Tag sap

The recent explosion of aphid activity in North Texas caused frustration and concern among tree owners and anyone who has encountered the sticky mess that aphids cause. When aphids have matured and are feeding (and producing honeydew), best practice guidelines do not recommend using chemical controls. Introducing natural aphid predators can help reduce the population, but the best course of action, especially with a fall aphid infestation, is simply to wait about a month for the aphids to die off and cooler weather to prevent another generation from maturing.

Are There Any Natural Ways to Get Rid of Aphids?

Chemical pesticides are not the only way to control aphids. One of the most effective and long-lasting ways of reducing aphid activity is to introduce natural predators of the aphid into the environment. With an autumn infestation, however, there is limited time to act and leaves may drop and temperatures fall before any aphid control has a chance to make a difference.

While lady beetles are a welcome addition to the garden, some non-native species can invade our homes during winter. These lady beetles often have an “M” or “W” mark on their shells, just behind the head. To keep your home lady beetle-free:

• Keep trees and bushes trimmed back from structures
• Avoid stacking firewood next to the house
• Seal up cracks around windows
• Use wire mesh to screen large vents

Taking a few precautions will not only keep lady beetles out of your house, but block larger and harmful pests as well!

Lacewings

• Two major varieties: green lacewings and brown lacewings, in order Neuroptera
  • Lay distinctive single eggs on stalks
• Larvae often called “aphid lions”
  • Can consume up to 200 aphids a week
  • Adults can feed on aphids as well
• Take about two to three weeks to hatch and mature from eggs

There are species of lady beetle and lacewing that are active in the spring and in the fall, so there is a potential for year-round aphid control. Introducing lady beetle larvae can have a serious effect on aphid activity, but keep in mind that, depending on the species, the predators may not survive winter and may need to be re-introduced in the spring.

In addition to predators, simple physical controls, such as using water to remove aphids from plants, can also help in the short term. Avoid using high-nitrogen fertilizers as these can stimulate rapid growth and attract more aphids. Luckily, with fall aphids, once the leaves drop and their food source is removed, the pests will die off quickly.

Why aren’t Chemical Controls Effective for Fall Aphids?

There are several chemical insecticides that target aphids. These products generally break down into two categories: systemic and non-systemic.

• Systemic Pesticides
  • Absorbed into the the plant they are applied to and transported throughout the plant’s structure
    • Can take up to a month for chemical to become present throughout mature trees and reach full effectiveness
  • Generally effective for longer than non-systemic
    • Resistant to being diluted or washed away by rain
  • While present in plant, can protect both new and old growth
  • Can be applied before growing season or anticipated increase in pest activity
• Non-Systemic Pesticides
  • Cling to the surface of treated plants
    • Effective immediately
  • At risk of dilution or removal by rain, sprinklers, etc.
  • May not protect growth after application
  • Can be applied preventatively, but timing more important due to risk of dilution/loss
  • Difficult or impossible to apply to large trees/plants
    • Large-scale spraying may lead to environmental contamination

Comprehensive pest management often uses both systemic and non-systemic chemicals to provide maximum protection. Before a growing season, in late winter for example, it is common to apply a surface spray and a systemic insecticide to crape myrtles and other trees that are susceptible to insect infestations in the spring. The surface spray provides protection while the systemic product has time to come to full effectiveness.

In the case of insect activity in fall, chemical controls should not be applied as they would be before a growing season. Non-systemic pesticide sprays can be effective against current pest activity, but in the case of large, mature trees, such as the pecans and oaks infested with aphids in the fall of 2022, applying sufficient quantities of external pest control is not only expensive, but is potentially hazardous to the surrounding environment with the high potential for overspray and excess application. Furthermore, as fall in North Texas often brings rain, any product applied may be washed away quickly, and possibly end up in the groundwater.

Systemic insecticides carry a much lower risk of environmental contamination, but take about a month to become effective. In the case of a fall application, systemic controls may take even longer, as trees begin going dormant and dropping leaves, slowing the uptake of both nutrients and chemicals. In general, it is not recommended to use any systemic insecticides in the fall, as the likelihood of their becoming effective before the pests naturally die off is low.

In summary, be wary of service providers who claim that they can control fall aphids chemically; they may be able to reduce activity, but full eradication is nearly impossible and runs a high risk of contamination and waste of chemicals, time, and money.

