Apple Pest Report: Saturday,
July 1,
2006
Vol. 14, No. 13
Apple Pest Report: Wednesday,
July 5,
2006
Vol. 14, No. 13
Flyspeck update
The Orchard Radar flyspeck fungicide respray tables for Monmouth (and other sites) have been updated to reflect the more conservative rules described in the July 1 Apple Pest Report. I also updated the rules by which wetness hours are accumulated. The updated flyspeck guidelines are available online at http://pronewengland.org/AllModels/MEmodel/RADARME-MonmouthLate.htm.
It is always difficult to decide how conservative to be with such guidelines. The new fungicide depletion rules may be overly cautious for Maine orchards with small, open trees and where flyspeck has not been a problem in the past. But our June accumulation of wet hours was much higher than normal. While we do not know the full consequence of the wet June, or how wet the remaining summer weather will be, it seems prudent to be cautious with flyspeck this season.
There was an error in the July 1 newsletter flyspeck article about estimated ziram depletion. The correct recommended fungicide respray intervals are used in the Orchard Radar tables, and are as follows:
The best fungicides for protecting against flyspeck are Topsin M and the strobilurins (Flint, Sovran, Pristine). Application of one of these materials with good coverage can be relied on for protection for up to 21 days or 2 inches of rain, whichever comes first.
Full-dose captan or ziram are reliable for up to 14 days or 2 inches rain, whichever comes first.
Reduced rate captan or ziram (i.e.
1 pound captan 50 WP per 100 gallons dilute) are reliable for up to
10 days or 1.5 inches rain, whichever comes first.
Captan leaf-burn
Leaf burn by captan can look very much like leaf spots caused by black rot. Both cause small light brown spots with the center a light tan color and the outer ring a dark brown or purple color. Cedar apple rust spots can also have the same color pattern.
One way to distinguish the two is by distribution of the spots within and between trees. Black rot leaf spots are more likely to occur where plumes of black rot spores are washed from overhanging limb cankers or mummified fruit from last year. Cortland and Empire are more likely to show black rot. Black rot is more common where prunings are left near the orchard, or where there is dead wood in the orchard from winter injury or other causes.
Captan leaf burn is more likely to be found with a distribution
throughout the tree where spray coverage is good and even, or where
spray deposit is highest. Captan burn is also more likely to occur
along leaf margins where spray water collects. McIntosh can be more
susceptible to leaf burn than some other cultivars.
The persistent wet weather in June increases the chance of both causes. A recent Maine case of leaf spotting seems to have been caused by captan burn because Cortland trees next to McIntosh trees had much higher degree of spotting and the spots were more or less uniformly distributed through the tree. On some, but not all, of the leaves, spotting was concentrated on the leaf edges.
Insects and mites
July 5 – 13 is a key time for European red mite sampling to detect an over threshold population (more than 2.5 mite per leaf, living hatched mites present on more than 59% of leaves) before they can lay 4th generation eggs.
Mite scouting guidelines are included in the apple pest scouting card online at http://pronewengland.org/INFO/PROpubs/AppleScoutCard-2006.pdf
Keep an eye out for apple aphid and spirea aphid (both commonly referred to as “green apple aphids”. Normally these pests do not become numerous enough to require insecticide, but with the cool wet weather trees may have more lush growth than normal providing abundant aphid food, and aphid predators may have been suppressed. If you find aphid colonies on more than 30% of shoot terminals than control may be needed to prevent staining of apples caused by sooty mold fungus growing on honeydew from the aphids that falls on fruit. Aphid colonies on first year trees can stunt growth. If you find aphid predators on 20% or more of the colonies, then a higher threshold of 50% of terminals infested is sufficient. Check at least 50 terminals per block.
Japanese beetles will be showing up soon. They particularly like peach foliage and fruit, but will feed on apples on other fruit trees. Japanese beetle feeding results in lacey leaves with only the veins remaining. Imidan or Assail are effective against Japanese beetle and also provide excellent protection against apple maggot. Carbaryl (Sevin) and Provado also have excellent activity against Japanese beetle.
Sincerely,
Glen