Preventing the spread of tomato yellow leaf curl

Tomato yellow leaf curl has the potential to temporarily eliminate tomato growing in certain areas, including your garden. This disease is the reason why tomatoes are generally not grown in tropical and semi-tropical regions. Cold winters tend to kill of the whitefly vectors, but the San Francisco Bay’s winters are not necessarily cold enough to provide that protection. Instead, you can use these tips to protect your tomato plants, and tomatoes, in general:

• quarantine all new plants to ensure they are disease and whitefly-free
• select varieties that are resistant to the tomato yellow leaf curl virus
• avoid transplants from affected areas (Mexico, Florida, Georgia, and Texas)
• manage whiteflies
• use crop rotation
• cover tomato plants with floating row covers
• remove weeds from the area
• remove and destroy crop residue, rather than leaving it in place

​Now you know.

    Prunus stem pitting causes later then normal leafing out. Leaves look pale and tend to wilt in summer, turning red or purple earlier in the season than is normal. Fruit size, quantity, and quality are significantly reduced. All of this is because the virus interferes with the flow of water and nutrients through the graft union, effectively starving the tree. These symptoms look very much like root damage caused by rats and voles, girdling roots, and fungal diseases of roots. The difference being that the tomato ringspot disease causes the bark, both above and below the soil line, to thicken and become spongy. This weakened area often allows the tree to topple over. Before that happens, you will also see pitting in the sapwood of the trunk. Usually the tree dies before pitting is seen in any branches.


How to control tomato ringspot

In a word - you can’t. The disease is incurable and infected plants put nearby plants at risk. The only thing you can do is remove the infected plants, and those nearby, and burn them or toss them in the trash. Just because symptoms disappear does not mean the infection is gone. Plants that no longer show symptoms are still carrying the disease, which can then spread throughout the garden. Once plants are removed, the affected area should be allowed to go fallow for at least 8 months, to starve out any dagger nematodes that may be lurking underground, and remove any potential disease-carrying weeds.


To prevent tomato ringspot, there are a few steps you can take:

• quarantine new plants
• use only disease-free plants
• plant disease-resistant rootstocks
• disinfect tools regularly
• remove infected plants and those surrounding them as soon as the disease is seen

Yes, removing plants from the garden or landscape is disappointing, but having to remove even more plants because of an initial delay could be both costly and heartbreaking. 


And you thought this post was going to be all about tomatoes…


So did I!

Tomato pinworm lifecycle

Moths lay eggs singly or in groups on leaves. When the eggs hatch, larvae spin protective webs. Then they burrow into the leaf to begin feeding. As the larvae move through 4 developmental stages, or instars, they may also fold leaves, or pull multiple leaves together, for added protection from predators. Tomato pinworms also move into stems and fruit, where they can make your crop inedible. ​

How to control tomato pinworms

​In areas with mild winters, tomato pinworm eggs and larvae can overwinter in the soil, on tools, or in buckets or baskets. Closely monitoring plants for signs of infestation is your first line of defense. Pheromone traps can be used to monitor for the moth and mating disruptants can make it more difficult for adult males and females to find each other. Be sure to thoroughly compost or remove plant residue at the end of the growing season, and always put new plants into quarantine.

       Soaker hoses can be spiraled around a tree, starting from the middle of the tree’s canopy and ending just beyond it.


Or, you can do what I do, which is simply to dig a shallow trench, 4” deep and wide, in a circle under or slightly outside of the drip line. If you have a semi-dwarf tree with a canopy that is 8’ across, and a trench 4” wide and deep, that trench will hold approximately 20 gallons of water. One added benefit of the trench method is that it helps keep turf at a distance. This type of irrigation ring is not suitable for newly planted trees. 


Newly planted trees

Newly planted trees need water close to, but not touching, the trunk. This is where all the roots are. As the tree becomes established and the root system spreads out, you can start using a trench irrigation ring. Of course, it’s a good idea to dig the trench before the tree’s roots reach that area. 


