Pest control. Thrips from A to Z
Ah…thrips, yes. If you don’t know them by now, you will someday. I feel like it is inevitable. They are everywhere! These are one of the most popular and most annoying pests seen among our beloved houseplants.
Recently, after a year of struggle, I’ve managed to finally win with a huge infestation of this insect on my beloved Philodendron xanadu. Today I want to introduce you to the thrip life-cycle, tell you how to recognise it and how to deal with the infestation.
What is a thrip
characteristics and life cycle
First some basics. They (Thrips tabaci Lind.) belong to the order of the adiphora (Thysanoptera) and the thrips family (Thripidae).
The body of a female thrip is very small, elongated, comma-shaped, about 1 mm long, yellow, but the summer form can be light brown. It has two pairs of narrow wings and 7 antennae. In our geographical zone, thrips reproduce mainly by parthenogenesis, and that means we, houseplant growers…are pretty much screwed (like you know…they don’t even have to mate, there is no chance of brake up, divorce, deciding to travel and not to have kids ;)). As they reproduce in this manner, males are not really observed in their population.
The larvae differ from adults only in color and the lack of wings. Initially, they are cream-colored, then yellow with a darker spot at the end of the body and darkening on the antennae and legs. They reach a length of up to 1 mm.
Ok now what is important to us-growers is that adult forms of insects hibernate in the surface layer of the soil and on debris.
Thrips start feeding in the spring on weeds and when the tobacco is planted in the field, they leave their original hosts and move to the tobacco. They can cover very long distances just to reach their beloved plant. As the name of the pest says, of the many different plant species (both cultivated – MEANING OUR HOUSEPLANTS and wild), that can host the insect, thrips prefer tobacco. After reaching a tobacco plantation, thrips are not very mobile and remain there until the end of the growing season. Are you thinking now about having a tobacco in your house? Me too :D.
They feed on the undersides of the leaves. The female thrips lays light cream, tiny, invisible eggs on the leaf tissues, about 100 pieces each.
How to recognise thrip infestation
look for early signs
Firstly, if you can see it right away, the infestation is probably already big, so look for the early signs.
First of all there are certain hours of the day, that it is best to do this, to see the adult forms. What are the foraging hours for thrips? From my observations it is either early morning or early evening. I never saw them during a day.
Look not only at the underside of the leaf, but on the very edge and along the veins. In case of Philodendrons and Monsteras that have boat-shaped leaf sheaths – look there, most of the time you will fins plenty of pests in this area.
As to the appearence of the sick plant, as thrips drink the juice from the plant tissues, the leaves will turn pale. Over time you will see silvery veins on the upper side of the leaves. Plant will cease to grow, even if you fertilise it and and ensure optimal conditions.
It is very easy to recognise thrip infestation on variegated plants as the white parts of leaves will start to brown very quickly.
Tabacco virus transmission
how it is transmitted and how to recognise
As to the tabacco virus that thrips can transfer on a plant and that can become an additional problem. The larvae hatch from the eggs are the only ones able to take the virus from the plant, but they do not transmit the virus. The larvae turn into sick adults who remain capable of infecting plants with TSWV for the rest of their lives. However the don’t pass this ability on to the next generations. Young larvae must re-infect in order to transmit the virus later.
In the case of infection with TSWV, the first symptoms of the disease are visible on the plants after about a month (the symptoms will appear faster on young plants). Adult thrip specimen infected with TSWV need only several minutes of feeding to infect a plant. The first symptoms are local light or yellowish discoloration and necrotic spot. With the development of infection, as the virus travels trough the vascular bundle, systemic paralysis will occur.
Plant growth is then inhibited. Leaves deformation and discoloration appears in the form of spots, rings and ribbons. Over time, the leaves turn yellow, brown and die. Necrotic spots may appear on the stem covering the core.
In my experience the plant dies after around 6 months.
Prevention and control
The development of symptoms of infection is influenced by temperature, humidity and light in both cases of infestation (virus and “normal”). Dry and hot weather favors the development of thrips. At the optimal temperature of 25-28 °C, the development of one generation lasts 18-28 days.
Here are some basic rules that will keep the plant as safe as possible.
- Quarantine your new plants. This is the most basic as in most cases this is how we bring pests to our house in a first place. Keep them separate for two weeks, wash them, repot the top layer of the soil (at least) as they residue there after the winter beauty sleep ;).
- Clean the leaves, make showers or use a towel to get rid of the dust and potential pests.
- Get rid of dead parts of the plant, they attract pests.
- Do the inspection once a week (it is the most crucial part…check check and once again check, use a magnifying glass!).
- Remember 2% Neem oil solution with a dish soap and water is for PREVENTION, not for pest control. But do use it, the smell is somewhat unpleasant for thrips and makes the meal not so tasty for them ;).
What worked for me so far are two plant protection products and I am providing links to them below (these are random pages, it is not sponsored).
I did a horrible mistake of using one if them more than twice in one year which led to resistance. And don’t make my mistake. It was really hard to get rid of them after that. This is, I think, the basic rule – do it once and properly. Don’t over-do it.
Remember to use gloves and mask, and wash everything after. Stay safe!
- Edialux – that worked for my Philodendron xanadu after a long fight
- KB multisect – worked for the rest of the jungle. Easier to use – already in a form of spray.
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