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Oregon grasshopper and Mormon cricket survey summary for 2011
Introduction

The 2011 Oregon grasshopper survey season, conducted by ODA in cooperation with USDA APHIS PPQ, was very similar to 2010 yet surpassed it as Oregon's greatest grasshopper challenge since the major outbreaks of the late 1980’s. Initially, grasshopper numbers were slow in developing, delayed by unseasonable cool and wet weather in May and June but erupted in great numbers late in the season as the weather finally warmed up. Most of the rangeland in the eastern third of Oregon was generally infested with economic populations by season’s end.
 
Surveying began on May 23rd and ended on September 1st. Nymphal survey takes place early in the season and is used to locate potential outbreak areas. Adult survey (4 July - 1 September) is used by APHIS to make predictions for the next year, estimating economic levels of 8 or more grasshoppers per square yard. In 2011, a total of  3,150 sites were visited of which 11 were Mormon cricket (MC) locations and  3,139 grasshopper. Of the grasshopper stops  1,880 were nymphal,  914 adult survey, and  345 treatment-related sites (Table 1). Approximately 2.89 million acres were estimated to be economically infested across 18 counties in eastern Oregon (Table 1). Sixteen of these counties had greater than 10,000 economically infested acres.
 
Table 1. Oregon Grasshopper Survey Statistics from 2005 through 2011. Economic infestation ⊃3; 8 grasshoppers / yd 2
   Grasshopper Sites Surveyed   
   
  
 Number Acres of     Samples Mean Number
 Counties Econ.     w/Econ GH / of GH
Year Infested Infest. Total Nymph Adult Treatment Density yd2* Surveyors

2011 18 2,888,455 3,139 1880 914 345 1093 20 6
2010 12 1,910,222 1,905 795 750 360 488 21 6
2009 11 151,974 998 491 507  108 18 4
2008 12 1,129,820 2,722 1116 1606  360 29 6
2007 13 798,358 1,585 706 870  298 18 6 (+2)
2006 14 97,399 1,368 750 618  100 16 6
2005 9 64,751 859 306 423  115 15 5
          

*mean of economically infested samples

 
Just as in 2010 the cool and wet May-June period delayed emergence which complicated our surveying efforts. Normally in outbreak years most grasshoppers are adults by early July since outbreaks are usually associated with hot, dry conditions. During these past two years we observed a unique situation where large populations of early instars were mixed in with a significant number of late instars to adult in mid to late July. Some grasshoppers hatched normally during the few warm periods we had during the spring, however when the bulk of the population hatched in late summer, control recommendations were complicated by the mix of young and older grasshoppers found together. Our preferred control product Dimilin, a growth regulator, is not effective on adult or late instar grasshoppers.
 
We participated in two suppression programs this season. For the first ODA and APHIS provided delimitation and consultation to the Burns-Paiute Tribe for protection of their riparian restoration program on the Jonesboro Ranch, Malheur County. They had mixed ages of immatures in their population, though biased toward the later instars. Carbaryl bait was thus selected for targeted ground applications. APHIS and ODA also delimited and baited ~ 240 acres in the Cow Hollow area of Malheur County. This effort was very successful.
 
