Gardening with Gary

Gardening Advice from an Expert

Insecticides

Insecticidal Soap:

The commercial insecticidal soap sells for $7.98 per quart. The homemade versions cost just pennies and do the same thing. I presented two different versions on KOTA Television.

Version # 1:

Mix two tablespoons of Ivory Soap Flakes powder with one quart of water. It will look a little milky. Put this in a quart spray bottle and use when you notice an infestation of white flies, mites, aphids, thrips, etc. Be sure to spray underneath the leaves too ... most of these critters like to hide!

Great-grandma used to pour her dishwater over plants that looked "sickly." She was using homemade insecticidal soap.

Version # 2. Mix two tablespoons of Dawn Dishwashing Liquid with one quart of water and put in a spray bottle. Use for the same insects as the version # soap mixture.

When I spoke with my County Extension Agent, he told me to warn folks that these are CONTACT sprays -- you have to squirt them directly on the insects.

He also cautioned against using these sprays OR the commercial version on a hot day, as they can damage (burn) the foliage of the plants if you get too much on the leaves.

My own personal preference is the Ivory Soap spray because most dishwashing liquids are detergents and I do not know what they do to the environment.

KOTA TV www.smart-penny.com

Alice writes~
I have a lot of aphids on one of my roses. I need a homemade insecticide recipe. Years ago I had one that called for Listerine and soap. Do you have it? If not do you have a good recipe.

A. This is what one poster at Global Garden wrote:

"By the time I have gone out to buy liquid Ivory soap, and Listerine, I have spent a whole lot more than going down to my local garden/greenhouse supply and bought a bottle of insecticidal soap. I have had really good luck with these commercial products and have never lost a plant. I have used both the 'Safer' brand and several brands that employ pyrethrums (a natural insecticide derived from chrysanthemums). Each one contains ingredients that at one time or another has gotten rid of aphids, white flies, and spider mites on my plants. Check the labels to see what the product is effective against."

To make your roses unpalatable to aphids and other pests, spray them with 1/2 cup Listerine and 1/2 cup water mixed with four drops of Ivory Liquid Soap [which makes the solution adhere to the plants]. Repeat spraying weekly for at least four weeks and reapply if there is rain in between since it will wash off.

But do not forget about ladybugs. They are a wonderfully beneficial insect for your garden, and aphids are one of their favorite meals.

John writes~
Looking at a rose spray for insects and the active ingredient at 1% is Canola oil with the all famous inactive ingredient being just other (water?) On the net at http://www.epa.gov/pesticides/biopesticides/factsheets/fs011332e.htm they talk about using Canola oil as an insecticide. Any thoughts for this product for use as an insecticide? Can Canola cooking oil be used or is there a difference?

Thank you for your time and thoughts not only for this question but for your excellent responses in your e-zine.

A. Thank you very much. Oils are used as a sticking agent. It makes the harsh killing chemicals adhere to the plants and insects, thus increasing the ability to kill and thus protect the plants. Here is what the article above states in part:

"Scientists believe that canola oil repels insects by altering the outer layer of the leaf surface or by acting as an insect irritant."

That seems harmless enough for human beings and pets.

"Whether or not a substance poses a risk to humans or other organisms depends on two factors: how toxic the substance is, and how much of it an organism is exposed to. Therefore, the EPA considers both toxicity and exposure data in determining whether to approve a pesticide for use."

Here is where I would express reservations. I would like to see further research reports before using myself.

I would be careful about using your canola cooking oil as a spray. Remember, you quoted 1%. I would wonder if that low percentage mixed with water would have any beneficial effect. I recommend other organic, nontoxic solutions. You can view some reports at my GardeningWithGary website here.

Q. What is this oil that you spray on plants to kill insects? I am curious if it is not harmful to animals.

A. Dormant oil is a nontoxic spray to control insects before they can do anydamage since you spray the plants early before the insects have become adults. Use on fruit trees, shrubs and evergreens in early spring while they are still dormant before buds develop. You can buy the spray from most garden centers or make your own using the following recipe from Garden Guides:

1 gallon mineral oil
1 pound soap (use fish oil soap if you can find it)
1/2 gallon water

Combine all ingredients, boil, and mix very well. Dilute 1:20 with water and use immediately because the ingredients separate quickly. Mix up only what you can use that morning.

