How to Manage Pests
UC Pest Management Guidelines
Scientific name: Brachycorynella
In this Guideline:
The European asparagus aphid is a small blue-green to gray-green aphid about 0.06
inch (1.5 mm) in length. The aphid is often covered with a powdery wax. Unlike
most aphids, the cornicles of European asparagus aphid are reduced to
practically invisible openings on the abdomen. The cauda, a projection at the
very rear tip of the abdomen, is relatively long compared with other aphid
species and has sides that are nearly parallel. The antennae are short.
The wingless forms of the
aphids like to feed where the needles of the fern attach to the petioles. Their
small size and coloration make them difficult to spot even upon close
examination. Winged forms often occur in very large numbers that may appear
as a large cloud. The aphid overwinters as eggs deposited on the old fern or in
cracks in the soil.
Damage from European asparagus
aphid is primarily from a toxin that the aphids inject into the plant when
feeding. The toxin causes shortened internodes on subsequent growth, resulting
in a tufted appearance that is called bonsai growth. While other factors can cause a limited amount
of this type of distorted growth, heavy European asparagus aphid infestations
produce this distortion in great profusion. Heavy populations also produce
massive amounts of honeydew that may lead to considerable ant activity.
Because asparagus is a
perennial plant, the important damage is the impact of the European asparagus
aphid feeding on the subsequent year's growth. The distorted growth is unable
to adequately nourish the plant's crown and it will desiccate after 1 or 2
years feeding by this pest. The toxin may also cause a delay in bud break in
spring followed by a profusion of small spears produced simultaneously. The
impact is especially pronounced on newly established or weak plantings, and in
Cleaning fields of crop debris
and encouraging natural enemies are important in managing this pest. Monitor
field edges regularly to detect the appearance of populations.
Natural enemies, especially
parasitic wasps and lady beetles, help control European asparagus aphid
populations. Most of the parasites, such as Diaeretiella rapae, have their greatest impact on heavy populations after the damage is done. A
species of Trioxys imported
and released to control European asparagus aphid has had little success to
date. General predators, such as the convergent lady beetle, may feed on some European asparagus aphids, but
the European asparagus aphid's rate of reproduction can overwhelm the
predators' impact. Encourage natural populations of parasites by delaying
pesticide applications where possible.
Mowing, chopping up, and then incorporating ferns during the dormant season may substantially reduce eggs in the area. Burning is also effective where permitted.
Cultural and biological control,
and sprays of insecticidal oils and PyGanic are acceptable to use in an
organically certified crop.
Monitoring and Treatment Decisions
European asparagus aphid
populations start very slowly and in widely dispersed patches, then seem to
nearly explode. Populations often begin near field edges, so monitor the edges
of fields regularly whenever fern is present. It is best to collect plant
samples and shake or beat them on a hard, light-colored surface (the side of a
white 5-gallon bucket or hood of a pick-up, for example) to dislodge both the
aphids and their natural enemies. Visual inspection of the ferns is not
reliable, even for experienced scouts.
No definite threshold has been
established and any threshold will vary with the condition of the field and
time of the season. A high percentage of plants infested is more important than
a high number of aphids on a few plants. The earlier in the season, the more
likely a small infestation will become a problem. Waiting for appearance of
distorted plants or large amounts of white cast skins under plants may allow
populations to reach dangerous levels before the infestation is detected. Treat
when numbers of aphids begin to increase faster than beneficials.
|The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, information related to natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
||MODE OF ACTION GROUP NUMBER1: 1B
||COMMENTS: Apply to the fern
stage. Limited to ground application. Avoid drift and tailwater runoff into surface waters. Use allowed under a Supplemental Label.
||MODE OF ACTION GROUP NUMBER1: 9B
||COMMENTS: Apply to asparagus ferns after harvest has been completed.
||MODE OF ACTION GROUP NUMBER1: 3
Apply in sufficient water for thorough coverage, and begin treatments when
insects first appear. Air blast applications are more effective than
concentrate applications. The restricted reentry interval is 12 hours.
Although OMRI approved for organically certified crops, check with certifier for any restrictions that apply.
||NARROW RANGE OIL#
||1–2 gal/100 gal water
||MODE OF ACTION: Contact including smothering and barrier effect.
||COMMENTS: Less effective than first two materials listed above but an option for organic growers.
UC IPM Pest Management Guidelines: Asparagus
UC ANR Publication 3435
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Insects:
R. J. Mullen, UC Cooperative Extension, San Joaquin County
W. E. Chaney, UC Cooperative Extension, Monterey County
C. B. Fouche, UC Cooperative Extension, San Joaquin County
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