WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Aphid

Insects & Invertebrates

 

Symptoms

Aphids can cause deformation, wilting and defoliation of new growth of blueberry plants. High infestations can reduce fruiting bud formation for the following year’s crop. Aphids produce copious amounts of honeydew and can cause secondary pest outbreaks of sooty molds on foliage and fruit. Aphids can also transmit blueberry scorch virus.

 

Identification

*Known vectors of Blueberry Scorch Virus (BlSV)

 

Aphis pomi Apple Aphid

Aphis Pomi

The apple aphid varies in size from 1.8 to 2.6 mm and in color from yellow to light green or dark green. The head, tips of the antennae, legs, and cornicles are dark. The stem mother is somewhat darker than other forms and is sometimes covered with a waxy bloom. The male is elongate, and the female is round. This aphid may be wingless or winged, or possess small wing remnants. Wings, if present, are transparent with brown veins and a smoky stigma. The first instar is dark green with dusky appendages. The nymph's color lightens as the nymph matures.

Aphis citricola (spireacola) Spirea Aphid

Aphis Citricola

Spirea aphid is small, approximately 1.8 mm long and light green with black cornicles. It is almost identical to the color of a young citrus leaf. Winged forms have a dark brown thorax with a green abdomen.

Aphis gossypii Melon/Cotton Aphid

Aphis Gossypii

Wingless adults are 1 to 2 mm in length. The color can vary from light green mottled with dark green is most common, but also occurring are whitish, yellow, pale green, and dark green forms. The legs are pale with the tips of the tibiae and tarsi black. The cornicles also are black. Winged females measure 1.1 to 1.7 mm in length. The head and thorax are black, and the abdomen yellowish green except for the tip of the abdomen, which is darker. The wing veins are brown. The egg-laying (oviparous) female is dark purplish green; the male is similar. The nymphs vary in color from tan to gray or green, and often are marked with dark head, thorax and wing pads, and with the distal portion of the abdomen dark green. The body is dull in color because it is dusted with wax secretions.

Ericaphis (Fimbriaphis) fimbriata Richards* and/or Ericaphis (Fimbriaphis) scammelli (Mason)*

Aphid Blueberry

Rather small to size, broadly spindle-shaped light-colored (yellow-green) aphids. Alatae (Winged) have a dark dorsal abdominal patch. No observation of the living aphids and biology is known. Closely related to, and possibly synonymous with F. scammelli.

Illinoia pepperi (MacGillivray) Illinoia azaleae*

Illinoia Pepperi

Medium-sized, green, spindle-shaped; siphunculi dark (sometime pale at base), distinctly clavate, legs and antennae also mainly dark. On Vaccinium spp. (corymbosum, pennsylvanicum, stramineum) in NE North America. Monoecious and holocyclic, with alatae males. Recorded as a vector of blueberry shoestring virus.

Myzus persicae Green Peach Aphid*

Myzus Persicae

Medium to large aphids, 2.3mm in length when fully grown. Wingless adults are green to pale yellow or pink. Winged females are darker green than the Wingless adults and have brown markings. In Winged females, the thorax is almost black and they have dark red eyes.

Macrosiphum euphorbiae (Thomas) Potato Aphid

This soft-bodied, pear-shaped insect may be solid pink, green and pink mottled, or light green with a dark stripe. Usually wingless, it is about 2.5 to 3.5 mm long and has a pair of long, slender cornicles. Although slightly smaller than the adult, the nymph is similar in color and shape. Cylindrical cornicles.



Biology

Aphids overwinter in the egg stage on the stems and bud scales of blueberry plants. Eggs hatch in spring and nymphs move to the new tissue to feed. Nymphs mature into female adults; these females reproduce by giving live birth. Following generations produce some winged individuals by April and May. Unchecked populations continue to build through the growing season. Towards season’s end, males and egg-laying females are present in the population to produce overwintering eggs.

Aphids have piercing-sucking mouthparts and rob plants of nutrients. This type of feeding causes deformation of the developing plant tissue. Aphids prefer to feed on the succulent new growth of blueberry shoots. They are often found in colonies on undersides of leaves and roping stem shoots.

 

Monitoring

Timing

Begin monitoring in the early season when buds break and begin to leaf out. Increase monitoring to once per week when leaves are developed in May and June. Develop regular aphid monitoring habits for the growing season.  In areas where Scorch Virus is present, increase incidence of scouting.

Tools

Use a hand lens and visually inspect plants. If you are pruning samples, practice sterile techniques to avoid transmitting Scorch Virus to other plants (gloves if hand picking and alcohol dips for pruning shears). Yellow card sticky traps or suction traps can be used to monitor the flight of winged adults.

Where to look

Sample for aphids on areas of the bush with tender tissue. These areas include new branch growth, buds and shoots (highlighted in red in diagram).

Parts of Blueberry plant

Be sure to inspect both sides of the leaves and look into leaf curls. Do not neglect the stubs and lower bush; this area can be difficult to achieve good coverage from pesticides. Sample the edges of the field and areas in the field that are water stressed and/or have high nitrogen levels in the plant tissue. In areas of Scorch Virus, pay particular attention to upwind borders of fields.

 

Thresholds and Management

Cultural

Aphid populations increase with higher nitrogen levels populations respond to high nitrogen content in plant tissues. Researchers have not studied this in blueberries, thus no recommendation is available at this time. Avoid over fertilization and excessive nitrogren levels. New Jersey growers generally use 650 lbs of 10:10:10, half of which is applied around bloom and the other half applied four weeks later. Minimize water stress, especially along edges of the field.

Biological

There are many natural enemies such as predators and parasitoids of aphids in Whatcom County. Conserve natural enemies by avoiding detrimental treatments to border vegetation (such as insecticide and herbicide applications).

Chemical

Aphids are inefficient vectors of Blueberry Scorch Virus (BlSV); treating borders or other vegetation is not needed. This disease is most likely transmitted by the natural dispersal of aphids from neighboring infected blueberry fields. Infected aphids could possibly be moved on equipment and harvesters; this is unlikely but keep this in mind.

Avoid aerial application of insecticides, use ground equipment. Be sure to get thorough coverage of both leaf surfaces with pesticide treatments. Maximize coverage of pesticides inside the blueberry bush. Winter moth applications should be also effective for overwintering aphids. Consider dormant oils and soaps before green tissue starts in late winter or early spring. Rotate different insecticides (with different modes of action for aphids) in a resistant management program.

Note

If blueberry scorch virus is present, intensive aphid control is required. Critical periods of management are early in the season when winged aphids are first observed. Post-harvest treatment of aphids is recommended, before eggs are laid for overwintering. Treatment of winged aphids also reduces movement of aphid vectors within the field.


Resources

Pest Management Guidelines for Small Fruits, 2001. Washington State Extension. EB 1491. http://www.agmrc.org/media/cms/eb1491_435CC653592E1.pdf

UC Davis IPM
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7404.html

Imidacloprid; Pesticide Tolerances for Emergency Exemptions
http://www.epa.gov/fedrgstr/EPA-PEST/1999/July/Day-21/p18190.htm

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • (360) 778-5800 • whatcom@wsu.edu