Spray on a day when the temperature is above 40F and no freeze is forecast for at least 24 hours. Drench the branches of the shrubs and trees thoroughly.

For citrus trees, buy a special dormant oil from your garden supply store because their leaves can be damaged by the film which remains on the leaves.

Dawn writes: I found a recipe in your question and answer section where Alice asked about the insecticide recipe including Listerine and soap. I would like to know if this also good for killing mosquitoes in the lawn, and what would be the ratio for an average size lawn located in a subdivision. I am extremely allergic to mosquitoes and unfortunately my lawn saturates very easily and stays wet for long periods of time. I need to find something that will help me keep the mosquito population down and had heard that a recipe including Listerine, soap and another ingredient worked very well when used regularly.

A. Try this formula:
Mix 1 cup each of Listerine™, liquid dish soap, and water. Add 2 cups lemon
juice [i.e. bottled from concentrate]. Spray on lawn and around plants. Apply in the morning and if it rains, reapply. Otherwise, treat lawn once every two weeks. Avoid wearing any strong perfume, deodorant, cologne or suntan lotion. Burn citronella candles around badly infested areas and patios where you sit. Remove any items with standing water. A bird bath must be emptied and cleaned at least twice a week. Kill mosquito larvae in ponds and puddles by sprinkling in plain powdered coffee or tea, just enough to change the color of the water. Caffeine makes mosquito larvae uncoordinated, and they can't come to the surface to breathe.

Carol writes~
I love the Recipe Goldmine and am always looking for safe treatment for my garden as I have pets and grandchildren. I am looking for a safe way to eliminate grubs from my garden. I resist the commercial as have many birds that feed from the flower seeds. However, this a.m. I discovered that skunks are working my garden, tearing up plants just starting to grow (RI) and this grrrr's me.

A. Try: Beneficial Nematodes, naturally occur in soil and are used to control soil pest insects and whenever larvae or grubs are present. Like all of our products, it will not expose humans or animals to any health or environmental risks. Beneficial nematodes only attack soil dwelling insects and leave plants and earthworms alone. They enter the larva via openings and feed. This causes specific bacteria to emerge from the intestinal tract of the nematode. These spread inside the insect and multiply very rapidly. The bacteria convert host tissue into products which can easily be taken up by the nematodes. The soil dwelling insect dies within a few days. Beneficial nematodes are a totally safe biological control in pest insects. The Beneficial nematodes are so safe the EPA has waived the registration requirements for application. Though harmless to humans, animals, plants, and healthy earthworms, beneficial nematodes aggressively pursue insects and can be used to control a broad range of soil inhabiting insects and above ground insects. More than 200 species of pest insects from 100 insect families are susceptible to them. When they sense the temperature and carbon dioxide emissions of soil-borne insects, beneficial nematodes move toward their prey. When the pest population is eliminated, the nematodes die off and biodegrade. Beneficial nematodes are so effective, they can work in the soil to kill the immature stages of garden pests before they become adults which are known to destroy lawns and plants. Beneficial Nematodes are very easy to use. Mix with water and spray or sprinkle on the soil along garden plants or lawn. Put the contents in a bucket of water and stir to break up any lumps, and let the entire solution soak for a few minutes. Application can be made using a water-can, irrigation system, knapsack or sprayer. On sprayer use a maximum pressure to avoid blockage and all sieves should be removed. Evenly spread the spraying solutions over the ground area to be treated. Continuous mixing should take place to prevent the nematodes from sinking to the bottom. After application keep the soil moist during the first 2 weeks for the nematodes to get establish. For a small garden the best method is using a simple sprinkling or water can to apply the nematodes. Apply before setting out transplants and whenever symptomatic damage from insects is detected. Best to apply water first if soil is dry. Nematodes can be stored in the refrigerator up to a month (not the freezer) before they are mixed with water, but once the nematodes are diluted in water, they cannot be stored. Nematodes need moisture in the soil for movement (if the soil is too dry or compact, they may not able to search out hosts) and high humidity if they are used against foliage pests. Watering the insect-infested area before and after applying nematodes keeps the soil moist and helps move them deeper into the soil. Care should be taken not to soak the area because nematodes in too much water cannot infect. If you would like to purchase Beneficial Nematodes for your garden, please visit http://www.buglogical.com and http://www.gardeninsects.com/beneficialNematodes.asp