In each case, the benefit to the tree is that water is allowed to seep into the soil slowly enough to be absorbed by the tree, rather than running off as urban drool, or percolating downward where tree roots cannot access it as well. And don’t forget to mulch under trees, keeping the mulch 6” away from the trunk. This will reduce water needs, thwart opportunistic weeds, and stabilize soil temperatures.

Avocados and exudates

Peach, citrus, and pecan are just a few of the more than 200 tree species impacted by this problem, as are grapevines, but the sugar volcano is specific to avocados and box elders.


Exudates are secretions. When an avocado tree is first attacked by shot hole borers and Fusarium dieback, it will respond by pushing a sugary exudate out of the borers’ entry and exit holes. This sugary secretion often includes frass and sawdust. As it dries, this sugary exudate forms a white, crusty ring or cone-shaped patch on the affected branch.


And these crusty white patches, dear readers, are sugar volcanoes.


Now you know.

Cutleaf geranium lifecycle

Cutleaf geranium can grow as either an annual or biennial plant, and is commonly found in disturbed ground and abandoned areas. Each plant can produce up to 150 seeds and those seeds can remain viable for 5 to 10 years.


Controlling cutleaf geranium

As with most the weeds, it is best to start controlling it early, before plants have a chance to go to seed. Hoeing is the best control.

The delicious leaves that surround an artichoke flower are also bracts. Tiny banana flowers are protected by bracts.

Conifer bracts

Pine cones are covered with scales used to protect seeds. Female cones have two types of scales, bract scales and seed scales. Bract scales grow under seed scales. This positioning is called subtending. Bract scales are more obvious at the time of pollination. Very often, seed scales will grow over bract scales as seeds mature.

If you grow members of the cabbage family, you need to know about hollow stem.


Hollow stem is a physiological condition that occurs within the main supporting stem that holds up your cabbage, broccoli, or cauliflower. At first, small cracks develop in the center of the main stem. As the stem grows, the cracks enlarge, creating cavities that are prone to pest infestations and disease, especially rotting.


If you cut open the stem of a plant that seems affected by hollow stem, the damage is obvious.

Causes of hollow stem

Too much nitrogen and hot temperatures are a bad combination for cole crops. The nitrogen causes rapid growth, but the heat puts too much strain on these cool weather crops. As cracks develop within the stem, pith is lost and the stem becomes weakened. This allows pests and disease to enter, damaging your harvest.


Hollow stem and boron

For many years, boron deficiencies were blamed for hollow stem. We now know that this is not true. If there is a boron deficiency and hollow stem has occurred, you will be able to see darkening around the edges of the damaged area, but the deficiency does not cause the condition. If you suspect your soil is deficient in boron, send a sample in for a soil test.

Baking soda as weed killer

Jump dump baking soda on top of weeds and they will die! True? Yes, probably. Good idea? No, definitely. Baking soda, or sodium bicarbonate, is a type of salt. Remember reading about victors salting the fields of their enemies? This was done so that the losers couldn’t grow any food in those fields. Sprinkling handfuls of salt around your garden is never in your plants’ best interest.


Baking soda and soil pH

Baking soda is highly alkaline. You will find countless articles pointing to the use of baking soda as a way to boost flower production and improve fruit sweetness because of this increased alkalinity. This is only partially true. While improper soil pH can impact fruit and flower production, simply adding baking soda is not the solution. Low flower production can have many causes: not enough or too much sunlight, improper fertilizing, irrigation, or placement, pests or disease, or nutrient imbalances in the soil. Fruit sweetness or acidity is more often a function of irrigation levels and overall plant health, than anything else. To boost the flavor of your tomatoes and many other crops, forget the baking soda and try deficit irrigation.


If soil pH is making it difficult for your plants to absorb nutrients, you can try altering it, or you could select plants better suited to your local soil. Altering soil pH is difficult and it requires accurate testing and regular treatments. Simply sprinkling baking soda on your soil is more likely to raise the salt content to toxic levels.


