Identifying Leaf Damage, Part 2 - Insects

Beyond the sunburn and nutrition damage I showed last week, pests can really do a number on your plants. There are many different kinds of pests, and the damage they do shows up differently depending on what they are and how they attack the plant.

Chewing insects leave holes in the leaf. I thought I had slugs, but when I used the old “cheap beer in a shallow dish” slug catcher, I found that I had a tuna can full of drowned earwigs and not a slug in sight. This made sense because many of my damaged leaves were pretty high off the ground and earwigs are unfortunately very mobile. Also there haven’t been many slime trails – which slugs leaves as they move.

Leaf damage from earwigs.

This chewing damage happened on leaves that are 18” off the ground.

I must have a major infestation because they seem to damage a large variety of species, like this gourd seedling, which is covered with plant hair…

and this weedy plantain. 

Of course since I have put a chip mulch down as a path, I have given them perfect hiding places. Earwigs eat aphids and can therefore be considered helpful, but they are doing too much damage and I am going to begin a major trapping event. Check out this page from the U of CA on integrated pest management for more information on earwig damage and control. 

Leaf cutter bee damage to peonies. The leaf cutter bees are a native pollinator,
and usually only cause cosmetic damage, not health damage, to the plant.

These peony leaves also sport insect damage. This is most likely a leaf cutter bee. All the damage is at the edge of the leaf and that is pretty typical. This insect can make your plant look like it has been attacked by pinking shears. Usually the damage is only cosmetic and the plant doesn’t lose vigor. These bees are beneficial native pollinators and shouldn’t be nuked with pesticides.

A skeletonizing leaf. It's best to take this to an extension agent
and ask for their help, as the type of insect varies with the plant.

This kind of damage is also indicative of an insect munching on my leaves. This is the results of insects eating the top and/or bottom layers of cells on the leaf and leaving one layer and the veins. This skeletonizing is unsightly, making the plant look like it is browning out and dying. If the damage is severe, the leaf will often drop off. If you have this, take a leaf into your extension service and ask what to do. Different plants get different kinds of insects.

These next two pictures show mite damage. Mites and aphids are sap-sucking insects and this kind of splotched discoloration is typical. Both these insects are very hard to control since they reproduce rapidly and they are hard to completely remove off your plant.

  

Mites are tiny but their presence can be determined in a couple of ways. You can bang the leaf over a piece of blank white paper and they fall off and gross you out. Or you can rub the back of the leaf across the paper and find mite guts left behind. If the infestation is bad enough, you can see greyish webbing on the back sides of the discolored leaves. If you have a magnifying glass or keen eyesight, it is also possible to see them on the leaf.

Aphids are bigger than mites, but still small. There are numerous kinds but none of them are good. Some have wings, but mostly they are slowly mobile on their tiny bug legs. They also suck sap from the leaves. Some species poop out that sap, producing a sticky substance called ‘honeydew’ (yes, the name puts you off the melon, doesn’t it?) and this is what makes your car sticky if you park it under a tree. It is also an attractant to ants, so if there are aphids, you will often finds ants all over that plant.

Here is an interesting article, the kind I call "gross but cool," about honeybees and honeydew. If you want some "just gross" pictures of aphids, google "aphids and honeydew" and look at the images that pop up. EWWWW! Another good read is this article about how long it takes to get aphids under control.

Identifying Leaf Damage, Part 1 - Sunburn and Nutrition

My daughter sent me this picture a few weeks ago and asked what was wrong with her plants (and by the way, if you have questions too, feel free to leave them in the comments or send an email).

Damage to leaves can have a myriad of causes. Some causes are easier to figure out than others. Possible problems include insects and the variety of ways they damage leaves, sunburn - which is easier to figure out, and nutrition – either a lack of, or an overabundance of a substance.

This kind of edge browning is usually caused by a nutrition problem. It means your plant needs more or less of something. Different needs show up in different ways. I get tip die-back on one of my indoor plants but I don’t know what it is missing. If it bothered me more, I would try to fix it. But the plant just keeps sending out more leaves, so I cut off the ugly ones. My daughter's plant put on a bunch of new leaves that are beautiful, so it started to get whatever it was missing after she transplanted it.

OK, this is not the best solution, but this kind of problem needs more chemical knowledge than I have. So if you have edge browning, take a leaf in to someone who is trained, like the extension agents, and have them diagnose the problem.

It's easy to mistake nutrition issues and sunburn. This picture is sunburn damage on my grape plant, which lives on the hot and sunny south side of my house. Most of the leaves emerged and grew in the beating sun and could adjust. But part of this plant was shaded by an annual poppy and when I removed that plant, these leaves weren’t prepared for the summer sun. The result is sunburn. This browning seems to occur at random and the injury varies in intensity, but there are no holes. I didn’t expect it, but I won’t let other plants shade my grapes next year.

Early garden design - making a design plan and flexible priorities

If you are doing a DIY yard and garden, you are undoubtedly working on a budget. Otherwise, you would hire people to do it for you and get it finished while you drink iced tea. As usual when doing a project: think it through, make a plan, check prices, decide priorities, and be realistic. I know my yard will be several years in the making and the plan will evolve during those years.

For my yard, I had certain priorities. I would start on the backyard, then the next summer, I would do the front yard. The beginning steps for both would be the same. First, I needed to remove the gravel. Second, I HAD to improve the soil. Once the soil amendments were tilled in, I could do some “design work.”