At Texas Tree Surgeons, we love trees and we love our community! These fall aphids have been a real nuisance, and we want to give our customers the best advice so that money and time is not wasted on ineffective treatments. While we don’t recommend chemical application for fall aphids, we are big fans of introducing some aphid predators while you still have time! As a woman-owned and women-led company, we are partial to lady beetles :-), but lacewings are great, too! Share this article and spread the word about aphids, and let us know if you have any other tree questions!

We have discussed the relationship between aphids and the sticky residue seen on patios and cars before, but the Fall of 2022 has seen an explosion in aphid populations and the resulting mess. While there is little that can be done to reduce aphid activity this season, it is unlikely that the aphid infestations will have a lasting negative effect on trees in North Texas.

Why Is My Tree Dripping Sticky Stuff? Is It Sap?

While it may be confused with sap, the sticky substance we are seeing dripping from trees is most likely honeydew, which is produced by aphids. Aphids are attracted to many different species of tree, but are most commonly seen in North Texas on crape myrtles, pecans, hackberries, and certain oaks.

• The aphids feed on sap and produce honeydew, which accumulates on the trees, eventually dropping.
  • Since honeydew is essentially sugar water, it can cause surfaces it comes in contact with to become sticky.
  • The sugary residue can also attract ants and other animals.
  • In large enough accumulations, honeydew can lead to the growth of molds and fungi, such as sooty mold, which is commonly seen on aphid-infested crape myrtles.

Why Is This Happening Now?

Like the trees they prey on, aphids are greatly affected by seasonal weather patterns and changes to their environment. In 2022, we had a long, dry summer that ended with heavy rainfall. The abundance of moisture at the end of the season combined with still-elevated temperatures caused rapid growth of many plants, blooming of flowering trees and bushes, and a resurgence in the insect population. The abundance of new growth late in the year was able to support many more species that feed on plants, like aphids, than the previous year’s late summer. While this is not the first time this has happened in North Texas (see our post about this same topic from October 2018), it happens rarely enough that it can be surprising when it occurs.

Is There a Spray or Other Treatment for Aphids?

• Foliar sprays to control insects are not recommended for large trees (such as pecans and oaks), and have a very limited window of effectiveness.
  • Additionally, any product that is applied to a tree rather than used systemically is subject to being diluted or washed away entirely by rain.
• Systemic insecticides can be used in trees of all sizes, but take about a month from application to be taken up by the tree’s vascular tissue and reach full effectiveness.
  • Because of this timing, systemic insecticides are best applied before a growing season or an expected surge in insect activity.
• Be wary of service providers who claim to be able to control an active aphid infestation quickly.
  • They will either not be able to deliver on that promise, or will use a wasteful, excessive, and potentially dangerous insecticide spray that could be rendered ineffective in the next rainstorm.
• Effective treatment takes time, and if the aphids are already active, they will most likely die off naturally before any chemical controls could make a difference.

What Can We Do About the Current Activity and Sticky Mess?

• Depending on the size of the host tree and the number of aphids present, it may be possible to spray some of them off the tree with a garden hose.
  • Ladybird beetles (laybugs) and some other insects are natural predators of the aphids, but trying to introduce them into the environment late in the season may not be effective.
• The sticky honeydew is water-soluble and easily cleaned up with a mild detergent solution or a mixture of vinegar and water.
  • If possible, avoid parking under infested trees and cover patio furniture until the activity dies down.
• Once their life cycle has run its course, the aphids will die off naturally.
  • With a lifespan of between 20 and 40 days, by the time the current generation of aphids dies, the weather will have cooled enough to prevent further activity until the next growing season.
• To help prevent future infestations, and stop current ones from getting worse, avoid using high-nitrogen fertilizer that stimulates rapid plant growth, as this will only serve to make your trees more attractive to pests like aphids.

Will the Aphids Cause Long-Term Issues in My Trees?

While an active aphid infestation can cause irritating honeydew production and unsightly mold growth, there are most likely no lasting effects on large trees. Increased insect activity late in a season is less likely to cause long-term damage. Additionally, even large populations of aphids rarely have any serious effect on mature trees. Once the aphids die off, any secondary issues, such as mold, will clear up.

At Texas Tree Surgeons, we love trees and we love our community! We hope that spreading the word about the current aphid issue will help put tree owners’ minds at ease. While nothing can be done to reduce aphid activity right now, there are preventative measures that can be taken in the winter to help reduce pests in the spring. We offer year-round plant health care programs that can help make sure your trees are prepared to handle issues at any time and bounce back from damage and stress. Ask one of our certified arborists to evaluate your trees today!