Voluntary Area-Wide Whitefly Monitoring Project Implementation 1995-1997, Gila Bend, Arizona
S.H. Husman, Pinal County Cooperative Extension
Growers, Pest Control Advisors (PCA), and University of Arizona Cooperative Extension personnel formulated and coordinated area-wide pest management strategies in the production area near Gila Bend, Az. from 1995-97. The primary pest target was whitefly with secondary control strategy implementation for pink bollworm in 1995. In 1995-1996, the coordinated effort encompassed approximately 10,000 and 6000 acres which included 10 and 8 cotton producers respectively and 6 pest control advisors. Due to producer interest and initiative in an adjoining production area, project acreage increased to over 18,000 acres and included 14 producers and 9 pest control advisors in 1997. The project cost of $3.00/acre was supported by participating producers with the monies used to hire University of Arizona trained students for field scouting of whiteflies. An economic development grant from the Electrical District #8 supported the project coordinator's salary who is a University of Arizona employee. Each field was sampled weekly for whitefly populations using recommended University of Arizona sampling procedure. The population data was then faxed to the responsible producer and pest control advisor on the date of sample. Treatment thresholds and chemistry class suggestions were made by Cooperative Extension with final control decisions and material choice at the producer and pest control advisor discretion. Weekly community wide meetings were conducted and used to discuss general area-wide and field specific population dynamics, treatment suggestions, crop condition, and agronomic and entomological area-wide production strategy recommendations.
Due to increasing cotton production costs and static cotton prices, profitable cotton production is increasingly challenging in the low deserts of Arizona. Whiteflies are a major pest in the Arizona cotton production system with control costs comprising a significant proportion of the production budget. Arizona cotton producers are keenly aware that production input efficiency will be a cornerstone future survival. As a result, producers are extremely interested in accurately identifying components within the production budget that may offer opportunity for increased efficiency and expenditure reduction.
Insect control costs have increased at a rapid rate in the last several years. Producers are interested in making cost effective control decisions based on individual field pest populations and technically sound threshold recommendations. In addition, it is recognized that due to the mobile nature of common cotton pests, communications relative to area-wide population distribution data offers opportunity for increased understanding and pro-active pest control approaches. In essence, producers recognize that standardized sampling and pest population distribution within their community offer excellent opportunities to make well informed and cost effective control decisions.
Program goals and objectives were the following:
The voluntary area-wide community based program was initiated in 1995 in an area near Gila Bend, Az. and has continued through 1997. Due to programmatic modifications which have occurred over time, the most logical description is annual. An extremely important component of this effort which has contributed significantly to it's success has been the voluntary and producer driven orientation. University of Arizona Cooperative Extension provides leadership, coordination, and technical information dissemination relative to area-wide practice of sound entomological Integrated Pest Management (IPM) principles. In many ways, the program can be simply described as implementation of sound and recommended IPM practices on an area-wide commercial scale. In order to offer a comprehensive program description, this section will essentially describe the fluid evolution of deployment.
1995 Pink Bollworm
In 1995, participants collectively decided to pursue an area-wide pinhead square treatment program for pink bollworm control. The criteria used for treatment was based on a heat unit model of spring emergence of overwintering pink bollworm moths (Figure 1). Emergence of 95% occurs by the time 1875 heat units (HU) (86/55 F threshold) have accumulated since January 1. Pink bollworm susceptible cotton square production occurs between 800- 900 heat units accumulated since planting. Individual field planting dates and heat unit accumulation measurements from January 1 to the planting date were recorded from a nearby UA Arizona Meteorological Weather Network (AzMet) station. Simple additive arithmetic enabled the implementation of a fundamentally sound heat unit driven pinhead square treatment program. For example, if a field was planted on April 1 with a hypothetical 500 heat units accumulated since January 1., the first susceptible square occurs at approximately 900 heat units after planting. The first treatable susceptible square will be when 1400 heat units have accumulated since January 1 which was tracked from AzMet. After initial treatment, fields were retreated weekly until 1875 heat units had accumulated since January 1, accounting for protection through the 95% emerging pink bollworm population. Fields were treated until 1875 heat units had accumulated but no more than 3 applications maximum.
The criteria used for the area-wide pinhead square treatment were the following:
The project coordinator tracked heat unit accumulation and informed by fax participants of pending treatable fields. Weekly meetings were also held where all fields were described relative to heat unit accumulation. Material selection and combining area-wide eligible fields were coordinated by producers and pest control advisors.
1995 Whitefly Monitoring
Whitefly sampling was coordinated on a systematic basis. Two summer temporary employees were hired and trained by UA personnel to use the UA whitefly leaf turn sampling technique. The project acreage was divided into quadrants. Each field within each quadrant was sampled at least once weekly. As fields approached a treatable threshold, sampling frequency increased to twice weekly.
The sampled field was divided in half for sampling unit purposes. Adult counts were made from a 15 leaf sample. The UA recommended leaf turn technique for adult evaluation was used. The leaf turn method involves turning up the bottom side of an attached leaf from the fifth mainstem node when counted from the terminal down. A leaf is considered infested when 3 or more adult whiteflies are present. The treatment threshold used was 5 adults per leaf which was equivalent through modeling to be 57% of leaves infested.
