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Ministry of Agriculture, Food and Rural Affairs

Mullein Bug

Young mullein bug nymph Adult mullein bug Adult mullein bugMullein bug damage to young fruitlets Damage to Red Delicious fruit Damage to fruit Monitoring mullein bug with tapping board
Click to enlarge.

Beginner

Scientific Name
Campylomma verbasci

Identification
Eggs:

  • 0.8 mm long,
  • White,
  • Flask shaped.

Nymphs:

  • 0.5-2.5 mm long,
  • Yellow,
  • Pointed head,
  • Red eyes,
  • There are five nymphal instars

Adults:

  • 3 mm long,
  • Oval,
  • Light green to tan in colour,
  • Antennae are segmented,
  • Hind legs have black spots and are spine covered. 

Damage:

  • Small, upraised, reddish bumps on the fruit surface,
  • Fruit often receive multiple stings and the large majority of these abort just prior to or during June drop,
  • Affected fruit that remain on the tree develop small corky warts or bumps surrounded by conical depressions.

Often Confused With

  • Aphids- Aphids have cornicles, which mullein bugs lack.
  • White apple leafhoppers- White apple leafhoppers have a more elongated body, and lack clubbed antennae.

Period of Activity
Nymphs begin emerging around bloom. Nymphs and adults can be found in orchards up until harvest. Most years the hatch is synchronized with peak emergence at early petal fall, but a cold snap during this time may result in split hatch making chemical control more difficult. During bloom to 2 weeks after petal fall period, mullein bug nymphs are a pest of apples.  After petal fall they become a beneficial insect.

Scouting Notes
During bloom to 2-3 weeks after petal fall, mullein bug nymphs cause economic losses to certain varieties of apple, particularly Red Delicious and Spartan. Northern Spy, Empire, Cortland, Gala, Jonagold and Golden Delicious are also sometimes affected.

Begin monitoring for nymphs during bloom and continue until two or three weeks after petal fall. Frequent monitoring (two to three times per week) is recommended from bloom until 3 weeks after petal fall. Monitor mullein bug using tapping trays. Sample at least 25 trees per block and one limb per tree. Tap each limb two to three times to dislodge the insects while holding the tray below the branch. Check tapping tray after tapping each branch. Newly hatched nymphs are quite difficult to see, and a hand lens is recommended to positively identify nymphs.

Choose limbs with fruit clusters since mullein bug are often present on these. Concentrate on sampling blocks of susceptible cultivars and blocks where mullein bug has been a problem. Conduct tapping on sunny days, once temperatures have warmed. Avoid tapping on cold, overcast days or when it is raining.

Thresholds
The following economic (action) thresholds can be used:

  • Red Delicious, Spartan – 7 nymphs/25 taps
  • Other susceptible cultivars – 10 nymphs/25 taps

Advanced

Scientific Name
Campylomma verbasci

Identification
Eggs are 0.8 mm long, white and flask shaped. Mullein bugs develop through five nymphal instars to adults. Nymphs are 0.5-2.5 mm long, yellow, with a pointed head and red eyes. Adult mullein bugs are 3 mm long, oval and light green to tan in colour. Antennae are segmented and hind legs have black spots and are spine covered. 

Feeding on fruit causes small upraised, reddish bumps on the fruit surface. Fruit often receive multiple stings and the large majority of these abort just prior to or during June drop. Affected fruit that remain on the tree develop small corky warts or bumps surrounded by conical depressions. As affected fruit sizes through the summer, it becomes distorted. If uncontrolled, mullein bug can damage up to 75% of apples in Ontario orchards.

Often Confused With

  • Aphids- Aphids have cornicles, which mullein bugs lack.
  • White apple leafhoppers- White apple leafhoppers have a more elongated body, and lack clubbed antennae.

Biology
The mullein bug has two major plant hosts, the mullein plant and apple. Occasionally it also attacks pear, grapes, wild rose, serviceberry and oak. The insect overwinters as eggs inserted deep into the bark of one- or two-year-old wood of apple. Eggs begin hatching during bloom and continue to hatch into the petal fall period. Most years the hatch is synchronized with peak emergence at early petal fall, but a cold snap during this time may result in split hatch, making chemical control more difficult.

Nymphs initially feed on plant sap attained from leaf veins, and also sting developing fruitlets. Several weeks after petal fall, nymphs become predaceous and begin feeding on prey such as European red mite and aphids. Nymphs with red bellies are an indication the nymphs have been feeding on mites. Nymphs progress through five instars before becoming adults. Both nymphs and adults are fast moving, and adults are often quick to take flight if disturbed. The adults migrate to mullein plants, common along ditch banks and the sides of roadways in Ontario, where they feed throughout the summer months. Season-long monitoring in apple orchards indicates some mullein bugs remain in the orchard during the summer. During that time they are considered important predators of aphids and mites. In late fall, female mullein bugs return to apple trees and lay overwintering eggs into young wood. There are two to three generations per year.

Period of Activity
Nymphs begin emerging around bloom. Nymphs and adults can be found in orchards up until harvest. Most years the hatch is synchronized with peak emergence at early petal fall, but a cold snap during this time may result in split hatch making chemical control more difficult. During bloom to 2 weeks after petal fall period, mullein bug nymphs are a pest of apples. After petal fall they become a beneficial insect.

Scouting Notes
During bloom to 2-3 weeks after petal fall, mullein bug nymphs cause economic losses to certain varieties of apple, particularly Red Delicious and Spartan. Northern Spy, Empire, Cortland, Gala, Jonagold and Golden Delicious are also sometimes affected.

Begin monitoring for nymphs during bloom and continue until two or three weeks after petal fall. Hatch is usually quite synchronous and frequent monitoring (two to three times per week) is recommended. First emergence and threshold can be missed if only monitoring once a week, and may result in fruit damage. Monitor mullein bug using tapping trays. Sample at least 25 trees per block and one limb per tree. Tap each limb two to three times to dislodge the insects while holding the tray below the branch. Check tapping tray after tapping each branch. Newly hatched nymphs are quite difficult to see, and a hand lens is recommended to positively identify nymphs.

Choose limbs with fruit clusters since mullein bug are often present on these. Concentrate on sampling blocks of susceptible cultivars and blocks where mullein bug has been a problem. Conduct tapping on sunny days, once temperatures have warmed. Avoid tapping on cold, overcast days or when it is raining.

Thresholds
The following economic (action) thresholds can be used:

  • Red Delicious, Spartan – 7 nymphs/25 taps
  • Other susceptible cultivars – 10 nymphs/25 taps

Management Notes

  • Once mullein bug populations have reached the economic threshold (usually around petal fall) insecticides should be applied. See OMAFRA Publication 360, Guide to Fruit Production - Chapter 3 Apples (PDF) or Apple Calendar only (PDF) :
  • Since some of the products targeting mullein bug can have negative impacts on bees it is important to remove honeybee colonies immediately after pollination is complete before applying an insecticide.
  •  Do not count on pre-bloom insecticides – particularly pyrethroids – to control mullein bug populations into the calyx period, especially during springs with prolonged bloom.
  • Economic thresholds for mullein bug are based on pest density, but it is important to note that damage caused by this pest also is affected by availability of food such as pollen, nectar, plant nitrogen or animal prey. As a result, high populations of mullein bug may not cause significant fruit damage. 
  • During the summer mullein bugs are important orchard predators, so include mullein bug counts in monitoring of beneficial insects and mites during the summer months.
  •  Record numbers of mullein bug nymphs and adults when during terminal inspections and in limb tap sampling throughout the summer.