Last year I shared this post about my great love for zucchini and my complimentary great hatred for squash bugs and vine borers. I also shared about my equally passionate distaste for white powdery mildew and anthracnose. All of these pests/problems plagued my curcurbits (zucchini, melons, squashes) in our 2012 season. Since then I’ve taken steps to minimize the impact of these Axis of Evil members on my garden, including:
1. No mulch around squashes (it provides a place for bugs to hide)
2. Companion planting of radishes as a trap crop for vine borers
3. Companion planting of beans to provide extra nutrients to cucumbers
4. A bi-weekly application of neem oil
I can’t comment on how effective my no-mulch system has been because it’s difficult to measure how much squash bugs hide. However I can say that with all of these methods combined, I have seen only one case of vine borer damage and only recently (last week) have I seen any squash bugs. Also, I have had zero anthracnose issues and only a limited powdery mildew issue on some golden zucchini. (The golden zucchini are planted in a hugelkultur bed where the soil is 100% native, sandy soil. These plants – presumably – are suffering from having fewer nutrients than our compost-planted crops in other hugels and they have struggled the most of all the producing plants this summer. That being said, they are still producing, even if only a small amount.) Though I clearly still have work to do regarding the insect invaders in my garden, I’m pleased to say that I seem to have found just the right trick to keeping mildew and anthracnose at bay: Neem oil.
What is Neem Oil?
Last year’s issues with these diseases was awful with a capital BAD! In researching the issue, I discovered that neem oil can be a natural solution. What is neem oil? So glad you asked…
According to Wikipedia:
Neem oil is a vegetable oil pressed from the fruits and seeds of the neem (Azadirachta indica), an evergreen tree which is endemic to the Indian subcontinent and has been introduced to many other areas in the tropics. It is the most important of the commercially available products of neem for organic farming and medicines.
The site goes on to say:
Formulations made of neem oil also find wide usage as a biopesticide for organic farming, as it repels a wide variety of pests including the mealy bug, beet armyworm, aphids, the cabbage worm, thrips, whiteflies, mites, fungus gnats, beetles, moth larvae, mushroom flies, leafminers, caterpillars, locust, nematodes and the Japanese beetle. Neem oil is not known to be harmful to mammals, birds, earthworms or some beneficial insects such as butterflies, honeybees and ladybugs if it is not concentrated directly into their area of habitat or on their food source. It can be used as a household pesticide for ant, bedbug, cockroach, housefly, sand fly, snail, termite and mosquitoes both as repellent and larvicide (Puri 1999)[not specific enough to verify]. Neem oil also controls black spot, powdery mildew, anthracnose and rust (fungus).
Where to Get Neem Oil
You can order neem oil online or you can buy it at most home improvement stores. I purchased Natria Neem Oil from Home Depot for about $15. Options include a concentrate which you mix with water or a ready-to-spray formula that has already been diluted with water. I selected the concentrate because I felt it would stretch farther based on the quantity in each bottle. (I also purchased a 1 gallon sprayer similar to this one so I could have a dedicated container.) The Natria Neem Oil says “for organic gardening” right on the package, however I’ve noticed since that other neem oils are listed as being organic themselves while this is not. The next time I purchase neem oil, I’ll select something from the OMRI (Organic Materials Review Institute) approved list, which you can find here. The OMRI website also has a “Where to Buy” section.
How to Use Neem Oil
The most important thing to keep in mind is that you must follow the direction on the container! My neem oil is concentrated so I combine a small amount with water. Because neem oil can burn plant leaves under lots of sun exposure, its best to spray plants early in the morning or late in the afternoon. I usually spray in the afternoon because there is still enough daylight/warmth to dry the leaves but I don’t have to worry about a noon-day sun showing up a few hours later. I use neem oil on plants which tend to have disease or pest issues in my garden: Broccoli, cauliflower, squashes, melons, cucumbers and tomatoes. Although the packaging gives no limitations regarding spraying greens, I don’t spray it on any crops where the leaves are going to be eaten. The packaging for my neem oil says that weekly applications are permissible and recommends use either once a week or every-other week. I started in May with weekly applications and transitioned to bi-weekly in June. (On off weeks I fertilize the garden with diluted fish emulsion. With that said, things grew well in July and I confess that I haven’t fertilized in over a month.)
For more info about neem oil – including info on toxicity in humans and animals (hint: there is little to none) check out this link: http://npic.orst.edu/factsheets/neemgen.html#whatis
So far, I’m thrilled with the results. Neem oil has enabled me to effectively stave off white powdery mildew and anthracnose in my garden. Although I can’t say for sure that it has been effective at warding off vine borers and squash bugs, its effectiveness might increase if I used it weekly instead of bi-weekly. Before I go there, my next attempt at squashing squash bugs is going to involve a hungry chicken! I’ll let you know how that goes…
Anyone else use neem oil? Other natural fungicides or pesticides? I’d love to hear your ideas!