Strangely beautiful and intricately designed, lace bugs are fascinating little plant pests.
Not to be confused with the eponymous lacewing, these tablecloth-like insects are not popular, especially on ornamental trees and shrubs. The damage they cause to leaves can be mistaken for thrips or spider mites. Fortunately, these pets are not nearly as severe or difficult to control.
So how to identify and the best ways for lace bug treatment. what are the control options? Read on, as this guide contains everything you need to know about these juice-sucking pests. Here’s what we’ll cover.
About Lace Bugs?
There are 140 known species of lace bugs in North America, belonging to the Hemiptera (or true beetle) family Tingidae.
Like all true beetles, adults and nymphs have needle-like mouthparts that they use to suck sugary plant sap.
The tipworms concentrate on the underside of the leaves of deciduous and evergreen trees and shrubs, leaving small white or yellow spots on the top.
Their hosts include rhododendron, linden, elm, hackberry, hawthorn, lantana, oak, pyracantha, rhododendron, and sycamore.
The damage is most pronounced when the population is high in the middle and late summer. If fed too much, the leaves may fall off prematurely.
They also produce small, black droppings where they feed. These are sometimes called paint spots.
The damage caused by these pests is mostly superficial and usually does not affect the health of the plant, especially if it is a healthy mature tree or shrub.
Species you find in your garden are usually from the Stephanitis genus, including Rhododendron (S. pyrioides), Corythucha, which includes Hawthorn (C. cydoniae) and Hackberry (C. celtidis), or Leptodictya, which includes those that attack ornamental grasses , such as L. plana.
There are many other types, but these are the most common.
While identifying these species based on their appearance is not easy, these insects are easy because most are host-specific.
So, if you’ve spotted a suspicious earworm on a rhododendron or other garden plants listed above, it’s not that hard to figure out what species it is.
However, as the details of biology, life cycle and management techniques are the same for all pest species, it is not important to determine exactly which species you are dealing with.
Generally, nymphs are dark in color, have no wings, and have a flat oval body with spines protruding in all directions.
Adults are one-eighth to one-third of an inch long and have finely sculpted, translucent, lacy wings that spread out from their abdomens.
Adult stephanitis and corythucha have flat, oblong bodies. They are usually clear to slightly amber in color. Their eggs are transparent, off-white and football-shaped.
For example, the rhododendron earworm S. pyrioides is transparent with dark patterns on its wings.
C. cydoniae, the hawthorn type, has dramatic, angular, translucent wings, an ear-like bra, and tan markings.
Adult Leptodictya is more slender than species in the other two genera, gray-green to light brown in color. They lay dark brown barrel-shaped eggs.
L. plana, for example, is light green-brown in color, and its wings appear to be made of finer lace than the other two species mentioned above.
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Biology And Life Cycle
The life cycle of these insects can last 30 to 40 days, with several generations per year.
In the spring, the moths fly to their hosts and eat the first fresh leaves. They mate and lay a small cluster of small eggs under the leaves near the midrib.
Some species will partially insert each egg into leaf tissue, and some will seal their eggs with a brown substance that hardens on top like a scab.
The nymphs hatch from the eggs after about two weeks. Nymphs feed for three to four weeks and go through five stages during their growth. They let their peeled skin stick to the leaves.
Once mature into winged adults, they mate and lay a second round of eggs, which hatch, molt, and become adults, feeding until late summer or fall.
Stephanitis species overwinter as eggs in bark cracks or leaf fragments, whereas Corythucha and Leptodictya species overwinter as adults in host leaf fragments. In evergreens, adults can overwinter on the surface of leaves.
Best Ways For Lace Bug Treatment
To determine when to begin management practices and what control methods to choose, you should keep a close eye on these pests before their population numbers and the uncontrolled damage they cause.
Damage to the top of the leaf may look like spider mite feeding damage, but you can easily tell the difference by flipping the leaf over and using a handheld lens to locate the insect.
Additionally, spiky bugs make the bottom look dirty and speckled due to the paint stains, scaly membranes and eggshells they leave behind. And these insects also jump when disturbed.
Begin monitoring susceptible plants in late spring. Damage is usually not discovered until late in the season, so waiting for damage is not a reliable preventative method for predicting problems.
Organic Control Methods
Overall, these insects are tolerable to your plants, as they usually do not cause enough damage to warrant control.
Healthy trees and shrubs are not significantly affected by feeding on spiky bugs, but damaging them can spoil the aesthetics of the plant.
In the case of severe damage, control measures may be required. While these control methods will not eliminate the damage, they will prevent further problems.
In this case, use an integrated pest management (IPM) strategy to reduce pest populations by combining the various approaches outlined below.
Cultural and Physical Control
Keeping plants alive long before pests become a problem is an essential step that will give your flora a better chance of surviving an insect infestation.
Shrubs such as rhododendrons seem to suffer the most from these insects when grown in full sun and heat. If possible, plant susceptible plants known to contain lace bugs in partial shade.
Nymphs don’t have wings, so use a strong stream of water in a hose to drive them away from the underside of the leaves.
Keep the soil under the plant bare, raking away any leaves or debris to remove overwintering adults or eggs that may be hiding, or plow debris into the soil.
Remove any weeds from the garden that could serve as alternative hosts for beetles.
Since each species of this pest has its own specific host, planting a variety of ornamental shrubs rather than a population of one species will help reduce spread in the event of an infestation.
Biological control that exploits the predator diversity provided by nature is a useful long-term control method. Predators are very effective at keeping populations down and controlling small outbreaks.
Assassin bugs, jumping spiders, pirate bugs, mites, ladybugs, green lacewings, and parasitic wasps (such as mymarids) all target spiky bugs.
Attract and maintain healthy populations of these beneficial insects by growing a variety of flowering plant species in your garden.
Pesticides can be effective against these pests if used wisely and properly, they come into contact with the bugs.
Because these insects hide on the underside of leaves, these areas need to be well covered.
Horticultural oils can also be effective
Monterey Horticultural Oil
Or try an insecticidal soap like this one from Bonide
Bonide Insecticidal Soap
Use these products when there are many nymphs. Usually these products need to be reapplied every two weeks or so to achieve and maintain control.
Chemical control is rarely guaranteed, but can be very effective.
Bifenthrin, cyfluthrin, permethrin and other pyrethroids are useful. Sibali products like Sevin are another effective option.
As with organic contact products, chemical contact pesticides must be applied correctly to completely cover the underside of leaves.
Systemic drugs such as imidacloprid and dinotefuran are also useful. These are chemicals that plants absorb and transport. However, avoid using them during the day or on flowering plants as they are toxic to pollinators.
Remember that chemicals are often toxic to beneficial insects.
Since many of the recommended methods for controlling spiky bugs are biological, using them can take away all your hard work and reduce or eliminate predator populations.
This gives the pests a chance to recover and continue to feed on the plants.
Little Uninvited Plant Doilies
If you look closely, you might think the carved lace wings of these insects are very pretty. But that doesn’t mean they improve the appearance of ornamental plants.
Their damage can be severe, but luckily you now know how to deal with these bugs, whether culturally, relying on beneficial insects already in the garden, or using pesticides.
Have you ever seen one of these bizarre insects? Let Answer The Question know in the comments which species you think you’ve spotted and what to do with them when you have to take control.