Citrus thrips are prevalent insect pests. Their presence on citrus trees can be a real threat to the commercial growth of citrus fruits.
This article discusses and describes these pests and shares information to help you prevent or deal with an infestation.
What are Citrus Thrips?
Citrus thrips are less than a millimeter in size. Adults have slightly furry oval bodies and fringed wings.
It’s hard to see these tiny little critters because their coloring causes them to blend in on the surface of the fruits they eat.
First instar larvae are miniscule and hard to see. Instars after that are about the same size as the adults.
This document provides excellent images of citrus thrips at all stages of development. Citrus Thrips Biology and Management.
What Damage Do Citrus Thrips Cause?
Citrus thrips pose a particular threat to orange, Meyer Lemon, lime, and other citrus-type trees. These very tiny yellowish-orange insects feed voraciously on citrus. They cause damaging and scarring on the surface of fruits.
It’s imperative to recognize the appearance of citrus thrips because they cause massive damage. Know them apart from other, less damaging insects.
Damaged citrus fruit in a commercial setting earns a lower grade due to lesser quality. Fruit that otherwise might receive the grade as “fancy” may only earn a “choice” label or a “juice grade” label if afflicted by citrus thrips damage. This reduces income for commercial growers.
When the fruit reaches approximately 1.5″ inches in diameter, the cells are harder for thrips to pierce. Still, after the fruit becomes too difficult for the thrips to eat, they will move onto and may defoliate young trees.
Citrus thrips multiply rapidly, producing as many as eight generations each year, as follows:
- Mature citrus thrips lay eggs on all parts of citrus tree.
- The larvae live underneath the sepals of the fruit and on the leaves of the tree during the first and second instars.
- They may pupate in cracks in the tree bark or drop into the soil to pupate.
- When the adults emerge, they may lay eggs and start the cycle anew.
The last generation of thrips each season lays eggs that overwinter and hatch in the spring. Each generation develops through four instars.
First generations of citrus thrips attack fresh, new leaves early in the season. Second and third generations attack young, emerging fruit.
Thrips are most damaging during the second instar because they eat tiny new fruits as they emerge. They cause damage to the fruit by poking their needlelike mandibles into the fruits at the dermal cells and sucking up the plants’ juices.
The adult thrips do not cause damage to the fruit, but the second instar is quite damaging.
Thrips are very hard to see because their coloration disguises them. They often like to stay in very tight, hidden places, such as underneath the fruit calyx.
You must inspect for them constantly because new ones come along regularly throughout the growing season.
These insects don’t just eat emerging fruit; they also eat the fruit buds as they appear.
Their predation causes white or silver trails on the surface of the fruit that only become more unattractive as the fruit matures. Very early scars on the citrus buds become large rings of damage.
Even though this damage doesn’t harm the edible parts of the fruit, it causes the fruit to look ugly and diminishes its value.
Is it Necessary to Control Citrus Thrips on Backyard Fruit Trees?
Even if you are only keeping a few citrus trees in your backyard for your own use, you should keep citrus thrips under control. If they survive and thrive on your tree, it won’t be long before they spread to commercial production.
Citrus thrips cause damage throughout the growing season as they feed on the flowers, buds, and immature fruits. They continue to feed on the fruit until it is about 1.5″ inches wide. Additionally, they feed on the leaves and can defoliate young trees.
In trees older than three years of age, damage to the leaves is not much cause for alarm. Trees more than three years old should be mature enough to withstand damaged leaves.
Even so, you should get rid of citrus thrips. Focus on managing the thrips in the time before the fruit attains the size of 1.5″ inches. Prevent them from reproducing, spreading, and eventually eating your trees’ leaves.
How To Control Citrus Thrips
You must begin citrus thrips control early in the growing season. Continue the effort throughout because of the rampant reproduction rate of these pests.
The best way to address thrips is to encourage beneficial insects in your citrus growth. Avoid the overuse of broad-spectrum pesticides.
Studies on citrus thrips populations show they reproduce more following broad-spectrum pesticide treatments. They can adapt and become resistant to these chemicals.
When you first see immature citrus thrips early in the season, you should do your first spraying. Be careful to identify thrips correctly.
Another type of thrips, western flower thrips, may also be present, but they do not cause any harm. They will appear a little bit before citrus thrips, and they look quite different.
Their bodies are long, and they move in a snakelike manner. Citrus thrips have very short, nearly round bodies and move about very quickly. Remember that citrus thrips have a trademark orange or yellow color.
These pests lay their eggs inside plant leaves and larvae and pupa hide in cracks in tree bark and pupate underground. This makes it difficult for any single type of natural predator to deal with them.
Yet, there are several types of natural predators that can help you keep citrus thrips and other pests under control:
- Euseius tularensis predatory mites
- Various types of spiders
- Minute pirate bugs
- Green Lacewings
It’s important not to overuse pesticides, which may wipe out your good bug population. Also, within eight generations, they will be utterly resistant to the product.
By the third instar, when the thrips mainly feed on the tree’s foliage, you may wish to treat it with an insecticide. But, you don’t need to do so continuously.
A single treatment of one of the products mentioned here could be helpful, but repeated treatments don’t seem to do more good.
One product that is effective against citrus thrips is Spinosad. Use of this organic product early in the springtime is effective against the first-generation of thrips.
You may also alternate your use of Spinosad with organophosphate or pyrethroids. These products are effective against thrips as long as no single chemical is overused.
The need to lessen the use of insecticides and rotate them is vital. Citrus thrips develop resistance very quickly.
They even developed resistance to DDT during the mid-20th Century. By the end of the 20th Century, they had also developed resistance to carbonates and organophosphates. They also have some resistance to pyrethroids.
Used on a rotating basis and very sparingly, these products can be somewhat effective; but, be careful not to kill off natural predators.