Baking soda as pesticide

You have probably read that you can mix baking soda with sugar to create the perfect DIY ant poison. Supposedly, the ants take the mixture back to their colony, where they eat it and then explode. Nope. Doesn’t really happen. Think about it. From an ant’s perspective, the sugar granules are probably about the size of a tennis ball and easily discernible from the baking soda bits. Plus, I could not find a single piece of scientific research to back up the ‘exploding’ claim. As for slugs and snails, well, baking soda is a salt. Salt does terrible things to slugs and snails. Better to feed them to your chickens or just step on them and be done with it.


Baking soda as fungicide

Countless ads and articles point to baking soda as a fungicide. This is because most fungi grow best in a slightly acidic environment and baking soda has a pH of 8.4, which is more alkaline. When conditions become too alkaline, fungi stop growing. Until conditions improve, that is! Then, they take up exactly where they left off. Because of this, baking soda is considered fungistatic, and not a fungicide. Also, while baking soda’s fungistatic properties are well documented in lab situations, those results have not translated to outdoor growing conditions, such as are found in your garden.


If you can completely cover a surface with a baking soda solution, you may be able to temporarily halt the development of any resident fungi, such as those that cause black spot or powdery mildew. But, right away, problems begin to occur. First, ever-increasing amounts of baking soda are needed for the same effect. Also, being water-based, the solution needs to be replaced after every rain, and each treatment adds more salt to the soil than is healthy for plants or important soil microorganisms. You can, however, mix baking soda with horticultural oil for moderate, but inconsistent, results. Just be aware that phytotoxicity can occur. [Phytotoxicity means ‘poisonous to plants’.] When combatting powdery mildew, better results can be obtained by using potassium phosphate, potassium carbonate, sulfur, or even milk sprays.


That being said, baking soda solutions can slow the development of certain fungi on produce after it has been harvested. Commercial growers frequently treat thick-skinned produce, such as citrus, with a boiling bath of baking soda in solution to prevent fungal growths while the fruit is in storage or being shipped. This is because the fungi that cause the blue and green molds on citrus are particularly sensitive to alkalinity caused by baking soda. In fact, that’s where the whole baking soda craze got started - from a test on citrus molds conducted in the 1930s.


You may be surprised to learn that the use of a coarse organic mulch, such as arborist wood chips, provides better disease suppression than baking soda treatments. This occurs because the wood chips make life more difficult for fungal spores.


Baking soda performs wonderful tasks in the kitchen, making muffins, deodorizing the fridge, and putting out grease fires. Let’s leave it there, whee it can do the most good, and not in the garden.

Sprinkle cornmeal in the garden to stop weed seeds from germinating! 


Cornmeal prevents fungal diseases, too! 


Wouldn’t that be convenient?

Like many other garden fantasies, the fallacy about cornmeal originated in fact, but the above claims have not been able to withstand the tests of time and science.


How the cornmeal myth began

In 1985, Dr. Nick Christians, from Iowa State University, found that corn gluten meal, a byproduct of the corn milling process, showed herbicidal effects during a turfgrass experiment. The corn gluten meal was found to desiccate newly forming roots of small-seeded plants in highly controlled greenhouse environments. As such, corn gluten meal can act as a pre-emergent herbicide, an idea that was patented in 1991, but those results have not been repeatable in outdoor environments, such as family gardens.


What is corn gluten meal?

Corn gluten meal is not the same thing as the cornmeal you find at the grocery store. Instead, it is what is leftover after the corn has been ground up to make cornmeal. Corn gluten meal is a byproduct used in livestock and pet food. It is the primary protein found in corn and does not actually contain true gluten. 


Corn gluten meal is not species specific, so it will, when conditions are just right, desiccate any new, small-seeded plant roots, including your lettuce, carrots, and many others. On the other hand, corn gluten meal contains 10% nitrogen, so sprinkling it on your lawn or garden will provide this important nutrient, leading to lush growth and healthier plants, weeds included. [Cornmeal has practically zero nitrogen.]