Whitefly populations were faxed on the same day to the responsible producer and PCA. In addition, weekly meetings were held where area-wide comprehensive whitefly populations were distributed to all participants. Chemical material choices were discussed with recommendations disseminated as a result of UA efficacy studies. Chemistry rotation was encouraged for resistance management purposes. In addition, the meeting content subject matter was general with UA dissemination of research based crop production information as well as general participant information sharing.
1995 can be described as a failure relative to effective or improved area-wide pest control. Whitefly populations were low through the middle of May. Populations began to increase in late June and became very high in July. Populations rapidly increased beyond the treatment thresholds with high frequency treatment intervals occurring on most fields within the area (Figure 2). The average number of treatments for whitefly control was 5.17 (Table 1). Efficacy was low which was documented at a later time to be the result of resistance increase within the area. Treatment records were used in support of a Section 18 request for the use of Insect Growth Regulators in 1996.
In spite of the apparent project failure to meet goals, the participants felt a great deal was learned and expressed interest in continued effort in 1996.
1996 Project Description
Many project participants felt that the area-wide pinhead square treatment efforts may have contributed to rapid and severe whitefly pressures in 1995 due to removal of natural enemy complexes early in the season from non-selective area-wide chemical applications. Area-wide strategy implementation included the planting of Bt cotton on approximately 70% of the acreage, effectively eliminating pink bollworm treatment necessity. The remaining 30% of the acreage was treated with pheromones in order to deploy a soft approach to early season pink bollworm management.
The Insect Growth Regulators (IGR), Applaud and Knack were made available in 1996 through a successful granting of a Section 18 for Az. This was an extremely important resistance management tool which enabled minimization or elimination of pyrethroid chemistry. The Section 18 allowed for the use of each IGR only once per season with the final application deadline of August 31. IGR treatment thresholds utilized for whitefly control purposes remained at 1-5 adults/leaf and 0.5-1.0 3rd and 4th instar nymphs. Sampling procedure and information transfer was the same as in 1995.
Whitefly populations were substantially reduced across the project area in 1996 (Figure 3). Populations were generally below treatment thresholds the majority of the season. Average whitefly treatments were reduced from 5.17 to 1.95 from 1995 to 1996 respectively (Table 2). Project implementation strategy which included efforts to maximize natural enemy preservation and IGR use whitefly control resulted in insecticide use reduction and effective whitefly control.
1997 Project Description
Due to producer interest and initiative from an adjacent cotton production area, the project was expanded to include 14 producers, 9 PCA, and encompassed approximately 18,000 cotton acres. Due to the project expansion, 10 field scouts were hired. Again, both districts were divide into quadrants. Each field within the quadrant was sampled once weekly using the UA recommended leaf turn technique for both adult whiteflies and large nymphs.
Treatment threshold language was modified based on a statewide UA modification. In lieu of numeric evaluation, the binomial or presence/absence technique was reported as percent infestation. The IGR treatment threshold used was when both the nymph and adult components were attained. The two component threshold was when 25-40% nymph and 40-57% adult infestation occurred. These thresholds were the equivalent of 0.5 -1.0 nymphs and 3-5 adults per leaf based on a 30 leaf sample.
Whitefly populations were at a low level the majority of the season (Figure 4). In general, the project participants feel that implementation of a plan which encompasses thorough and repeatable whitefly population sampling coupled with an incorporated strategy to minimize broad spectrum insecticides when possible has contributed to successful area-wide whitefly management. Treatment application records indicate that an average of 2.81, 1.48, 2.55 treatment applications were made for whitefly, lygus bugs, and lepidopteran pests respectively (Figure 5). In addition, it was found that 33% of the fields received no IGR treatments, 62% received 1 IGR, and only 5% received both IGR's (Figure 6). In 1997, chemistry class use distribution for whitefly control was evaluated. The results indicate that of the average area-wide 2.82 treatment applications, 0.66 treatments were IGR's, 0.45 were pyrethroids, and 1.70 were non-pyrethroids (Figure 7).
These analysis offer valuable insight relative to area-wide whitefly treatment patterns. In 1997, it appears that chemistry choice was driven significantly by economics as evidenced by the distribution of non IGR chemistry and the acreage which received either 0 or 1 IGR application . It is suggested that continued improvement in area-wide whitefly control can be realized by chemistry selection which is specifically targeted at a treatable specific pest population. The IGR's should be considered the front line artillery for whitefly with remaining chemistry distribution used for non whitefly pest targets.
The area-wide voluntary pest management concept can work in Arizona. Reflecting on the previous three years, voluntary coordinated pest management can result in integration of sound scientific principles and research based information on a commercial scale. Communication between participating parties including producers, consultants, and the scientific community is a very powerful tool when used to address specific area-wide problems. Most participants have communicated very positive viewpoints relative to the coordinated project effort and wish to continue and refine strategies. The structure of this project is a true partnership with received input from all parties contributing towards implementation strategy and goal accomplishment.
This is a part of publication
AZ1006: "Cotton: A College
of Agriculture Report," 1998, College of
Agriculture, The University of Arizona, Tucson, Arizona,
85721. Any products, services, or organizations that are
mentioned, shown, or indirectly implied in this
publication do not imply endorsement by The University of
Arizona. The University is an Equal
Opportunity/Affirmative Action Employer.