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Fuchsia Gall Mite

 
Some older gardeners may remember the days when fuchsias were free of this tiny pest. Fuchsia gall mites were inadvertently introduced into California in the 1980s and very quickly spread throughout the state. Because fuchsias grow best in areas with cool, foggy summers, the coastal areas of California were particularly hard hit by fuchsia mites.
 
When the mite is introduced to a plant, it begins to feed and multiply. The feeding activity introduces toxins to the plant, which cause the leaves and stems to develop galls and flower production to stop. Fuchsia mites are microscopic in size and very contagious. They can be moved from plant to plant by pruning tools, hands, gloves – almost anything that contacts an infested plant and then moves on to a clean plant. In this respect, hummingbirds are not among the “good guys.” I think we all like to see hummingbirds visit and feed on fuchsia flowers. However, the hummingbird takes more than nectar and pollen from flower to flower. Research has shown that hummingbirds are a major vector of fuchsia gall mites and probably account for the speed of the spread of fuchsia mites once they were introduced into California.
 
What can be done to suppress fuchsia gall mites? Since the galled plant tissues will not recover, I suggest you prune off the galled tissues and dispose of them in the green waste. Prune back to where the tissues appear normal. After pruning apply insecticidal soap and/or summer oil. These products help suppress the mites. Since the mites are tiny and feed in the buds and leaf axles, thorough coverage is very important to achieving even moderate control. Also the plants should be treated every seven to ten days throughout the summer to maintain control.

If your plant is badly infested, I suggest pruning it back this winter similar to the winter pruning of a rose bush. Also treat the pruned, dormant bush with oil as a clean-up spray during the winter. Next spring start your insecticidal soap and oil treatments as soon as new growth is a few inches long. Treatments are especially important when flowers appear and when hummingbirds begin to visit. If you are planting new fuchsias, select mite-resistant cultivars and species. See the following list for possible selections.
Susceptibility of Fuchsia Species and Cultivars to Fuchsia Gall Mite Damage in California.

LOW SUSCEPTIBILITY OR RESISTANT1
Baby Chang, Chance Encounter, Cinnabarina, boliviana, minutiflora, microphylla ssp.
Hindalgensis, radicans, thymifolia, tincta, venusta, Isis, Mendocino Mini, Miniature Jewels, Ocean Mist, Space Shuttle
MODERATE SUSCEPTIBILITY2
Dollar Princess, Englander, aborescens, denticulate, gehrigeri, macrophylla, procumbens, triphylla, Golden West, Lean, Macchu Picchu, Pink Marschmallow, Postijon, Psychedelic
HIGH SUSCEPTIBILITY3
Angel’s Flight, Bicentennial, Capri, China Doll, Christy, Dark Eyes, Display, Firebird, First Love, magellanica, Golden Anne, Jingle Bells, Kaleidoscope, Kathy Louise, Lisa, Louise Emershaw, Manrinka, Novella, Papoose Raspberry, South Gate, Stardust, Swingtime, Tinker Bell Troubadour, Vienna Waltz, Voodoo, Westergeist
 
1 No control needed.
2 Merely pruning off galled tissue whenever it occurs provides adequate control.
3 Pruning galled tissue followed by spraying may be necessary every several weeks to provide high aesthetic quality.

Sources: Koehler, Allen, and Costello 1985; Costello, Koehler, and Allen 1987.