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Cucumber mosaic virus (CMV) is a plant disease-causing virus that has a worldwide distribution and a very broad host range. It was named so for one of the first plants in which it was found, the cucumber.
CMV is found predominantly in temperate areas around the world. CMV cannot live in extremely dry conditions. The optimal temperature at which CMV expresses itself and shows symptoms appears to be between 79 and 89 deg. F.
The CMV is very minute and is made up of ribonucleic acid core which is surrounded by a protein coat. They have no mode of self-dispersal; hence rely on various vectors to transmit them from infected to healthy plants. Once the virus infects a plant cell, the protein coat dissolves and the nucleic acid portion takes over the cell’s nucleic acid and protein synthesis systems and directs them to produce more viruses, thus disrupting and affecting normal activity in the cell. CMV cannot survive for long outside a cell or if the cell dies and can multiply only inside a living plant cell.
CMV may be spread from infected plants to healthy plants in the following ways:
- Several aphid species serve as vectors for CMV
- Mechanically by humans and tools through cultivating and even touching healthy plants after touching infected plants
- Through grafting
- Can also be transmitted by seed
Vegetables and fruits such as cucumbers and other cucurbits, squash, melons, bananas, artichokes, peppers, beans, peas, potato, tomatoes, carrots, celery, lettuce, spinach, beets, various weeds and many ornamental and bedding plants such as lily, delphinium, primula and daphne.
Damage and Symptoms
The following symptoms are may be associated with CMV:
- Mosaic yellowish patches or green and yellow mottling on leaves
- Stunted growth due to shortening of the internodes (length between stem and leaves)
- Downward curling of leaves that are distorted and small in size
- Distinct yellowing of the veins only
- Ring-spots or line patterns on leaves or fruits
- Reduced yields and distorted fruit and flowers
- White streaks on flowers known as “breaks”
CMV shows symptoms on leaves known as the “Shoestring” effect for most host species. This phenomenon causes young leaves to appear narrow and the entire plant to be stunted.
Specifically CMV can cause cucumbers to turn pale and bumpy. The leaves turn mosaic and their rugosity is changed, making leaves wrinkled and misshapen. Plant growth is stunted, few flowers are produced, and fruits are oddly shaped and appear gray. Cucumbers like this are often referred to as “white pickles”. Infected cucumbers are often bitter.
In celery, CMV can cause streaking and spotting. In lettuce, infected plants show symptoms of chlorosis, stunting and often do not properly form heads.
Pepper plants often have severe foliar damage, noticed as mosaic and necrotic rings. The peppers are often misshapen and contain chlorotic rings and spots.
Tomato plants when infected by CMV are usually stunted and have poorly shaped leaves, or “fernleaf”.
The CMV overwinters in perennial weeds, flowers and often crop plants. In spring when plants bloom and grow the virus emerges in the top leaves where it may be transmitted to healthy plants by aphid vectors (although tomatoes are not the preferred host of aphids) or by mechanical means. CMV cannot withstand very dry conditions nor can it persist in the soil. It also is more difficult than tobacco mosaic to transmit mechanically. Thus, cucumber mosaic tends to progress more slowly than tobacco mosaic in a field or garden.
Organic Means of Control and Prevention of Cucumber Mosaic Virus
There aren’t any known substances that cure a plant of CMV, nor any that can protect it from getting infected. Hence control measures for plant viruses include prevention and eradication.
– When purchasing seeds and plants, ensure that they are virus-free.
– Strictly maintain and prevent aphids from infesting your plants. Here’s an Aphid control guide.
– Remove all weeds as they are likely sources of both CMV and aphids. Groundsel and chickweed are particularly likely to harbor CMV.
– Immediately set aside suspect plants and obtain a diagnosis. CMV infected plants must be destroyed.
– Apart from aphids, CMV can be transmitted through gardening tools and by contact with infected plants. Maintaining clean and sanitized tools, machines and hands can go a long way in preventing the transmission of CMV.
– Use resistant varieties whenever possible. Zucchini- ‘Supremo’, ‘Defender’. Bush marrow- ‘Badger Cross’, ‘Zebra Cross F’, ‘Tiger Cross’. Cucumbers- ‘Bush Champion’, ‘Crispy Salad’, ‘Jazzer F’, ‘Paskia Fi’, ‘Petita’, ‘Country Fair’. Aubergine- ‘Bonica’. These varieties have shown some resistance to CMV.
