Good Bugs, Bad Bugs by Marilyn Holt


Marilyn Holt certainly knows her bugs and has great photos as well!  We had a lot of fun guessing whether each “featured creature” was a “good bug” or a “bad bug”.  We knew quite a few from our own gardening experiences, but there were a lot that had us either surprised or stumped!

Bug Number 1 was the Lacewing.  Did you know that it is one of the best predators of those nasty aphids?  (Marilyn called it an assassin! LOL!) You’ll definitely want to learn how to recognize them and keep them around!

There are a lot of “bad bugs” that wreak havoc and destruction in our precious gardens!  These include carrot rust flies, tomato hornworms, click beetles and their larvae (wireworms), Colorado potato beetles, red lily leaf beetles, sawflies, chafer beetles, black vine beetles, fruit flies, fungus gnats, whiteflies, and of course, aphids.  We also have to deal with BC non-natives such as Gypsy moths, beech leaf miner, Japanese beetle, Apple coddling moth and its apple maggot larvae, and some species of stink bugs.

Here are a few notes from the presentation.
*Carrot Rust flies stay low to the ground and are attracted by the scent of carrot plants.  You can use row covers, plant flowers that are scented and low growing to hide the carrot scent, or grow your carrots in raised containers above the flies’ “flight height”.
*Red lily leaf beetles get inside the flower buds!
*Chafer beetles don’t like perennial rye grass so mix it in your lawn seed. July to September is the time to use nematodes for the larvae.
*Black vine beetle damage can be identified by the leaves being eaten on the outside edges. Leaves with holes in the centre are more likely due to slugs.
*Be sure to wash your fruit to avoid fruit flies. Wipe your finger in apple cider vinegar and wipe it on the yellow sticky traps to attract them.
*Fungus gnats like organic decomposition so are attracted to bark. Use aquarium gravel or diatomaceous earth on top of the soil.
*Whiteflies are hard to control, but yellow sticky traps as well as spraying with soapy water can help. Safer’s has a 3-in-1 spray, but it does requires contact with the insects.
*If you see white wiggly lines in leaves it’s probably the larvae of leaf-miner beetles.
*The Apple coddling moth lays eggs right on the blooms so the maggots develop inside the fruit without there being an entry hole.


Gardens need predators such as birds, bees, some types of beetles, lacewings, hover fly, spiders, and ladybugs.  We were surprised that even ants can be “good” for gardens!

Our best known “good bug” is probably the Ladybug. They are voracious eaters in all stages of life.  One adult can eat 400 aphids a day and they also snack on spider mites!

Hoverflies are nearly as effective in destroying aphids as lacewings and ladybugs! Marilyn noted that long narrow white eggs are often beneficial insects so don’t destroy them unwittingly!


This next one definitely gave us reason to look more closely at our garden bugs before giving them the boot!  Most of us were familiar with “stink bugs”, but quite unaware of the look-alike “spine soldier”.

The brown marmorated stink bug is a nasty pest which feeds on fruit, vegetables, ornamental trees and shrubs. On the other hand, the Spine soldier bug (also a type of stink bug) feeds on pollen and nectar and is a good pollinator. The larvae feed on slugs and snails, and the adult feeds on aphids!

Marilyn explained how to identify the difference, which was fairly simple (thank goodness)  if you take the time to look closely.  Pointy shoulders indicate it is a good Spine Soldier bug and rounded shoulders indicate it is the nasty marmorated stink bug!


There have been many types of pesticides and insecticides developed throughout the years, but as Marilyn explained, many have been discontinued due to their disastrous effects on beneficial insects and other wildlife.  Do NOT spray insecticides arbitrarily! They are non-selective and indiscriminate. We need to protect our pollinators such as bees, butterflies, hover flies, wasps, and mason bees.

Fortunately, Marilyn did have some suggestions for us!
Safer’s BTK (Biological insecticide) can be an awesome biological control.  It is only for above ground insects, so is ineffective for larvae pests in the soil.  It won’t hurt other things like bees or birds.  You do have to do your homework, however, and make sure that the caterpillars you are trying to get rid of are not one of our precious butterflies or moths!

Nematodes are one solution for in-soil pests. The powder is placed in a syringe with water (note: use bottled water so that there is no chlorine). Nematodes won’t hurt worms, just larvae. There are different types of nematodes and times of application depending on the pest, for example, chafer beetles versus black vine beetles.

Marilyn advised that keeping the “good bugs” happy and well-fed is an important part of your defence strategy!  Diversify your plants and flowers, thinking about colour, heights, and blooming times.  Low rowing herbs will attract good beetles. Water is needed by all your good insects! Beetles need cover from sun.  If you purchase Ladybugs, release them at night so they are encouraged to stay.  Don’t forget that once they have eaten all your pests, they will head off to someone else’s garden!

One question that came up was about the terms “translocate” and “systemic”.  Marilyn explained that systemic pesticides are water soluble and absorbed by a plant so that an insect feeding on the plant will ingest the pesticide.  Translocate is a similarly used term, meaning that the substance “travels” from the point of application.

It certainly was a fascinating presentation and we all were inspired to look a little more closely at our insect visitors before reaching for the fly swat or bug spray!

Thank you so much, Marilyn, for all the information and tips!

Marilyn Holt Speaker Bio (by Melanie G.)

Marilyn is a gardening enthusiast, international speaker and previously owned and operated a Pelargonium nursery, exporting plants internationally. Her interest is strongly in the direction of organic gardening.  She was the Editor of the B.C. Council of Garden Clubs Bulletin for seven years and was the Garden Centre Manager for the Abbotsford Buckerfields store, for twelve years.  She shares her knowledge by giving workshops and seminars throughout the year on a variety of gardening related topics.


Marilyn gave us a great photo handout of Garden insects – pests and friends!

Photos of Pest Insects and Beneficial Bugs\

The Good, the Bad, and the Bugly (or How to Hire an Assassin)

Buckerfield’s Gardening Videos


Ants – good and bad

Diatomaceous earth link

Fungus gnats

Hover flies


Lacewings – make a  lacewing home DIY


Marmorated stink bugs

Spined soldier bugs

Systemic pesticides



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