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One of the most common complaints from homeowners during the growing season is the appearance of a black, soot-like coating on leaves, stems, patios, vehicles, and outdoor furniture beneath landscape plants. While many assume this black growth is a plant disease, the real culprit is often an insect infestation. Sooty mold is a fungal growth that develops on honeydew, a sticky, sugar-rich waste product excreted by sap-feeding insects. Common honeydew-producing pests in Texas landscapes include aphids, whiteflies, scales, mealybugs, and psyllids. As these insects feed on plant sap, they remove more sugar than they can utilize and excrete the excess as honeydew. Sooty mold fungi then colonize this sticky residue, forming a dark coating on plant surfaces. The mold itself does not infect plant tissues or directly damage leaves. However, heavy accumulations can block sunlight and reduce photosynthesis, leading to decreased plant vigor and aesthetic quality. In severe cases, leaves may yellow, growth may slow, and plants can become stressed, particularly when combined with other environmental challenges. Several landscape plants are commonly affected by sooty mold in Texas, including crape myrtle, gardenia, holly, hibiscus, magnolia, citrus, and many ornamental trees and shrubs. Crape myrtle bark scale, for example, is a frequent cause of heavy honeydew production and subsequent sooty mold development on crape myrtles. Likewise, whiteflies and aphids often contribute to outbreaks on ornamentals and flowering plants. Successful management requires addressing the underlying insect problem rather than focusing solely on the mold. Begin by inspecting plants carefully, especially the undersides of leaves and stems, where many sap-feeding insects congregate. Look for live insects, cast skins, sticky honeydew, or ant activity. Ants are often attracted to honeydew and may indicate the presence of hidden pest populations. An integrated pest management (IPM) approach is the most effective strategy. Encourage natural enemies such as lady beetles, lacewings, parasitic wasps, and predatory bugs that help suppress aphids, scales, and whiteflies. Avoid unnecessary broad-spectrum insecticide applications that may disrupt beneficial insect populations. When pest numbers exceed acceptable levels, select insecticides based on the target pest and follow all label directions. Once the insect population is reduced, honeydew production will decline, and existing sooty mold will gradually weather away through rainfall, irrigation, and normal leaf growth. In some situations, washing leaves with water can improve appearance, but this will not solve the problem if the insects remain active. When blackened leaves appear in the landscape, remember that sooty mold is usually a symptom rather than the primary issue. Identifying and managing the honeydew-producing insects will provide the most effective long-term solution and help maintain healthy, attractive landscape plants throughout the season.
Figure: Sooty mold on crape myrtle leaves (A) caused by crape myrtle aphid (B), and sooty mold on crape myrtle stem/bark caused by crape myrtle bark scale (C)
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When growers and landscape professionals think about insects, the first thought is often pests and the damage they cause. However, not all insects are harmful. Many beneficial insects play an important role in naturally suppressing pest populations in greenhouses, nurseries, and landscapes. These “good bugs” are valuable partners in Integrated Pest Management (IPM) programs and can help reduce reliance on chemical insecticides. Beneficial insects are a key component of Integrated Pest Management (IPM) programs. They help suppress pests naturally and can improve long-term pest management success when properly conserved or introduced into production systems. Two important groups of beneficial insects are predators and parasitoids. Predators actively consume pests throughout their life cycle. Common examples include lady beetles, green lacewings, minute pirate bugs, predatory mites, and hover fly larvae. These natural enemies feed on aphids, whiteflies, spider mites, scales, thrips, and other soft-bodied pests commonly encountered in Texas greenhouses and landscapes. Parasitoids are specialized insects, usually tiny wasps, that develop inside or on a host insect and eventually kill it. Several parasitoid species are commercially available and widely used in greenhouse biological control programs, especially for whitefly and aphid management. Parasitoids are specialized insects, usually tiny wasps, that develop inside or on a host insect and eventually kill it. Several parasitoid species are commercially available and widely used in greenhouse biological control programs, especially for whitefly and aphid management. Greenhouse environments often provide ideal conditions for biological control because temperature, humidity, and pest populations can be monitored more closely. In landscapes and nurseries, conserving naturally occurring beneficial insects can also provide significant pest suppression over time. Unfortunately, beneficial populations are frequently disrupted by unnecessary or repeated applications of broad-spectrum insecticides. One of the