Mites in Desert Citrus
David Kerns
University of Arizona
Yuma Agricultural Center
Primary Mites of Concern
„
Yuma Spider Mite
„ Eotetranychus yumensis
„
„
„
Occasionally a problem.
Has been prevalent in large numbers in
Yuma County for the past 2 years.
Flat Mite
„ Brevipalpus lewisi
„
„
Common every year.
Sometimes reaches damaging levels.
Yuma Spider Mite
„
„
Identified in 1934 on lemons in
Yuma, AZ.
Habits
„
„
„
„
„
Wide host range, prefers
lemons.
Feeds primarily on the
underside on the leaves, often
along the edge of the grove
along dusty roads.
Deposits webbing on the
underside of the leaves which
collects dirt.
Little is known about its life
cycle.
Identification
„
„
„
Medium sized.
Yellowish color with small red
eye spot and some dark
pigmentation.
However, color can vary
depending on host and climate.
Yuma Spider Mite
„
Damage
„
„
Feeding on leaves causes
stippling and when
abundant may result in
leaf drop and may
contribute to “fall
dieback” or “buggy
whipping”.
Feeding on the fruit
„
„
Thought to cause a
“bleached” or “bronzing”
appearance.
May cause scabbing and
pitting.
Flat Mite
„
„
Identified in 1942 on lemons in
Porterville, CA.
Habits
„
„
„
„
„
„
Wide host range.
Feeds primarily on the fruit, but
may be found on the leaves.
Does not deposit webbing.
Eggs are reddish and are laid on
the fruit or leaves.
Present year around and hide in
crevasses in the winter, become
most prevalent beginning in
July.
Identification
„
„
„
Extremely small, ~ 0.25mm in
length and are flat.
Adults are amber to reddish with
black pigmentation.
Immatures are usually bright
red.
Flat Mite
„
Damage
„
„
„
Feeding begins where
thrips or other pests have
fed.
Infestation usually begins
under the button and then
spreads.
Injury due to mites is
more irregular than thrips
and more corky in
appearance.
Mite Damage Study
„
„
„
„
Flared mites in an 8 ac block of 12 years old
lemon using acephate.
Used a randomized complete block design with 2
treatments and 4 reps per treatment.
Each plot was 5 trees by 5 trees.
Treatments
„
„
„
„
Untreated
Danitol at 21 oz/ac + Kinetic at 0.1%v/v.
Applications made using an orchard sprayer, 150
gal/ac.
Counted the number of mites per fruit.
Mite populations in lemons, 2002
2.00
Untreated
1.75
1.25
1.00
0.75
0.50
0.25
Ju
n
1
Ju 8
n
26
Ju
l
Ju 2
l1
Ju 0
l2
Ju 6
l3
1
Au
g
Au 8
g
Au 14
g
Au 21
g
28
Se
p
Se 3
p
11
7
0.00
Ju
n
# per fruit
1.50
Flat mite
Yuma spider mite
Two-spotted spider mite
Total mites
Mite populations in lemons, 2002
2.00
Treated
1.75
1.25
1.00
0.75
0.50
0.25
Ju
n
1
Ju 8
n
26
Ju
l2
Ju
l1
0
Ju
l2
6
Ju
l3
1
A
ug
A 8
ug
1
A 4
ug
2
A 1
ug
28
Se
p
Se 3
p
11
7
0.00
Ju
n
# per fruit
1.50
Flat mite
Yuma spider mite
Two-spotted spider mite
Total mites
Mite populations in lemons, 2002
2.00
Untreated
1.75
1.25
1.00
0.75
0.50
0.25
Ju
n
1
Ju 8
n
26
Ju
l
Ju 2
l1
Ju 0
l2
Ju 6
l3
1
Au
g
Au 8
g
Au 14
g
Au 21
g
28
Se
p
Se 3
p
11
7
0.00
Ju
n
# per fruit
1.50
Flat mite
Yuma spider mite
Two-spotted spider mite
Total mites
Typical Damage
Damage Rating
„
„
Used a rating scale.
Divide each fruit into four longitudinal
quadrants.
All quadrants clean
„ One quadrant with damage
„ Two quadrants with damage „ Three quadrants with damage „ Four quadrants with damage „
1
2
3
4
5
Mite damage in lemons, 2002
0%
25%
50%
75%
100%
Treated
Untreated
0
20
40
60
Percentage in each category
80
100
Mite Efficacy Trial
Treatments
Rate
Agri-Mek
8.0 oz/ac
Danitol
21.3 oz/ac
Kelthane MF
6 pts/ac
Microthiol 80 WP
10 lbs/ac
Nexter
8.0 oz/ac
Untreated
-
All treatment included Kinetic at 0.1%v/v
Treatments were applied with a vertical boom sprayer at 80 gal/ac
Mite Efficacy Test
3
Agrimek
Danitol
Kelthane
Microthiol
Nexter
Untreated
Number per fruit
Application July 17, 2002
Yuma Spider Mite - Lemons, Yuma, AZ
2
1
0
6 Dat
14 Dat
22 Dat
28 Dat
35 Dat
Conclusions
„
„
„
„
„
It was evident that mites can cause significant damage
in regard to fruit appearance.
These data suggest that Yuma mite may be as important
as flat mite in damaging the fruit.
Mites should be scouted for throughout the summer, at
least through July.
We are not certain at what density miticides should be
applied, but the number maybe as low as one mite per
fruit.
All miticides evaluated have proven effective for at least
two weeks.