The development of accurate data on insecticide usage is important to
the assessment of our IPM programs in Arizona. Reliable estimates of
insecticide use patterns are one of our most objective tools for assessing
change in management practices. This information allows us to build
relevant databases for measuring user behaviors and adoption of new
IPM technologies. For PCAs, it can translate their efforts into economic
terms for their clientele and confirms their value to the lettuce industry
by showing the importance of their cost‐effective management in desert
lettuce production. This summary over the past nine years (2004‐2013)
provides real world data on estimates of insect management costs,
insect losses and insecticide usage to prevent key insect pests from
reducing yield and quality.
UA VegIPM Update, Vol. 5, No. 8, Apr 16, 2014
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The data was developed through the administration of a three‐part
survey that was conducted in an interactive process with stakeholder
input. Growers, PCAs, Extension personnel and industry professionals
attended Lettuce Insect Losses and Impact Assessment Workshops in
Yuma and completed surveys in a guided process. The workshops were
conducted in an interactive manner where participants were given a
presentation that established the incentives for participation, explained
the crop insect loss system, and further walked the participants through
the estimation process.
In the first part of the survey information was collected on
the actual lettuce acreage represented by the respondent, and overall
percent reductions in yields due to several biological, environmental and
management factors. In addition, intensity of and costs associated with
insect scouting were estimated. To provide data consistent with head
lettuce production in the desert southwest, separate information was
collected for fall lettuce acres (crops grown from September through
November) and spring lettuce acres (December‐March) because of
differences in weather and insect pressures.
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This table presents data on survey participation by local PCAs. Surveys
completed by local PCAs represented a large proportion of the lettuce
acres grown in Yuma (~45‐75%). Furthermore, the table reflects the
large number of acres, that on average, PCAs scout and make
management decisions on.
UA VegIPM Update, Vol. 5, No. 8, Apr 16, 2014
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The average costs associated with scouting are shown in this table. Not
surprising, the surveys showed that annually 100% of the acres are
scouted in both spring and fall crops. Scouting for lettuce pests in Yuma
is also very intensive where lettuce fields during the fall and spring were
visited on average 4.1 and 3.1 per week, respectively. Finally, IPM
scouting comes at a cost; average scouting costs were estimated to be
greater then $20/acre over the past nine years.
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Information was collected on IPM and crop insect losses through
estimates of the percentage of acres where key insect pests were
present and insecticide sprays were required to prevent yield reductions.
Included with those estimates are the frequency and costs of insecticide
applications directed towards those insects. Overall, these costs
represent an economic loss to the grower associated with preventing
insects from damaging plants and reducing yields. Finally, actual percent
yield losses (heads not harvested due to insect damage or reduced
quality) for individual insect species were estimated .
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On fall lettuce, PCAs estimated that the Lep larvae complex (beet armyworm,
corn earworm, cabbage looper) was the most consistently present pest on
lettuce, as well as the pest requiring the most insecticide treatment. In fact
over 95 % of the lettuce acreage annually required insecticide treatments.
Thrips, whiteflies and seedling pests (flea beetles, crickets, grasshoppers)
were the next most important pest species found on fall lettuce, annually
requiring control on over 50% of the acreage. Finally Trash bugs, leafminers
and aphids were less important on fall lettuce. Note: This data shows that just
because a pest is present on the crop, it isn’t automatically treated with an
insecticide. The one exception to this would be if plants were infested with
these pests during stand establishment or present near harvest.
UA VegIPM Update, Vol. 5, No. 8, Apr 16, 2014
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On spring lettuce, PCAs estimated the Lep larvae complex is still important but not at the same intensity as in fall lettuce. However, thrips and the aphid complex are the pests that are present on the largest number of acres and these acres require the most insecticide treatment to prevent economic losses. All other pest are present are varying levels, where at most about 25% of the acres require treatment.
UA VegIPM Update, Vol. 5, No. 8, Apr 16, 2014
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In general, Lep larvae annually cause the greatest amount of yield loss to both
fall and spring lettuce (1‐2% / year). In fall lettuce, seedling pests are also
important in yield losses. On spring lettuce, thrips and aphids cause about 1‐
1.5% yield loss each year. On average, yield losses to insect pest is less than
5% per year.
UA VegIPM Update, Vol. 5, No. 8, Apr 16, 2014
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These graphs show economic losses in terms of how much growers spend
annually on each pest to prevent yield losses on a per acre basis averaged
over the past nine years. In general, the greatest costs in management of fall
lettuce are associated with the Lep complex and whiteflies where an average
of 4.8 applications are required / acre at a cost of $338.17 per acre. In
contrast, thrips and aphids are the drivers for crop protection of spring lettuce
requiring on average 4.6 applications at a cost of $305.61 / acre. Estimates of
acres treated and costs for imidacloprid are included in these estimates under
whitefly in fall lettuce and thrips in spring lettuce.
UA VegIPM Update, Vol. 5, No. 8, Apr 16, 2014
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Data on insecticide use patterns was collected annually. These data identify
the frequency of use of various chemistries (identified by both product name
and IRAC mode‐of‐action classification) and the percentage of treated acres
for each product. The data in the following two graphs shows usage for the
2012‐2013 growing season.
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This graph shows the ten most commonly used products in fall lettuce in
2012. Data represent the average % acres treated and the average number of
applications reported by PCAs. The pyrethroids were the most commonly
used products both in terms of acreage treated and frequency of application.
This was followed by Radiant and Imidacloprid , both used on over 90% of the
acreage. The remaining products were used on considerably less acreage and
largely aimed at Leps (Proclaim Vetica, Coragen and Volaim Xpress).
UA VegIPM Update, Vol. 5, No. 8, Apr 16, 2014
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Similarly, the pyrethroids and Radiant were the most commonly used
products in spring lettuce in terms of acreage treated and frequency of
application for thrips and Lep control in 2013. This was followed by
Imidacloprid , used on over 80% of the acreage and targeted at aphids. The
remaining products were used on considerably less acreage and largely aimed
at Leps, aphids and thrips.
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