Skip to main content

Thrip control: peppermint and clove

Here's a question: how many natural plant scents do you find repellent? The one that comes to the top of my mind is the scent of the newly blossomed corpse flower, Amorphophallus titanum. It smells very much like the name implies. If I could produce a scratch-and-sniff blog post, I would be tempted. The odor is horrible to humans, but sweet to some flying insects which are also attracted to rotting flesh. But perhaps you cannot tolerate the scent of clove, or eucalyptus? Insect pests are like us in this respect.

Pests in the garden and greenhouse

Insects, arachnids, fungi, and viruses. Their numbers are legion. The battle is constant. The most effective weapon is vigilance. In addition to vigilance, there are biological controls made from natural compounds which are generally non-toxic to humans. Included in this category are essential oils. For example cinnamon, rosemary, sage, neem, clove, peppermint and many others. These oils are repellent, and even toxic, to many of the pests in the garden.

It's thrips (singular) and thrips (pleural)

My task in the garden today was to monitor and treat plants for thrips insects. There are more than 6000 different species of thrips, most of them tiny in size measuring about 1 mm. They evolved to feed on fungi, but some feed on plants. The largest thrips feed on other insects. There are thrips species that are beneficial in the sense that some tropical plants (cycads) require specific species of thrips to pollinate their seed cones.

Of those thrips that feed on plants, they are particularly attracted to the blossoms and soft parts of the new growth. Thrips use their mouthparts to slice into the plant and suck out the cell liquid, leaving a scar on the surface. Damage from thrips typically looks like silvery gray spots and curled leaves and petals. They also cause damage by spreading plant viruses between host plants.

Insect repellent of peppermint and clove oil; 6 drops of essential oil per liter of water.

When I found thrips today, I was instructed to give them a good soaking spray with a dilute solution of peppermint and clove oil. There are scientific articles which show this combination is effective to repel and kill some insect pests.

Common thrips (photo from the provincial govt. of Ontario, CA). Adult and two larval (nymph) stages.

Cancer bush (Lessertia frutescens), S. Africa. This plant was noted to have thrips feeding on the orange blossoms. They're attracted to red and yellow colors.

I found a few thrips on this cancer bush, from South Africa. The plant has attractive orange blossoms in the spring. They morph into attractive papery seed-containing sacks. The plant has been used in traditional tribal medicine to treat some forms of cancer, hence the nick-name cancer bush. But, I couldn't find any scientific articles to back up the practice. That doesn't mean it is not useful, just not validated in Western literature.

We also found thrips on a gloxinia, Sinningia macrostachya. Sinningia is a genus of plants from S. America that features a tuberous stem and a preference for growth on stony surfaces. They generally have very attractive blossoms. This particular plant is infested with hundreds of little thrips, although the damage is relatively minor at this point.

Gloxinia leaf infested with tiny white larvae

Bench in 3C, the subtropical room

My work for the day was spent mostly on the collection side of the fence, but also on the display side of the subtropical room. I found most of the infested plants on the collection side, where there are more plants in flower. I used a spray bottle to treat all of the plants on this bench, whether I found thrips or not.

Subtropical collection room, lime tree in the foreground (with one lime fruit way at the top)

Solitary remaining lime on this small tree


Labels:

Comments

Post a Comment

Popular posts from this blog

I celebrate learning this about cycad plants

I didn't know that the cardboard palm - Zamia furfuracea - is a cycad. It isn't a palm tree (don't judge me, I'm not a botanist). But it also doesn't look like the other more familiar types of cycads with their fluted upright palm-like fronds. I didn't know it is said to be the second most commonly cultivated cycad, after Cycas revoluta . I didn't know this plant is unrelated to the common ZZ plant - Zamioculcas zamifolia - although they have a similar appearance. Before today I didn't know any of these things, but now I am happy to have learned them. From the parking lot I walked to the U of M Conservatory greenhouse in near-zero F weather. Stepping into the tropical spaces was a joy of its own. But being able to learn new information and experience new procedures was a compounding factor. Joy squared. During my 3-hour volunteer shift, my initial task was to clean the parasite critters (mealybugs and scale) from the stems and leaves of the cycad, Zami...
Post a Comment
Read more

Mobile indoor green wall

Finally, after three years... my plant vines have grown and spread to be green wall that I had hoped for. I'm not sure it would have taken as long if the plants were in a more humid, sunny climate, et cetera. But given our indoor Minnesota location - even with a southwest exposure - the vines have needed that amount of time to climb the six feet from the base to the top rungs of the metal grid supporting them. The result has been worth the effort. And to be honest, I didn't have to wait three years to begin enjoying the green wall. The vines were already attractive when only half way up the trellis. A metal grid is filled with mix of Epipremnum aureum cultivar "Marble Queen", Epipremnum aureum aka golden pothos, and Philodendron Brasil . Architecture of the green wall The initial intent of the project was to grow a green wall, in an apartment, that could be moved around to be able to clean underneath, and also to provide a mobile room divider for our open-plan loft....
Post a Comment
Read more

Strung out in the greenhouse

The assignment for my four-hour volunteer shift at the University of Minnesota Conservatory greenhouse was clearly listed on a whiteboard, with my name attached. Since most of the tasks involved working with strings of overhead cables or air tubing, much of my shift was spent at the top of a ladder. Vining plants are limited to only a few of the many benches in the greenhouse. Steel cables are strung above the benches to support their growth. Because many plants grow in a small space, part of the challenge is to untangle and separate the vines so that they don't strangle each other. Not many of the vines are blooming at the moment, as it is winter. However, Thunbergia grandiflora is producing a few lovely blue flowers (its tendrils grow clockwise, hence the common name Bengal clockvine). It's a popular houseplant, but it has become an invasive weed in parts of the world, like Australia, especially around waterways. Thunbergia grandiflora; notice small brown scale insects sucki...
Post a Comment
Read more