Last updated on October 23rd, 2023 at 08:19 pm
Today I come to tell you a little bit of an oar that we may find in one of our crops this season. I speak to you of Polyphagotarsonemus latus, better known as white spider or white spider. Throughout this article I will introduce you to this bug that can damage any of our plants.
What do white spiders look like?
Actually, precisely speaking, it is not a spider. We are talking about a species of mite belonging to the order Acarina and the family Tarsonemidae. That is why it is more correct to use the term “white mite” or white spider mite.
In Latin America it is also known as chili mite, chili mite, tropical mite or yellow mite.
There are four stages in the life cycle of this mite: egg, larva, pupa and adult.
Females lay eggs in inconspicuous holes in the leaf or fruit surface. The eggs are firmly attached to these surfaces. The white spider mite prefers to develop on the underside of leaves, where it finds the optimum climatic conditions of humidity and shade, and the necessary food.
Larvae have 6 legs (3 pairs) and adults have 8 legs (4 pairs). In adults, there are important differences between males and females.
What females look like
Female mites are about 0.2 mm long and oval in shape. Their bodies are swollen in profile and are transparent, light yellow to pale brown or green, and waxy with a faint median stripe that forks near the posterior end of the body.
The female’s fourth pair of legs is reduced to a thin, long hair extending from the tip.
What males look like
Males are small (0.11 mm) and have relatively long legs. They are similar in color and lack the median stripe found in females.
The fourth pair of legs of males end in strong claws that are used to pick up the female nymph and place it at right angles to that of the male for transport and subsequent mating.
What the eggs look like
Broad mite eggs are elliptical, shiny and colorless, about 0.08 mm long, and are covered with 30-40 white eggs scattered on the upper surface of each egg.
The distinctive egg is a key identification feature to be used to confirm that plant damage is being caused by this type of mite. When the eggs hatch, larvae emerge that are approximately 0.05-0.1 mm long and because of the tiny ridges found on their skin appear white, but then become transparent.
What larvae look like
The larvae have three pairs of legs. After 2-3 days, the larva becomes a quiescent “pupa” that appears as a clear, immobile, swollen body that is pointed at both ends.
What pupae look like
The “pupa” is about 0.08 mm long. Once they molt from this stage they become adults, which have four pairs of legs.
Multiplication and longevity
In conditions of high temperature, humidity and shaded environment, it multiplies very rapidly. At 25°C the development of one generation of these mites (from egg to egg) takes four to five days.
The longevity of a female is about ten days under normal conditions. During this period she lays about 50 eggs. Unfertilized females produce only male offspring, while females are produced from fertilized eggs.
In winter, the reproduction rate and activity of the mite decreases. For survival, this mite depends on living plant material, so it cannot hibernate in parts of the greenhouse structure, as red spider mites do.
What are the symptoms and damages of white spider mite infestation?
It is a species that especially affects crops grown in greenhouses, but it can also attack crops grown outdoors or indoors. This white spider mite attacks both ornamental and horticultural crops.
The white spider mite is a polyphagous spider mite that affects different species in our vegetable garden. Throughout the world, Polyphagotarsonemus latus develops preferably in humid areas with warm temperatures.
This mite is an important pest in tropical areas throughout the year. In subtropical areas, it is an important pest during the summer and autumn if conditions
summer and autumn if weather conditions are warm and humid.
And in temperate zones it is a pest during the summer months, but under the right environmental conditions of warmth and humidity it can cause severe damage.
About 50 recognized host plants are recognized, including bell pepper, raspberry, tea plant, citrus, tobacco and potato. In greenhouses, they cause damage mainly to bell pepper, eggplant, tomato, cucumber and ornamental crops such as azalea and begonia.
Damage caused by Polyphagotarsonemus latus consists mainly of leaf and stem deformation.
The mites prefer young, developing tissues such as young leaves and flowers. The white mite sucks the sap and produces deformations and corky scars.
On leaves, sucking occurs on the petiole part, which causes the leaf to curl up. The apical part of the plant is deformed, and brown discolorations appear locally. If left unchecked, it can cause the death of the plant.
In tomato, a tan discoloration occurs on the stem, terminal buds and undersides of young leaves. The leaves of the shoots dry out, causing the upper parts of the plant to appear burned, with shriveled and discolored stems. Leaves become bulging and have protruding veins.
In potatoes, it forms blackish spots of oily appearance on the underside of young leaves, giving them a reddish coloration, and the leaf folds at the edges in an irregular manner.
The same occurs on bell pepper plants, where it also prevents flowering or causes the flowers to fall off.
How to control the white spider mite?
Preventive cultural measures
To control the white spider mite pest it is important to use cultural measures such as eliminating the remains affected by the mite.
Keeping crops in a good sanitary condition helps to control all mite species. It is recommended to keep the area around the crop free of weeds or wild plants that can act as hosts, which will reduce the sources of infestation.
In seasonal crops, such as tomato or bell pepper, once the harvest is over, crop residues should be destroyed to prevent them from becoming breeding grounds for mites.
It is also recommended to prune the affected plants, eliminating the leaves and stems that are attacked.
Other advice to follow is to avoid depositing dust on the leaves. Dust deposited on leaves facilitates mite attack.
In tomato it has been seen that it is important that the plants are well watered and nourished. The use of organic fertilizers such as mulch is recommended. Water stress (lack of water) favors the appearance of mites.
It is not advisable to over-fertilize, because an excess of fertilizer also favors the development of this pest.
Control methods in organic farming
In organic farming, the use of sulfur and neem oil is recommended to combat this pest. Both give good results. There are commercial products available in both cases.
If you want to make a homemade acaricide, you can use chili bell pepper, garlic and liquid dishwashing soap. There are scientific studies where it has been tested and found that this mixture gives good results to control this white mite (5).
Chili contains capsaicin, which is an irritant to insects and mites, causing them to flee the area, stop feeding and die (5).
Garlic contains certain sulfur compounds, which affect the nervous system of insects and mites, acting as an irritant and repellent (5).
The soap serves to make the product adhere better to the stems and leaves of plants. In addition, when it comes into contact with the fatty tissues of the mites, it causes them to die by dehydration (5).
How to make a homemade acaricide
- 100 grams of chili
- 28 grams of dishwashing soap
- a whole head of garlic (10 or 12 cloves)
- 1 liter of water
Grind it all together and let it stand for 24 hours. Once it has rested, filter it and dissolve it in a container with 20 liters of water.
If you want to make less quantity reduce the proportions.
If conventional agriculture is carried out, acaricide active substances such as Abamectin, Tau-Fluvalinate or Cypermethrin can be used.
These active ingredients are usually found in the acaricides sold in stores.
Biological control is allowed in both organic and conventional agriculture.
In this case, white spider mites have natural predators, that is, there are other animals that eat them. In this case, insects and other mites can be used to combat this pest.
They are sold in sachets, which are placed on the plants. The effects are greater in closed environments such as greenhouses, although they can also be released outdoors.
The main species used are:
- Amblyseius swirskii
- Eretmocerus mundus
- Eretmocerus eremicus
- Encarsia Formosa
I leave here a link to an article about white bugs and white bugs in the soil in case you also find it helpful.