Because the ornamental landscape is composed of a combination of different species and varieties of plants, designing a single management program for the entire landscape is extremely difficult. Each species has its own requirements for maintaining plant health, and each has its own level of tolerance to arthropod damage before its health and/or aesthetic value is threatened.

Selecting Pest-Free Plants

One of the key components of IPM is selecting the right plants. When establishing new landscapes, select low maintenance, environmentally adapted, pest free species. Plant breeders are constantly improving plants to be pest-resistant.

• List of plants that are susceptible to arthropod pests from Know It and Grow It (Whitcomb 1983)

• Select Plants by Adaptability Region – Earth Kind web site

• The Importance of Using Native Plants in the Landscape:
  • Native Plants: An Overview
  • The Native Plant Database
  • Using Native Plants in the Golf Course Landscape
  • Introducing Native Plants
  • Texas Native Trees

Pest Suppression

Determine your goals for management. Decide what level of damage can be tolerated prior to taking action to suppress pest populations. In general, little or no damage can be tolerated on plants produced for sale, or highly valued plants in prominent positions in the landscape, whereas plants in a landscape maintenance program can sustain some damage from pests before their health and/or aesthetic value becomes impaired.

Pest suppression tactics are best implemented when the pests causing sufficient damage (or threaten to cause sufficient damage) first appear. Take action during the most vulnerable life stage(s) of the pests. Scout and monitor for insect and arthropod pest populations using

• Visual inspections of randomly selected sets of leaves
• The “beat method” where pests are dislodged from their host plants by beating plant parts on a piece of paper (this method is great for detecting mites, thrips and scale crawlers)
• Using yellow sticky traps to attract winged aphids, thrips, whiteflies, fungus gnats and shore flies (this method is best suited to the greenhouse)
• Black light traps
• Pheromone traps

Remember that the mere presence of the pest is not necessarily justification for treatment. Inspect plants to determine that the pest is beginning to cause plant damage prior to treatment.

For some pests, notably scale, aphids and phylloxera, management begins during the winter when dormant oil can be applied prior to the swelling of the buds. On evergreen plants, use a lighter (summer) oil or check the label to ensure that application of the oil will not result in plant injury (phytotoxicity). Selection of pesticides for the suppression of pests on ornamental plants is extremely important since some species are sensitive to them. Follow the label directions and use products on plants listed there. If the label is general (i.e. “use on ornamentals”) test pesticides on a few of the plants and observe any phytotoxic reactions that may develop prior to treating all the plants.

Practice good sanitation in the landscape, removing dead limbs, dead leaves (particularly those harboring insect-caused galls), and remove hiding places for trash pests such as millipedes, sowbugs, pillbugs, snails and slugs. During the off-season, repair and maintain equipment and update your pesticide product label and material safety data sheet file. Don’t depend solely on your memory to remember label instructions and rates. Labels change over time.

Table 1. The approximate seasonal occurrence of major arthropod pests on ornamentals in the coastal regions of Texas (X’s indicate the period of peak occurrence and possible treatment periods).

Aphids: Many species of aphids exist and they mainly affect ornamentals. High populations of some species build up during winter months on evergreens or bedding plants and populations build up rapidly on new growth in the spring. Some species, such as wooly aphids, are favored by hot dry weather.

Scales: Like aphids, species are numerous and biologies differ. Generally, control includes applying dormant oil and/or insecticide treatments timed to correspond to the hatching of scale eggs and the appearance of the crawler stages. Control may require 2 to 4 applications at 7 to 10-day intervals.

Bagworms: Hand-pick bags in the winter to eliminate spring populations. If impractical, treat in spring when new bags are less than 1/2-inch long.

Cankerworms: If practical, prevent wingless females from depositing eggs in the fall by placing a band of sticky material around the base of the tree 3 to 4 feet from the soil.

Tent caterpillars Eastern, Western, Forest and Sonoran): Inspect trees for egg masses in the winter and remove them, if practical. After eggs hatch and tents appear, prune nests from trees and/or destroy them or spot treat if feasible.

Fall webworms: There are 2 to 4 generations per year. In winter and early spring, egg masses and webs can be removed and/or destroyed if practical. Otherwise, webs can be spot-treated or plants can be sprayed when webs are numerous and worms are not fully grown.

Walnut caterpillars: There are 2 to 3 generations per year in Texas, with the last one being the most damaging. Monitor for egg deposits and hatch on the undersides of leaves and treat if small worms are numerous.

Lacebugs: Populations begin to build up in early spring. If feasible, wash off nymphal populations. Otherwise treat when damage becomes evident on highly valued ornamentals.

Elm leaf beetles: Check undersides of leaves for yellow eggs and young larvae in March or April. If present treat 3 weeks after leaves have emerged and again in 2 to 3 weeks. Continue to monitor at 2 to 3 week intervals throughout the summer and treat if reinfestation occurs.

Borer beetles (roundheaded, flatheaded, and caterpillars; many species): Maintain tree health to make trees less attractive to borer beetles. Practice proper pruning and use wound paint during the summer months. To protect highly valued or stressed trees, chemically treat regularly at 3 to 5 week intervals throughout the summer unless the biology of the borer species involved is known.

Twig girdlers (Genus Onciders, three species): Remove and/or destroy girdled limbs in fall or protect small highly-valued damage-proned trees during the fall with insecticide treatments applied at 3 to 5 week intervals until trees lose their leaves.

Mites: Outbreaks occur anytime during the year, particularly during dry months or following use of certain broad-spectrum insecticides. Treat when mites are present and damage becomes noticeable.