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Oregon Grasshopper and Mormon Cricket Survey Summary for 2012

The 2012 Oregon grasshopper survey season, conducted by the Oregon Department of Agriculture (ODA) in cooperation with the Oregon United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ) office, revealed that the grasshopper population is still a significant concern in many areas for the state, though perhaps declining from the infestation levels of 2011. Surveying began on 4 June and ended on 4 September. Nymphal survey takes place early in the season and is used to locate potential outbreak areas. Adult survey (10 July - 4 September) is used by APHIS to make predictions for 2013 and estimated economic levels of 8 or more grasshoppers per square yard.

In 2012, a total of 1,135 sites were visited. Though we heard report of some Mormon Cricket activity this year it was limited and none were found in our survey. Of the total stops 387 were during the period for nymphal grasshopper survey and 748 during the adult period. Approximately 1.18 million acres across 17 counties in eastern Oregon were estimated to be economically infested. Sixteen of these counties had greater than 10,000 economically infested acres. 

Oregon Grasshopper Survey Statistics from 2005 through 2012. Economic infestation ³ 8 grasshoppers / yd2.


                                                               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


2012        17        1,178,872       1,135        387      748      34               526          34             2.5

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 sample

Climatic conditions and range fires affected the survey this year. Unlike the previous two summers cool and wet weather did not persist well into June during 2012. In fact drought conditions developed over much of the southeastern OR grasshopper range. Ultimately these dry conditions coupled with fuel load from 2011 produced some major range fires locally impacting this year’s densities and likely those in the following years.

While it appears the economically infested acreage in OR is declining, it is dangerous to conclude the outbreak of the last few years is waning. Budget limitations forced us to reduce our sampling efforts by ~2/3 during 2012. To do that we had to reduce scouting personnel to ~2.5 / week and the total number of sites surveyed to ~1/3 of 2011. Thus we estimate survey for only ~3.5 million acres in 2012 compared with 7.4 million in 2011. 


A comparison of grasshopper (GH) infestation densities (/ yd2) adjusted for effort.


             Percent of Total Surveyed Acres                               Estimated Acres Surveyed          

Year      Economic      non-Econ         No GH             Total       Economic      non-Econ        No GH


2012          33.7              46.8             19.6           3,503,235   1,178,872   1,639,468      684,895
2011          38.9              43.4             17.7           7,422,908   2,888,455   3,220,585   1,313,868


Map of the 2012 estimated areas of surveyed showing three levels of infestation.

We participated in one suppression program this season at the Klamath Marsh, Klamath County. June scouting on the Klamath Marsh National Wildlife Refuge (KMNWR) and surrounding private holdings indicated the marsh would again experience the high population densities it had in the previous two seasons. A collaborative effort was undertaken between the Fish and Wildlife Service (FWS), APHIS and the private landowners to attempt a suppression of the population. Due to logistics and various complications it took over three weeks to actually begin treatments. During this time the grasshopper populations increased in age, density and geographic spread. Landowners applied Dimilin, an insect growth regulator, too late in the grasshopper development and APHIS was only able to treat ~590 ac of KMNWR land using Carbaryl bait. In the end 7,497 acres were treated by private landowners on their lands and ~ 590 on the Refuge were treated by APHIS.

Though there may have been declines in some local grasshopper populations, economic densities were still found widely across eastern Oregon during 2012. Thus, we recommend landowners and managers be prepared for the outbreak in Oregon to continue in 2013. 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 economic densities will continue in 2013. If conditions cause the crash of this 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 2012 to be especially proactive in early 2013 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

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