Plant Stress and Disease Management

(Soil bacteria can cause Potato Scab. Acidic soil prevents this.)

Planning for the next growing season should include stress and disease management strategies because they can significantly change the layout of your garden, your gardening activities, and your choices of plants. Strategies (in no particular order) include rotation, 2 season holidays from some plants, mulching, target watering, companions, weeding, isolation in containers, quarantine, surgery, thorough debris clean up, disinfecting tools & supports, and total plant destruction.

To every solution there is usually both a plus and a minus. Do not expect garden perfection as there are too many variables which change from year to year: weather, soil quality, seed viability, compost composition, mulch, insects, viruses, fungus, bacteria, weeds, critters, curious people, and gardener’s practices. What worked well last season may not be so terrific this season (e.g., this year we had to discard over 2/3 of our garlic and ½ our onions).

Healthy plants need sufficient sun, nutrients, root room, air circulation throughout the foliage, and healthy soil that is biologically diverse, mycorrhized, aerated (yes, air at the roots), moist, and well drained, — never swampy. Actually, more plants die from drowning (slow process not too obvious until leaves turn yellow) than die from thirst (fast and obvious in the sad, drooping plants). Plants also experience less stress if we reduce competition for nutrients, sun, and root room.

Facts:

Gardens have helpful & harmful fungus, bacteria, insects, plants, animals, people, and weather.
Plants do well in some soils but poorly in others, and soil composition affects taste (e.g., mild globe radish or hot globe radish).
Healthy plants can tolerate a few bugs and some fight back by increasing leaf toxins when under attack (e.g., potato, rhubarb, tomato).
Plants have different nutritional needs and draw different quantities of nutrients at different depths in the soil, and at different times of the season. Soils are weakened by too much water. Excess water brings salts to the surface (looks just like salt on your winter boots), and washes away plant nutrients.
Weeds thrive in specific conditions, which we gardeners are very good at creating! Weeds grow faster and compete with our plants for food, water, sun, and root room, thereby weakening the crop.

Some Signs of Distress

(Nutrient deficiency — e.g., pale-yellow leaves = nitrogen deficiency; purple leaves = phosphorus deficiency; tomato/pepper blossom end rot = calcium deficiency) – for tomatoes/peppers, add calcium, potassium, and magnesium (Epsom salts & powdered milk ¼ cup each, raked & watered in per plant).
Septoria leaf spots from fungus shows on older leaves 1^st (add potassium to soil — the K in NPK — K is in banana peels in your compost).
Powdery mildew: spray 1 Tsp baking soda + 1-liter water, or milk & water 50/50 – do not rinse (I have used both; milk seemed to work better!).
Thirst: drooping leaves and weak stalks (add water to the roots).
Drowning: leaves turn yellow and then shrivel to brown and dry (reduce water, aerate, and/or re-pot).

Air borne and soil plant stressors

Fungus has fruiting bodies that produce spores [some of these have fascinating shapes and colours! But not a particularly happy find!].
Bacteria start as a dimple and eats into the skin of the leaves & fruit in spots; [e.g., tops of wet tomatoes].
Viruses produce odd motley colours, deformed parts, & irregular variation in leaves and structures (e.g., mosaic virus via cucumber beetles destroyed our zucchini and cucumber plants; parrot tulips are created by the deliberate introduction of controlled viruses).
Surgery: On a dry day (no rain or dew), cut and green bin, yard waste, trash, or burn (propane torch) diseased material, clean up all disease debris from soil [do not compost], and clean garden tools and gloves [hot soapy water, rubbing alcohol, hand sanitizer, or diluted bleach] to avoid transfer of diseases. Add compost 4 cm 2x/year [fall or early spring & mid-season] – compost neutralizes disease over time, balances pH, adds nutrients, retains moisture, and improves soil structure.

(Bacteria Dimple + Fungus in the breach)

Tips

A: wet tools and gloves can pass disease to other plants as you work.
B: if the whole plant is diseased, put a bag over the plant first, pull it out of the pot or plot, and empty the plant into the green bin, yard waste, or trash.
C: blossom end rot on tomatoes and peppers is a nutrient deficiency, not a disease so compost these asap – don’t let the plant feed energy to fruit you will not eat! Epsom salts and powdered milk adds magnesium sulfate & small amounts of potassium & calcium but this is not a quick fix! When transplanting, place crushed eggshell or bone meal and compost in the bottom of the transplant hole to help tomatoes and peppers.

(Tomato Blossom End Rot)

Pro-active anti-stress strategies for plants

Organic mulch (e.g., shredded leaves, grass clippings, straw) + an underlay (cardboard, newspaper, or landscape fabric) will reduce weed pressure, conserve water, reduce erosion, discourage some hurtful bugs from egg laying, protect the life in the soil, reduce soil splash, and keep leaves & fruit from contacting soil.
Tip: Compost is not a mulch; it may increase weeding because it is so fertile and it only becomes a new bed for migrating weed seeds, cat toileting, and squirrel gardening. Best to spread organic mulch over the compost. We have had best results with shredded leaves (use a leaf vacuum or a mulch mower – I use both depending on how wet the leaves are).
Note: Plastic sheeting, whatever the colour, and old floor coverings are not recommended as mulch: plastic prevents water and air from getting to the soil and floor coverings add chemicals and synthetic materials to the soil as they weather. Cover the soil – if you don’t, nature will!

