Volume 52 Number 18 August 10, 2007 Weather and Pests Widespread rainfall this week brought variable levels of moisture to the state. Portions of the southern agricultural areas received generous amounts of precipitation, and this has improved the prospects for late-planted sweet corn, soybeans and alfalfa regrowth. High temperatures and humidity favored an increase in some diseases that were relatively inactive during the prolonged period of dry weather. Crops in the central and northern areas remain under severe drought stress. Corn growers from the east central area report poor grain fill and attribute it to the continued dry conditions. Second and third crop hay cuttings are short and yields are generally below normal. Corn rootworm beetles are now very active and being encountered in high numbers in several counties. Growing Degree Days through 08/09/07 were GDD 50F 2006 5-Yr 48F 40F Historical GDD Dubuque, IA 2115 1989 2006 2194 3379 March 1 - August 9 Lone Rock 2037 1924 1934 2058 3277 Beloit 2098 2071 1996 2106 3357 Madison 2004 1879 1907 2028 3236 Sullivan 1932 1912 1883 1923 3139 Juneau 1922 1803 1850 1967 3127 Waukesha 1885 1804 1806 1933 3083 Hartford 1909 1789 1803 1961 3010 40 50 Racine 1875 1774 1751 1912 3067 Milwaukee 1870 1785 1739 1906 3063 10 78 20 40 0 Appleton 1876 1818 1731 1909 3051 2 48 Green Bay 1752 1703 1609 1798 2915 0 12 Big Flats 1885 1890 1831 1846 3058 0 Hancock 1875 1858 1802 1836 3026 Port Edwards 1869 1899 1765 1873 3035 43 45 36 76 La Crosse 2178 2133 2037 2063 3462 30 20 15 Eau Claire 2004 2078 1903 1982 3227 State Average 24 9 Very Short 41% 1 Cumberland 1833 1828 1679 1822 2986 1 0 Short 32% Bayfield 1465 1478 1312 1471 2500 Adequate 26% 5 2 Wausau 1744 1689 1598 1754 2861 Surplus 1% 21 Medford 1690 1707 1568 1708 2804 22 21 63 35 Soil Moisture Conditions 73 57 Crivitz 1687 1638 1530 1727 2799 0 0 1 Crandon 1588 1522 1449 1568 2634 as of August 5, 2007 WEB: http://pestbulletin.wi.gov z EMAIL: [email protected] z VOLUME 52 Issue No. 18 August 10, 2007 PAGE 161 Corn rootworm - Adults continue to emerge in high Looking Ahead numbers and silk damage is evident in fields with fresh silks. Surveys revealed individual fields with economic Annual or dog-day cicada – Hot and humid weather in the averages of 1.0 to 11.6 beetles per plant in Calumet, past week inspired the emergence of nymphs and Columbia, Dane, Dodge, Fond du Lac, Green Lake, Iowa, courtship singing by male annual cicadas. A DeForest Jefferson, Manitowoc, Outagamie, Ozaukee, Rock, Sauk, resident reported a flurry of cicada activity in the downtown Sheboygan, and Winnebago counties. Plants in these area on August 4. Two nymphs were encountered on the fields had been already pollinated and should not be sidewalk; one was a final instar searching for a tree upon greatly affected by silk feeding. However, an average of which to transform into an adult. From Portage to Wausau, 1.0 beetle per plant or greater indicates a high potential for choruses of males could be heard in the tree tops larval damage to corn roots next season. The western producing high-pitched, shrill songs on the warmest species, Diabrotica virgifera, was encountered in virtually afternoons. Annual cicadas are biologically and every field as far east as Lake Michigan. In Columbia, morphologically distinct from the Brood XIII periodical Dodge and Green Lake counties, the northern species, cicadas that emerged in May and June. Nymph Diabrotica barberi, appeared to be more numerous. As development in annual cicadas is not synchronized, adults more fields mature, expect adults to concentrate in later are green and black and larger than the black and orange planted fields with fresh silks. periodical cicadas, and emergence occurs in July and August. These cicadas have two- to five-year life cycles Two-spotted spider mite – Prolonged dryness over the and are usually associated with oaks, maples, and other central and northern counties has been highly conducive to mature well-established trees. Adults are commonly found spider mite outbreaks. Scouting at 4- to 5-day intervals on blacktop surfaces that retain heat overnight, especially throughout August is strongly advised in fields under on mornings with temperatures below 55°F. drought stress. Examine the plants along the margins of fields for stippling or speckling associated with early two- spotted spider mite infestation. A hand lens should be used to view the eggs, nymphs and adults. Mites may be dislodged and counted on by tapping leaves over a sheet of white paper. White mold of soybean – A report from Barron County indicated that light infections of fluffy, white mycelium are appearing in localized spots within fields. The incidence of white mold is heavily dependent on weather conditions during soybean flowering and early pod development. Conditions