biggest challenges in pest management is recognizing when beneficial insects are already helping control a pest problem. In some situations, professionals may apply insecticides before evaluating predator or parasitoid activity. This can eliminate natural enemies and create secondary pest outbreaks or pest resurgence. In addition, repeated use of the same insecticide groups can contribute to pesticide resistance, making future pest management more difficult. Scouting remains one of the most important tools in preserving beneficial insects. Correct identification of both pests and beneficials allows professionals to make informed treatment decisions. When insecticide applications are necessary, selecting reduced-risk or selective products can help preserve natural enemy populations while still managing key pests. Habitat also plays a role in supporting beneficial insects. Flowering plants, reduced dust, proper irrigation management, and minimizing unnecessary pesticide exposure can all encourage beneficial activity in landscapes and production systems. Biological control is not always a complete replacement for insecticides, but it is an effective management tool when incorporated into a broader IPM strategy. As greenhouse and landscape industries continue to face challenges from invasive pests, environmental concerns, and pesticide resistance, beneficial insects should not be viewed as forgotten tools. Instead, they should be recognized as valuable partners in sustainable pest management programs. Photo credit: Rafia Khan, Ph. D. Assistant Professor and Extension Specialist Texas A&M AgriLife Research and Extension Center Overton, TX.  Rafia Khan, Ph. D. Texas A&M AgriLife Research and Extension Center Overton, TX. Texas A&M AgriLife Research and Extension Center Overton, TX Spring represents a critical period for greenhouse crop production because increasing temperatures and the availability of tender plant growth create favorable conditions for the development of several insect pests. Among these, aphids are one of the most common and economically important pests encountered during this time. Aphids are small, soft-bodied, winged or wingless, phloem-feeding insects. Aphids feed by piercing plant tissues and sucking plant sap. Their feeding can cause a variety of symptoms, including curled or distorted leaves, stunted plant growth, and reduced plant vigor. In addition to direct feeding damage, aphids excrete a sticky substance known as honeydew. Honeydew can accumulate on leaves and stems, leading to the growth of sooty mold fungi that reduce the aesthetic quality and market value of ornamental plants. Some aphid species can also transmit plant viruses, making early management even more important. Many aphid species reproduce through parthenogenesis and give birth to live nymphs, allowing populations to increase exponentially within a short period. As a result, even low initial infestations can quickly develop into significant pest outbreaks if not detected and managed early through regular monitoring and timely intervention. Early detection is the key to effective aphid management. Growers should inspect plants frequently, especially new growth and the undersides of leaves, where aphids often congregate. Yellow sticky cards can only help to monitor the winged aphids, but not the wingless adults. An integrated pest management (IPM) approach is the most effective strategy for managing aphids. Cultural practices, such as removing heavily infested plant material and managing weeds inside and around the greenhouse, can help reduce aphid populations. Maintaining good sanitation practices and carefully inspecting incoming plant material can also prevent new infestations. Biological control can be an effective tool in greenhouse systems. Natural enemies such as lady beetles, lacewings, and parasitic wasps can help suppress aphid populations when released at appropriate times. High pressure wash water spray can reduce the population of aphids. When aphid populations reach damaging levels, insecticides may be necessary. Growers should select products carefully and rotate insecticides with different modes of action to reduce the risk of resistance development. By combining monitoring, cultural practices, biological control, and responsible pesticide use, greenhouse growers can successfully manage aphids and protect the quality and productivity of their crops during the spring season.
Figure: Bean aphid (A), Crape myrtle aphid (B), and Green peach aphid (C). Photo courtesy: Rafia Khan
Rafia Khan, Ph. D. Texas A&M AgriLife Research and Extension Center Overton, TX. Spring is the most important production and sales season for Texas nurseries, and thoughtful preparation during late winter can significantly influence crop quality, pest pressure, and overall profitability. As temperatures begin to rise, the priority should be a thorough inspection of all overwintered plant material. Carefully examine plants for cold injury, root health issues, nutrient deficiencies, and early signs of insect or disease activity. Pests such as aphids, mites, whiteflies, and scale insects often establish tender new growth early in the season. Removing dead, damaged, or heavily infested plants reduces overwintering populations and minimizes the risk of rapid outbreaks once favorable conditions develop.
