Tomato Russet Mite: Symptoms and Control Guide

Russet Mites Damage

This is a small mite, invisible with naked eye which attacks the green part of the plant. Russet mites remove cell contents from leaves, stems, and fruit cells.

Usually starting near the ground, infestations of this mite progress up the plant and lower leaves dry out, giving the plant an unhealthy appearance. The color of the stems and leaves frequently becomes greasy bronze or russet colored. If not controlled, this pest can kill plants.

Damage is caused by the mites sucking out the contents of plant cells. Affected leaves are slightly curled and acquire a silvery sheen on the underside. Later they become brown and brittle.

Badly affected tomato leaves and stems lose their trichomes (leaf hairs). Affected stems turn a rusty brown colour, and in serious cases they may snap.

The fruit can also be affected, and when this happens in tomatoes, the skin becomes coarse and turns reddish brown and the fruit itself is sometimes deformed.

Considerable damage can occur, especially at high temperatures when population growth is most rapid and affected leaves dry out quickly. The damage is first seen on the lower part of the plant and moves upwards as the mites ascend.

Read Also: Planting, Growing and Harvesting Tomatoes

Adults and nymphs have cigar-shaped, yellowish-tan or pink bodies and require a microscope to observe. Tomato russet mites have multiple, overlapping generations per year. They overwinter as adults in crop debris. They are primarily a concern when the weather conditions are hot and dry.

Adults and nymphs feed with piercing-sucking mouthparts causing bronzing or “russeting” of the surface of stems, leaves, and fruits. Damaged leaves may turn yellow, curl, wither, appear “deflated”, and fall from plants. Mite feeding on fruits can cause longitudinal cracks and bronze coloration.

Symptoms and Damage

Some of the symptoms that are being displayed by the plants when being affected by this disease include:

• Leaves turn yellow and dry from the top

• Brown areas appear on stem
• Attacked fruits have a cracked aspect and keep a small size

Habitat

This mite attack and lives on solanaceous crops in a warm and dry habitats and dies when it gets too cold since it cannot sustain normal physiological functions.

They enter a deep sleep to withstand the unfavourable temperatures unless it can get a perennial alternate host on which they can  overwinter (Smith 2015).

They first inhabit the lower part of the plants before slowly moving up the plant as they damage the lower parts of the plant through feeding (Park et al. 2010).

Food

Aculops lycopersici feed on the foliage, inflorescence and young fruits of tomato plant, causing shriveling and death of leaves, dropping of flowers, and russeting of fruit (CABI 2020).

The tomato rust mite may feed on other plant species such as brinjal, peppers, potato, wild and Cape gooseberry and many other solanaceous plants (Smith-Meyer & Creamer 1999). Injury to these host plants is only frequently observed on tomatoes and rarely on other Solanaceous species (Kawai & Haque 2004).

Sex and life cycles

Sex: Tomato russet mites go through  a few generations per growing season and its population can double in a few days at high temperatures and they die if exposed to sub-freezing temperatures (Duso et al. 2010). Females lay over 53 eggs in their lifetime and newly hatched females begin laying eggs just after two days.

The larval stage lasts for about a day, and the nymph stage last for about two days (Smith-Meyer 1981). The complete lifecycle of this mite last for about five to nine days under the most favourable temperatures for their growth, reproduction and success. This mite uses the plant host for reproduction (Duso et al. 2010).

Family life: They usually live in large numbers on a green surface just ahead of the damaged area and exhibits a patchy distribution in the host field (Duso et al. 2010). They work together when migrating from a dying plant to the alternative plant host (Smith-Meyer 1981).

Damage Prevention

They can be prevented through the following means:

• Favor sprinkling irrigation on leaves
• Apply specific and systematic preventive acaricid
• Remove crop residue after harvest

Related: 4 Steps to help an Orange Tree Produce Sweet Oranges

General Management

• The presence of tomato russet mites often goes unnoticed, due to their tiny size, until injury is evident.
• Watch for injury symptoms especially during hot, dry conditions.
• Look for bronzing on lower leaves and stems.
• Use a microscope to check damaged leaves and surrounding healthy leaves for mites.

If not controlled, this pest can kill plants. Tomatoes are most commonly affected, especially during hot, dry conditions.

• Avoid planting during hot, dry periods.
• Promptly remove or destroy infested plant debris.
• Clean tools used on infested plants before using on healthy plants.
• Applications of pesticides.

Insecticides

Once russet mites are present on plants, insecticide treatment (sulfur, abamectin) is the primary control option.

In summary, Tomato russet mite (Aculops lycopersici) causes bronzing of tomato stems and yellowing and drying of leaves. Damaged fruit remain small, turn brown, and have a russetted appearance.

Aculops lycopersici, commonly known as tomato russet mites, are so small that they are invisible to the unassisted eye and their presence can usually only be determined by symptoms observed on the plant. When observed under a  microscope, they appear orange to yellow in color and have a shape that become narrower towards one end (Smith-Meyer 1981).

Some common symptoms may include presence of heavily yellowish-brown coloured stems or branches or dried leaflets, the discolouration of flowers, flowers that fail to open, premature drop of the fruits, enlarge buds, premature bud drop and abnormalities in shape of the leaves (Smith-Meyer & Craemer 1999). The Eriophyid mites can be identified with certainty only by examining properly cleared and slide-mounted specimens under high magnification (Smith-Meyer 1981).

Symptoms move up plants from lower areas. Presence of this mite can only be confirmed with a hand lens (10X or greater) or microscope. Look for minute, cone-shaped mites on the green tissue. While this mite feeds on various solanaceous vegetables, damage has only been observed on tomato in Kentucky.

Management:

• Watch for characteristic damage; once tomato russet mite is confirmed, treat with an approved miticide. Miticides that control spider mites are not necessarily effective against russet mites. Evaluate miticide effectiveness by tagging the limits of stem bronzing on a plant and monitoring it for additional damage.
• Remove alternate hosts, such as nightshades, bindweed, and morningglory, from in and around structures.

Biological control:

• If your structure has a history of tomato russet mite infestations, consider releasing Amblyseius fallacis predatory mites. 

Tomato russet mites. (Photo: Ric Bessin, University of Kentucky)

Bronzed, greasy appearance to stems from tomato russet mites. (Photo: Ric Bessin, University of Kentucky)

Undersized, dark, russetted fruit from tomato russet mites. (Photo: Ric Bessin, University of Kentucky)

Read Also: Tomato Leaf Curl or Leaf Roll – Causes and Preventive Measures

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