Gardening: How to minimize garden pest and disease problems next year
How do I avoid pests and diseases? Give plants what they need for optimal growth. Plants growing in great soil with appropriate amounts of sun and moisture are generally healthy plants. It has been scientifically proven that healthy plants are less attractive to pests and diseases.
A corn plant that is pumped up with chemical fertilizer, for example, is more attractive to corn borers than one that has been raised organically and had its soil amended with manure.
I attended a lecture by Dr. Larry Phelan of Ohio State University in which he presented results of trials comparing conventional corn with organic corn. His data was convincing. Yes, chemical fertilizers can produce big yields, but excess nitrogen from chemical fertilizers will attract borers.
Then there is the problem of tomato hornworms. These nasty, aggressive critters are a real problem for some gardeners, but I have not seen one in my tomato patch in years.
Why? I'm not sure, but the last time I saw one, it was being parasitized by small wasps.
If you see what look like grains of rice on a tomato hornworm, they are being attacked by a braconid wasp. The "rice" grains are larvae that are slowly sucking the hornworm dry. If you see this happening, don't kill the hornworm. Just remove it (wearing gloves) and carry it far from the tomatoes. The larvae will do the rest.
How can you encourage parasitic wasps to live in your garden? First, do not kill them — though they are not very noticeable. And do not use chemicals to kill other pests such as Japanese beetles or potato bugs.
I have a small "home" for solitary wasps attached to my barn. It is a box filled with bamboo tubes of different sizes, their ends facing out. These tubes offer shelter for insects and places where they can lay eggs or stay out of danger. I don't see it used much, but I know that solitary wasps do need such places. Nature offers the best places, I'm sure, so if I don't rake and manicure every inch of my property, a naturalistic setting offers many sites for good bugs. Mother Nature, left to her own devices, tends to have a balance of good critters and bad. I try not to second guess her too often.
But what about introduced species that are a problem with our crops? They can easily cause damage and get out of control. One such pest is the spotted winged drosophila (SWD), an Asian fruit fly that arrived in 2011.
Instead of just eating overly ripe fruit laying on the ground (as most native species do), this one will attack good fruit on the bush. Mushy fruit (complete with bugs) is the result. Blueberries have been severely affected in some places.
I recently phoned Dr. Alan Eaton, the state entomologist for New Hampshire, to see if any progress has been made in controlling this pest. No, he explained, they are still in the learning phase at present. Early reports had suggested that early-ripening crops of blueberries and strawberries were less susceptible to SWD. But he told me that this year they were finding earlier and earlier reports of damage. And this year they had reports of SWD on cherries for the first time.
These fruit pests are just one twelfth of an inch in size, so netting (always a friend to organic gardeners) musts be very fine to keep them off our crops. Most commercial growers are resorting to chemical sprays. Me? I'm rooting for the birds and other insects to take charge.
So what can you do to reduce chances of pest and disease problems next year? Clean up your garden well this fall. Apple scab, for example, causes deformed, inedible fruit. The disease can be minimized by simply raking up leaves and fruit - right now. This year I took it a step farther and used a pole to knock off any apples left on the tree, and raked them up, too. Many of those left on the tree were clearly rotten. I've read that spreading compost under apple trees introduces beneficial microorganisms and might help control diseases, too.
According to Dr. Eaton, destroying vines and leaves of plants in the squash family — cucumbers, squash, pumpkins, melons etc. — is important at this time of year. Striped cucumber beetles over-winter in plant debris, so getting your garden clean is important. I put vine and tomato plants on my brush pile and burn it once snow has fallen, but you can also bag it and send it off with household trash. Composting is not usually an effective way of ridding your garden of these pests.
Remember: well-tended plants are less susceptible to diseases and less attractive to pests. I am always amazed at how healthy my garden is despite — or because — I use no chemicals and have always used organic methods. It takes a while to develop a good supply of beneficial insects, I suppose, but get started.
Henry Homeyer is a UNH Master Gardener and the author of four gardening books. He is available to give talks at garden clubs and libraries. Reach him at firstname.lastname@example.org or P.O. Box 364, Cornish Flat, NH 03746.
TALK TO US
If you'd like to leave a comment (or a tip or a question) about this story with the editors, please email us. We also welcome letters to the editor for publication; you can do that by filling out our letters form and submitting it to the newsroom.