– Trap crop method: In this method farmers plant resistant varieties around the perimeter of their fields and place susceptible plants in the middle. The intention of this that aphids will first land on the resistant varieties and by the time they have eaten their way to the susceptible varieties they will no longer be carrying the virus.
– Avoid your tomato plants from getting infected by CMV by not planting tomatoes next to cucurbits, spinach, or other vegetables and flowers susceptible to these diseases.
What is the difference?
What are the best practices for you and your yard or garden? Below, organic gardening, sustainable agriculture and permaculture are discussed. They are similar to each other yet have key differences and are applicable in different scenarios. Mix and match the best of them to best suit your purposes.
Organic gardening is a form of agriculture that relies on techniques such as crop rotation, green manure, compost, and biological pest control.
Simply put organic gardening is growing food without the use of chemical pesticides, herbicides and inorganic fertilizers. It relies on the use of beneficial insects, diversity of plants, and the use of compost to supply the soil with nutrients. Organic gardeners don’t use synthetic fertilizers or pesticides on their plants.
An organic gardener looks at plants as part of the whole system within nature that starts in the soil and includes the water supply, people, wildlife and even insects. An organic gardener strives to work in harmony with natural systems and to minimize and continually replenish any resources the garden consumes.
Sustainable agriculture has been defined as an integrated system of plant and animal production practices having a site-specific application that will last over the long term. In simplest terms, sustainable agriculture is the production of food, fiber, or other plant or animal products using farming techniques that protect and conserve the environment, public health, human communities, and animal welfare. This form of agriculture enables healthy food to be produced without compromising the future generations’ ability to do the same.
A sustainable garden works in harmony with nature. There are many techniques that can improve the health of your garden and minimize any negative impact on the environment. Most are easy and will save you time in the long run.
Sustainable gardening includes: organic gardening, double digging, worm composting, backyard composting, integrated pest management, and more.
It is to cultivate in a way such that there are enough resources to live well and survive in a varied and flourishing environment for a long time. It involves using renewable resources properly.
Permaculture, originally ‘Permanent Agriculture’, is often viewed as a set of gardening techniques, but it has in fact developed into a whole design philosophy and for some people a philosophy for life. It is more inclusive of everything, and is an entire way of living, not just gardening or growing things.
Permaculture teaches us how to build natural, energy-efficient homes, build waste water treatment systems, use recycling techniques, grow our own food, raise our own animals (chickens, cows, pigs, bees, etc.), restore diminished landscapes and ecosystems, catch rainwater, build communities, and much more. Its principles are constantly being developed and refined by people throughout the world in very different climates and cultural circumstances.
Combining the best of natural landscaping and edible landscaping, permaculture aims for a site that sustains itself and the gardener. The purpose of permaculture could be to ultimately develop a site until it meets all the needs of its inhabitants, including food, shelter, fuel and entertainment. Permaculture emphasizes the use of native plants or those that are well adapted to the local area.
Do What Works Best For You
As a gardener you will find your own way as you garden more, and try different and varied techniques. What works best for you may not work for someone else, so look around for ideas, try them, keep what works and toss out what doesn’t.
The best thing is to try new techniques and have fun doing it!
Putting It All Together
Here are five basic ideas to get you thinking:
1. Compost Your Lawn: Instead of reaching for the chemical fertilizers to feed your lawn, compost your lawn instead. It works better, is longer lasting, and it is fast and easy to do. Choosing to use fewer chemical-based products is always the better option.
2. Use Neem and Other Organic Sprays: Companies like Bayer and Ortho have brainwashed a lot people into thinking you need to bomb disease and pests with heavy duty chemicals to rid your houseplants or garden of your problems. Actually there is a nice balance that can be reached, and using more natural based sprays like neem oil, baking powder solutions and homemade organic sprays can go a long way. They may not always entirely rid your plant of the problem, but most plants, if given optimal growing conditions and nutrients, can still grow and be productive as long as the disease or pests are kept at bay.
3. Double-Digging: This means to dig out the first 12 inches (30 cm) of topsoil, take a portion of it for your compost pile, then dig down another 12 inches (30 cm). This aerates 24 inches (61 cm) of your soil, improving its texture and ability to absorb and drain water and nutrients.
