
You can also buy lures like this one that attract beneficial insects like ladybugs and lacewings. Once the insects you want are lured in, they are tempted to stay a while instead of just flying away, as live ladybugs often do.

If you want to work harder at it, you can spray aphids off your plants with a forceful stream of water. I don't think that's as permanent a solution as getting them eaten by beneficial insects who like to dine on them. "Honeydew' and black sooty mold, byproducts of aphid infestations, can be gently washed from plants with a mild soapy water rinse. Since most of my plants are edible or next to something edible, I wouldn't even consider a pesticide that has toxic substances in it.

To discourage aphids from taking over your garden, keep ants from nesting in your garden or get rid of any you find there. Using a reflective aluminum mulch in early spring may also discourage flying adult aphids from laying eggs.

As for me, I prefer to let the ladybugs do the work.

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This is my sixteenth post for the 2016 AtoZchallenge, a Blogging Challenge for the month of April, 2016. My theme is plants, since this is a gardening blog. Here are links to the other posts if you missed them.

A is for Apple Blossoms
B is for Bottlebrush
C is for Carnations
D is for Daisy
E is for Elderberry
F is for Flowers
G is for Gazania
Hollyhocks are Edible
Irises Are Garden Survivors
Jupiter's Beard: A Mystery Finally Solved
Kale for Lunch
Lion's Tail - A Perennial Summer Burst of Orange
Miner's Lettuce is Tasty and Free"Naked Ladies" Bloom in August
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