New pests rose to the top in threats to Wisconsin's major and minor crops this year while the populations of a few of the most well-known pests plunged significantly.
This information is according to the Wisconsin Pest Bulletin (WPB) summary report for 2012 issued by entomologists at the Department of Agriculture, Trade, and Consumer Protection.
An early start to the growing season and the accompanying movement of migrating insect pests started during early May with the arrival of unprecedented numbers of variegated cutworm moths, the WPB indicated.
By a month later, damage by variegated cutworm larvae was reported throughout the state in alfalfa, corn and soybeans with Fond du Lac, Green Lake, Marquette, and Sauk counties documenting severe infestations.
Moths of the black cutworm, which attacks young corn plants, arrived in "remarkably high" numbers from March 19 through May, the WPB reported.
As a result, relatively high infestations of the cutworm occurred in early-planted corn in southern counties and in early June in later-planted corn in counties along the Lake Michigan shoreline.
Because both the growing cycle of the alfalfa weevil and the first cutting of alfalfa were weeks ahead of normal, the amount of defoliation from very high populations of the pest was limited, the WPB reported.
The highest concentration of the weevils was in the southwestern and south central counties.
Extremely early migrations of the potato leafhopper were also documented, leading to the presence of nymphs by early May in southern areas and very high populations by mid-June.
Following two years without having to do so, many alfalfa growers decided to treat their fields in June and July this year, the WPB noted.
As drought and high temperatures took hold in most of the state by the official start of summer, major outbreaks of the two-spotted spider mite - the highest in eight years - occurred in soybeans, the WPB stated.
It cited informal estimates, which indicated that about 25 percent of the state's soybean fields were treated at least once for the pest.
Corn earworm moth flights, which continued from late June to mid-September resulted in the collection of 10,656 moths at 15 sites - 57 percent more that in 2011.
The late season flights were high but much of the sweet corn, which they infest, was past its silking stage by that time, the WPB observed.
Late in the growing season, infestations of spotted wing drosophila were detected in raspberries and blackberries in counties scattered throughout the state, increasing the list of counties to 13, which with known infestations in the past two years.
Counties added to the list in August and September of this year were Bayfield, Brown, Door, Fond du Lac, Marinette, Monroe, Pierce, Vernon, Winnebago and Wood.
On the other side of the pest ledger for 2012, the WPB reported that surveys in the early autumn found the lowest population of European corn borer larvae in 71 years.
It attributed the low concentration of .03 borer per plant, the lowest since the .05 at the end of the growing season in 1998, in large part to the fact that more than 50 percent of the corn planted in Wisconsin has the Bt trait, which controls the corn borer.
In the same vein, the population of soybean aphids in 2012 was the lowest since the presence of the insect was identified in the state 10 years ago.
The WPB stated that the combination of the extreme heat and the widespread treatment for the two-spotted spider mite was probably responsible for the suppression of the aphid.
A minor overall decrease in corn rootworm beetles per plant was calculated with five of the state's nine crop reporting distracts tabulating somewhat lower numbers than in 2011.
With increases being recorded in the southeast counties and with higher numbers being found in the north compared to 2011, the WPB advises corn growers in the south to expect root damage if they plant non-Bt corn in a continuous rotation in 2013.
The 2012 trapping program for Western bean cutworm moths yielded 3,290 catches this summer compared to 4,895 a year ago. Most of the catches were in the third and fourth tiers of counties north of Wisconsin's southern border.
A new soybean virus - vein necrosis-associated - was confirmed in Wisconsin in early October from leaf samples taken in September. The virus, whose symptoms are yellowing and browning of leaf veins and leaves, could be transmitted by soybean thrips.
It was first reported in Tennessee in 2008 and has since also been detected in Arkansas, Kentucky, Missouri, Michigan, and Ontario in Canada.
An early growing season survey found phytophthora root rot in eight of the 49 fields with three of the samples containing a new species of the rot. All of the plants roots collected in that survey tested positive for pythium.
A special survey was conducted at 598 sites during the growing season for invasive species of weeds with a focus on spotted knotweed, common tansy, and black swallow-wort.
Spotted knapweed was found at 12 percent of the sites (mainly in the central and northwest distracts) and common tansy was found at 10 percent of the sites (mostly in the north central and northwest).
No black swallow-wort was found.