4. Worm Composting: A plastic bin with holes can house a family of red wiggler worms, who will eat your kitchen waste (eliminating it from the city waste stream), and they will make it into good, odor-free compost.
5. Backyard Composting: Using a myriad of techniques, you can compost your yard waste, kitchen waste, and create nutrient rich organic matter to add back into your garden soil.
Botrytis is a plant pathogenic fungus that is found virtually everywhere plants are grown and prefers damp, cool to mild weather. It grows quickly, can grow utilizing many different sources of nutrients, prevails easily in greenhouses, and attacks numerous plant types. The disease caused by Botrytis fungus is commonly called Botrytis blight or gray mold. There are several species of the fungus Botrytis which can cause blights; the most common is Botrytis cinerea.
Botrytis can infect many ornamental plants including: anemone, begonia, calendula, chrysanthemum, cyclamen, dahlia, dogwood, fuchsia, geranium, hawthorn, heather, hydrangea, marigold, pansy, periwinkle, peony, petunia, rose, snapdragon, sunflower, sweet pea, tulip, violet, zinnia.
Among vegetables and fruits Botrytis can infect asparagus, bean, beet, carrot, celery, chicory, crucifers, cucurbits, eggplant, endive, grape, lettuce, onion, pepper, potato, raspberry, rhubarb, rutabaga, shallot, strawberry, tomato, turnip, and others.
Initial contamination is usually through fungal spores carried about in the wind which infects host plant through a point of damage such as insect damage, decaying plant tissue or pruning wounds. Botrytis overwinters on plants, in or on the soil, and as sclerotia (compact mass of hardened fungus containing food reserves with the capability to remain dormant until favorable growth conditions return).
Spores develop when conditions are optimal, and are moved around by wind or splashing water onto blossoms or young leaves, where they germinate and enter the plant. Spores require cool temperatures (45-60 deg. F) and high humidity (93% and above) to germinate. Green, healthy tissue is rarely penetrated by germinating spores, but they can enter through wounds on growing plants. Cuttings are particularly prone to infection.
The soil surface and the densest areas of plant canopy are likely places for Botrytis to be found. It usually develops on wilted flowers first, and then quickly spreads to other parts of the plant. Harvested fruits and vegetables in storage are also potential targets of the disease.
Symptoms and Damage
On flowering plants, the first symptoms you may see will be water-soaked spots on the leaves, flowers, or stems. These spots will quickly develop fuzzy gray or whitish growth. Infections often start as flower blights because older petals are more susceptible. Damage will soon spread to other flowers and parts of the stem, which then collapse as the flowers dry and turn brown.
On fruiting plants, a gray, tan, or whitish fluffy mold grows on berries and other fruit, which when disturbed, will emit of a puff of gray spores that scatter. Infected fruit will have water-soaked spots, which later appear light brown and crack as the fungus grows. On berries the entire fruit becomes water-soaked and rots.
Organic Control and Prevention of Botrytis Blight
1. Practice good sanitation: Strict sanitation is of utmost importance and cannot be overemphasized. Remove dead or dying tissue from the plants and from the soil surface as the fungus readily attacks them and produces tremendous quantities of airborne spores. All old blossoms and dead leaves should be removed, and all fallen leaves and plant debris in the garden and greenhouse should be carefully collected and burned or hauled away with the trash. Ideally, all diseased plants and plant parts should be removed and destroyed. Botrytis spores are always present, but they don’t germinate until exposed to cool and moist conditions, especially high humidity. Try and prevent these conditions from being prevalent for long.
2. Avoid overhead watering: Water on foliage and flowers from overhead watering, especially on cool, cloudy days, promotes the disease. Try keeping the plant parts above the surface dry. Soil surface irrigation and watering in the morning is recommended.
3. Properly space plants for maximum air circulation: The fungus thrives in areas that are cool and moist and in densely packed areas. Prune or stake the interior of dense plants to increase air movement. In greenhouses, ensure maximum air circulation by either increasing heat in the greenhouse or inculcating forced circulation and ventilation. Even lowering the humidity slightly can have a significant effect on Botrytis.
4. Avoid over-fertilization: Do not over-feed your plants, especially with nitrogen as tender growth is susceptible to fungus.
