Bougainvillea Pest and Disease Issues
Aphids are small, soft-bodied insects with long, slender mouth parts that they use to pierce stems, leaves, and other tender plant parts and suck out plant fluids. Almost every plant has one or more aphid species that occasionally feeds on it and this is true with bougainvillea.
Aphids may be green, yellow, brown, red, or black depending on the plants they feed on. In bougainvillea it is usually the green aphid that is found feeding on the tender new tissue. All are small, pear-shaped insects with long legs and antennae.
Low to moderate numbers of leaf-feeding aphids are usually not damaging in gardens or on trees. However, large populations cause curling, yellowing, and distortion of leaves and stunting of shoots. They can also produce large quantities of a sticky exudates known as honeydew, which often turns black with the growth of a sooty mold fungus.
Biological control: or natural enemies can be very important in the control of aphids.
Cultural Control: before planting bougainvillea, check surrounding areas for sources of aphids and remove them.
Chemical Control: Insecticidal soap, neem oil, and narrow-range oil (e.g., supreme or superior parafinic-type oil) provide temporary control if applied to thoroughly cover infested foliage.
Leaf miner feed by creating shallow tunnels, or mines, in young leaves of bougainvillea bushes. Leaf miners have four life stages: egg, larva, pupa, and the adult moth. Adults do not damage plants and live only 1 to 2 weeks. Eggs hatch about 1 week after being laid by the adult moth. The newly emerged larvae immediately begin feeding in the leaf and initially produce tiny, nearly invisible, mines. As the larva grows, its serpentine path of mines becomes more noticeable. Numerous mine like paths traversing the leaves of bougainvillea plants, the adults are virtually undetectable.
Leaf miners can survive as a larva only in the tender, young, shiny leaf flush of bougainvillea. Older leaves that have hardened off are not susceptible unless extremely high populations are present. The larvae mine inside the lower or upper surface of newly emerging leaves cause them to curl and look distorted. The leaves never recover from this distortion and make the plant look unsightly given a heavy infestation.
Hang pheromone traps about shoulder height on the affected plant. Follow the manufacturer’s recommendations for maintaining the trap, such as how often the pheromone dispenser should be replaced.
Bacterial and Fungal Leaf Spot
These usually develop when environmental conditions are favorable for example when there is an excessive amount of moisture on the leaves of bougainvillea for an extended amount of time. Lesions will develop either at the periphery of the leaf or between veins and will spread from there. In time, leaf edges may become ragged as the necrotic tissue turns dry and papery. Infection of developing leaves and bracts results in puckered, distorted growth.
Control of this type of infection can be achieved by avoiding moist foliage of the plants. Prune large branches back and away from each other or if they are overlapping. Remove infected leaves and plants from the growing area and make sure to destroy the debris.
If the infection is increasingly difficult one may have to resort to chemical sprays and as always the label must be followed with precision.
Armored scales, family Diaspididae, have a flattened, platelike cover that is less than 1/8 inch in diameter. The actual insect body is underneath the cover. The covers often have a differently colored, slight protuberance. Concentric rings form as each nymphal stage (instar) secretes an enlargement to its cover. Armored scales do not excrete honeydew. Damaging species include Florida red scale and Oriental scale.
Soft scales can be smooth, cottony, or waxy and are 1⁄4 inch long or less. They are usually larger and more rounded and convex than armored scales. Their surface is the actual body wall of the insect and cannot be removed. Soft scales feed in the fluid-conducting phloem tissue of the plant and excrete abundant honeydew, which is sugary water that drips from their bodies. Soft scales include black scale, brown soft scale and mealie bug.
Females of many scale species reproduce without mating (there are no males). At maturity, adult females produce eggs that are usually hidden under her body or cover. Eggs hatch into tiny crawlers (mobile first-instar nymphs), which are yellow to orangish in most species. Crawlers walk over the plant surface, are blown by wind to other plants, or can be inadvertently moved by people or birds. They settle down and begin feeding within a day or two after emergence.
When plants are heavily infested with scales, leaves may look wilted, turn yellow, and drop prematurely. Scales sometimes curl leaves or cause deformed flowers and fruit.
Scales are often controlled by small parasitic wasps and predators including beetles, bugs, lacewings, and mites. Horticultural oils are specially refined petroleum products, often called narrow-range, superior, or supreme oils. Some botanical (plant-derived) oils are also available. Thoroughly spraying plants at the proper time with oil alone usually provides adequate control.