Cornmeal as fungicide

Popular claims also state that cornmeal will help control fungal diseases, such as brown patch, black spot, and dollar spot. That’s strikes me as funny, because cornmeal agar is produced as a medium specifically designed to grow fungi for laboratory work! 


Finally, for the record, ants do not “explode” or die in any other fashion when they eat corn gluten meal, cornmeal, or other foodstuffs. In fact, ants, rats, squirrels, and many other garden pests love cornmeal and corn gluten meal, so choose your battles wisely.

Popular claims about mothballs in the garden

In one article, you are urged to add a few mothballs to a potted plant and then cover the whole thing with a plastic bag for a week as a sure-fire way to get rid of insect pests. In another post, you are told that adding mothballs to the garden will repel mice and rats. Then a friend urges you to scatter mothballs throughout your garden to deter squirrels, snakes, and rabbits. Is any of this a good idea?


No, it isn’t.


What are mothballs, anyway?

You might remember smelling mothballs in your grandmother’s closet, attic, or basement. That distinct scent is unmistakable. Mothballs are spheres or disks of pungent chemicals that slowly evaporate into a gas that is toxic to moths and moth larvae. This is why people have used them to protect clothing and other fabric materials while in storage. 


The chemicals used to make mothballs can be naphthalene or paradichlorobenzene, both of which are carcinogenic neurotoxins that have no business near your food. There are clear and important instructions on how to use mothballs properly, if you must. For one thing, containers must be completely sealed to prevent long term exposure and the associated health risks.


The truth is, it is illegal to use mothballs as a pesticide in many states. According to the National Pesticide Information Center, using mothballs outside poses a risk to children, pets, and local wildlife. Mothballs can also contaminate soil and water. 


So, the next time someone suggests using mothballs in the garden, you can protect them by educating them.

The nature of egg shells

When a chicken lays an egg, the shell provides protection. That shell is made up of calcium, magnesium, potassium, sodium, and sulfur, which are all important plant nutrients. The thin, inner lining also contain organic matter, equally important to healthy soil structure. Plus, if you don’t wash your egg shells, they will also contain nitrogen, which is an important plant food. 


All of these nutrients are would be a great addition to the garden, if the egg shells actually broke down into small enough particles - but they don’t.


Egg shells and decomposition

As stated above, egg shells are designed to provide protection. Unless you are dropping them off the roof of the gym for a high school physics class, egg shells are surprisingly tough. So tough, in fact, that they don’t break down in boiling water. The moisture and microorganisms normally responsible for decomposition do not have a ghost of a chance at breaking down an egg shell in your lifetime.


For example, 170 years ago, Thomas Jefferson raised chickens and ducks. An archeological excavation of the site found that egg shells from those birds were still intact in the soil. This tells us that, no matter how many times you flip that compost pile, those egg shells will never significantly improve anything in the garden.


Even if you let them dry and crush them into smaller bits, those bits are very unlikely to breakdown enough to be useful to your plants. Unless you have very acidic soil (<6.8 pH) and the egg shells are ground up into a very fine powder, they will add nothing to your soil.


Egg shells and blossom end rot

Blossom end rot is a condition that occurs when plants are unable to move calcium around to where it is needed. This is rarely the result of insufficient calcium in the soil. Most soils have plenty (or too much) calcium already. More often, it is a case of irregular or insufficient watering. Before adding calcium, in any form, to treat blossom end rot, get a soil test from a reputable lab and check your irrigation schedule.


Egg shells as a pest deterrent

Crushed egg shells are also touted as a barrier against slugs and snails, cutworms, and even deer. Those claims are false. The only thing you might find is some birds will be attracted to the shells, either through natural curiosity or as a calcium source during egg-laying season, and some rats, looking for a snack.



Personally, I crush my egg shells and feed them back to my chickens. I don’t know if they actually eat them or not, but I think they do. Just in case, I offer oyster shell, as well.

