Mullein Bug (Campylomma)

Mullein Bug (Campylomma)

Hosts

Apple, pear, rose, saskatoon, mullein, potato, corn

Damage

Fruit - A corky pustule 1-2 mm in diameter on the skin of young fruitlets is produced by nymphs feeding during a 3-week period starting at bloom or early petal-fall. On apple fruitlets the tissue around feeding punctures fails to grow normally, resulting in misshapen fruit. Apple fruits become more distorted with the number of feeding punctures. Apple fruitlets up to 12 mm in diameter are most susceptible to injury. Injured pear fruitlets retain normal shape and the pustules do not expand so that one or a few pustules may pass unnoticed at harvest.

campylomma damage Campylomma damage on Red Delicious

Identification

Nymph - 0.5-2.5 mm long, with pointed head and red eyes; fast-moving; body colourless, pale green, tan, reddish or brown, depending on food.
Adult - Oval, winged, 3 mm long, light green to tan.

campylomma nymph Campylomma nymph
Photo courtesy Agriculture & Agri-Food Canada

Life History

During September and October females lay eggs in the bark of young twigs on apple and pear trees and on saskatoon and wild rose bushes. Overwintered eggs begin to hatch near bloom. Nymphs feed mainly on small insects and mites, but will feed on plant sap when prey is scarce. First generation adults appear in June. Most of the adults migrate to annual plants to feed and produce one or two more generations during July, August and September. A small population may remain on apple and pear trees to reproduce during the summer if there are enough mites, aphids or pear psylla to attract them. In the fall, adults migrate back to apple and pear and other woody plants to feed and lay eggs. High populations of mites and aphids in the fall have sometimes been associated with high populations of mullein bug in an orchard the following spring.

Monitoring

A pheromone-baited trap is commercially available to monitor blocks of susceptible fruit varieties for returning adult mullein bugs in September and October. Research in conventional orchards in the Okanagan has found that high numbers of adults in the fall will result in high numbers of nymphs the following spring. By monitoring adults in the fall, growers can determine which blocks are potentially at risk of mullein bug damage. Use a beating tray in the spring to determine if mullein bug populations are high enough to cause damage. Because this insect tends to be very unevenly distributed among trees in an orchard, it is important to sample thoroughly, especially where damage has occurred in the past. Sample susceptible apple and pear blocks at the rate of 50 taps per hectare and calculate the average number of nymphs per tap for each block. Begin sampling at pink of apple and continue through bloom and every 3 days after bloom until hatch is completed. Rows adjacent to pear blocks should be checked carefully to detect migration from the pears where mullein bugs are encouraged for biological control of pear psylla.

Because sampling efficiency varies with tapping style used, growers and advisors should develop their own treatment levels. Very susceptible varieties may need a spray at levels as low as 1 per tap, while less susceptible varieties may need a spray at levels of 4-15 per tap. Gala, Sunrise, Golden Delicious and spur Red Delicious apples are very susceptible; Braeburn, Elstar, Red Rome, Spartan, Jonagold, Empire and non-spur Red Delicious apples and Bartlett pear are moderately susceptible. McIntosh, Granny Smith and Fuji apples and Anjou pear are tolerant to mullein bug.

Control

Cultural - Removal of mullein in and around the orchard may be helpful. Avoid large plantings of corn or potatoes in or near orchards.

Chemical - Apply Diazinon at pink if mullein bug nymphs are at or above the action threshold. Treatment at this time will reduce the number of nymphs that can cause damage during bloom. Alternatively, apply Diazinon or Admire at early petal-fall if needed once the bees are no longer foraging in the block. Diazinon applied at petal-fall for leafrollers or fruitworms will also control mullein bug. Do not apply Admire more than twice per season for all registered pests. See the precautions regarding use of Admire and Assail under apple aphid control.

February 2004

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