Thrips are tiny, slender insects with fringed wings. They feed by puncturing their host and sucking out the cell contents. Certain thrips species are beneficial predators that feed only on mites and other insects. Pest species are plant feeders that scar leaf, flower, or fruit surfaces or distort plant parts.
Most adult thrips are slender, minute (less than 1/20 inch long), and have long fringes on the margins of both pairs of their long, narrow wings. Immature thrips (called larvae or nymphs) are similarly shaped with a long, narrow abdomen but lack wings. Most thrips range in color from translucent white or yellowish to dark brown or blackish, depending on the species and life stage.
Thrips prefer to feed in rapidly growing tissue. Feeding by thrips typically causes tiny scars on leaves and fruit, called stippling, and can stunt growth. Western flower thrips are primarily pests of herbaceous plants, but high populations occasionally damage continuously or late-blossoming flowers on woody plants such as roses.
Although thrips damage to leaves is unsightly, thrips activity does not usually warrant the use of insecticide sprays. For ornamental nonfood plants, a licensed pesticide applicator can use the systemic pesticides, but oils will provide control of adults.
Mites are common pests in landscapes and gardens and can be found feeding on many fruit trees, vines, berries, vegetables, and ornamental plants. Although related to insects, mites are not insects but members of the arachnid class along with spiders and ticks.
To the naked eye, spider mites look like tiny moving dots Spider mites live in colonies, mostly on the under-surfaces of leaves; a single colony may contain hundreds of individuals.
Mites cause damage by sucking cell contents from leaves. A small number of mites is not usually reason for concern, but very high population levels high enough to show visible damage to leaves can be damaging to plants, especially herbaceous ones. At first, the damage shows up as a stippling of light dots on the leaves; sometimes the leaves take on a bronze color. As feeding continues, the leaves turn yellow and drop off. Often leaves, twigs, and fruit are covered with large amounts of webbing. Damage is usually worse when compounded by water stress.
Spider mites have many natural enemies, which limit their numbers in many landscapes and gardens, especially when undisturbed by pesticide sprays. Cultural practices can have a significant impact on spider mites. Dusty conditions often lead to mite outbreaks. Apply water to pathways and other dusty areas at regular intervals. Spider mites frequently become a problem after the application of insecticides. Such outbreaks are commonly a result of the insecticide killing off the natural enemies of the mites.
Slugs and Snails
Snails and slugs move by gliding along on a muscular “foot.” This muscle constantly secretes mucus, which later dries to form the silvery “slime trail” that signals the presence of either pest. Slugs and snails are hermaphrodites, so all have the potential to lay eggs. Adult brown garden snails lay about 80 spherical, pearly white eggs at a time into a hole in the topsoil. They may lay eggs up to six times a year. It takes about 2 years for snails to mature. Slugs reach maturity after about 3 to 6 months, depending on species, and lay clear oval to round eggs in batches of 3 to 40 under leaves, in soil cracks, and in other protected areas.
Snails and slugs feed on a variety of living plants as well as on decaying plant matter. On plants they chew irregular holes with smooth edges in leaves and flowers and can clip succulent plant parts. They can also chew fruit and young plant bark. Because they prefer succulent foliage or flowers, they are primarily pests of seedlings and herbaceous plants
A good snail and slug management program relies on a combination of methods. The first step is to eliminate, to the extent possible, all places where snails or slugs can hide during the day. Boards, stones, debris, weedy areas around tree trunks, leafy branches growing close to the ground, and dense ground covers such as ivy are ideal sheltering spots. There will be shelters that are not possible to eliminate e.g., low ledges on fences, the undersides of wooden decks, and water meter boxes. Make a regular practice of trapping and removing snails and slugs in these areas.
The bougainvillea looper is a green or brown caterpillar that is roughly 1″ long. It is also known as the inchworm or measuring worm. The looper larva mimics stems and branches very well and feeds primarily at night, which is why you may see the damage but fail to find the culprit on the plant.
Bacillus thuringiensis (sold as a variety of products) is effective against the larval stages of the looper. Bt, as it is commonly known, is a bacterial preparation that causes a disease in many kinds of caterpillars but does not harm beneficial insects, birds, man, or other organisms. Loopers stop feeding within hours after feeding on a sprayed leaf and die several days later. Thorough spray coverage of the tree is required for control. (Bt will also control other caterpillars present at the time of application.) Bt is only effective on fruit tree leaf roller larvae when they are small (less than 1/2 inch long) and usually requires more than one application. Caterpillars must ingest the pesticide to be killed.