The backyard when I moved in - Ack!

My backyard is long and narrow, has a young blue spruce at both ends, a spring blooming forsythia, a clump of chrysanthemums and not much else. I needed a path. I laid out potential lines for the garden path using a garden hose. This is a cost-free process that gives you a big visual aid that you can shift around easily. A hose is heavy so it won’t blow around if you have wind - far better than string, and it is visible enough that you can really get a sense of the layout of potential gardens and paths. Then, it is simple to make the lines straighter or curvier as you work with the design and walk through the future garden.

My first path from my backdoor to my shed was curvy and lovely. I shifted it several times as I walked it because in fact, I would rather walk a straighter line and just get to where I am going.

Next, I placed my plants in the backyard. The spring before I put my house on the market, I had potted up a bunch of plants that I knew would be able to withstand the move and neglect while I was packing and unpacking. This is not something that everyone can do, but because I was moving across town and doing it over the course of several weeks, I could take part of my old garden to help establish the new one.

I set the pots out so I could visualize what they would look like. Unlike the hose which gave a strong visual, I had to really put my imagination to work for the end picture. Now if I had a formal design, I would have had a paper plan to help me picture the final garden. (And this is what I will do with my front yard, since I live in an HOA.) I shifted the pots around over a couple of days and then planted the poor neglected plants into the improved soil and rolled up the hose.

The backyard by the middle of my 1st summer. Many of these plants came from my old house. Some are annuals from seed. I used old fence panels to reduce the amazing reflective glare off the white plastic fence. That project isn’t finished yet.

When the the sprinkler system was finally installed the next summer, I put the hose down again, so the garden borders were obvious.

Digging the main trench for the irrigation line during my 2nd summer. The plants are again a mixture of perennials and annuals from seed. You can see the hose outlining the garden.

I don’t know if I would do it again in that order, but I couldn’t afford to do both front and back yard in the same year, and the irrigation system couldn’t go in until both yards were gravel-free and improved. I wanted my plants to get established before that. I watered by hand and celebrated when I got my first sprinkler system ever to water for me.

I wasn’t planning to buy trees in my first year, but here is where flexibility pays off. I found good quality trees and shrubs on sale during the fall of my 1^st year. I bought them and put off the purchase of stepping stones instead. Later priorities include planting for shade, trellises to disguise my shed, getting my front yard design submitted to the HOA, finding low water grass and plants for front yard for xeriscaping, and putting in the paths around the sides of my house to my front door. Many updates to come!

Spring and summer allergies, brought to you by pine pollen

If you have spring and summer allergies, much of your discomfort is caused by the pollen from wind-pollinated grasses and trees. We think of pollination occurring as bees, butterflies and other insects, or bats visit a flower for nectar, then share pollen between flowers. But a surprising number of plants depend on their pollen blowing to the right place.

One of the interesting things about these plants is how they reproduce because they don’t make flowers as we generally think of them. They do have male and female reproductive structures, which are called flowers in grasses and cones in evergreen trees such as pine, spruce, and fir. In these evergreen trees, there are male cones which make the pollen, and female cones which produce the seed. You may have seen the male cones and not known what they were. But if you have been around pine trees in the early summer and seen the yellow clouds of ‘dust’ that blow off them, you know what the pollen looks like! 

Baby male cones full of pollen. They will expand to be a bit bigger and let their pollen loose in huge waves. Picture from http://www.statesymbolsusa.org/.

Male cones shedding pollen. Picture from here.

This is an energy-inefficient way of reproducing, having to produce large amounts of unused pollen in hopes that some of it will hit a fertile female cone of the same species. Insect pollinated plants are considered to be more efficient and advanced. 

Baby female cones: When they are this small, the pollen blows onto them and fertilizes the tiny seed-beginnings inside.
Image from http://forestry.usu.edu/.

Once the seed is fertilized, it will grow inside the expanding cone until the seed is mature. If it is nut-like, as in pinyon trees, the seed is heavy, and will fall out of the cone onto the ground.

Female pinyon cone with mature seeds. Image from Wikimedia.

Other needled trees produce seed that is winged and can be carried in the wind. Like the cone-bearing trees, male flowers of grasses produce lots of pollen to ensure fertilization of the female flowers and the subsequent seed development. In the grasses, the reproductive parts are not very obvious, but are quite interesting to look at if you have a magnifying glass. 

As a young plant geek, I stumbled upon the most breathtaking displays of flowers made out of glass at a museum on the Harvardcampus near Boston. A master glass-blower made flowers of exquisite beauty and amazing detail and this was my introduction into how beautiful the floral structures of grasses can be. It is easy to be impressed when they are displayed many times life-size and show the extraordinary detail that is hard to see with the naked eye. If you are any kind of a flower lover, you can spend hours and hours in this place. The picture below is one of the displays – a banana flower, made out of glass but so lifelike that it is breath-taking. If you ever go to Boston, check out this museum. It is one of the wonders of the world.

A banana flower made of glass at the Harvard Museum of Natural History. Image from Curious Expeditions's album Glass Flowers at the HMNH.

Anyway, I digress – back to pollen. Grasses flower on stems that look like seed, which they eventually will be. But before there are seeds, there are flowers, pollen – lots of pollen, fertilization, and seed development.

Blooming wheatgrass. Image from www.statesymbolsusa.org