Solving plant problems requires knowing what the enemy is


A couple weeks ago somebody brought me a Ziploc bag full of blueish gray bugs with orange stripes and spots on them. He told me they were killing his crape myrtles. Many of the leaves were falling prematurely.

He also brought a few leaves that were curled, sticky and discolored. Some of the leaves had a powdery black substance on them. Others were almost totally black.

I immediately asked him if he sprayed or in any other way tried to kill these bugs. He hadn’t. He wanted me to tell him what to spray and if the trees were even savable.

The insect specimens he had were lady beetle larvae. Most people call them ladybugs. In another week or so he would have recognized them.

They weren’t what was causing his problem. In fact, they were in the process of partially solving his problem. Some folks buy lady beetles specifically to eat pests on their plants.

Using predators to kill pests is a type of biological control. Sometimes people use other insects like parasitic wasps to accomplish the same goal.

The insects responsible for the damage to his crape myrtles were aphids, most likely crape myrtle aphids. They are small, nearly clear and often hard to see. Aphids are a favorite food of ladybugs.

The sticky substance was honeydew produced by the aphids. It became the food for the black powdery stuff called sooty mold. While sooty mold is unsightly, it doesn’t greatly affect the health of the plants. It usually shows up in fall when trees lose their leaves anyway. The aphids weaken plants by sucking fluids from leaf cells. Aphids also can transmit viruses.

So often what we perceive are our problems really aren’t. Sometimes plant leaves and stems on our houseplants start to wilt. Many folks immediately assume the plant isn’t getting enough water. They feel the soil and it isn’t dust dry. However, they water the plants anyway, assuming they’d rather be safe than sorry.

Their beloved houseplant usually winds up dying. The problem was not dryness. It was lack of oxygen to the roots caused by wetness and usually compounded by insufficient light.

This summer I lost a mature white pine. Someone suggested it must have been too cold last winter. However, white pines live as far north as central Canada, where winter temperatures often reach 40 below. Cold wasn’t the problem. Too much water was. White pines don’t like wet feet.

Until the end of August, most places around here have been much wetter than normal. Prior to last week I haven’t been able to mow parts of my lawn since early June. Even then I got stuck a few times and had to pull the mower out with the truck and a chain. Try that without getting covered with mud.

This has been a crazy year. From the start, we have experienced extreme cold, unseasonably warm late winter weather, and a wet spring and summer. Farmers and homeowners have had many problems to contend with. Misdiagnosis only adds to the problems.

 

Lady beetle larva crawling under a crape myrtle leaf

Newly emerged adult

Pupa ready to emerge

 

Ted Manzer teaches agriculture at Northeastern High School (tmanzer@ecpps.k12.nc.us).

Advertisements

About tedmanzer

I grew up in Old Town Maine and got a B.S. at the University of Maine in Plant Sciences/ minor in Botany. From there I moved to West Virginia and earned a M.S. in Agronomy at WVU. I also met my wife there. She grew up in rural WV as the daughter of tenant farmers who raised cattle and hogs. Their lifestyle at times was one of subsistence and I learned a lot from them. I've always been a foraging buff, but combining my formal botanical knowledge with their practical 'Foxfire-type' background opened up my eyes a little more. I now teach agriculture to high school students at Northeastern High School in Elizabeth City, NC. My wife teaches with me and we make a great team. I also write a weekly nature/foraging column for the local paper (dailyadvance.com). I also have written several Christian nature/adventure novels that I plan to publish eventually. One is a five book family saga I call the 'Forgotten Virtues' series. In the first book, Never Alone, a young boy comes of age after his father dies in a plane crash, and he has to make it alone. Never Alone is now available in paperback, Kindle and Nook. The second book, Strange Courage, takes Carl from his High School graduation to his recovery from a nasty divorce. The third book, Second Chances, takes Carl from his ex-wife's death and the custody of his son to his heroic death at age 59. The fourth book, Promises Kept, depicts how his grandchildren react and adjust to his death. In the final book, Grandfather's Way, his youngest and most timid granddaughter emerges from the shadow of her overachieving family and accomplishes more in four months than most do in a lifetime. I use many foraging references with a lot of the plants I profile in these articles in those books.
This entry was posted in general nature and tagged , , , , , , , , . Bookmark the permalink.

3 Responses to Solving plant problems requires knowing what the enemy is

  1. tonytomeo says:

    Back in the 1980s, while I did my internship as an arborist, clients still wanted their valley oaks and coast live oaks sprayed for ‘whatever’ was in them at the time. We did not spray them, but had a referral for such services. We tried to talk clients out of it, but many insisted. Each of these trees has such a crazily active ecosystem going on in them. Taking out just one type of insect throws the who thing out of whack. Well, you know that. The problem was that after spraying a tree, the same tree would need to be sprayed for something else within the year. I always felt that it was easier to park the cars inside or somewhere else, and just deal with the mess, or just cut the trees down. Sadly, many clients really did cut the trees down.

    • tedmanzer says:

      So many people want 100% control. It’s sad. Sometimes no matter how much I explain things and dumb them down (like I do in these columns) They still refuse to listen. Many do though, so we have to savor our small victories.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s