5. Avoid unnecessarily wounding plants: Wounds are possible entry sites for pathogens of all types including Botrytis, so avoid injuring plants in any way. Do not leave large stubs of tissue on stock plants when taking cuttings.
6. Store harvest immediately in proper conditions: Only blemish-free, flowers, fruits, vegetables and plant material should be stored in clean, cool and dry environment without moisture on the walls, ceilings or floor. The temperature should be as close to freezing as possible.
7. Preventative biological fungicide: Developed from naturally occurring bacteria, Streptomyces griseoviridis, Mycostop biological fungicide thrives in the root zone of plants. When applied as a drench or spray the dried spores and mycelium of the Streptomyces culture in Mycostop germinate and begin to grow on and around the plant roots. In doing so, they create a biological defense against root infecting pathogenic fungi which cause disease such as wilt and root rot. This is a preventative treatment, and must be used at the time of seeding or transplanting. Mycostop has been shown to promote the growth and yield of plants even in healthy crops.
8. Plant resistant cultivars: Whenever possible grow plant varieties that are known to be less susceptible to Botrytis.
9. Organic fungicides: Spray susceptible plants with an organic fungicide like Neem oil or Soap-Shield to keep fungal diseases and other pests at bay.
Grow amazing juicy tomatoes every year
If you want to consistently grow juicy, full-flavored tomatoes every year, try these growing tips used by top tomato growers:
1. Choose a bright spot with good air circulation.
Plant your tomatoes in a spot that will receive at least 10 hours of light during the summer. Ensure that there is room between plants for air to circulate.
2. Practice crop rotation.
Alternating your tomato beds between even just two spots will diminish the chance of soil borne diseases such as early blight and bacterial spot.
3. Plant tomatoes deep.
Plant your tomato seedlings up to the first true leaves. New roots will quickly sprout on the stems. This makes your tomato plants establish a much larger root ball and gives you a higher yield.
4. Keep plants warm.
Temperatures cooler than 50 deg. F (13 deg. C) slow tomato plant growth and prevent fruit from setting. Protect them with heavyweight row covers or cloches to shield them from chilly nights until the nights are naturally warm enough.
5. Feed the soil appropriately.
A common mistake one should avoid is over-feeding the soil. Tomatoes thrive in soil that is rich in humus for extensive, well-developed root systems and potassium for strong stems. Adding too much nitrogen will produce overly lush plants with little fruit.
Homemade compost will typically supply all the necessary phosphorus the tomatoes need for good flowering and fruiting. A weekly spraying of liquid kelp or seaweed extract will increase the health and yield of your tomato plants.
6. Grow them up.
Tomato vines that are left to sprawl over the soil are more prone to attacks by pests and diseases than ones that have been staked or caged.
7. Choose indeterminate varieties.
Indeterminate tomato varieties tend to produce more fruit but require more space to grow, so make sure everything is in place and that you have enough room.
8. Water deeply but infrequently.
Tomato plants that are established in the soil have their roots spread deep inside the soil and as a result require deep watering less frequent than those growing in containers. Soak your tomato bed once a week, or every five days at the height of summer. Water evenly and consistently and water directly on the soil and not on the leaves to help avoid blossom end rot, fruit splitting and other tomato problems brought on by uneven watering.
9. Pluck, prune and trim.
Many tomato growers pull off the first flowers, so that the plant does not devote energy to forming fruit before its roots and foliage have filled out. Pinch off the sucker (non-fruiting branches) too to direct the plant’s energy into growing bigger, better fruit.
As your tomato plants grow, remove the bottom leaves as these are the oldest leaves and are usually the first to develop fungal problems. Go easy on pruning the rest of the plants though, as it’s the leaves that are photosynthesizing and creating the sugars that give flavor to your tomatoes.
Many organic gardeners rely on plastic mulch to warm up the soil in the start of spring and prevent weeds from sprouting up. Study after study has shown that beds covered in black plastic in spring produce tomatoes earlier and in abundance all season long. Infra-red transmitting plastic mulch is very effective researchers have found, as it reflects just the kind of light that plants need.
All natural mulches also help tomatoes grow. Surround your plants with a layer of straw, leaves, dried grass clippings or pine needles to prevent weeds from growing and retain moisture in the soil. Natural mulches keep the soil cool, so don’t apply them until the soil warms to a minimum of 65 deg. F (18 deg. C).
