Cooperative Extension
No. 4
Community-Wide Lygus Action Plan
June 9, 2000
The University of Arizona • College of Agriculture
The seed alfalfa dry-down period has already begun, and the suitability of this crop as a host for
Lygus bugs is in decline. A major objective of this
project is to help identify periods and locations of
Lygus movement.
Field Specific Trends
Individual field trends continue to be quite dynamic
(see Fig. 1, below). The total Lygus per 100 sweeps
are depicted below for 7 representative field sites
(field codes below each graph) for each major host
crop at this time (seed alfalfa, alfalfa hay, and
weeds). Most seed alfalfa fields are trending downward in Lygus numbers as the crop continues to
dry down.
250
We have added over 120 cotton field sites to our
weekly sampling, and Lygus numbers are detectable in some fields but at extremely low levels.
Many fields of alfalfa hay are increasing in Lygus
numbers. Adults especially have increased there
in recent weeks. This may reflect the relative attractiveness of alfalfa to Lygus over cotton. This
underscores the importance preserving a strip-,
block-, or alternate field cutting strategy.
As an aside, it is interesting to note that at the same
time that Lesquerella (20 A at MAC) dried down
and ceased to be attractive to Lygus, adult numbers in adjacent forage hay increased dramatically.
Lygus adults will move to locally-preferred hosts.
Seed Alfalfa
Mean(Total/100)
200
150
100
0
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
50
210531518
210731518
280231518
280431518
100431523
350131523
350731523
250
Alfalfa Hay
Mean(Total/100)
200
150
100
0
3/28/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
3/28/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
3/28/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
3/28/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
3/28/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
3/28/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
3/28/00
4/18/00
4/26/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
50
180131518
200131518
210131518
50131518
30731518
31131518
330831523
250
Weeds
Mean(Total/100)
200
150
100
0
4/18/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
4/18/00
5/3/00
5/10/00
5/17/00
5/24/00
5/31/00
6/7/00
50
40231518
50831518
70831518
100431523
31131518
330831523
350731523
Figure 1: Individual field trends for Total Lygus per 100 sweeps are depicted above in a series of graphs for 7 representative field sites for each of the 3
major hosts, seed alfalfa, alfalfa hay, and weeds. Field site identification numbers are located below each graph.
Community Trends
Our weekly samples are summarized in chart form
below (Fig. 2). Some trends are evident:
35
30
Hay
25
Sd Alfalfa
20
• Lygus, including reproduction (note nymphs),
are in decline in seed alfalfa, though there are
exceptions (see Fig. 1),
• Weeds are of little importance at this time,
• Cotton numbers are exceedingly low, but dominated by adult numbers,
• Lygus in alfalfa hay are on the rise,
• Adult numbers are quite volatile.
Cotton
15
10
5
9-Jun
2-Jun
26-May
19-May
12-May
5-May
28-Apr
21-Apr
14-Apr
7-Apr
31-Mar
24-Mar
0
40
60
Weeds
35
50
Hay
30
Adults / 100
Sd Alfalfa
25
Cotton
20
15
Hay
40
Sd Alfalfa
30
Cotton
20
10
10
5
9-Jun
2-Jun
26-May
19-May
12-May
5-May
28-Apr
21-Apr
120
70
Weeds
Weeds
60
Hay
50
Total Lygus / 100
Sd Alfalfa
40
Cotton
30
20
100
Hay
80
Sd Alfalfa
60
Cotton
40
20
10
Peter Ellsworth, IPM Specialist1
Steve Husman, Area Extension Agent2
Dave Langston, MAC Farm Superintendent1
1
2
9-Jun
2-Jun
26-May
19-May
12-May
5-May
28-Apr
21-Apr
24-Mar
9-Jun
2-Jun
26-May
19-May
12-May
5-May
28-Apr
21-Apr
14-Apr
7-Apr
31-Mar
24-Mar
Figure 2: Number of Lygus per 100 ‘cotton-style’ sweeps in various crops
in the western Pinal County area. Each chart represents an average of
multiple sites in multiple fields each week. Due to differences in the
number of sites each week, these numbers are for general information
only. No sample was taken from seed-alfalfa on 28 March. Each site is resampled each week unless it has been recently sprayed, cut or otherwise
removed, or watered. Each chart shows the results for the entitled life
stage. Small Nymphs are instars 1–3; Large Nymphs are instars 4–5; All
Nymphs is the sum of these 2 nymphal categories; Total Lygus is the sum
of all stages of Lygus including adults.
7-Apr
0
0
31-Mar
All Nymphs / 100
14-Apr
7-Apr
24-Mar
9-Jun
2-Jun
26-May
19-May
12-May
5-May
28-Apr
21-Apr
14-Apr
7-Apr
31-Mar
0
24-Mar
0
31-Mar
Large Nymphs / 100
Weeds
14-Apr
Small Nymphs / 100
Weeds

Department of Entomology, Maricopa Agricultural Center, Maricopa, AZ
Pinal County Cooperative Extension Office, Casa Grande, AZ
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