Jane writes~
I have as problem in my garden and flower beds. There is something eating the flowers off my plants or eating tender new plants. It is either earwigs or I do not know the name of the bug, but it looks like an armadillo, but tiny. I have a problem with them when the ground is wet, and as we have had a lot of rain this past winter and spring there are a lot of them. What can I do to get rid of them?

A. Sowbugs are light gray to slate-colored, with slightly elongated bodies that can reach 1/2" length. The body is distinctly segmented, has 7 pairs of legs, 2 pairs of antennae and 2 prominent tail-like appendages. They are nocturnal in habit, due to their susceptibility to desiccation. Pillbugs are dark gray to black, and are not as flat as sowbugs. The body is distinctly segmented with 7 pairs of legs and 2 pairs of antennae. The abdomen has no tail-like appendages. Unlike sowbugs, pillbugs can roll into a tight ball when disturbed. This response makes them easy to distinguish from sowbugs and has earned them the nickname "roly-poly." Pillbugs are nocturnal and remain inactive and hidden under objects during the day to reduce water loss. Avoiding water loss is important for them because they lack an outer waxy layer and cannot close their respiratory system. This leads to dehydration at low humidities. Pesticides may be used in areas where sowbugs, pillbugs, and millipedes persist despite sanitary measures. To reduce migrations into homes, treat the outside foundation and adjacent ground in a strip about 3' wide with a dust or aerosol spray that is labeled for these pests. Read the label and follow all label directions when using pesticides. If the label does not include sowbugs, pillbugs, millipedes or centipedes, it should not be used to manage these pests. For homes in or near wooded areas that contain large amounts of organic matter and moisture, it may be necessary to treat a strip around lawn edges and adjacent to the woods. A dust or granule formulation is best in this case. Reapplication is needed after a heavy rain. CAUTION: When using aerosol formulations of pesticides, do not allow small children or pets access to the treated areas until they have completely dried. When using dusts or granule formulations, keep children and pets out of treated areas following rain or watering.

Holly writes~
I live in the Phoenix area and have a garden in both winter and summer. Last year I grew melons, squash and watermelon and was inundated by what I call 'squash bugs'. They look like on oversized tick. What are they and how do I keep them from coming back again this year?

A. Adult squash bugs Squash Bug (Anasa tristis) are flat, gray colored insects, 13-19 mm long, with wings that do not extend the length of the abdomen. Unmated adults overwinter near field edges and in crop debris. They become active again in June as they emerge from overwintering and begin to lay eggs. Orange colored eggs 1.5 mm long are deposited on the underside of leaves, usually along two veins. Egg laying continues for approximately 45 days at a rate of 10-20 eggs/day. Because of this extended period of reproduction and the fact that squash bugs develop through 5 nymph stages, squash bugs in all life stages can be found at any one time during the summer. Eggs require 7-14 days to hatch into wingless, pale green nymphs and pass through 5 nymph stages over 5-6 weeks. Approximately 1-2 generations are completed each summer. Squash bugs prefer Hubbard squash, summer squash and pumpkin but any variety can be attacked. Nymph feeding on leaves causes them to yellow and wilt. Rapid wilting attributed to squash bug feeding can be reversed if the infestation is halted. Nymphs and adults will also feed on and damage fruit. Control of squash bugs is difficult since the nymphs feed primarily on the undersides of leaves, protected from insecticide applications. This makes scouting for the insects very important in a management program. Observation of one egg mass per plant is enough to warrant insecticide treatment at flower stage. Insecticides are most effective while nymphs are small. Check with your local pesticide suppliers for the best product to use and follow directions. Insecticide control options include Carbamates, Pyrethroids and Organophosphates as Diazinon. Repeat applications will be necessary throughout the season making sure to spray the undersides of foliage and when rain is not forecast. Wash vegetables completely and carefully when harvested.

A portion from Department of Entomology, University of Minnesota.