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How to Manage Pests
UC Pest Management Guidelines
Apple
Lygus
Bugs
Scientific Names: Lygus
hesperus and Lygus elisus
(Reviewed 8/06,
updated 8/06)
In this Guideline:
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Lygus bugs vary in color from pale green to yellowish brown with
reddish brown to black markings, but can be distinguished by a prominent
triangle in the center of the back. The lygus bug adult is about 0.25 inch long
and 0.1 inch wide, flattened on the back. Nymphs resemble adults, but are smaller and do not have wings.
Lygus bug damage may occur in all major apple districts and
sometimes is severe. Lygus attack is more frequent in orchards that have a
permanent cover crop and in orchards adjacent to crops or vegetation that host
lygus.
Lygus bugs may feed on developing flower buds early in spring,
causing the buds to exude gum and shrivel up. Usually this damage is not
serious unless a very heavy infestation is present. Lygus cause their most
serious damage by feeding directly on fruit. Midseason feeding results in round
pits, and late-season feeding causes irregularly-shaped depressions that are
similar to stink bug damage.
The potential for a lygus bug population to cause damage is
difficult to assess. Lygus bugs may be present in substantial numbers in the
orchard and cause no damage; however, they can often cause damage and may
attack fruit at any time from petal fall to harvest. Annual preventive
treatments are costly and subject to failure because lygus bugs have been quick
to develop resistance to chemicals. In orchards with a history of lygus damage,
monitor fruit at least biweekly between petal fall and harvest to assess need
for treatment.
Biological Control
The role of
predators and parasites in controlling lygus in orchards has not been
investigated, but in cotton and strawberries, beneficials have been shown to be
helpful.
Cultural
Control
Eliminate or
suppress weed host plants before fruit forms on trees and thereafter throughout
the growing season to minimize lygus populations. Yellow
starthistle,
Russian thistle, tarweed, sweet clover, wild mustard, lambsquarters, pigweed, shepherd's-purse, wild radish, and vetch are
important hosts. Do not mow cover crops or weeds when lygus bugs are present or
they will move into the trees.
Organically Acceptable Methods
Cultural and
biological control are organically acceptable.
Monitoring and Treatment
Decisions
After fruit
has formed, sample the cover crop with a sweep net to determine if lygus bugs
are present in the orchard. If they are, or if an orchard has had a history of
lygus injury, take fruit samples at least every 2 weeks starting soon after
petal fall and continue until harvest. Lygus bugs may be present in the orchard
but not feeding on the fruit, so you need to check the fruit for damage.
Examine a minimum of 100 fruits from trees throughout the block. Because lygus
damage is often spotty in distribution, check each block thoroughly. Lygus may
migrate into the orchard at any time during the growing season and damage
frequently appears first along orchard borders. One damaged apple in 100 is
significant for concern and calls for further sampling and evaluation of
control needs. When sampling fruit for other pests, also look for the presence
of lygus bugs on fruit or in the trees to determine if they are still present
in the orchard. Especially be on the lookout for lygus when weeds start to dry
up. Because the bugs move quickly and may be difficult to see, the number seen
will depend on the skill of the observer. When lygus are migrating into an
orchard, periodic spraying of border trees will hold down numbers and reduce
damage.
| Common name |
Amount to Use |
P.H.I.+ |
| (trade name) |
(conc.) |
(dilute) |
(days) |
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| When choosing a pesticide, consider
information relating to the impact
on natural enemies and honey bees
and environmental impact.
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| A. |
ACETAMIPRID |
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(Assail) |
3.4 oz |
0.85 oz |
7 |
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MODE OF ACTION: A neonicotinoid (Group 4A)1
insecticide.
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COMMENTS: Do not make more than 4
applications/season. Do not exceed 13.5 oz/acre/crop. Repeat applications of any neonicotinoid insecticide (acetamiprid-Assail;
imidacloprid- Provado; and thiacloprid-Calypso) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an
insecticide that has a different mode of action to help delay the development of resistance. |
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| B. |
IMIDACLOPRID |
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(Provado) 1.6F |
8 fl oz |
2 fl oz |
7 |
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MODE OF ACTION: A neonicotinoid (Group 4A)1
insecticide.
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COMMENTS: Repeat applications of any neonicotinoid insecticide (acetamiprid-Assail;
imidacloprid- Provado; and thiacloprid-Calypso) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an
insecticide that has a different mode of action to help delay the development of resistance. |
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| C. |
DIMETHOATE E267 |
4 pt |
1 pt |
28 |
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MODE OF ACTION: An organophosphate (Group
1B)1 insecticide.
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| D. |
FORMETANATE HYDROCHLORIDE |
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(Carzol)SP |
1 lb |
4 oz |
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MODE OF ACTION: A carbamate (Group 1A)1
insecticide.
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COMMENTS: Do not apply more than 1.25
lb/acre/season. Do not apply after petal fall. See label for second application restrictions. |
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UC IPM Pest Management Guidelines: Apple
UC ANR Publication 3432
Insects and Mites
J. L. Caprile, UC Cooperative Extension, Contra Costa County
L. R. Wunderlich, UC Cooperative Extension, El Dorado County
P. M. Vossen, UC Cooperative Extension, Sonoma and Marin counties
W. W. Coates, UC Cooperative Extension, San Benito County
H. L. Andris, UC Cooperative Extension, Fresno County
L. G. Varela, UC IPM Program, Sonoma County
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
Acknowledgment for contributions to the insects and mites section:
C. Pickel, UC IPM Program, Sutter and Yuba counties
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