University of California

Dispersal behavior of the first instar nymphs of the woolly apple aphid


Stanley C. Hoyt
Harold F. Madsen

Authors Affiliations

Stanley C. Hoyt was Formerly Research Assistant in Entomology in the Experiment Station, Berkeley; now Associate Entomologist in the Washington State University, Tree Fruit Experiment Station, Wenatchee, Washington; Harold F. Madsen was Associate Entomologist in the Experiment Station, Berkeley.

Publication Information

Hilgardia 30(10):267-299. DOI:10.3733/hilg.v30n10p267. December 1960.

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The woolly apple aphid, Eriosoma lanigerum (Hausmann), has been known for over 150 years as a pest of apple trees that causes a loss in tree vigor and that produces honeydew which drips on the fruit. Only in recent years. has it been considered a pest of the fruit itself. In 1942, Essig4 reported its presence in the cores of Yellow Newtown Pippin apples from the Watsonville area of California. This condition was reported again in 1954 by Madsen, Borden, and Koch. It was found that these apples have an opening through the calyx into the core of the fruit. The aphids can enter this small opening when they are first instar nymphs and can establish colonies. inside the fruit. Almost the entire crop of this variety of apple is used for canning. During the canning process the cores are removed mechanically, but the coring machines are not always accurate, and portions of the core may escape removal. If aphid colonies are present in those cores which are not removed, insects or insect fragments would be contained in the finished product.

In the course of investigations on preventing the presence of aphids in the cores of the fruit, it was felt that some attention should be given to when and why the aphids moved into the fruit. In addition, woolly apple aphids were observed to be continually moving up and down the tree between limbs and roots. For these reasons, studies were undertaken of the time and direction of the movements, the number of aphids involved, and some of the factors controlling the movement.


Eriosoma laniqerusn is a member of the family Aphidae, subfamily Eriosomatinae, according to (Palmer (1952)). The species was first described by Hausmann in 1802 as Aphis lanigera. Since that time it has been given several generic and specific names by various authors.

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Hoyt S, Madsen H. 1960. Dispersal behavior of the first instar nymphs of the woolly apple aphid. Hilgardia 30(10):267-299. DOI:10.3733/hilg.v30n10p267
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