What is destroying my bougainvillea plants?

Dawn dish soap in water will kill the fungus now I can’t help with the insect problem

Hi Francesca, The Bougainvillea Looper caterpillar will eat the plant's leaves away. Aphids feed off of tender new leaves and leave a secretion that attracts ants while also promoting mold growth. Mealybugs create mold, too, though it's often black and sooty-looking. Any flying insect can get up to your floor as well.

Here is a list of pests and how to kill them

Aphids

Aphids are tiny insects that come in a variety of colors but they’re most commonly pale green. A stressed or neglected bougainvillea attracts the cowpea aphid (Aphis craccivora) and the melon aphid (Aphis gossypii). You may not notice an individual aphid but they typically cluster together on the bougainvillea’s leaves and new growth. Aphids suck the juices from the plant and then excrete a substance known as honeydew that attracts fungus that then creates sooty mold, a black powdery substance. A hard jet of water from the hose will knock aphids off the bougainvillea. If they persist, create an insecticide that contains 1 tablespoon of dishwashing soap added to 1 cup of vegetable oil with 1 tablespoon liquid dish-washing soap. Add 1 1/2 teaspoons of the solution and 1 cup of warm water to a spray bottle and spray the insecticide directly on the aphids.

Other Sucking Pests

The citrus mealybug (Planococcus citri), the longtailed mealybug (Pseudococcus longispinus), brown soft scale (Coccus hesperidum) and giant whiteflies (Aleurodicus dugesii) feed on the bougainvillea much like aphids. Mealybugs on the plant resemble small tufts of cotton. Brown soft scale resembles a brown or yellowish brown small bump on the bougainvillea. Both of these can be managed by spraying the leaves thoroughly with a mixture of 2 tablespoons of neem oil in 1 gallon of water, or according to label instructions. If you notice a white, waxy substance on the bougainvillea, suspect the giant whitefly. These pests are tiny and white and tend to congregate on the undersides of foliage. Like aphids, they are easy to wash off the plant with a strong blast of water or use neem oil.

Bougainvillea Looper

The bougainvillea looper (Disclisioprocta stellata) is a 1-inch-long yellow, green or brown caterpillar. It feeds in the evening, leaving ragged leaf edges and may strip the plant of its leaves. Hand-removing the caterpillars is the best way to manage an infestation. Because they feed at night, you may not be able to find them in the daytime. Insecticides with the active ingredient spinosad are effective against the bougainvillea looper. Spray a ready-to-use spinosad product on the bougainvillea to completely cover every leaf, top and bottom.

Pest Prevention

A bougainvillea performs best when it is slightly stressed, so there’s a fine line between urging it to flower and inviting pests. Keep the soil somewhat dry between waterings and fertilize it in spring and again in midsummer with a general-purpose fertilizer diluted to half strength, usually 1/2 tablespoon per 1 gallon of water. Brands vary, so make sure you follow the label's instructions. Over-fertilizing your bougainvillea will kill it.

Looking at the beige and crispy areas, it looks like sun scorch or wind burn to me. Has the plant been exposed to more sun recently, or you said it's windy, is more than normal?

Francesca, I suggest that you take a mixture of leaves, such as that which you have shown us, and see if a professional gardner can help you. The gardener who takes care of your building's plants could help. I am sure he is used to the desert air and wind and would probably be glad to help you. 💖🌹😘

Spraying with Neem Oil will kill the aphids and keep them away. It also treats all kinds of powdery mildew and won't harm the plant.

Thank you all I will take the leaves to a garden Center. I have watered the plants regularly so I will try and allow it to dry a little more. Will cut the plant back and use the Neem Oil on it so I can see if something changes.