Viewed in terms of insect damage to crops, 2014 was a good or even great year in Wisconsin as multi-year population lows were established for some of the major pests that attack crops.

That's according to the year-end Wisconsin Pest Bulletin (WPB) summary report issued by the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP), which was compiled by entomologist Krista Hamilton. An update is issued nearly every week during the major part of the crop growing season in the state.

Corn pests minimal

In corn fields, the WPB surveys did not document any economic level damage from black cutworms despite a near doubling to 1,068 in the number of moths caught in 34 traps. The cutworm is the year's first likely pest in corn fields.

The catch of 521 western bean cutworm moths in 108 traps in an extensive network was the lowest in the 10 years of this tracking project. The number of moth catches peaked at 10,807 in 2010 but the totals have declined every year since.

Of the 229 corn fields which were checked, 193 did not have any evidence of European corn borer larvae, the summary report indicated. The state-wide average of a corn borer larva in .03 percent of the plants tied the previous low rate set in 1998. Corn borer populations have been tracked for 73 years in Wisconsin.

Corn rootworm beetle populations dropped to the second lowest count in 10 years. The state-wide average was .4 beetle per corn plant in August compared to .5 in 2013.

Compared to 2013, the rootworm beetle populations were up slightly in western parts of Wisconsin and down in the east. Of the 229 corn fields which were surveyed, 36 had a population above the .75 per plant which is considered to create the likelihood of an economic loss.

Soybean pests low

Except for a late August surge, populations of soybean aphids were also quite low this year. The WPB noted that through July the average count of aphids was only four per plant.

That number jumped to an average of 118 in late August, Hamilton noted. This put about 20 percent of the surveyed fields above the 250 aphids per plant that is the standard for a yield loss, making those fields candidates for an insecticide treatment, she remarked.

By early September, however, the soybean aphid populations crashed. Hamilton attributed this to a combination of natural biological controls such as lady beetles, lacewings, parasitic wasps, and fungal pathogens along with the dropping nutritional content of the soybean foliage as the plants matured and some environmental factors.

The WPB summary report also indicated that Japanese beetle populations were down across the state in 2014 and no soybean field that was in the DATCP survey had enough defoliation to justify an insecticide application. The report noted, however, that the Japanese beetle's range continues to expand in the west central and northern parts of Wisconsin, where there were a few reports of moderate damage to various crops in 2014.

Root rot a soybean problem

On the disease front, however, it was not a good year for soybeans. DATCP plant pathologist Anette Phibbs reviewed those findings in the WPB summary report.

The survey of 57 fields in 35 Wisconsin counties for phytophthora sojae root rot conducted from June 2 to July 16 found that 26 of the fields tested positive for this pathogen. This was the highest incidence of this species of root rot since the testing began in 2008. The infected fields were in Barron, Clark, Dane, Green, Jefferson, Kenosha, Lafayette, Manitowoc, Marathon, Ozaukee, Rock, Sheboygan, St. Croix, Walworth, and Winnebago counties.

Two new phytophthora species — pini and personii — were detected for the first time in soybeans in Wisconsin in Eau Claire and Winnebago counties respectively. Phibbs pointed out that pini is common on many shrubs and trees while personii is so new to science that it hasn't even been formally described.

Sansomeana, another root rot species, was detected in Calumet, Dunn, and Eau Claire counties this year. Phibbs noted that this species was first identified in Jefferson, Marathon, and Sheboygan counties in 2012.

Soybean dwarf virus was found in 24 percent of the 155 fields which were tested from July 28 to Aug. 28. This was an increase from 9 percent in 2013. On the flip side, the incidence of the new vein necrosis-associated virus which was first detected in Wisconsin in 2012 was down to 5 percent of the tested fields this year compared to 12 percent in 2013.

Alfalfa fields clean

Pest populations were also down across the board in alfalfa fields this year, the WPB report indicated. No economic threshold for yield loss was determined for any of the 534 fields which were surveyed this year.

In line with the delay to the start of the 2014 growing season, alfalfa weevil larvae were late in appearing. Populations of the weevil remained low and, unlike in recent years, no crop damage was documented.

Potato leafhopper populations did not reach the economic threshold level for losses in any of the 534 surveyed fields. The first migrants arrived in the southern part of the state from May 8 to 14.

Pea aphid populations in alfalfa fields peaked from June 20 to 26. For the remainder of the summer, the populations were very low.

Source - http://www.wisfarmer.com/