False claims about Epsom salts


The sheer volume of claims made about Epsom salts should be the first clue that there is a problem. Epsom salts are said to improve flower blooming, germination, photosynthesis, the uptake of other nutrients, fruit production and flavor, and to act as a valuable nutrient for overall health. Epsom salts are said to “enhance a plant’s green color” and “help plants grow bushier” while deterring pests, reducing blossom end rot, transplant shock, leaf curling, and chlorosis (yellowing). Epsom salts are also said to be a safe, reliable weed killer. 


With all these miracles provided by Epsom salts, why isn’t everyone using it all the time? Many advertisements and articles also state that Epsom salts are not persistent in the soil, so you cannot overuse it. Wouldn’t it be wonderful if all those claims were true? Unfortunately, they are not.


The truth about magnesium sulfate

Epsom salts, also known as magnesium sulfate (MgSO4), is made up of magnesium, sulfur, and water. Magnesium and sulfur are plant micronutrients. This means plants use them, but only in very small amounts. If a magnesium or sulfur deficiency has been identified via a lab-based soil test, Epsom salts can be safely used to counteract those deficiencies (assuming your soil is equally deficient in both nutrients at the same time). That’s also only after you are certain that the deficiency is not being caused by too much or too little of another nutrient. For example, too much phosphorus in the soil can make it difficult for plants to absorb magnesium, regardless of how much is present. [Are you beginning to see how important that soil test is?]


Adding too much magnesium can cause just as many problems as having too little. More often than not, your soil probably has more magnesium than plants need. When I bought my house in 2012 and sent a sample out for a soil test, my results came back with 798 parts per million (ppm) for magnesium. The optimal range is 50 - 120 ppm. Whoever lived here before me kept adding more fertilizer (or Epsom salts), long after it was needed.


Crops that commonly need magnesium include apples, beets, citrus, peppers, potatoes, tomatoes, and watermelon. Usually, deficiencies only occur when these and other crops are being grown intensively, and rarely in the home garden. 


There is no scientific evidence of Epsom salts repelling slugs, insects, grubs, voles, rabbits, or anything else. As for the blossom end rot claims, adding Epsom salts may actually interfere with your plants’ ability to take up calcium, making it more likely that your tomatoes will develop blossom end rot, rather than preventing it.


Epsom salts may sound like a garden cure-all, but those claims should be filed under “too good to be true”. A healthy, productive garden does not come with quick fixes. Before jumping on a bandwagon, be sure you take the time to read the science behind those claims. 


And get a soil test.


Your plants will be healthier and more productive, and you can save Epsom salts for the bath, where they belong.

Also known as biennial bearing, this tendency can explain why your fruit or nut tree doesn’t produce the same amount each year. It is not caused by pests or disease. It is simply the way some trees grow, mostly.


Generally speaking, fruit and nuts are produced on long stems or on short, stubby stems called spurs. The spurs of alternate bearing trees tend to produce blossoms one year and leaves the next. This allows the tree to gather more of the sun’s energy, carrying it through its two year cycle of production. Therefore, it is not the tree, as a whole, that alternates production each year. Instead, it is the individual stems and spurs.


Other causes of alternate bearing include weather conditions, such as a heavy frost that damages the blossoms, can result in a low production year. Since resources were not used to produce as much fruit that year, the following year will tend to be a heavy production year. Some trees may even take two years off after a particularly heavy year. In other cases, mineral deficiencies or excessive fertilization, especially nitrogen, can result in a cycle of alternate bearing to begin.


Most perennial fruit crops start making fruiting buds during the previous season. If conditions are especially good or bad, those developing buds will become stronger or weaker, respectively. There is also some research that suggests the developing ovules of a heavy production year produce hormones that inhibit next year’s flower production. Scientists are still learning the details about what causes alternate bearing.


Some commercial growers reduce the impact of alternate bearing trees by thinning blossoms and fruit on heavy production year. This is done to counteract the fact that fruit produced during heavy years tends to be smaller, while fruit produced during low production years tends to be of poor quality and more susceptible to pest and disease damage. Evening things out improves crop quality and tree health.


Citrus, apple, pear, avocado, apricot, plum, mango, cranberry, blueberry, olives, pecan, and pistachio are common plants that exhibit alternate bearing behavior in the home garden. Grapes almost never do.


