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Looking Ahead

Forages & Grains





Nursery & Forest

Degree Days

Volume 63 Number 11 Date 07/12/2018

CODLING MOTH - Several apple orchards are 1,000 or more degree days (modified base 50F) beyond the first biofix, and treatments for second generation larvae are starting. An increase in moth counts from the spring to summer flight suggests that some degree of fruit injury is probable and fruits should be closely inspected for damage. Apple growers are reminded to rotate insecticides between generations to prevent resistance to chemical materials. Localized larvicide applications are usually an acceptable alternative to orchard-wide treatment for sites with variable larval pressure between cultivars or blocks.

APPLE MAGGOT - Captures on red spheres and yellow sticky traps have increased, with reports of flies appearing on traps at 11 of 27 cooperating locations from Kenosha to Bayfield County. The highest count for the week was 12 flies on a yellow sticky board at Sinsinawa in Grant County. Maintaining traps will be important as emergence continues and oviposition on apples increases in late July and early August.

SPOTTED TENTIFORM LEAFMINER - The second flight should peak soon at most monitoring sites. Several orchards reported counts above 500 moths per trap in the past week, with a high of 1,053 moths per trap registered in Marquette County. Heavy egg laying can be expected as long as pheromone traps are attracting high numbers of moths. Apple orchards with populations greater than one mine per leaf or a history of infestation should consider controlling second-generation larvae to reduce build-up of leafminers before the third flight begins in late July or August.

JAPANESE BEETLE - Beetles are appearing in southern and Wisconsin apple orchards and vineyards. Damage to fruits, ornamentals and field crops is expected to intensify later this month and control may be necessitated to prevent fruit loss. Most chemical treatments are only effective against Japanese beetle when populations are low and the beetles are first immigrating into vineyards and orchards. Fruit growers should note the daily location of beetles when timing an insecticide application since the beetles feed in trees during the day and move to the ground at night.

SPOTTED WING DROSOPHILA - Berry growers in southern and western Wisconsin have reported finding initial larval infestations in their blackberries and raspberries in past two weeks, indicating sampling for larvae in fruit should begin. To sample from a planting, place at least 15 ripe fruit in a plastic bag and lightly squeeze each fruit. Add a strong salt solution (1 cup salt to 1 gallon water), enough to cover all of the fruit, to the bag. If present, small white SWD larvae will emerge and rise to the top of the liquid after 30 minutes. A more complete guide to the sampling process is available at http://www.canr.msu.edu/ipm/uploads/files/SWD/SWD_2013-Salt_Sugar_Boil_Test-6-20-2013.pdf. Managing SWD requires persistence and the use of as many control techniques as possible.

-- Krista Hamilton, DATCP Entomologist