Natural ‘enemies’ can attack garden pests

Summer months may stress plants because we often see periods of increased rainfall and then periods of drought along with intense heat.

And, when plants are stressed, they may be more susceptible to pests.

When it comes to combating these pests, don’t forget there are many natural enemies that eat pest insects.

Aphids are the favorite food source of the adult convergent ladybeetle, Hippodamia convergens. (Courtesy of James Castner and Lyle Buss, University of Florida/IFAS)

These natural enemies, that are considered good or beneficial, include lacewings, ladybeetles, assassin bugs, spiders, hover flies, dragonflies and mantids.

Some commercial companies raise these natural enemies and ship them to gardeners who then release the insects for pest control.

Prior to purchasing natural enemies, identify the pest insect or mite. This will help you match the appropriate control with the pest.

If you need help identifying the pest, reach out to your local county Extension Office.

Natural enemies that are available from commercial companies may include predatory mites, predatory insects and parasitic wasps.

Ladybeetles (also known as ladybugs) are one of the most common beneficial insects purchased for home gardens. There are many different kinds, or species, of ladybeetles. Some eat specific pests such as aphids or whiteflies, which is why it is important to identify the pest so you know what beneficial insects to purchase or to encourage in your garden.

These beetles help home gardeners – and farmers – because they are phytophagous, which means they eat plant pests that feed on ornamental plants and crops, such as cabbage, corn, melons, peaches and potatoes. Some ladybeetles also attack the Asian citrus psyllid. It is this psyllid that transmits the bacterium that causes the citrus greening disease.

Ladybeetles undergo a complete metamorphosis, starting off as a tiny yellow or orange egg. They look very different as they go through their life cycle (egg, larva, pupa, adult).

However, many ladybeetles are field collected from natural areas where they aggregate (form large groups) and overwinter. They may carry parasites or pathogens. If they are collected when they are reproductively immature, they may be less effective as a biological control.

Adult ladybeetles will often fly away when released. Because of these reasons, it may be better to encourage ladybeetles through your gardening practices rather than purchasing adult ladybeetles.

Did you know that the larval form of the ladybeetle is a more voracious pest-eater than the adult form?

Ladybeetle larvae (some people say they look like small alligators) eat aphids, leafhoppers, mites, mealybugs, scales, thrips, whiteflies and some other insects, such as pest beetles, caterpillars and lacebugs.

There is a variety of colors and patterns among the larvae of various ladybeetle species.

The life cycle of the ladybeetle reminds us that insects may look very different as they grow and develop through their different stages. Because the larvae can look very different from the adults, knowing how to recognize insects can help you figure distinguish between the good insects from the pests.

Of the many different ladybeetles, some prey on specific plant pests. Delphastus catalinae eats whiteflies. Cryptolaemus montrouzieri, also known as the mealybug destroyer (my favorite) eats mealybugs. Hippodamia convergens larvae can eat between 30 and 50 aphids per day.

If you purchase adult ladybeetles, be sure to match the ladybeetle species that will eat the pest you’ve identified in your garden. Purchase ladybeetle larvae when possible, and buy from reputable companies that sell ladybeetles that are parasite- and disease-free. Check the Association of Natural Biocontrol Producers (ANBP) website for a list of companies.

There is a variety of colors and patterns among the larvae of various ladybeetle species.

Interestingly, the UF/IFAS Extension Entomology and Nematology department explains that ladybeetles are pollinators, and they will also feed on pollen, honeydew and nectar from flowers, when prey is scarce. But, in order to reproduce, they need to eat live prey.

You can encourage ladybeetles – and other beneficial insects – without having to buy them.

To attract the good bugs to your garden:

  • Plant a variety of flowers that bloom at different times of the year and that have different colors and flower shapes
  • Provide a refuge for insects by reducing or eliminating pesticide use.

Alternatively, soft pesticides, such as insecticidal soaps, horticultural oils, spinosad and Bacillus thuringiensis (also known as Bt), may be used for many pests

The soft pesticides pose less risk to non-target organisms, such as beneficials and pollinators. Consider native plants that may attract specialized pollinators. Plants that contain structures called extrafloral nectaries are especially attractive to beneficial insects.

If you’d like more information about this, consult these sources, which were used in this column:

For additional information, email or call (813) 744-5519, ext. 54145.

Nicole Pinson is the Urban Horticulture Agent in Hillsborough County.

Published July 24, 2019

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