Issue
Integrated pest management (IPM) plans must be flexible enough to accommodate different insect pest pressures from year to year. After years of lesser recognition as a cotton pest, Lygus bugs have become the number one pest of cotton since 1998. Among growers, typical control measures for Lygus have involved tank mixing combinations of broad-spectrum insecticides in the unfounded hope that this practice will give more control over the pest.

What has been done?
The UA College of Agriculture and Life Sciences has developed an integrated pest management program (IPM) for Lygus in cotton aimed at reducing insecticide use through adequate field sampling, adherence to threshold guidelines, and using the right compound for the job. Above all, it emphasizes avoiding pest pressures wherever possible. These measures are being incorporated into the larger cotton pest management program, and focus on reducing spray applications from mixed broad-spectrum insecticides to more selective, targeted single insecticide applications. One key to the success of the program has been the accurate identification of single spray compounds that perform consistently against Lygus and knowing precisely when to use them. The education component of this program has assisted growers in implementing this strategy during the last seven seasons.
Because Lygus bugs survive and multiply on many different hosts, a collaborative project was conducted with growers in a large agricultural area and with the Arizona Cotton Research and Protection Council to determine the factors that contribute to the abundance of Lygus populations. These studies, part of a larger cross-commodity program in the UA College of Agriculture and Life Sciences, identified key sources of Lygus populations and provided guidelines on planting patterns and distances that should help avoid Lygus problems in the future. 

Impact
In response to this IPM program, more than 50 percent of the region's cotton growers have changed their chemical tactics against Lygus by switching to single compounds used strategically and at appropriate rates as part of an IPM system. In 1999, growers applied the fewest number of sprays statewide against Lygus in cotton since 1993, thus reducing their costs per acre while protecting the environment. Education efforts across the border in Mexicali, Mexico have resulted in the majority of cotton growers there adopting threhold and other IPM guidelines for Lygus management. This has resulted in a 66 percent reduction in the number of acres receiving spray mixtures for Lygus, while increasing effective rates by about 20 percent. 

Arizona extension entomologists have been able to teach and demonstrate to growers that single compounds are as effective or even more effective than broad-spectrum combination sprays, and that this practice helps reduce the risk of resistance in Lygus and other insects while minimizing negative impacts on beneficial insects. More growers are now aware of the specific midseason timing (thresholds) required for the control of Lygus and for providing maximum economic return. They are also aware of new information on when precisely to discontinue sprays against this pest late in the season. 

Some growers reported immediate savings of $25 per acre by curtailing sprays earlier than they would have done otherwise, because research showed that they were not cost-effective. The success of this program has led for the first time to efforts to control Lygus across multiple crops (Lygus are highly mobile and feed on several crops in addition to cotton.) Through community-wide cooperation with growers in a large agricultural region, researchers were able to collect enough information about distributions of Lygus across multiple hosts to formulate concrete recommendations for planting patterns and distances from sources. 

Through use of spatially-explicit information in a geographical information system (GIS), educators can now advise growers that sensitive cotton crops will be negatively affected by other Lygus sources, such as seed alfalfa, grown within 1.5 km of their crops. Further, researchers found that clustering many cotton fields together provided "safety in numbers" by helping to dilute the negative impact of Lygus migrating from non-cotton sources. This information helps pest managers address decades-old nagging questions about Lygus movement and will help guide them in the introduction, placement and cultivation of other crops on which Lygus reproduce. 

Funding
Hatch Act 
Smith-Lever 3(d) (e.g., IPM) 
Western Region IPM; Pest Management Alternatives Program
UA program enhancement (CES); UA IPM and CROP programs 
Cotton Incorporated, Arizona Cotton Growers Association
Agrochemical companies), NSF's Center for Integrated Pest Management
ADA's Specialty Crop Program, Arizona Cotton Research & Protection Council

Contact
Peter Ellsworth, IPM specialist 

Maricopa Agricultural Center 
37860 W. Smith-Enke Road 
Maricopa, AZ 85239-3010 
Tel: (520) 568-2273, FAX: (520) 568-2556 
Email: peterell@ag.arizona.edu
 

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