I have a hawthorn tree that is struggling with little white blister like structures on the branches that seem to be sucking. The sap out of the tree. Picture is provided below. Is there anything I can do to help my tree? - Ask Extension
I have a hawthorn tree that is covered with little white blister like structures that seem to be sucking the sap out of the tree. Can we identify and ...
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I have a hawthorn tree that is struggling with little white blister like structures on the branches that seem to be sucking. The sap out of the tree. Picture is provided below. Is there anything I can do to help my tree? #873633
Asked June 18, 2024, 2:30 PM EDT
I have a hawthorn tree that is covered with little white blister like structures that seem to be sucking the sap out of the tree. Can we identify and treat?
Larimer County Colorado
Expert Response
Hi Doug,
This is hawthorn mealybug and populations seem to be high this year. It's a difficult insect to control and control is best done when the insects are in their nymph stage (immature). Mealybugs overwinter on branches and in cracks of the bark - using a dormant oil as the nymphs emerge in spring tends to control many populations. You can also consider controlling in the fall (September/October) when they move back to the trunk for overwintering.
Most hawthorns have not bloomed yet, so using insecticides should be done with extreme caution - aside from oils, the products that control these insects best are neonicotinoids, which can harm beneficial pollinators. So it's best to use these AFTER bloom.
Refer to the publication from CSU about additional details on this insect and management recommendations: https://webdoc.agsci.colostate.edu/bspm/Hexapoda%20(Insects)/Hawthorn%20Mealybug%20December%202014%20Revision.pdf
From that publication:
Management: Hawthorn mealybug has proven fairly difficult to control with foliar treatments, due to its waxy body covering and habit of living under loose bark and in other protected sites. Insect growth regulator insecticides, such as pyriproxifen (Distance) or buprofezin (Talus) should be effective for this species - and have selective effects that limit adverse impacts on other, desirable species (e.g., natural enemies, pollinators). Spring treatments applied to coincide with the return of overwintered stages to the twigs appear to be most effective and the addition of a horticultural oil is useful in providing penetration and coverage of the waxy body of these insects. Alternatively, applications made in late summer or early fall against nymphs on branches and limbs should provide some control. If dormant season applications of oils are made they should be applied to the trunks and under surfaces of branches where hawthorn mealybug overwinters. Systemic neonicotinoid insecticides applied as soil drenches (imidacloprid, thiamethoxam) or trunk drench (dinotefuran) sprays also can provide control. However, these types of insecticides are capable of moving into pollen and nectar, posing risks to visiting pollinators. Furthermore, hawthorn is one of the landscape plants that is particularly heavily used by honey bees in Colorado, further increasing risks. Therefore these insecticides should not be used until after bloom.
This is hawthorn mealybug and populations seem to be high this year. It's a difficult insect to control and control is best done when the insects are in their nymph stage (immature). Mealybugs overwinter on branches and in cracks of the bark - using a dormant oil as the nymphs emerge in spring tends to control many populations. You can also consider controlling in the fall (September/October) when they move back to the trunk for overwintering.
Most hawthorns have not bloomed yet, so using insecticides should be done with extreme caution - aside from oils, the products that control these insects best are neonicotinoids, which can harm beneficial pollinators. So it's best to use these AFTER bloom.
Refer to the publication from CSU about additional details on this insect and management recommendations: https://webdoc.agsci.colostate.edu/bspm/Hexapoda%20(Insects)/Hawthorn%20Mealybug%20December%202014%20Revision.pdf
From that publication:
Management: Hawthorn mealybug has proven fairly difficult to control with foliar treatments, due to its waxy body covering and habit of living under loose bark and in other protected sites. Insect growth regulator insecticides, such as pyriproxifen (Distance) or buprofezin (Talus) should be effective for this species - and have selective effects that limit adverse impacts on other, desirable species (e.g., natural enemies, pollinators). Spring treatments applied to coincide with the return of overwintered stages to the twigs appear to be most effective and the addition of a horticultural oil is useful in providing penetration and coverage of the waxy body of these insects. Alternatively, applications made in late summer or early fall against nymphs on branches and limbs should provide some control. If dormant season applications of oils are made they should be applied to the trunks and under surfaces of branches where hawthorn mealybug overwinters. Systemic neonicotinoid insecticides applied as soil drenches (imidacloprid, thiamethoxam) or trunk drench (dinotefuran) sprays also can provide control. However, these types of insecticides are capable of moving into pollen and nectar, posing risks to visiting pollinators. Furthermore, hawthorn is one of the landscape plants that is particularly heavily used by honey bees in Colorado, further increasing risks. Therefore these insecticides should not be used until after bloom.
