Aphids are soft-bodied insects with piercing mouthparts. They insert their sharpened straws into plant tissue, where they slurp up copious amounts of sugary sap. They eat so much and so quickly, that much of what they eat simply goes in one end and out the other. This “honeydew” can be contaminated with pathogens and it attracts the attention of protective ants, but aphids have many enemies. We’re not just talking about gardeners here, either. In most cases, aphid killers are either predators or parasites, though there are exceptions.

Parasites

Parasitoids are insects that lay their eggs in, on, or near host insects. Those hosts end up being the first meals for parasitic larvae. There are many parasitic wasps that bring death to aphids. They do this by laying an egg in every aphid they can. When the eggs hatch, they eat their aphid hosts from the inside out. Gruesome, right?

Many varieties of parasitic wasps and other aphid killers are available for purchase, but you can often attract these garden helpers to your landscape with plants that provide abundant nectar and pollen. Queen Anne’s lace, coreopsis, coneflowers, cosmos, coyote brush, dandelions, dill, goldenrod, sweet alyssum, and sunflowers look lovely and they create a natural welcome mat to insects that see aphids as the perfect meal. Hedgerows also provide beneficial insects with good hiding places.

Cicadas are well-known on the East Coast for their epic numbers, mind-numbing noise, and littering trees and shrubs with exoskeletons. What I didn’t know was the West Coast has cicadas, too. And this is the year, coast to coast, they all come out of the ground to mate in record numbers.

Cicadas (Magicicada) are grouped by species and broods. Periodical cicadas include M. septendecim, M. cassini, and M. septendecula species. Each species has 13-year broods, 17-year broods, and different cycles of each of those broods. Each cycle is labeled with a Roman numeral.
Limited numbers of cicadas emerge any one summer. This year is different. This year, we will see the co-emergence of several cycles of both 13-year and 17-year broods. This generally happens every 221 years. Lucky us.

As you may know, I use sticky barriers around the trunks of my fruit and nut trees to thwart crawling insect pests. These barriers also let me see which insects are out and about, though the sticky sheets hanging in the trees do a much better job of that. I was surprised to find cicada exoskeletons caught in the barriers protecting my navel citrus tree. I thought cicadas were only on the East Coast, but I was mistaken.

Cicada sounds

If you’ve ever been present for a cicada emergence, you know how incredibly noisy these insects can be. At up to 120 dB, they are the noisiest insects on Earth. They are so loud that they can cause permanent hearing loss when experienced at close range.

I lived in Virginia during an emergence year. It was an experience I’d rather not repeat. While not as bad as the Midwest’s plague of locusts, cicadas were everywhere. They coated windshields, driveways, and roads. They flew into you, clinging to your clothes and hair. The noise was enough to drive any sane person crazy. And then it was over. Like it never happened, except for the hollowed-out exoskeletons attached to every tree you saw. But finally, it was quiet.

Both males and females have membranous structures called tympana that detect sounds. When a male cicada sings, he turns his tympana off so as not to damage his own hearing. {I used to have a neighbor like that. I had to move to a new apartment.]
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Male cicadas create all that noise using organs called tymbals found on their abdomen. In some species, both males and females rub their wings over a series of ridges found on the thorax. These bugs have resonating cavities and membranes that amplify the sound. While we can’t tell the difference, it ends up that each male cicada has a unique song composed of modulated clicks that sound, to us, like continuous notes. I have to assume that the female cicadas can tell the difference. To me, they’re very noisy. I did learn that one of the Australian cicada species does not produce audible sounds. Instead, they produce vibrations transmitted through whatever tree they are on, which sounds far more civilized. And some cicada songs are so high-pitched that we can’t hear them. Another interesting note about cicada courtship is that different species may be found on the same tree but at different levels.

Purple scale lifecycle

Females lay 40 to 80 eggs under their protective covers. After the eggs hatch, crawlers emerge and scuttle to nearby fruit, leaves, and twigs, where they begin forming their own covers. At first, purple scale crawlers are covered with a mass of waxy threads. When they are about half-grown, their purplish-brown covers begins to develop. Once a female attaches herself, she stays put.

Purple scale management

Temperatures above 80°F are hard on purple scale, so their numbers are greatly reduced by the time summer is in full swing. But a second generation may appear in autumn and, in some years, a third generation may occur before winter cold brings them to a halt.

Natural predators, such as parasitic wasps, twicestabbed lady beetles, and Australian lady beetles, take a big bite out of these pests. We can help them do their job by avoiding broad-spectrum pesticides and applying sticky barriers to the trunks of trees. Argentine ants are known to protect scale insects, so sticky barriers remove that protection.

Purple scale prefer dusty conditions, so giving your citrus trees a quick shower with the hose can help.

Rather than steamy backseat interludes, frenching describes the way leaves can become discolored or distorted.

Frenching most commonly occurs in cotton and tobacco but may also occur in citrus, sorrel, squash, and tomatoes. Peppers seem exempt from this condition, but no one knows why.
 
