|
|
|
Nursery & Forest
Volume 56 Number 20 Date 11/17/2011 JAPANESE BEETLE - Beetle counts in Wisconsin nurseries increased sharply after a two-year decline. The nursery trapping survey yielded 37,829 beetles in 160 traps, a 57% increase from 16,079 in 2010. High counts of 201 or more beetles per trap were registered in Grant, Kenosha, Pierce, Racine, Rock, Sauk, Walworth and Waukesha counties. Moderate counts of 51-200 beetles were found in Columbia, Dane, Dodge, Eau Claire, Iowa, Jefferson, Manitowoc, Marquette and St. Croix counties. Twenty counties averaged fewer than 50 beetles per trap and eight counties reported no beetles. ORIENTAL BEETLE - The number of Oriental beetles collected at garden centers also increased significantly this year, from 13 in 2010 to 55 in 2011. Twenty one were trapped in Racine County, 16 in Dane County, 10 in Milwaukee County, 6 in Ozaukee County, and 2 in Kenosha County. Surveys in 18 additional counties were negative. VIRUSES - Plant viruses have become an increasing problem in the Wisconsin nursery trade. Nearly half (101 of 224) of the nursery stock samples collected this season were tested for viruses. Hosta virus X and tobacco rattle virus were again encountered most frequently. Other viruses found were Arabis mosaic virus, cucumber mosaic virus, impatiens necrotic spot virus, rose mosaic virus and tomato spotted wilt virus. All nursery stock expressing viral symptoms was removed from sale and destroyed. REJECTED NURSERY STOCK - Nursery inspections often detect plants infested with regulated insects or diseases and stock which fails to meet pest cleanliness, labeling and quality standards. Such plants cannot be offered for sale. Included in this category in 2011 were daylilies with daylily rust, barberry with stripe rust, elm with gypsy moth, monkshood with root rot, non-viable stock, and pear with fire blight. A variety of trees and shrubs were rejected for having scale insect infestations and wood-boring insect damage. Also rejected this year were plants listed in the NR 40 Invasive Species Rule, such as autumn olive, leafy spurge, tansy, lyme grass, Oriental bittersweet, Russian olive and tartarian honeysuckle. --Liz Meils, DATCP Nursery Inspector EMERALD ASH BORER - The 2011 detection survey included 5,341 traps distributed in 64 Wisconsin counties. Eleven beetles were captured on four separate traps in northern Racine County and six others were collected on one trap in La Crosse County. An infestation affecting six ash trees was also discovered in the City of Kenosha in July. Emerald ash borer has now been detected in nine Wisconsin counties, including Brown, Crawford, Kenosha, La Crosse, Milwaukee, Ozaukee, Racine, Vernon and Washington. GYPSY MOTH TRAPPING - Trapping program statistics documented a 52% increase in male gypsy moth counts in 2011. The 25,001 pheromone traps deployed as part of the survey registered 233,990 moths, as compared to 142,409 last year. Significantly more moths were trapped in Ashland, Bayfield, Clark and Jackson counties this season, while counts in some southern and northwestern areas decreased from 2010 levels. GYPSY MOTH TREATMENT - Larval emergence and the start of the treatment program were delayed by two weeks due to cool spring weather. Aerial applications began on May 23 and approximately 233,857 acres (82 sites) in 23 counties were treated during the eight-week control program. Btk treatments totaled 53,852 acres, Gypchek applications totaled 2,577 acres, and mating disruption totaled 177,158 acres. Applications were completed by July 19. Suppression activities were conducted by the DNR from May 24-June 2 in the quarantined eastern counties of the state. Btk was applied to 2,285 acres and Gypchek was applied to 600 acres. Counties treated were: Brown, Dane, Marinette, Menominee, Milwaukee, Rock, Sauk and Shawano. GYPSY MOTH DEFOLIATION - DNR aerial surveys found no apparent gypsy moth defoliation in 2011, despite higher larval populations. Last season larvae defoliated 346,749 acres, greatly surpassing the previous record of 65,000 acres set in 2003. Forested areas that suffered heavy defoliation in 2010 showed little or no tree mortality due in part to adequate rain late in the season, which helped alleviate tree stress. --Nkauj Vang, DATCP Gypsy Moth Program PHYTOPHTHORA ROOT ROT ON CHRISTMAS TREES - Symptomatic Christmas tree samples, mostly balsam and Fraser firs, from 27 fields were submitted to the Plant Industry Laboratory for diagnosis this fall. Testing recovered Phytophthora isolates from trees grown at eight of the 27 locations. All isolates were one of two newly-described Phytophthora species: Phytophthora sansomeana (2009) or Phytophthora europaea (2002). The first of the two species, P. sansomeana, has a host range that includes several agronomic crops and weed species. Phytophthora sansomeana has been reported on corn in Ohio, soybean in Indiana, Douglas fir in Oregon, and weeds in alfalfa fields in New York. This finding may have important implications for crop rotation as a disease management strategy. The second species, Phytophthora europaea, is associated with European forest soils and has been recovered from oak forests in Minnesota, Pennsylvania, West Virginia and Wisconsin. It is considered a weak pathogen of oak. The Wisconsin Fraser firs from which P. europaea was isolated showed only mild foliar decline symptoms, but the extent of lower trunk decay indicated death was probable. More research is needed to evaluate its pathogenicity on fir. --Anette Phibbs, DATCP Plant Industry Laboratory 
|
|