It’s a war to the death in local gardens, and it’s bug against bug in some battles.

How many bugs is too many?

“It’s all up to the individual what their threshold is for the number of bugs they have,” said Dennis Culley, a Butler County master gardener. “Is one your threshold or do you wait till the plant is eaten?”

But some bugs are great to have in the garden because they feed on their fellow insects.

Culley said there are plants that will attract the beneficial insects.

Culley said Penn State Extension’s “Good Bug Tub” can draw the “good” insects to a garden. Examples of plants for the tub include golden basil, curry, dill, catmint, nasturtium, scabiosa, sweet alyssum and yarrow. A gardener can plant these plants in a metal, bushel-size tub and put the tub in the corner of a garden.

“It depends on what you want to attract. If you want the ladybugs, plant the dill,” said Culley

He said it will also attract spiders and hoverflies. Wasps and spiders will eat aphids that suck the nutrients out of plants.

“The number one good one would be the ladybug,” Culley said.

We know them as ladybugs, but Jack Layne, professor of biology at Slippery Rock University, said in most other parts of the world, they are called ladybird beetles.

“You need to have the plants that they want to be on,” Culley said.

Yarrow is another plant that will attract ladybird beetles that will eat asparagus beetle larvae, aphids, Colorado potato beetle larvae, lacebugs and mealybugs.

The trick is to keep the ladybird beetles in the garden.

Layne said while the beetles are in the garden, they will mate and lay eggs.

“If you have a small garden and there’s really not a large number of aphids and pests that they can feed on, they’re going to move on,” Layne said. As the beetles reduce the pest insects, they may leave, but some may stay in the vicinity.

“For aphids, ladybird beetles are really good,” he said. “If you have problems with grasshoppers, (ladybird beetles) are not big enough.”

Instead, Layne recommended something bigger.

“Praying mantises are much larger insects, so they can take on larger herbivorous insects like grasshoppers,” Layne said.

They lay egg cases at the end of the summer. Gardeners can buy egg cases and put them out in the spring to hatch.

When they are small they feed on small insects. Once they are larger, the mantises will eat bigger insects.

He said they won’t eat pesky worms or slugs.

“A tomato hornworm is very big, very green and very ferocious,” Culley said. “They can eat the whole plant.”

“If someone has a problem with those you probably want to go with a parasitic wasp,” Culley said.

Nicole Dafoe, assistant professor in the biology department at Slippery Rock University, said parasitic wasps can recognize gasses released by a plant when a caterpillar feeds on the plant.

“It’s like a distress signal,” Dafoe said.

She said parasitic wasps are the enemy of the plant’s enemies.

Parasitic wasps attack the eggs or larvae of other insects, according to Layne. The wasp will insert its own egg into them and when the wasp hatches, “it will eat the other insect from the inside out.”

Layne said there are lots of parasitic wasps and wasps help gardeners. Each kind goes after a specific insect.

He said it’s possible to buy them, but the gardener has to know what pests are in the garden.

Fighting insects with insects has its advocates.

“For people who are into organic gardening and they are worried about secondary effects of spraying on their children or pets, it’s a reasonable approach to follow,” Layne said. “The whole idea is to avoid using chemical controls.”

Layne said that pesticides may kill off beneficial insects but he said pesticides are used for a reason.

“You can get much more effective elimination and much less damage to crops,” Layne said. “Biocontrol works well especially if done with some reinforcement. You may have to order more than one batch and put them out two or three times over the course of your growing season.”

Layne said that when many plants of the same type are grown together it usually attracts more of one type of garden pest. Smaller garden patches and alternating the rows of crops may help decrease the problem.

“Nothing is really foolproof of giving you the perfect solution,” Layne said.

Search “Good Bug Tub” online to find Penn State Extension’s advice for building your own good bug tub.