Well, I have a problem. All of the broccoli and cabbage transplants that I put out a couple of weeks ago are now gone. Something has eaten every last one of them. So, this weekend I will be replanting and trying to figure out how to control whatever it is that is eating my brassicas. Since I will be applying organic pesticides this weekend I thought this would be a good opportunity to review some of the major organic herbicides and pesticides available to the home gardener.
- Bt– Bacillus thuringiensis has been used to kill soft bodied pests in the organic garden for a very long time. I suspect that what is eating my broccoli is either a little green caterpillar called the cabbage worm or another green caterpillar called the cabbage looper. Both of these pests can be controlled fairly well with Bt. Like all pesticides, organic or not, Bt should be mixed for a single use. Bt rapidly degrades in the sunlight. Because of this, spray the plant late in the evening, covering all areas of the plant where the bug will eat. If you mix too much Bt, add more water too the mixture and leave it out in the sun. In 48 hours the mixture will be completely inert. NOTE: Bt does not kill pests mmediately. You may need to apply three times to get maximum effectiveness
- Spinosad –. If you pests are tougher than caterpillars you will need to use spinosad. Spinosad is a live bacterium that speeds up a pest’s metabolism to the point where they stop eating and die within a couple of days. Spinosad has been shown to be effective against caterpillars, leaf miners, fire ants, hornworms and even fleas. Like Bt, spinosad breaks down in heat and sunlight. However, it can remain active for five to seven days. Only use spinosad if Bt has failed as it will kill bees and other pollinators
- Neem oil – Neem oil is a plant extract that is mostly effective against aphids and scale insects. It can kill some insects if they are covered when they are very young (rigt after hatching). It has also been shown to prevent some insect eggs from hatching. It is not very effective against mature beetles like stink bugs or other leaf footed bugs
- Acetic Acid – Acetic acid is available in concentrations up to 20%. Concentrated acetic acid is very effective on a wide range of both grassy and broadleaf weeds. I have seen dandelions and crabgrass begin to wither 30 minutes after the initial application. Vinegar is best when applied to young plants. Established weeds may need a second or third application to finally kill them. Be careful when applying vinegar. Overspray can kill things you don’t want to die. I use a spray bottle and a shield when spraying close to my desirable plants. If you want to spray a wide area, then a pump sprayer works well too.
- Horticultural Molasses – Neil Sperry recently said that Nut Sedge (grass) is the cockroach of the gardening world. I agree. I have tried everything to control nut sedge. This year I read an article by Howard Garrett (The Dirt Doctor) about using horticultural molasses. Well, I tried it and it works—kind of. While it killed all nut grass in the cracks of my brick patio, it did not do much damage to the nut grass that was growing in my beds. I applied the molasses at full strength.
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