Aphids are a pest to many garden and landscape plants. Each type of aphid prefers a certain type of plant. They are what is called a soft bodied insect and come in many different colors- white, green, gray, and black. The females can reproduce at a rate of 100 offspring per week and the offspring mature in as little as 2 weeks.
In plotting your strategy against the ever multiplying aphid, you need to understand what they are doing to your plants. They suck the sugars and sap from plants. This causes the leaves to curl. The aphid is then protected in the curled leaves while they feed. Pretty clever strategy.
Aphids produce a sticky, honey dew substance that covers the leaves. Sticky leaves are further evidence you have been invaded. While you were giving little thought to the garden in the early spring, aphid eggs are overwintering just waiting for the weather to warm so they could fly to your trees or garden and begin feasting. Knowing this you should have made the first strike by using a dormant oil on fruit trees, woody landscape plants, and berry bushes. This is best applied in early spring when the sap begins to flow.
Two beneficial insects that feed on aphids are lady beetles and lace wings. If you have aphids the lady beetles and lace wings will find you.
The lavae of both insects feed on aphids. Make sure you are able to recognize the lavae because they look nothing like the adult insect. Also it's a good idea to know what lady beetle and lace wing eggs look like.
This is a lace wing larvae. The eggs of a lace wing look like lollipops on a stem. I included a picture of them on dill but the are hard to see. Dill seems to attract lace wings.
This is the larvae of the lady beetle. Seeing both these insect larvae is a good sign that re-enforcements have shown up to help with the aphid problem.
Plan of Attack
If damage or infestations are severe you can use an insecticidal soap or neem oil. These suffocate the aphid. They must be applied directly on the aphid to be effective. Insecticidal soaps should not be sprayed if temperatures are high so be sure to read the label.
Another option is to remove any severely infected plant or prune off infected branch tips. Once the leaves, especially on fruit trees, begin to curl it is very hard to reach the aphid with your spray so prevention and early detection are important.
If it is a mild infestation you can spray them off with water.
Monitoring for aphids
In the garden they seem to like plants in the brassicaceae family including cabbage, broccoli, cauliflower and other cole crops. They also like kale. It's important to plant these crops in early spring. Late plantings and warm weather are a sure invitation to aphids.
In the orchard, while leaves are budding out, look on the underside of the leaf with a magnifying lens for aphids. Also watch for curling leaves.If you see signs of aphids spray with Neem oil and fish emulsion before the leaves begin to curl severely. Follow the recommended spray routine for organic orchards to prevent.
This is a plum tree with sure signs of aphids. Notice the curling leaves.
As I unrolled the leaves you can see the little grayish green aphids on the bottom of the leaf. I sprayed this tree with Neem oil, fish emulsion, and kelp. I will probably repeat that spray in another 3 days only because this tree has aphid issues every year.