Handy solutions for spot weeding in lawns, patios and driveway brick: propane blow torch, boiling water, pure vinegar spray (but spray twice and drench plant roots both times), or dog urine (sure burns holes in my lawn!).

No-Till gardening –– disturbing the soil as little as possible keeps weed seeds buried and protects the helpful life in the soil (e.g., worms, insects, nematodes, fungus webs….). Tilling disturbs all living things in the soil, brings weed seeds to the surface, and chops up weeds which can re-grow from the many cuttings. Gardens that do not need tilling are raised beds, box beds, cold frames, large immovable containers, and all movable containers.
Tip: when weeding, wear gloves, remove and discard seed heads (especially dandelion heads), and compost the weeds (full of plant ready nutrients) or cut and drop them on the soil surface to act as fresh mulch.

Containers are very helpful additions to rotate plants, inter-plant flowers and herbs, and to isolate invasive plants (e.g., mint, lily of the valley). Containers have fewer insect and disease stressors, but they do dry out quickly and increase the need for water and protection from wind and a hot sun.

Follow watering guides: wet & dry periods for some (e.g., aromatic herbs), vs. continually moist for others (e.g., especially tomatoes and peppers) – but no swamps! Water 2x each session, and water plant roots only, not leaves (wind blown fungus spores & bacteria cling to water droplets on wet leaves).
Tip: use a watering can, soaker hose, or hose with a bubbler or water wand to target the root systems. However, a watering can allows the gardener to closely observe each plant and catch problems caused by insects, wind, water, sun, disease, nutrient deficiencies, animals, or people before they become major issues. Sprinklers and hose guns keep gardeners at too great a distance.

(Excess Water : carrots are hairy with center rot)
Tip: A thirsty plant needs a drink, not a bath. Apply water to the roots only so water is not wasted through evaporation, watering weeds, and wetting unproductive garden spaces like walkways and borders.

Plant Rotation offsets nutrient loss to leaching and heavy feeders, disease collecting in the soil from bacteria and fungus spores, and insect eggs & larvae in-ground near their favoured plants.

(Septoria)
Heavy feeders – the larger the plant & fruit, the heavier the feeder, and the sooner the nutrients are depleted (e.g., Corn, Cabbage Family, Rhubarb, Tomatoes, Vines).
Rotation Cycles of 3 to 4 years are best! Rotation suggestions: Greens (lettuce, endive, herbs) followed by Fruits (tomatoes, squash, corn, …), then Roots (carrots, turnip, beets, …) and finally Legumes (beans & peas replace nitrogen). Then start over with Greens.
Add compost (4 cm) every year regardless of plantings, and try adding containers for a year or two to help with rotation. Also consider plant holidays (1-2 years), or simply do not grow plants that are always in trouble and demanding frequent attention. We are taking a holiday from squash and cucumbers because of persistent. cucumber beetles which have brought mosaic virus 2 years running, and we also have squash vine bore! Yes, we even tried containers. We will wait a few years and try again.

(Mosaic Virus from aphids or from cucumber beetles)

Other Preventative Measures

Ensure sun requirements by trimming bullies that shade other plants, planting tall plants on the north side, and protecting shade tolerant plants from too much sun.

Increase the strength of the sun: brick wall, stone wall, light coloured siding, aluminum foil covered cardboard, mirrors, cold frame, greenhouse, plastic or glass shelters, domes, or cloches .
Reduce the strength of the sun: window screen, plastic mesh (black or green available), borrow a canopy mosquito screen, or add tall plants (e.g., sunflower).

Set a windbreak if necessary, to reduce windborne diseases, wind destruction, & premature drying (use other sturdy plants, hedges, row covers, fences …).

Add vertical plant supports (tripods, trellis, netting) to get plants up off the ground and away from the problems that stress them. I have even used cardboard or bees wax coated cloth to separate plants and fruit from the soil — ugly, but effective.

Maintain air circulation (thin bushy plants) to lower humidity and reduce fungus growth, and aerate dense soil (container soil condenses with each watering or rainfall, preventing air from getting to plant roots) — loosen the soil but do not cut roots. A 2-prong Jekyll weed fork is ideal.

Choose companion plants that will attract pollinators and insect predators, discourage the harmful insects, and encourage plant growth (e.g., put basil with tomatoes and both will prosper, or put marigolds with tomatoes to create a scent that will confuse or repel bugs. Sage and the Brassicas family help each other).
Tip: the effects of companion plants are subtle & not immediately noticeable, but they do work! Nevertheless, don’t hold your breath while waiting for a result.

Keep an eye on the individual vegetables, herbs and flowers – a lot can happen in a very short time, as many weekend-only gardeners will tell you. Bugs can defoliate, weeds can overtake, and rain can cause a spurt in growth just when you thought the garden had stalled. With rain, plants will stand tall and green, fruit will swell and ripen, and flowers will add colour, texture, and fragrance.

A Happy Garden Makes a Gardener Happy!

(Happy Sun Screened Greens)