From The Garden of Ed. Submitted for publication in The Towne Crier on July 26, 2006
What's Goin' on in the Vegetable Patch? "The Da Veggie Code"
About this time in the growing season, some home vegetable growers are seeing less than satisfactory results with some of their crops. As promised, this is a continuation of my last column (introductory), "Questions to ask when diagnosing Flora's problems". It is Part 1, "Vegetable Problems Diagnoses". It consists of lots of questions to ask and lots of information about preventing or correcting crop problems and their potential failure. I'll even point out some problems that aren't your fault at all.
Remember I asked you to engage all your senses! Here we go! Do you have a notebook? It's invaluable for each year you garden.
Question about Symptoms:
Are plants wilting? Are there signs of leaf damage? About the leaves that are affected: Yellow or brown? Where most noticeable? Leaf edges, or center of leaf? Which leaves are showing symptoms? Young at top and outside of branches, or older, mature leaves lower on the stems? Are there spots on leaves and stems? Are they all about the same size and shape, or are they a mix of many? Are leaf symptoms evident on both sides of leaves?
Do all the vegetables have the same symptoms or is it confined to one or two vegetables, maybe in the same family? Are the affected plants along a garden edge or defined area, or are they uniform throughout their planting area? Are the affected plants in a wet or poorly drained area, or in an area once compacted by heavy equipment?
When did you first spot the trouble? Any fertilizer used? What type (NPK) and what rate (#s per 100 feet, or whatever)? Did you record the weather conditions before and during the appearance of the problem? Have you mulched any of the vegetables? If so, with what and when? Have you or a neighbor applied any kind of broadleaf herbicide to control weeds?
Here begins the hands on detective work. Examine the plants carefully. Take an impacted leaf sample and look closely for insects or evidence of insect feeding damage. I use a small 10-power hand held lens. Works great, and it's inexpensive. Early morning or late afternoon is the best time to look. If you find an insect, don't assume it is the culprit. Drop it in a little rubbing alcohol (35mm film canisters are my favorite and this preserves all the body parts, so they are recognizable when examined very closely), and try to identify it, or, have it identified. Don't forget to check the stems, too.
This next step is still investigative, but now we are seeking signs of disease. Are there dead areas on stems, leaves or flowers? Are plants wilting even though there is adequate moisture? Are leaves covered with spots or yellowing areas? Are any of the plants stunted or showing growth abnormalities? If so, is it all plants, or just certain ones? Where are they located?
Nutrient deficiency is one possibility, but not normally the likely one.
Nutrient surplus resulting in toxicity usually from excess salt injury will show up as wilting even in moist soils. Excess fertilization may cause leaf margins to appear scorched or browned.
Application of wood ash is equivalent to a half application of lime, about one to two. Never use more than 4 to 5 pounds of wood ash per 100 square feet of garden area. It is the same as 2 to 2.5 of lime. A soil pH of 6.5 to 6.8 (slightly acidic) is near to ideal for growing most vegetables. Too high a pH prevents plants from taking up necessary nutrients, or makes others toxic.
Moisture supply is essential, but it can be overdone. Every year I hear about someone who waters the garden every morning. Two inches of moisture per week is usually adequate. If you are growing on compacted soils or poorly drained soils, the soil may be staying too wet and the results can be severely stunted plants or plants whose roots are beginning to rot from lack of oxygen.
Were any pesticides applied recently? If done in hot weather or in full sun, plants could experience a phyto-toxic reaction and be damaged. Fungicides usually contain either copper or sulfur, or both, and can burn foliage when applied in these conditions.
Herbicides such as Round-up and other broad spectrum weed killers can drift on the slightest breeze and damage or even kill tomatoes, for example, which are especially sensitive. Unless you know where your mulch came from and that it has no residues of herbicides, it, too, could be a possible cause of plant stress or failure.
Temperature extremes, wind, hail; drought and flood all can play a key role in the garden's success or failure. No recent frosts have been reported. But, yes, high winds and hail are always possible in summer thunderstorm conditions.
You are probably seeing a trend in these questions and comments. Many of them overlap or suggest one another. I know this is a lot from many points of view, but in review, you'll find it worth the trouble. I promise you, if you were to take a vegetable problem to a Cornell Coop. Ext. Master Gardener, these are some of the very questions you'd be expected to answer on a questionnaire. I know. I developed and updated many of them myself.
The plant and its history:
Name of plant, particular cultivar, disease resistance, and date planted? Planted from seed or small transplant? How are weeds controlled in the garden? How much sunlight do plants receive per day? How is the garden irrigated? Hose, sprinkler, overhead? How often?
Nutrient deficiency (too little), and toxicity (too much) can elicit disturbing symptoms in foliage, growth habit, bud growth and so on. I will go out on a limb and say that most of these occurrences are where the soil pH is below 5.5 or above 7.2.
To get a clear picture of nutrient deficiency or toxicity, almost always, fresh foliage samples need to be submitted to a lab for verification. It's real botanical science. Keep the soil pH in the right range and you should be surprised to have any nutrient problems if you are growing in average to improved soils.
Fruit set: If I had a nickel for every question/complaint about healthy looking plants that fail to set fruit, I'd be, well, "okay" for sure. Fruit set in most vegetables is a problem in a few special cases, and these are not rare: High temperatures (90s) and low temperatures (50s to 60s) disrupt pollination processes and result in poor fertilization or complete lack of it.
Plants suffering from drought or severe wilting during flowering will also not be successfully pollinated.
