Natural Born Killers
Manage pest insects by calling on their natural enemies
By Mary Phillips
If you spend any amount of time outside in Texas you know there is no shortage of creepy crawly things lurking beyond the back door. And if you garden, chances are many insect pests are household enemy number one. What is a well-meaning organic gardener to do? When even the best preventative and plant health maintenance measures aren't enough - and you find your prize roses under attack by a platoon of aphids, or your basil succumbing to a squadron of mealy bugs - then call in an army of your own!
Managing pest insects by using their natural enemies is one of the most successful methods of pest control available. These beneficial insects are harmless to humans, plants and the environment, and they are born to hunt, capture and consume your plant-devouring pests without taking any prisoners. Below is a list of common beneficial insects, their target prey, best release dates and important notes about using them successfully.
The common ladybird beetle (Hippodamia convergens) – otherwise known as the humble ladybug – is probably the most famous and outstanding trooper in an otherwise clandestine defense force against unwanted landscape terrorists. They feed on aphids and other soft-bodied leaf suckers that attack young, tender growth. Release about a half pint of them (4,500 ladybugs per average suburban lot) in early spring when these pests are likely to emerge.
Ladybugs may fly away soon after release. You can prevent this by releasing them in the late afternoon close to sunset. They may also seek other areas if pest levels become too low; ladybird beetles require a certain amount of food in order to reproduce. If they cannot find enough food in your garden, they will try to find it elsewhere. Not to worry, if you don't see your ladybugs in your own garden, chances are they are helping out a neighbor. A half pint only costs about $10, so even if you find yourself treating the garden with them every spring, the investment is inexpensive and well worth it. Interesting note: you can store your ladybugs in your refrigerator until they are ready for release! Just don't mistake them for the red pepper flakes - their bitter coat is what makes them unappealing as prey themselves.
The green lacewing (Chrysoperla rufilabris) is a widely used beneficial insect which naturally controls many different pests including aphids, mealybugs, cottony cushion scale, spider mites, thrips and some caterpillars. The adult lacewings are actually herbivores, so it is their ravenous, reptilian-looking offspring that gobble up soft-bodied pests. As larvae, green lacewings will use pinchers to pierce their victims and inject them with paralyzing venom so that they can then be sucked dry.
Lacewings are distributed in the garden as eggs and should be used at the first sign of pest problems. Because they will pupate into adults about two to three weeks after release, it is a good plan to set more eggs out in the garden again at that time. Eggs usually are shipped in rice hulls, and are easily dispersed by placing this mixture close to infected plants. The average garden will need about 1,000 eggs if pests are found.
An important note for using both ladybugs and green lacewing larvae: ants love to feed on the sugary sap left behind by aphids. If you have ever parked under a crape myrtle infested with aphids, no doubt you are familiar with this sticky substance, which is otherwise known as 'honeydew'. Ants are very protective of their food supply (the honeydew) and will attack any creature that threatens it (your beneficial insects). If you have ant problems, be sure to control it using beneficials – particularly the rather defenseless lacewing larvae. Yes, it is a battle out there.
If you notice the decline of your aromatic, evergreen shrubs and trees such as rosemary, juniper or cypress, and the presence of wispy web-like threads on their needles and branches - then spider mites are the most likely culprit. Predatory mites are an effective control if you catch the problem before it gets out of control. These tiny creatures love the heat, so your best bet is to release some in the early summer so they can do their job before the humidity drops. (Mesoseiulus longipes) is the species most tolerant to lower humidity (40% at 70 degrees Fahrenheit). It is a good predator for up to 100 degrees Fahrenheit, although it requires more humidity as the temperature increases.
Don't be fooled by its name – the trichogramma wasp is incapable of stinging or harming a human. Their full wingspan is a mere 1/50th of an inch, yet these tiny flying soldiers are capable of destroying the eggs, which hatch into the harmful caterpillars (larvae) of over 200 types of moths and butterflies. This list includes armyworm, bagworm, corn borer, peach borer, squash borer, cankerworm, alfalfa caterpillar, cutworm, corn earworm, wax moth, tomato hornworm, cabbage looper and codling moth. Be sure to request the species best suited for your needs from your supplier: for either field crops or orchards.
These parasitic wasps are shipped as pupae glued to tiny paper squares, almost ready to hatch out as adult wasps. Distribute in the areas to be controlled at the rate of one square per week for six weeks starting when you first notice the presence of moths outside.
One praying mantis egg case will yield about 50 to 100 predators. These hungry ‘generals of the garden’ are so voracious that they will even eat other beneficial insects. It is hard to resist their intriguing form though and they can be particularly fun for children to observe. If you want to try tying a praying mantis egg case in your yard, be sure to hang it about three feet above the ground, and place it inside a protective cover – like an old toilet paper spool – to keep it safe from birds and rodents. Egg cases can be set in the garden any time after the danger of freezing has passed in the spring.
Many online sources will ship beneficial insects right to your door, but as organic practices become more popular, these nature born killers can also be found at garden centers locally.
With regular releases, you will find that you need fewer and fewer beneficials each year. Be sure to discourage your neighbors from using harmful pesticides – which not only kill the 'bad guys', but the 'good guys' (including our ever important bees) as well! Using beneficial insects is a wonderful way to help restore balance in your environment, and will officially list you as an officer in 'the good fight' for Mother Nature!