that favor its development are rain, cool temperatures (< 85°F), high humidity, and moist soil in a closed canopy. It seems unlikely that this fungus will increase in intensity on soybeans in the northwest and cause damage before the crop reaches maturity. Forages Roundup Ready alfalfa - Conventional and organic farmers who raise alfalfa can determine if there are nearby fields of genetically engineered alfalfa by contacting a toll-free hotline offered by the USDA Animal and Plant Health Inspection Service (APHIS). Alfalfa genetically engineered to resist the herbicide Roundup has been available in the United States since 2005. As a result of a recent lawsuit, the USDA APHIS has been directed to restrict and regulate the use of Roundup Ready alfalfa. APHIS has made available a toll-free telephone number for use by conventional and organic alfalfa farmers and prospective alfalfa farmers to inquire about the proximity of their farms or fields to Roundup Ready alfalfa. These measures offer some protections for organic farmers and others who wish to avoid growing genetically engineered crops. WEB: http://pestbulletin.wi.gov z EMAIL: [email protected] z VOLUME 52 Issue No. 18 August 10, 2007 PAGE 162 According to the APHIS website, genetically engineered of the fields examined. Illustrated below are images of the alfalfa is being grown in 58 Wisconsin counties. Location mobile laboratories used by DATCP specialists to test field information can be accessed by calling 1-866-724-6408. corn for transgenic traits. The line will be staffed beginning August 6, 2007 from 9 a.m. to 5 p.m. Eastern time, Monday through Friday (except holidays). To receive information, callers must be a person who either currently plants conventional or organic alfalfa or plans to do so, and must be ready to provide the operator with either the latitude and longitude coordinates or the mailing address of their farm or field where the alfalfa is or will be grown. Potato leafhopper – Despite recent rains, leafhopper populations in many central and northern Wisconsin alfalfa fields remain above treatment thresholds. Counts ranged from 1.9 to 11.5 per sweep in 6-8, 10-12 and 14-18 inch Adams, La Crosse, Marquette and Monroe County fields, and severe yellowing was evident in some of the more mature stands. Cooperators reported moderate to high numbers in the east central and northeast regions where most of the recent rains have missed. Hopperburn is very apparent in areas that had only minimal amounts of rainfall in past weeks. The combination of continued dryness and conditions favorable for reproduction has caused persistent and widespread potato leafhopper problems this season. Corn Corn rootworm – Preliminary results of the annual corn rootworm beetle survey revealed high populations in Calumet, Columbia, Dane, Dodge, Fond du Lac, Green, Green Lake, Jefferson, Manitowoc, Outagamie, and Ozaukee counties. Corn fields in these areas contained averages greater than 1.0 corn rootworm beetle per plant, which indicates a high potential for egg laying and larval damage to roots in continuous corn next season. Fall armyworm – Several plants infested with small larvae Intermediate averages of 0.5 to 1.0 beetle per plant were were observed in Dodge County field corn. Feeding was detected in Iowa, Sauk, Washington and Waupaca confined to the whorl area. Populations were light, but counties, although individual fields with high populations concentrated in areas where a number of adjacent plants may occur in these areas. Generally non-economic or low were infested. On average, fewer than 5% of the plants populations less than 0.5 beetle per plant were were affected. documented in Adams, Marquette, Richland, Waupaca and Winnebago counties. The corn rootworm beetle Western bean cutworm – The annual flight of western bean survey is timed to coincide with peak beetle emergence cutworm moths has ended. Moths emerged earlier than and egg laying. Final results will be published in the expected in Wisconsin and over the Midwest, and activity August 31 issue of the Wisconsin Pest Bulletin. concluded rather abruptly. With a few noteworthy exceptions, including Centerville (27 moths), Eau Claire For the second year, the corn rootworm survey will be (34 moths), New Holstein (27 moths), and Princeton (21 correlated with use of transgenic traits. DATCP survey moths), pheromone traps registered very low numbers of specialists are testing plants at each field for the two Bt moths during the last week. The highest seasonal total corn proteins available for control of corn rootworm larvae: number of western bean cutworm moths captured was 448 YieldGard® and Herculex® rootworm technology. Results at Princeton in Green Lake County (July 2 to August 9, may reveal how widely these rootworm products are used 2007).