The gentlest breeze pollinates plants that are "perfect" or "complete". Peppers and tomatoes are examples.
Plants that have separate flowers for pollen production (male), and fertilization (female) need to be blossoming at the same time, and rely on insects or birds to carry the heavier pollen. When weather conditions don't favor their interplay, the flowers remain unfertilized. Everything has to be right, or you will have to step in with a small paintbrush and do the job normally entrusted to nature.
Remember all cucurbits have male and female flowers that both need to be present at the same time with pollinators ready to do the job. This means squash, pumpkins, cucumbers, muskmelon, watermelon and cantaloupe need bees or other flying insect pollinators to complete the process. Rain, pesticide use, too cool temperatures can all play a role. Keep the small paintbrush handy.
Fruit set is a small miracle! Don't overlook this marvel of nature. One element out of sync, and there may be no fruit set. Too wet, too dry, too stressed a plant. Look at the questions again. They spell out a lot of the answers.
Close on the heels of poor fruit set is the common cry, "My plants are so big and strong and healthy. Why isn't anything being produced?" This can apply not just to fruit set, but to heading of cauliflower, cabbage, broccoli, Brussels sprouts, development of carrots and radishes, onions, parsnips, potatoes, and the other produce we hope for. The first and most obvious explanation is these plants are likely suffering from what might be the equivalent of steroid abuse. Excess nitrogen results in luscious green foliage.
Two things about this: First, all this tender abundance is extremely inviting to all manner of leaf sucking and chewing insects; second, this practice of over fertilizing with nitrogen sources keeps the plants in the vegetative mode. We're in this for produce. We need to have plants in the reproductive mode. This is generally in the mode where they are nutritionally (as far as N goes) deprived, so that as a result, they wish to reproduce, to propagate themselves in response to the N shortfall. This might be storage roots, delectable fruit, and even flower heads (cauliflower and broccoli, for example). Too much manure or other source of Nitrogen is very common, and the insects that find all the good eatin' are usually blamed (wrongly).
Some plants, even when properly fertilized, will switch from vegetative to reproductive mode when least desired. This is called bolting. Witness spinach, lettuces, and chard, as well as many herbs. The heat and long days send a signal that it's time to produce flowers and seeds. Out of your control. Plant earlier or later, when temps are more moderate. Or seek a shadier spot for these cooler loving plants.
Make every effort to keep soil moisture even, with as few wide fluctuations as possible. I recommend using a moisture meter if you have doubts. They are generally around $10 to $12. But, then you'll need a notebook, too. Blossom end rot in tomatoes and peppers are usually a result of uneven moisture to the roots.
Did you know that even snap bean flowers won't develop in temperatures above 90 degrees F. So, if the easiest isn't going to work, forget about tomatoes, peppers, eggplant, and other nightshade family members. Favorable conditions rule.
A word about Insects:
I haven't said a lot about insects up to this point. It's time I did.
There are two classes of insects if defined by their eating habits: those that chew and those that suck.
Chewing insects include many types of beetles and larvae (worm-like or caterpillar forms) because their mouthparts are designed for just that. Flea beetles, garden slugs, tomato hornworms are examples.
Sucking insects have slender beaks, not unlike mosquitoes, that they insert into leaves and stems and extract the plant juices. Aphids, whiteflies, and leafhoppers are examples. These come with the added threat of injecting viruses into the plant as they feed. These viruses can do more damage than the feeding itself.
There are many more insect pests including general leaf feeders like grasshoppers, crickets, katydids, earwigs, stinkbugs, thrips and several others. There are as many again that are larvae that feed on squash, onion, spinach, tomato, and corn among other crops. There are beetles that will feed on asparagus, beans, cucumbers, potatoes, melons, tomatoes, etc.
As far as diseases of vegetable plants go, there are far fewer than insects you need concern yourself with. Some of the fungal diseases are soil borne, and for these there is no cure. If they do not show up in your garden, be grateful and be sure to rotate your crops each year and you will likely not introduce anything so damaging.
Always choose disease resistant or tolerant plants when available. If you usually put in transplants, bring your hand lens with you to market and examine them closely for insect or disease symptoms before purchasing them. The seller will have that much more respect for you.
I must repeat what I said a few columns back. The number of pests you are likely to encounter in your vegetable garden will probably not surpass a dozen or so, including both insects and diseases. A watchful eye is your best defense. Best cultural practice in the garden is your strongest partner. Soapy water is great against many insect pests. Good garden sanitation is best to control diseases.
Assuming your garden is in a sunny, well-drained location, and assuming your soil has been improved somewhat by incorporating rich compost and/or well-aged manure, the rest is up to you. Space plants far enough apart so that when mature there will still be plenty of air circulation between them. Poor air drainage encourages disease and its spread. Use a rain gauge and aim for even moisture for all your vegetables. Mulch to conserve moisture and control weeds. Work on your garden when plants are dry. Remove any unhealthy plant matter as soon as noticed (clean, sharp tools are best) and throw in the trash. At the end of the season, clean up and discard all crop debris. Then sow a cover crop that will grow this fall. Plan to plough in or turn under this "green manure". This practice encourages friendly bacteria and discourages infectious ones.
So, "The Da Veggie Code" excerpt is before you. Fact or fiction? You decide. If you've got a patch, I hope you are a believer.
From The Garden of Ed. Submitted for publication in The Towne Crier on July 26, 2006
© 2006 Ed Mues. All Rights Reserved.