Areas of Special Mention
Klamath Marsh National Wildlife Refuge. Due to repeated outbreaks of the clear-winged grasshopper, Camnula pelucida, we continue to watch the area in and around the Klamath Marsh National Wildlife Refuge very closely. During the 2010 adult survey one isolated parcel of Refuge property, the "Buck Pasture", and several areas in the northeast region of Refuge, known as the “Lane Ranch.” had high densities of C. pelucida mating and laying eggs. During 2011 nymphal and  adult survey efforts economic, and very high densities, of the grasshoppers (predominately the clearwinged grasshopper), we found in both northern and southern areas of the Refuge and bordering private holdings. Water levels receded very late this season and by the time treatment was possible most populations were beyond effective use of Dimilin. The Refuge administration decided to hold off on any chemical application during 2011 and plan for early scouting and consider the potential for aggressive treatment of nymphal populations in 2012.
Fort Klamath Basin. Recently outbreaks have plagued the area around Fort Klamath. In 2010 a few of the private landowners in the basin made treatments. Survey of the Basin during 2011 indicated little development of significant populations until late in August. Given the densities seen at the Klamath Marsh National Wildlife Refuge to the north, as well as reports from other areas in the county, land owners and managers would do well to monitor their holdings early in the 2012 season.
Cow Hollow Suppression. Economic densities of grasshopper were found widely across Malheur county during 2011. The local BLM Office requested APHIS and ODA evaluate several areas where BLM rangeland borders irrigated cropland to determine if suppression was needed and feasible. Ultimately one suppression program was undertaken. Carbaryl bait was applied at a rate of 10lbs/A using ATVs to ~ 240 acres of BLM lands bordering private crop land in the Cow Hollow drainage. This suppression was made on August 2nd with assistance of the PPQ group from Idaho. Densities were reduced to 5/yd2, a 70.6% reduction.
Burns-Paiute Suppression. The Burns-Paiute Tribe has a long-term riparian restorationproject underway at the Jonesboro Ranch. During 2010 they suffered extensive damage to their riparian plants from the local grasshopper populations. ODA and APHIS were contacted for assistance in survey and delimitation of this year's populations before they could repeat the damage of 2010. Our survey work was used by the Tribe to ground treat selective areas associated with their riparian work using carbaryl bait.
Portland International Airport . After successfully treating a problematic grasshopper population at the Portland International Airport (PDX) with a well timed Dimilin application in 2009 Port of Portland continues to enjoy the effects of that successful suppression. Very few grasshoppers were found in our 2011 survey and the densities were well under any level of economic or operational concern.
Umatilla Chemical Depot. In 2010 at the request of the Department of Defense Umatilla Chemical Depot APHIS treated 4242 acres with Dimilin to prevent grasshoppers from migrating from the Depot to surrounding high value cropland. A similar but smaller outbreak in 2005 was not treated and resulted in heavy crop damage to fields bordering the Depot. The treatment in 2010 resulted in an 85% reduction, and this year densities remained low in our survey.
Malheur Wildlife Refuge. Grasshopper densities from 2009 and 2010 resulted in complaints from ranchers bordering the NWR and suggested economic densities might be a problem again in 2011. However, probably do to the extremely wet conditions persisting well into the summer coupled with the early unseasonable cool temperatures, this situation did not materialize.
 
Mormon Crickets
A low density migration of Mormon crickets were monitored in Gilliam County this year. Another single sighting was noted in Umatilla County. We heard rumor of other MC activity but have no actual data to report. It appears MCs were not an issue this year in Oregon.
 
Summary
Based on continued increase in the grasshopper densities and expansion of the affected geographic area during 2011 we recommend landowners and managers be prepared for a muchworse outbreak in Oregon in 2012. We cannot accurately predict where grasshopper outbreaks will occur because they depend greatly on many factors at the time of hatch and early development, variables that cannot be accurately forecast. However, we consider it likely that the patterns of increasing density and geographic spread will continue in 2012. If conditions cause the crash of this progressing outbreak we can consider ourselves fortunate, however, planning for a continuation of the patterns of the past few years is the only prudent course of action.
 
We encourage landowners in areas with high or building populations in 2011 to be especially proactive in early 2012 if they are concerned about grasshopper impacts to crops and rangeland. Control is most effective on young grasshoppers. Contact us or your local Extension Office for advice, assistance, or to report grasshopper populations.
 
Full report with maps (pdf, 1.64 MB) 
 
Paul Blom , Oregon Department of Agriculture, Salem, OR, 503-508-1253, pblom@oda.state.or.us
Gary Brown , USDA-APHIS Portland, OR, 503-326-2814 (ext. 239), Gary.W.Brown@aphis.usda.gov
 
December 15,  2011