Understanding Aphids and How To Control Them On Fruit Trees
Aphids are small bugs that suck the sap from underneath the fruit tree’s leaves. This loss of sugar and moisture causes the leaves to curl, yellow, and drop. They also deposit honeydew, which attracts ants. If left unchecked, aphids can damage the fruit tree’s health and potentially stunt or kill it.
When aphids suck the sap from the tree, they’re taking the tree’s sugar, which is its energy source. The fruit tree created this sugar through photosynthesis and uses it for just about every function: canopy growth, root development, bearing fruit, maintaining its immune system, and more.
Not only do the aphids take the tree’s energy, but they damage the leaves—reducing the amount the tree can photosynthesize and create new sugars. If this goes on long enough, the tree will be so deprived of energy that its health will start to decline and can result in the tree’s death.
Various species can appear white, black, brown, gray, yellow, light green, or even pink! Some may have a waxy or woolly coating. They have pear-shaped bodies with long antennae; the nymphs (young aphids) look similar to the adults. Most species have two short tubes (called cornicles) projecting from their hind end.
Aphids seem to find their way into every garden. They are small, soft-bodied insects that feed by sucking the nutrient-rich liquids out of plants. In large numbers, they can weaken plants significantly, harming flowers and fruit. Aphids multiply quickly, so it’s important to get them under control before reproduction starts. Many generations can occur in one season.
Adults are usually wingless, but most species can develop a winged form when populations become crowded so that when food quality suffers, the insects can travel to other plants, reproduce, and start a new colony. Aphids usually feed in large groups, although you might occasionally see them singly or in small numbers.
You can tell if your fruit tree is affected by aphids if you start seeing leaves curl and notice small white, black, or yellow dots underneath the leaves.
What Does Aphid Damage Look Like?
Nymphs and adults feed on plant juices, attacking leaves, stems, buds, flowers, fruit, and/or roots, depending on the species. Most aphids especially like succulent new growth. Some, such as the green peach aphid, feed on a variety of plants, while others, such as the rosy apple aphid, focus on one or just a few plant hosts.
- Look for misshapen, curling, stunted, or yellowing leaves. Be sure to check the undersides of leaves; aphids love to hide there.
- If the leaves or stems are covered with a sticky substance, that is a sign that aphids may have been sipping sap. This “honeydew,” a sugary liquid produced by the insects as waste, can attract other insects, such as ants, which gather the substance for food. When aphids feed on trees, their honeydew can drop onto cars, outdoor furniture, driveways, and so on.
- The honeydew can sometimes encourage a fungal growth called sooty mold, causing branches and leaves to appear black.
- Flowers or fruit can become distorted or deformed due to feeding aphids.
- Some aphid species cause galls to form on roots or leaves.
- Aphids may transmit viruses between plants, and also attract other insects that prey on them, such as ladybugs.
How to Get Rid of Aphids
- Try spraying infested plants with a strong stream of water; sometimes all aphids need is a blast to dislodge them. Typically, they are unable to find their way back to the same plant.
- Neem oil, insecticidal soaps, and horticultural oils are effective against aphids, but these substances need to come into contact with the aphids in order to work. Be sure to follow the application instructions provided on the packaging.
- You can often control aphids by wiping or spraying the leaves of the plant with a mild solution of water and a few drops of dish soap. Soapy water should be reapplied every 2-3 days for 2 weeks.
- One variation of this soap-water mix includes cayenne pepper: Stir together 1-quart water, 1 tsp liquid dish soap, and a pinch of cayenne pepper. Do not dilute before spraying on plants.
- Diatomaceous earth (DE) is a non-toxic, organic material that will dehydrate aphids.
Warning: Do not apply DE when plants are in bloom, as it will kill pollinators such as bees and butterflies if they come into contact with it.
How to Prevent Aphids
- For fruit or shade trees, spray dormant horticultural oil to kill overwintering aphid eggs.
- Beneficial insects, such as ladybugs, lacewings, and parasitic wasps, will feed on aphids. Attract these insect to your garden by providing an environment that features a range of flowers and foliage plants, as well as access to water. Supplemental populations of these insects can be ordered online and should help keep the aphid populations controlled from the start.
- Companion planting can help to keep aphids away from your plants in the first place, or to draw them away from the plants your really want to grow. For example:
- Aphids are repelled by catnip.
- Aphids are especially attracted to mustard and nasturtium. Plant these near more valuable plants as traps for the aphids. The aphids will likely go for these plants before your prized tomatoes. (Check your trap plants regularly to keep aphid populations from jumping to your valued plants.)
- Nasturtiums spoil the taste of fruit tree sap for aphids and will help keep aphids off of broccoli.
- Garlic and chives repel aphids when planted near lettuce, peas, and rose bushes.
Can Fruit Trees Recover From Aphids?
Fruit trees can recover from aphids if you catch them in time and apply a proper solution. If aphids are allowed to multiply on fruit trees for a month or more, they can cause enough damage to stunt or kill the tree. For best results, check your fruit tree’s leaves for any signs of aphids such as curling or dots.
While a small number of aphids won’t harm the fruit tree, they can multiply quickly and overwhelm it, especially if it’s a younger tree. For best results, check your fruit trees every 1-2 weeks for any signs of aphids.
Unlike some other fruit tree pests, aphids are visible to the naked eye. If you get close enough to the leaves and see small moving dots underneath them, it’s most likely aphids.
In general, it’s a best practice to inspect your fruit trees every 1-2 weeks. Not only will this mean catching aphids early on, but by checking the tree’s water, sunlight, and issues such as yellow leaves, you can increase the chance your fruit tree will stay healthy and thriving.
However, if your fruit tree does get aphids, it’s typically not too big of a deal and it can be treated rather quickly using the above methods.