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Looking Ahead

Forages & Grains

Corn

Soybeans

Fruits

Vegetables

Nursery & Forest

Degree Days

Looking Ahead
Volume 64 Number 4 Date 05/23/2019


BLACK CUTWORM - The peak damage window for corn is forecast to open over the weekend of May 25-26. A considerable portion of the state's acreage is under a high threat of larval infestation this year based on delayed field preparation and planting, prevailing weedy conditions, and the consistent, moderate spring moth flights documented since mid-April. Localized outbreaks are expected. Scouting corn, including Bt hybrids, over the next several weeks is particularly important. The economic threshold for black cutworm is reached if 3% of plants have been cut and larvae are still present in the field. Spot treatment is an option for sites with patchy damage.

ALFALFA WEEVIL - Adults have become more common in alfalfa and spring egg deposition is increasing. Surveys to assess larval populations and defoliation levels should begin at this time.

EUROPEAN CORN BORER - Most overwintered larvae are in the pupal stage, but a few early spring moths could emerge before the end of the month. Degree day accumulations at advanced locations such as Beloit and Platteville will surpass the 374 heat units (modified base 50°F) required for corn borer moth emergence by May 27. Black light trappers are advised to carefully examine trap contents during the next two weeks. In 2018, the first corn borer moths appeared by May 30.

PLUM CURCULIO - Beetle migration into the orchard perimeter is expected to begin as spring temperatures rise. Apple growers who have experienced past problems with this pest should begin checking early-sizing cultivars such as Ginger Gold, Ida Red and Liberty for crescent-shaped oviposition scars. The minimum size of fruitlets preferred for egg laying is 5 mm. Applications are not effective until fruit damage is observed.

POTATO LEAFHOPPER - Migrants were collected in low numbers on May 20-22 from alfalfa fields in Dane, Grant, Iowa, Monroe and Vernon counties. Their recent appearance confirms that the first distinct migration event of 2019 has occurred.

CODLING MOTH - Evening temperatures will be appropriate for moth flight this weekend. Close monitoring of pheromone traps is suggested for southern and central Wisconsin orchards until the biofix is documented. Conditions required for codling moth flight are wind speeds between 3-5 miles per hour when temperatures are above 62°F without rain. If temperature fluctuations lead to inconsistent moth activity, the biofix date should be assigned to the warmest, calmest night.

-- Krista Hamilton, DATCP Entomologist