Is frenching a disease?

Well, yes, and no, and maybe. Since botanists do not entirely understand frenching, its causes are currently called frenching factors. These factors include fungal diseases, insufficient iron, poor drainage, alkaline soils, and temperatures above 95°F. Frenching is also more likely when plants are grown in soil that stays moist during drought conditions.

In some cases, specific bacteria commonly found in the soil, such as Bacillus cereus and Macrophomina phaseolina, the latter being one cause of damping off disease, cause frenching.

How to identify frenching

Leaves can turn the wrong color or take on an abnormal shape for many reasons, but frenching has some consistent characteristics:

• Short internodes
• Leaf thickening
• Vein darkening
• Chlorosis along leaf margins
• Downward curling
• Rosette, or witches’ broom growth
• Slowed overall growth
• Loss of apical dominance*

*Apical dominance refers to some plants’ natural tendency to have one main shoot that actively inhibits the growth of others (think Christmas tree).

Today, we are learning about the Krebs cycle. Wait! Come back!
 
The Krebs cycle is how plants get energy from their food. Also known as the citric acid cycle, it won’t tell you how to grow bigger tomatoes or sweeter melons, but understanding the Krebs cycle gives you a better understanding of how plants grow and what they go through to make all those delicious things we eat.

We’ve already discussed the nitrogen cycle, the carbon cycle, and the water cycle. Those cycles describe how things needed by plants become available (and unavailable) as they change forms, moving through the environment.

​We’ve also discussed the Calvin cycle, which is part of photosynthesis. In the Calvin cycle, several anaerobic chemical reactions occur that allow plants to transform the carbon from CO2 into sugars. After those sugars are formed, the Krebs cycle begins.

Messrs. Krebs and Johnson
 
In 1937, a man by the name of Albert Szent-Györgyi was studying pigeon muscles. Stay with me, now! He received a Nobel Prize for his efforts, part of which was discovering several aspects of what later became known as the citric acid cycle. His discoveries were taken further that same year by Hans Adolf Krebs and William Arthur Johnson. [I guess they decided the Johnson cycle didn’t sound as impressive.] Krebs received the Nobel Prize for Physiology in 1953 for that work. [I don’t know why Johnson didn’t. Maybe he was too difficult to work with. I don’t know.] The Krebs cycle is part of the aerobic respiration process plants use to produce usable energy.

Respiration, not what I expected

When I hear “aerobic respiration” I start thinking about increased heart rates and time spent on a treadmill, but that’s not it. Aerobic respiration refers to one way that usable energy is formed. That usable energy is adenosine triphosphate or ADT. ATP is a molecule that carries usable energy around within a cell, taking it wherever it is needed. ADT is created when food (sugar) is burned with oxygen. I don’t know how plants burn anything but I keep getting images of little campfires in plant cells, so that’s kinda fun.

Sugar as plant food

I always thought plants simply drank sugar solution as food, but that’s not exactly how it works. Let’s put our steampunk magnifiers on and see what’s really going.

To start, you need to know that sugar molecules are relatively large. To use them, plant enzymes go to work, breaking down those acidic glucose molecules into energy and pyruvic acid. That process is called glycolysis. More reactions occur, breaking the remaining bits down into carbon dioxide. As energy is released through these processes, it is moved to other molecules, called electron carriers. Electron carriers are like tiny cargo trucks. They form a chain called the electron transport chain. This transport chain creates ATP. As a side benefit, the processes also create the building blocks of several other molecules, such as amino acids.

For perspective, let’s say that a plant cell is the size of Arizona and the mitochondria are Phoenix. Arizona has a railway system that transports food. All the food comes from Texas and is too big to be packaged. This giant-sized food is taken to Phoenix where it goes through a 9-step process that converts the giant food into snack-sized portions that are small enough to fit on the trains. The trains take the food wherever it is needed. Put simply, that’s the Krebs cycle.

But what does all this have to do with your garden?

The bottom line, healthy plants produce bigger, tastier crops with less effort on our part. They are better able to defend themselves against pests, diseases, and weather extremes. All you have to do is make sure they get the right amount of water regularly and that the soil they are growing in contains the correct range of nutrients.

Have you had your soil tested yet? What did you learn?

Runoff

Water moving across the land is called runoff. Surface runoff, or urban drool, is wasteful and potentially dangerous. As suburban sprinklers miss their mark and water streets and sidewalks instead of lawns, they also carry oil, excess fertilizer, trash, and pollutants into waterways. Please make sure your sprinklers water where you think they do and adjust them as needed.

As you can see, the water cycle is a series of steps that pass through various filters along the way. A student of mine once created a variety of natural filtering systems for a science project. She used rocks, leaves, sand, and soil in separate containers to filter muddy water. Which material do you think did the best job of cleaning the water?

I thought it would be the rocks, but I was wrong.

It was the soil.