Thrips are Microscopic Insects but Big Problems

Thrip on a flower

I never knew thrips existed until I started growing African violets. I don't have a picture of them on violets, but most likely if you've ever bought an African violet at a grocery store or big box, you've seen the signs of them. Their larvae love to eat the pollen of the violets, and when they do it falls onto the petals, making it obvious. It is always noticed more on dark colored violets, as the yellow shows up best against the dark color. If you see pollen on the petals, do not buy the violet. You are bringing home trouble. When I come home from an African violet show, if I've purchased plants, the first thing I do is take all the flowers off the plant. This is not an easy thing to do. Heartbreaking, in fact. It is necessary, though to get rid of any pests, such as thrips that may be lurking in the flowers. I also quarantine my plants for a few weeks to make sure they don't have any other insects or diseases.

The pollen sacs are the yellow in the middle of the flower

 Thrips are very small insects, almost impossible to see with the naked eye. The most common on greenhouse plants are the Western Flower Thrip, Frankliniella occidentalis. These pictures are enlarged quite a bit. If you breathe on flowers that you suspect have thrips, you can see them run, if you have good eyesight. Thrips have piercing, sucking mouth parts. The biggest problem that thrips cause is damaged areas that disease can then enter. They are vectors for virus to enter the plant. You will notice the damage before you see the microscopic insect. On flowers the damage may appear as streaked or discolored areas, on leaves they will be dried out and have a silvery appearance. They attack plants inside and out, but we are going to deal with indoor plants, of course.

The best way to deal with thrips is to not allow them to enter your plant area. They are so small, they can fly through most window screens. They can also come in on cut flowers, either from the florist or from your own yard. I know people who would never open a window in their plant room.

If you have them, how do you remove them? Systemic insecticides may not work well, as the systemic does not easily pass into the flowers of the plant where the thrips are feeding. Also, thrips feed on cell content, not the xylem or phloem where the systemic is contained. The amount that does go into the flowers may not be enough to kill the thrips. Also, flowers do not last as long as leaves, so there is less time for the insecticide to accumulate. Spinosad and neem oil also work on thrips and are less toxic than other chemicals. Removing the flowers is a good way to rid yourselves of thrips, especially if growing African violets. Keep the flowers removed for quite some time. Using sticky traps to monitor thrips works, but use blue sticky traps instead of the usual yellow.

Thrip on a streptocarpus flower

If you want to rid yourselves of these pests with biological controls, there is more than one that will work. Predatory nematodes, Steinernema carpocapsae help control thrips, as well as Steinernema feltiae, Orius insidiosis, the pirate bug, and the thrip  predatory mite, Amblyseius cucumeris. These are all biological controls that could be used to eat the larvae and/or adults. Once again, I'm listing these biological controls, knowing that it may not be practical  for many people to use them. That being said, I wanted to list all the ways that one could control thrips. 

Once again, I can't stress enough, that a healthy plant is the best way to deter pests. Check your plants every time you water for pests and disease. Keep your plants well watered, fertilized and in the correct light to keep them healthy and happy. 

Put Plant Health First

 So, I've had some controversy on my last post about insects on your houseplants. First, the use of imidicloprid was brought into question. Of course, I am not telling you to run out and  buy an insecticide and use it on every plant you have to kill everything in sight and out of sight. I always try the least toxic solution first. This includes using soap and alcohol, or neem oil in the form of Rose Rx. Now, if that doesn't work, I will use a houseplant insecticide. Some of my plants are over 30 years old and belonged to my great-grandma. I am not going to lose those plants to scale or mealybug.  I have also listed the biological controls that one could choose to use in their home. Whereas this may seem contradictory to some, these bugs are the good guys. They destroy the bad guys and the plus is that you don't have to use insecticides in your home.  After those good bugs have eradicated the bad bugs, they won't take over your home. In fact, without something to eat, they will probably die.