Equipment readiness is equally critical. Before spring applications begin, calibrate sprayers, fertilizer spreaders, and chemigation systems to ensure accurate delivery rates and uniform coverage. Check nozzles for wear, confirm pressure settings, and repair leaks. Proper calibration not only improves pest control efficacy but also prevents phytotoxicity, reduces product waste, and ensures compliance with label requirements. This is also a good time to review pesticide inventory and verify that products are properly stored and within expiration dates. Updating and reinforcing your Integrated Pest Management (IPM) program should be part of spring preparation. Establish a consistent scouting schedule and designate trained personnel responsible for monitoring crops. Use tools such as sticky cards, pheromone traps, and regular plant inspections to detect pest activity early. Accurate identification and threshold-based decision-making allow for targeted treatments and help prevent unnecessary applications. Early detection remains one of the most cost-effective pest management strategies in nursery production. Inspect irrigation systems before peak demand by checking drip lines, emitters, sprinklers, and pumps for leaks or uneven distribution, as poor irrigation can stress plants and increase susceptibility to disease and pests. Test growing media for pH and soluble salts, and ensure fertilization programs, especially controlled-release fertilizers, are properly applied to support healthy growth. Implement early weed control with uniform pre-emergent applications and winter weed removal to reduce competition and pest reservoirs. Provide staff with refresher training on scouting, safety, equipment use, and recordkeeping. A well-organized spring plan strengthens plant health, reduces pest pressure, and supports a successful nursery season. Rafia Khan, Ph. D. Texas A&M AgriLife Research and Extension Center Overton, Tx. Winter freezes often bring hope that cold weather will eliminate insect pests in landscapes and nurseries, offering a natural reset before the next growing season. After several nights of subfreezing temperatures, it is common to expect fewer insects and reduced pest pressure in spring. While freezing temperatures can suppress or temporarily reduce some exposed pest populations, they rarely provide complete control. Many insects are surprisingly resilient and well-adapted to surviving winter conditions through protective behaviors and physiological adaptations, allowing them to rebound quickly once temperatures warm.
Insects are exothermic or cold-blooded; their activity slows as temperatures drop. Feeding, reproduction, and development pause, and extreme cold can kill exposed individuals. However, many species avoid lethal temperatures by seeking protection in soil, mulch, bark crevices, plant crowns, or greenhouse structures. These microhabitats stay warmer than the surrounding air, thereby improving survival. Many insects can survive through dormancy (diapause) or by producing “antifreeze” compounds such as glycerol, sorbitol, antifreeze proteins, etc. that protect their tissues from freezing injury. Eggs, pupae, scales, borers, and soil-dwelling pests are especially resilient. As a result, even after a hard freeze, enough individuals often survive to quickly rebuild populations in spring. Freezes may temporarily suppress exposed pests such as aphids or caterpillars, but they should not be relied upon as a primary management tool. Warmer temperatures can lead to rapid reproduction and early-season outbreaks. Instead, winter is an ideal time to strengthen integrated pest management (IPM) practices. Remove plant debris, prune heavily infested branches, inspect bark and crowns for overwintering stages, and consider dormant oil applications for scales, mites, and aphids. Continue monitoring in greenhouses where pests may survive year-round. Rafia Khan, Ph. D. Assistant Professor and Extension Specialist Texas A&M AgriLife Research and Extension Center Overton, TX Winter greenhouse production in Texas may appear quiet, but insect pests often persist and slowly build inside protected structures. Mild winters and heated houses allow aphids, whiteflies, thrips, mites, and scale insects to survive and threaten spring crops. Choosing between spot treatments and whole-house applications during this period can strongly influence pest pressure later in the season.
Spot or localized treatments focus on infested plants or areas such as near doors, vents, or long-term crops. In winter, pest populations are often low and confined, making spot treatments an efficient choice. This approach reduces pesticide costs, limits disruption of beneficial insects, and lowers the risk of resistance by decreasing overall product use. This approach often work efficiently especially for early aphid, whitefly, thrips, and mite infestations when detected through regular scouting. However, spot treatments depend on careful monitoring. Dense canopies, mixed ornamental crops, and hidden feeding sites can allow pests to escape treatment and spread as temperatures rise. Missed infestations in winter often become difficult and expensive to manage in spring. Whole-house applications may be necessary when pests are widespread, prevalence of multiple pests, a pest outbreak, or the presence of highly susceptible ornamental crops. During winter, slower insect development and reduced plant growth can improve residual control from insecticides. Whole-house treatments are also useful between crop cycles to reduce carryover populations before new plants are introduced. The drawbacks of this strategy include higher costs, increased exposure to non-target organisms, and greater potential for resistance if products are not rotated properly. For most Texas greenhouse and nursery operations, the best winter strategy is a combined approach. Intensive scouting should guide early spot treatments, while whole-house applications should be reserved for high-risk infestations or pest outbreaks. Winter is also the ideal time to rotate modes of action, strengthen sanitation, and prepare a strong IPM program for spring production. Couldn’t make it to the Innovation Summit this year? Good news — the recordings are now available, and you can still earn CEUs while learning how technology is reshaping the green industry. These sessions were designed to give you real takeaways you can bring back to your business today. Here’s a look at what you’ll find: Innovation in Sales & Promotions – What the Green Industry Needs NextThe message from participants was clear: businesses want better visibility into the technology market.
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September 2026
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