Pest Control Strategies

Many thanks to Judith for her excellent presentation on pest control at our last general meeting! For those who weren’t able to attend or would like a recap, here is the information:

Pest Control Strategies

The “big” growers in our club have offered some ideas as to how they manage the pest problem with dahlias.   Some other ideas have been gleaned from the Internet, with website addresses given where you might want to check out a Youtube video or read for more detailed information.  Happy hunting!


Barry: use 2 ½ inch plastic pots and paper napkins from Costco – check every 2 days

Cathy: earwig traps

Internet: containers with narrow slits near base, filled with a little oil – they crawl in and drown.  Refill with oil as needed  (google “how to make an earwig trap – chemical free” –

Internet: another oil idea – use shallow tin cans (tuna, cat food, etc) and fill with ½ inch of oil – place a ground level

Internet: rolled up, dampened newspaper laid in beds – shake out in the morning into soapy water (or a short length of hose); fill a flowerpot with crumpled, dampened newspaper – place upside down on ground, propped up with a stick; bait a container with pencil-size holes in sides with oatmeal or bran; beer baits – jars on sides (might get slugs with one too!) – google “natural earwig control”


Barry: no sprays but hand squeezing on a daily basis when seen

Cathy: Safer’s Trounce (on contact only so no residue to harm beneficial insects)

Ryan: Safer’s Soap (but watch out for residue affecting blooms and leaves)

Internet: hand crush (sends out warning to other aphids); snip off affected section; encourage or purchase ladybugs and lacewings; plant mint, fennel, dill, yarrow, cosmos, larkspur, asters, zinnias, nasturtiums to attract aphids to those plants; plant garlic and onions near dahlias – aphids don’t like the smell; use a homemade garlic spray on aphids. Mix crushed garlic and water together, allowing the water to become infused with the scent of garlic. This smell acts as a deterrent against aphids, driving them away; create a home remedy to protect your plants against aphids. Mix together 1 cup of vegetable or white mineral oil with 2 cups of water and 2 teaspoons of bleach-free dish soap. Put the mixture in a spray bottle and spritz it on infected plants to suffocate the aphids. Keep the treated plants out of direct sunlight, however, since the spray could magnify the light and burn the leaves. Google “how to control aphids” –

Internet: 1. Water, water, and more water.  Blast aphids off of the plants with a strong spray of water. Nothing is more eco-friendly than water! As aphids are attracted to the color yellow, a bright yellow pan one-quarter full with water will draw aphids, who will then land on the water mistaking it for a plant, sink, and drown.

2. Pruning – Isolate the problem area.  Often this is an excellent solution, as the females of many aphid species produce live young during the summer, without a mate. Aphid populations can “explode” in this way, making the sacrifice of a few infested plants a strong, immediate, and eco-friendly action that protects the rest of your crop.

3. Nitrogen fertilizer.  Reduce your use of fertilizer heavy in nitrogen; high levels of nitrogen helps aphids reproduce. An alternative is to spread out application of nitrogen instead of applying it all at once.

4. Natural pesticide: diatomaceous earth.  Diatomaceous earth (DE) appears as a fine talcum powder, and is made of miniscule fossilized water plants. DE is lethal to aphids and many other types of common pests, including fleas, ticks, flies, cockroaches, ants, mites, and earwigs. A regular dusting with natural DE (not crystalline DE available at pool supply stores, which can be dangerous to humans and pets) with keep your garden, backyard, and even living room pleasantly insect-free.


Paul: At planting time, use Corry’s Slug Bait (no problem for his cat)

Barry:  Corry’s at planting; slug hunting at night which are then dumped into salt water and dumped next morning

Cathy: Safer’s Slug bait at planting and later if necessary

Ryan: resident frogs at Mill Bay plot! 

Judith: copper mesh over plastic collars (juice bottles, etc) at planting time (can remove collars or leave in place (use Coke or vinegar to remove tarnish)

Internet: newspaper soaked in sugared water and placed under boards attracts more than just plain damp paper; instead of beer in bait cups, use ½ tsp yeast, 1 tsp sugar, 1 tsp flour, 1 cup water.  Google “controlling slugs organically”

Internet: Iron phosphate containing slug baits – pet safe, last 2 weeks or more, act as fertilizer if not consumed (ex: Sluggo); grapefruit and orange halves (melon rinds also work) – discard slugs in salted water; use deep bait cups for beer or yeast mixes (yogurt containers buried to rim); dry cat or dog food placed under an overturned foil pan with “doors” cut in for slugs to enter – scoop and discard slugs in morning; copper banding or wire – gives them a slight shock – must be high/wide enough that big ones cannot just bridge over it; spray slugs with vinegar and water mix, or 1 part ammonia to 4 parts water with a bit of liquid soap (avoid salt – it will damage soil); 2 TBSP cornmeal in jars placed on their sides – desiccates the slugs! Google “how to kill snails and slugs” –

Internet: avoid watering in the evening when slugs come out – water in the morning and soil surface will be dry by nightfall; use seaweed as a mulch (dried is best); coffee grounds as mulch.  Google “natural slug control” –

Deer and other four-legged critters:

Paul: totally lined property with nine foot high hedges (I wish for this!)

Barry: high fence for deer; rabbits present a small problem at start but once plants are larger there is little damage from them

Judith: “Wireless Deer Fence” – – these can be moved around in the garden to surprise the deer; Bobbex on hostas, roses seems to discourage deer from coming into garden (try giant Q-tips with Bobbex!)


Barry: try to keep spraying to a minimum but if mildew shows up early, spray all plants near affected ones

Cathy: keep good air flow by removing bottom leaves and those from inside the plants.  Use foliar fertilizer to heighten resistance within leaves themselves.  Remove mildewed leaves immediately and wash hands before touching any other plants.

Internet: Homemade Sprays
Research studies in 1999 and 2003 on infected zucchini and winter wheat (respectively) indicated that spraying cow’s milk slowed the spread of the disease.  To try this at home, mix 1 part milk with 9 parts water and spray the stems and tops of leaves with the solution. Reapply after rain. 

Spraying leaves with baking soda (1 teaspoon in 1 quart water) raises the pH, creating an inhospitable environment for powdery mildew.

More on using milk (explains why it works & recommends ratios)


Cathy: (yellow vein lines can indicate virus) – use clean shears/scissors for each plant when cutting flowers or cleaning up – 70% alcohol solution to “sterilize” between plants.  When deadheading, just take off the flower heads by hand and then go back and cut stems with “sterilized” scissors.  Chuck any unhealthy looking plants (NOT composted).  Maybe try Epsom salts to see if a missing nutrient might be at root of discolouration before discarding.

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