A well grown crown of thorns

The number one thing to remember is that a healthy houseplant is a happy houseplant. A healthy houseplant also is much better able to ward off insect pests and disease. That being said, everyone is going to deal with pests at one time or another. Bringing houseplants home from a store or even a  friend's house can bring unwanted visitors into your home. Even if a plant looks pest free, quarantining your plant from your other plants is very important. Four to six weeks should be long enough to allow any pest or pest eggs that are lurking to show themselves. Checking your plants on a regular basis for insects can help prevent them from becoming a problem. Every time you water, take time to inspect your plants. Look under the leaves and in the areas where the leaf petiole meets the plant stem. Insects love to hide in these areas. Keeping them clean is extremely important. A dusty, dirty plant is blocked from photosynthesizing, preventing the production of  food they must have to live and grow. I like to put my plants in the shower on occasion. Of course, this only works for the ones I can lift. The other plants are washed with a sponge and mildly soapy water. I like to use Ivory dish soap or Murphy's Oil Soap. Using a de-greasing dish soap can mar the foliage of some plants.
Refreshing their soil, or re-potting them on a regular basis is also beneficial. The growing media your plant is growing in can break down and disintegrate over time. Giving them new soil can be like fertilizing the plant. It gives them renewed vigor and strength. 
Another way to ensure your houseplant stays happy and healthy is to place your plant in the right light for the plant you are growing. A high light plant growing in low light is a stressed plant. And just as stressful is a low light plant growing in high light.

Crossandra

Watering your houseplant correctly is also a huge factor in the health of your plant. Too much water can suffocate your plant and rot the roots. Not enough water can shrivel your roots and your plant will wilt. It may come back from being under watered, but it still takes its toll on the plant's health. 
And lastly, air circulation is a plus. I have a ceiling fan running 24/7 in my greenhouse and in my African violet room. Pests do not like wind and by running a fan, the stems of your plants are strengthened. This also helps prevent diseases such as powdery mildew and fungal diseases that can result from wet leaves.
Just remember, healthy plants are pest and disease resistant plants. Try to nip those problems and pests in the bud before they negatively affect your plants.

A Day for Houseplants

We love our houseplants!

 Today is Houseplant Appreciation Day. I think every day is Houseplant Appreciation Day, but I realize that people who aren't obsessed with them like I am, probably could use a day like this. I have researched this day and found that Bob Matthews of Gardenersnet.com came up with this day. Why? Because he felt that after the holiday rush our plants could use some attention. The decorations are down and put away and its time to turn our attention back to our neglected houseplants. What a great idea! Thank-you Bob!
Why do we need to appreciate our houseplants? Because, they are cleaning our air, giving us life-sustaining oxygen, and making us happy. So we need to show them how much we appreciate them by taking care of them. Today is a day to show our plants how much we love them. How do we do that? Here a few ways you can show your houseplants some love and also some things not to do. 
First, give them a shower in the sink or in the bathtub if you can get them there. Dust is a huge detriment to plant growth, (as are dirty windows!). Hopefully you washed your windows last fall when you brought any houseplants in that were summering outside. So, back to showering your houseplants......
Nothing is more unattractive than dirty, dusty houseplants. Plants get their food from light, sun or artificial. When plants are dirty, the light can't get through to the leaves, so they need to be kept clean. If your plant is too big or heavy to be moved to the shower or sink, a sponge and a bucket of warm water is the next best thing. Washing your plants also helps get rid of any unwanted visitors that may be lurking, as well. 
After washing your plants, do we spray some nice plant shine on them to make them pretty? Absolutely not! I am NOT a proponent of gooping up plants with shine. It is not natural, unless you use Neem oil, which is also a wonderful pest control product, by the way. Anyway, I have never used plant shine and do not plan on starting. A natural clean plant is the best way to go.
Another practice that should not be done, is fertilizing your plants at this time of year. At least here in the frozen north, our plants aren't actively growing at this time of year, and so do not need fertilizer. I normally start fertilizing my houseplants in early March, or late February. I wait to see some new growth before adding any nutrients.
Some people think you should talk to your plants. That's up to you. I don't talk to my plants, but when washing them and grooming them, you are breathing on them, which gives them the carbon dioxide they need. So if you talk to them while you are near them you will provide them with even more CO2, so start talking. 
Remove any dead or yellowing leaves. These leaves may have a fungus or disease, so by removing them you will be helping stop the further spread of any diseases.  

Make sure your plants are watered, clean, and have any yellowing leaves removed and it will be Houseplant Owner Appreciation Day.