Tapping Beneficial Insects to Combat Pests (Part 2)

Tapping Beneficial Insects to Combat Pests (Part 2)

 Click here for Part I that focuses on how natural insect predators helped fight the ACP pest in Florida

Add plant diversity to your gardens. Also make sure you have flowering plants year-round. Ecologists say these key recommendations will usher in natural predators to our gardens and orchards to combat pests.

These tips can even help ward off the Asian citrus psyllid (ACP) that is alarmingly moving into our citrus trees after devastating the citrus in Florida.

Nicola Irvin PhD is a specialist in biological control at UC-Riverside. Irvin, a native of New Zealand, began work 15 years ago with the sharpshooter insect that was devastating the grape industry. Not surprising, her research today is focused more on the ACP.

Enlisting our natural predators

This article doesn’t have room to discuss the many amazing aspects of beneficial insects, which not only help in pollination, but also kill pests. However, here’s some important background:

  • Thousands of overlooked insects that are native to our locales play vital roles in pest management.
  • Some (called parasitoids) work by parasitizing the pest, that is they lay eggs in them so their hatched larvae then feed on the pest. Others just eat them outright.
  • Also, many beneficial insects and most pests go through many forms or instars (much like the monarch caterpillar). For example, the Asian psyllid goes through five forms, or instars before it’s an adult that can carry the bacterium that causes citrus greening disease

Irvin emphasized that having an abundance of different types of predators and parasitoids can prevent pests from achieving its adult size, because these natural enemies will attack them in their various forms.

The Importance of Spiders, Native Flies and Wasps

“[Buckwheat that I planted] attracted a lot of hoverflies. Hoverflies eat scales, thrips, aphids, and even the larvae form of ACP.  –Nicoli Irvin PhD, UC-Riverside

The hoverfly (Genus: Melangyna) here on Brittlebush, is an effective ACP predator

Native flies and wasps are particularly disregarded insects that are receiving more notice these days. For example, many adult female wasps perform double duty. They parasitize the host pest by laying eggs in them, and also kill hosts, such as scales and whiteflies, by feeding on them.

It’s important to note that none of these native wasps sting people, and they don’t build group nests. Some are tiny – the smallest the size of a grain of sand – while medium sized ones such as tachinid flies get mistaken for houseflies.

Irvin carries out research at UCR investigating the benefit of native flowering plants on the survival of parasitoids of ACP.  “When I planted some red California buckwheat in my yard, I also noticed it attracted a lot of hoverflies. Hoverflies eat scales, thrips, aphids, and even the larvae form of ACP. They’re generalists, so will eat many soft bodied pests, and are very ravenous,” she says.

Spiders are an especially important ally, as most spiders feed entirely on insects, including the psyllid. Spiders are also one of the first things that get destroyed with insecticide sprays. “Spiders are valuable because they not only attack the Asian psyllid nymphs but they’re around 24/7 and can eat the psyllid adults that don’t fly at night,” said Irwin.

While lady beetles (ladybugs) appear to provide the most control of ACP in Florida, this is not mirrored in southern California. Hoverflies and lacewings (those flitty light green insects at night) appear to be the most important predators of ACP nymphs in California, Irvin says. “Their combined effect can kill 86% of ACP nymphs.”

Other natural predators of pests include spiders, beetles, predatory mites, and a group called true bugs. Then there are natural predators such as birds, reptiles and even mammals such as the opossum.

Next we discuss what plants to plant, but first here is a gallery of good bugs and plants.

Adding diversity and year-round flowering plants

Irvin says the most important thing you can do is add different types of plants to your yard. “Increasing plant diversity in your garden attracts more beneficial insects by providing a wider variety of habitats and alternative foods to predators, parasitoids and pollinators,” says Irvin, especially lots of native plants, which also attract native birds and insects like native beeflies and robber flies that reduce mosquitos and insect pests.

Also, make sure you have flowering plants year-round to provide them nectar and pollen. Otherwise beneficial bugs will move off. “It’s especially good to plant flowering plants that are composites or from the Asteraceae family, which have shallow flowers that most natural enemies can feed from,” she says.

Native plants, including the California poppy

The various varieties of California buckwheat, goldfields and tidy tips are good examples of flowering plants to attract beneficial predators. Another Irvin mentioned is California poppies, because this heavy pollen producer attracts ladybugs, lacewings and hoverflies. Plus, they reseed and come back year after year. Sweet alyssum and common buckwheat also work well if you prefer non-native annuals.

She also recommends letting herbs go to flower such as coriander and dill, because they attract a lot of beneficial insects.

Aphids among the peskiest pests

Irvin views aphids, mites, and caterpillars as the most prevalent pests for backyard gardeners in the Southern California area, adding that mites can be particularly problematic in dusty environments. “However, if you forcefully spray the leaves with water and keep the dust down, that will help reduce mite populations. Be sure to provide adequate irrigation as water-stressed trees and plants are also less tolerant of mite damage,” says Irvin.

The hornworm becomes the beautiful Sphinx moth

For cutworms, loopers, and hornworms, three common types of caterpillar, she recommends Bacillus thuringiensis, commonly called Bt, a targeted organic insecticide that only affects caterpillars. Remember, however, that the despised tomato hornworm turns into the beautiful sphinx moth.

For more info:

Habitat Planning for Beneficial Insects (Xerxes.org)- comprehensive and informative

Biological Control and Natural Enemies of Invertebrates  (UC Pest Notes) – informative, California focus

Asian citrus psyllid fact sheet – UCalifornia- IPM


About Linda Richards

My goal is to educate about the science of nature in layperson speak, through my writing, science and education background. I grew up in the Chicago area, loved living in Minneapolis before gravitating to the West, which is now home.


  1. An excellent book for ID insects is Milkweed, Monarchs and More by, Be Rea, Karen Oberhauser, Michael A. Quinn. Bas Relief, LLC Excellent column Linda. California Butterfly Lady Monika Moore

Speak Your Mind