You can reduce the negative impact of alternate bearing on your fruit and nut trees with proper pruning, irrigation, and feeding, along with regular fruit thinning, soil tests, and protective treatments against pests and diseases.


Now you know.

Unlike people and animals, plants do not have an active immune system. Instead, injured or infected areas are walled off to prevent further injury or the spread of infection or infestation. Gumming refers to the way sap oozes out of an injury site or canker to provide protection. ​

For example, gummosis caused by insect infestation or mechanical injury will often exhibit bits of bark or sawdust mixed in with the gum. Look for other damage around the gumming site: Do leaves look sick or chewed upon? Has the bark’s integrity been breached? Do you see discoloration under the bark near the gumming?

• Environmental conditions such as sunscald, frost damage, improper pruning, planting too deeply, excessive irrigation, and over-bearing can all cause gumming.
• Mechanical injury by lawnmower collisions, rubbing branches, and outgrown tree supports can all lead to gumming.
• Insect infestation by peach tree borers, flathead borers, and other boring insects can cause gumming.
• Diseases such as Eutypa dieback, cytospora canker, Fusarium dieback, and bacterial spot may cause discoloration under the bark, as well as leaf dieback and stunting.

How to manage gumming

You can help your fruit and nut trees stay healthy by avoiding mechanical injuries, and monitoring for pests and diseases on a regular basis, along with proper feeding and irrigation. If you suspect disease, scrape some of the bark away from the area surrounding the gum. If you see discoloration or streaking, it is probably a disease that needs further attention. In many cases, diseases can be halted by removing affected branches below the infected area, just be sure to sanitize cutting tools between each cut.


If the gum emerges from circular holes and contains insect larvae, the tree is taking care of the problem itself, though further monitoring is a good idea.

Like other ichneumon wasps, Exochus females insert their eggs into the larval stage of many leaf rolling caterpillars, such as the orange tortrix and the obliquebanded leafroller. The eggs then hatch inside the caterpillar and begin feeding. You can see video of an Exochus female attacking a caterpillar here. The video is bit long, but fascinating.


​These tiny wasps serve us well in the garden, so avoid using any broad spectrum pesticides and let nature take its course.

Who knew apples could get the measles?


Unlike the human variety, which is caused by a virus, apple measles is a symptom of manganese toxicity.

Treating apple measles

Since apple measles is a symptom of too much manganese in the soil, you need to alter the soil chemistry to help your apple tree. Apple measles occurs most commonly in acidic soil, so increasing the soil pH with lime or other alkaline soil amendment will help reduce future damage.


Unfortunately, it is very difficult for trees to recover from apple measles, so get your soil tested every 3 to 5 years, so you know what they are dealing with - before the damage is done.

Bourse-over-bourse

A common term among apple growers is bourse-over-bourse. This refers to bourse shoots emerging from existing bourse shoots, in a waterfall style growth pattern. Too many bourse shoots on one stem can lead to spur extinction. Spur extinction describes the point where a spur is no longer productive. If you see multiple bourse shoots on a stem, you can improve fruit production by pruning back to the innermost bourse shoot.


Pruning apple trees

Standard dormant season apple pruning involves removing all dead, diseased, or rubbing branches, as well as 15 to 20% of the previous year’s growth. Next, you should remove excessive bourse-over-bourse growth, and bourse shoots that are especially long, as they tend to be less productive than shorter or medium-length bourse shoots. Don’t remove too much, however. One study, published in the Journal of Horticultural Science, explains how the removal of too many bourse shoots significantly reduces return bloom [next year’s crop].


Bottom line: next year’s apple (or pear) crop is highly dependent on the number of leaves produced during the current year. If your apple tree has more bourse shoots, it is more likely to have more leaves, ergo, more fruit. But this is only true if those bourse shoots are spread evenly throughout the tree.

The best news about yellow sticky sheets? They’re cheap. And if you are having problems with indoors pests, you can always cut the sticky paper into a decorative shape and put it to work for your container plants!