Damping off or damping-off is a horticultural disease or condition, caused by a number of different pathogens that kill or weaken seeds or seedlings before or after they germinate. It is most prevalent in wet and cool conditions.
Damping off is caused by several soil-borne fungi including Pythium, Phytophthora, Rhizoctonia and Fusarium, which infect seedlings and cause them to “damp off” or collapse and decay.
Damping off can affect any seedling, particularly under high humidity levels, in cold wet soil, poor air circulation, poor soil drainage, use of green compost, and planting too deeply. Damping off is a huge problem when sowing seeds indoor early in the season or under glass, but can affect seedlings sown outdoors when specified conditions are prevalent.
Damage and Symptoms
Infected seeds don’t germinate; instead they turn mushy and brown. Seeds may be infected as soon as moisture penetrates the seed coat or a bit later as the radicle begins to extend, all of which rot immediately under the soil surface. This pre-emergence damping off results in a poor, uneven stand of seedlings, often confused with low seed viability.
When seedlings are attacked after they emerge, stem tissue near the soil line decays, weakens and gets a dark, water-soaked area, usually causing the plants to topple over and die. When only roots decay, the plant may continue standing but will remain stunted, wilted and will eventually die.
Older plants that are infected have stem lesions that cause stunted growth, and can die.
Seeds and seedlings of most plants.
Organic Control and Prevention of Damping off
– Cultural control of damping off diseases is based on providing favorable conditions for germination of the seeds and growth of plants while minimizing the conditions that favor fungi. This means growing seeds in well-drained soil, with adequate air circulation and dry conditions.
– Use sterile well drained soil mediums. Avoid wet or compacted soil. Raise seedlings in treated commercial growing compost. If home-produced compost is being used, steam-sterilize the compost to destroy pathogens. Soil mix has to be held at 140 deg. F for at least 30 minutes to ensure sterilization.
– Purchase disease free plants and seeds from a trusted supplier. Seed borne diseases can be avoided by soaking seeds for 15 minutes in bleach soak (1 teaspoon per quart of water) prior to sowing.
– In warm regions, practicing soil solarization can reduce pathogens in outdoor soil. To solarize, place clear plastic tarps over soil for extended periods.
– Use plant containers that have drainage holes, water from the bottom only and strictly avoid over-watering. Do not allow pots to stand in water as the excess water will starve the roots of oxygen.
– Ideally, use new pots and trays to raise seedlings. If re-using old ones, make sure to disinfect them thoroughly. Never reuse pots and trays in which damping off has been a previous issue.
– As a rule of thumb, do not cover seeds with soil mix more than 4 times the thickness of the seed. Do not allow for the crowns of plants to be below the soil line.
– Use only well-decomposed compost. Do not use the green compost as its overly moist environment will encourage damping off fungi. Use well aerated composting soil to reduce chances of infection. Composted hardwood bark has been reported to reduce damping off.
– Cover seedlings with a thin layer of perlite, vermiculite, sand, or peat moss to keep the soil surface dry and keep fungal growth to a minimum.
– Avoid overcrowding and overfeeding of seedlings. Maintaining constant levels of growth through proper lighting and adequate control of growth environment is important and helps prevent damping off.
– Avoid working with plants (cuttings or transplants) when the soil is wet.
– Disinfect tools, containers and hands after working in areas that are likely to harbor damping off fungi.
– Drench starting soil mix with an anti-fungal agent. Chamomile tea, clove tea and garlic infused water have anti-fungal activity.
– Use water that you know is free from pathogens. Your mains water will mostly be safe for use on seedlings grown in pots and trays. If using rainwater, ensure that the water butt is covered to prevent the entry of leaves and other organic debris that could harbor pathogens.
– Remove and discard diseased plants.
– Avoid planting the same crops in the same place year after year.
– Unfortunately infected seedlings usually die, but sometimes you can save the rest by improving growing conditions by making them as warm and dry as possible.
– Spray plants with seaweed extract as this will help strengthen them.
– Spray plants with Neem oil as it has anti-fungicidal properties as well as providing systemic benefits to the plant.
If your plant leaves appear like a kid was doodling squiggly lines, you have leafminers. Leafminers are larval (maggot) stage of insects that live in and eat the leaf tissue of plants. They appear in spring, like young robins and daffodils, but are nowhere near as welcome. The vast majority of leaf-mining insects are moths (Lepidoptera), sawflies (Hymenoptera), flies (Diptera), though beetles (Coleoptera) also exhibit this behavior.
