Cooperative Extension
No. 5
Community-Wide Lygus Action Plan
June 16, 2000
The University of Arizona • College of Agriculture
As the agricultural complexity increases within a
community so does the potential for cross-commodity interactions. This is especially true for highly
mobile and polyphagous pests like Lygus or whiteflies. It is these two qualities, the abilities to readily
move and to feed on many different host plants,
that make Lygus a shared pest within this community. While controlling nymphs in sensitive crops
is important, the distribution and abundance of Lygus adults are key to understanding the potential
for cross-commodity interference.
Our analytic approach so far has been to chart the
average population growth trends in several host
crops (Fig. 2). This information is useful in understanding the relative “productivity” of these various Lygus hosts and in alerting everyone of potentially damaging levels of these insects. They cannot definitively show us how Lygus move from
host to host. At best, we can infer this transfer by
observing declines in one host’s adult levels with
simultaneous increases in another host’s adult levels.
Understanding & Tracking Adult Movement
Our working group identified several potential
problems when it comes to movement (and establishment) of Lygus populations. Overwintering
Lygus adults move to early spring hosts such as
alfalfa from weeds and desert habitat. Seed-alfalfa
producers identified forage alfalfa as a potential
source of emigrating adults flushed by cuttings during a critical pollination period. Cotton producers
viewed seed-alfalfa as a productive host for and
source of migrating adults during critical squaring
periods.
With the advent of more powerful geostatistical
techniques, we can now begin to explore trends in
“movement” more explicitly with spatial information. In our case, we have recorded the locations
of systematically-selected sites for each sample
taken. By simultaneously analyzing Lygus abundance data along with this spatial information, we
hope to better infer the causes and extent of adult
movements within this community (e.g., Fig. 1).
Once enough data is collected, we may be able to
provide information about the effective range of
this mobile pest. This could lead to better and more
accurate recommendations for locating and managing sensitive crops in a cross-commodity community.
Bemisia Lane
Orius Rd
Multiple-Host
Community
Ch inch Rd
Our survey now extends to over 180 sites in the
western Pinal County area and involves the efforts
of 6 samplers, 2 days a week. The result is a large,
systematic set of data that may help in understand- This process takes time! We hope to offer up preing adult movement within this complex commu- liminary analyses of these data in the near future.
nity.
Figure 1: Geographically-explicit (i.e., mapped) data on the abundance of Lygus may help explain this pest’s movement through the community. This
example above shows carefully selected samples (circles) arranged along transects across multiple hosts.
35
30
Hay
25
Sd Alfalfa
20
Cotton
15
10
5
16-Jun
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
Community-Wide Trends
Seed-alfalfa is moving at or ahead of the projected
production time line. The crop is drying down very
quickly and is devoid of any Lygus where it is completely dried. Our samplers have relocated some
of their samples in an attempt to find greener areas
within fields. Lygus are still abundant there including a large fraction of large nymphs. Should these
nymphs successfully develop into adults prior to
desiccation, we may see one last flush of adults
from these areas. At this time, forage alfalfa is the
likely “recipient” of most moving adults. Thus,
cutting management remains critical at this time!
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
16-Jun
9-Jun
2-Jun
26-May
19-May
12-May
5-May
28-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
16-Jun
9-Jun
2-Jun
26-May
19-May
12-May
5-May
28-Apr
21-Apr
14-Apr
24-Mar
16-Jun
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 re-sampled
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
21-Apr
7-Apr
24-Mar
16-Jun
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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