June 3, AppleTalk Call Summary

AppleTalk Conference Call Summary
Tuesday, June 3rd, 2014, 8:00 – 9:00 a.m.
Presenter: John Aue, Threshold IPM.
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

June 3rd Call download: Click Here

Tree phenology
Orchards from the Twin Cities to Green Bay are at petal fall while growers further south are close to ten days after petal fall. Warmer weather has increased this month’s average temperature to a seasonal normal.

Disease
Apple scab
Scab legions are becoming visible in orchards in southern Wisconsin, northern Illinois and Iowa. In northern orchards legions may not become visible for another one to two weeks. Scouting for apple scab, post petal fall, allows growers to confidently plan fungicide applications for the prevention of further infections. On sunny days, scan the undersides of leaves of scab susceptible varieties, or in blocks with a history of damage, for light gray legions. If legions are found, look for trends on terminal shoots and fruit clusters to help determine when an infection took place. By linking an infection to tree phenology growers can compare rain events with fungicides to see where they missed. Resistance issues may be a concern if an infection happened after an application of a single-site fungicide, i.e., Scala (pyrimethanil) or Vanguard (cyprodinil), and a protectant, i.e., Penncozeb (mancozeb). Legions present now will infect new leaf tissue, if legions are found focus control measures on problem blocks for next six weeks, until the leaves stop growing. If no legions are found proceed with reducing fungicides applications for the remainder of the season.

Powdery mildew
Scout for powdery mildew in developing shoots of new plantings. Powdery mildew is a warm weather disease that sporulates in dry weather. Spores are washed away in heavy rains, thus reducing the likelihood of an infection.

Black rot
Warm, humid temperatures and an abundance of winter injury, and tree stress, has provided optimum conditions for the spread of black rot. Early season removal of dead and dying limbs and trees will help reduce inoculum and the spread of spores. Remove all trees that have died or are extremely stunted in development, the chance of survival of these trees are low.

Insects
Green fruitworm
Feeding damage to fruitlets and foliage, i.e., large smooth holes and chewing along leaf margins of terminal shoots, is typical of green fruitworm (GFW). Because GFW develop quickly and have one generation, populations are usually not large enough to justify control. If defoliation is a concern, note: in southern Wisconsin most GFW are too large to control, as they increase in size, nearing pupation, the less leaf tissue they consume. Galesville to La Crescent still have populations that can be controlled. High numbers of GFW have been observed this season.

Spring cankerworm
Spring cankerworm are common, small dark grey to brown, larvae that move in an inchworm fashion. Damage can be seen as foliar feeding to all sections of the leaf excluding the midrib, and to fruitlets. In two to three weeks the larvae will be pupating. Old feeding can be determined by observing the amount of new growth beyond the damaged tissue.

Forest tent caterpillar
Forest tent caterpillars look similar to the eastern tent caterpillar but do not form tents; is not an economic pest.

Obliquebanded and redbanded leafrollers
The larvae of obliquebanded (OBLR) and redbanded (RBLR) leafrollers can be distinguished by inspecting their head and thoracic shield; OBLR is tan to brown or blackish and RBLR is yellow or green. Now is the time to set OBLR traps. Generally OBLR and RBLR are not a primary pest for growers but with multiple generations they have the potential to build populations quickly. Scouting for foliar feeding now may help predict future management decisions later in the season: feeding damage on less than 5% of terminals or 3% of fruit clusters indicates acceptable populations.

Rosy apple aphid and woolly apple aphid
While scouting for scab also look for rosy apple aphid (RAA) and woolly apple aphid (WAA). Damage caused by RAA can be seen as curling leaves, WAA can be observed around pruning cuts. Low numbers of rosy apple aphids have been observed this season.

Tarnished plant bug
Tarnished plant bug populations appear larger than previous years. Damage can be seen as a pinpoint prick on fruitlets. Tarnished plant bug populations may correlate with stink bug populations.

Plum curculio
Plum curculio (PC) pressure in orchards seems to vary considerably over the region. Populations have been down in the last few years, this year numbers look high. The closer you are to the Wisconsin and Illinois state line the greater likely hood of feeding during the last week. If damage is noticed on the perimeter of a block scout interior rows to determine how far PC has traveled into the orchard. If your orchard has treated for PC with a perimeter sprays scout for continued activity. In blocks with high pressure a perimeter and spot spray for PC may prove beneficial. Feeding and egg laying will slow down with cooler temperatures. Note: to effectively monitor PC scout for multiple times a week.

Codling moth
The majority of orchards across the region have already set codling moth (CM) biofix. Biofix helps to effectively time an insecticide application. For CM a larvicide is usually applied at 250DD post biofix, but new research suggest that 60% of CM hatch 350-650DD after biofix. If trap counts have been low it is suggested to wait until 350DD to make an application. If significant numbers of CM have been caught apply at 250DD. Large orchards with block with varying trap counts have the potential to spot spray for first generation CM.

Fire blight
Monitor blooming, nonbearing trees for fire blight. With high numbers of bacteria present it is suggested to remove blossoms or apply streptomycin before the next rain event. Streptomycin applications to established plantings is not necessary unless high winds and hail result in extensive damage.