Host plants include apple, beans, beets, blackberries, cabbage, citrus plants, Swiss chard, lettuce, garlic, peppers, tomatoes, onions, spinach and a variety of ornamental flowers especially chrysanthemum and nasturtium, trees and shrubs.
On vegetable crops, the most common leafminers belong to the genus Liriomyza.
Adults are small (1/10th of an inch or 2.5 mm long) black and yellow flies with clear wings and are similar in appearance to small, hunch-back house flies. Sometimes the flies are more silvery-gray in color than black.
The only leafminers that lay masses of eggs on the underside of leaves in gardens are Pegomya fly species (Anthomyiidae), on Amaranthaceae (spinach, chard, etc.) and Polygonaceae (docks, garden sorrel; occasionally rhubarb, but the larvae always seem to die pretty quickly in rhubarb leaves). All agromyzid flies (such as Liriomyza) insert their eggs in plant tissue, and these are impossible to see, although sometimes you can see discolored spots where the female inserted her ovipositor. They are tiny, cream-colored and oval.
The larvae of leafminers are bright yellow or pale green, stubby, translucent maggots that are about 2 mm long when they emerge from the leaves to pupate. Pupae look like tiny brown grains of rice. Leaf-mining flies though, don’t make cocoons.
Adults emerge from overwintering cocoons in early spring and lay their eggs in clusters just under the surface of the leaf epidermis. The larvae mine leaves for 1 to 3 weeks till mature, then drops down to the soil and pupates for 2 to 4 weeks. There are normally 2 to 3 generations per year; more in greenhouses.
Larvae mine between upper and lower leaf surfaces, creating winding, whitish tunnels that are initially narrow, but then widen as the larvae grow. This may cause leaves to dry out, resulting in sun-burning of fruit and reduction and yield and quality. Excessive damage from larvae on young plants and seedlings can cause them to die due to lack of chlorophyll and reduced photosynthesis.
Mines and feeding punctures also open up ways for pathogenic organisms to enter. Excessive leaf mining may cause death of the plant.
Organic Control and Prevention of Leafminers
1. Check your transplants for leaf mining damage before planting them out in your vegetable garden.
2. Cover plants with floating row covers to keep adults from laying eggs on leaves. Protect small seedlings by covering them with a protective cloth or a cold cap.
3. Pick off and destroy infested leaves.
4. Do not plant vegetables in areas where you’ve had previous leafminer infestations.
5. Cut forage crops, remove remaining old plants and till the ground after harvesting your crops. This can significantly reduce leafminer populations by destroying pupae in the soil and eliminating several sources.
6. Scout for egg clusters on susceptible plants regularly and destroy them as soon as they are visible.
7. If available, plant vegetables varieties that are less susceptible to leafminer infestation, such as tomato with curled leaves.
8. Leafminers on vegetable crops have been kept under control by their natural enemies, in particular parasitic wasps such as Diglyphus begini and Chrysocharis parksi. These wasps feed on leafminer larvae and can significantly reduce leafminer populations. Diglyphus isaea is a commercially available beneficial insect that will kill leafminer larvae. Encourage these parasitic wasps by planting nectar-and pollen-rich flowers such as dill and yarrow.
9. Leafminer infestation can be reduced or prevented by planting trap crops near the plants to be protected. Lamb’s-quarter, columbine and velvetleaf will distract leafminers, drawing them to these plants and thereby reducing the incidence of attacks on nearby crops.
10. Spray infected plants with Spinosad, an organic insecticide, which will control the leafminer. Spinosad does not kill on contact but will have to be ingested by the leafminer to take effect.
11. Spray Neem oil to control or prevent leafminer infestations. Neem oil will break the leafminer’s life-cycle by preventing larvae from reaching maturity. It also acts as an anti-feedant, a repellant and it interferes with egg laying activities.
12. Use sticky yellow traps to catch egg laying adults.
13. Cover the soil under infested plants with plastic mulch to prevent the larvae from dropping down into the soil and pupating.
14. If using trap crops to distract leafminers is not on your agenda, control weeds such as lamb’s-quarter and dock which are known leafminer hosts.