Apple Scab other diseases, pests

2016 was the first year in a long time to have apple scab (Venturia inaequalis) arriving so late. This fungus affects apples as a skin blemish and reduces crop by as much as 50%. The scab has 2 parts to it’s infection-one: the overwintering leaves on the ground and two: the leaves and fruit on the tree. The 1st part-leaves on the ground can be reduced by sanitation or decay (by Urea fertilizer to enhance decay). So what happened in 2016? The stage 1-leaves on the ground- disseminated 100% of the ‘ascospores’ by April 23rd – based on the biofix model using 900 growing degree days (base 32° F.). During the infection period of “1/4 inch green”, before blossom, to waxy cuticle (when the leaves resist infection, about July) the leaves/flowers/fruit need to be wet for a certain period of time at a certain temperature – higher T.= shorter wetting period (WP) to germinate the ascospores on the fruit/leaves. April 23rd we had such a WP, but it was very close to failure due to drying conditions. Only interior foliage (slow-drying) was affected on susceptible varieties. Bloom was complete, and fruit 1/4 inch.

^the scabby apple

Ok, my question, now that all the ascospores have been disseminated and are floating around, I am to assume an air sample in the orchard would be higher a month ago and that today the ascospore count in the atmosphere around the orchard is going to be quite low due to the air exchange/breezes. So far we have had a short, late wetting period (based on the Mills Chart) that offered little germination on the fruit. Cool. Clean, clean, clean! But what if there is another WP? Is the ascospore count in the air we breath high enough to perpetuate the (now thought to be insignificant) scab spore? I would love to see an air sample!

Today, May 28th, about a month after the WP, we have another WP-through the last week mostly-rainy. I will be looking for increasd infection on fruit/leaves. Lime Sulfur spray will interfere with ascospore and conidia germination as much as 36 hours after a WP. Applied at 1.25 to 1.5 gallons per 50 gallons (my sprayer capacity) is the safe rate but don’t get it in your eyes as it’s caustic and smells of sulfur (bad eggs).

Avoiding Lime Sulfur altogether would be my aspiration as it is hard on beneficial soil fungi and worms. The quest is to use compost tea with sufficient beneficial microbes to outnumber the ascospores-known as “competitive colonization”.

Here is a biofix model for Apple Maggot

==========================MODEL INPUTS================================
 Model species/general links:       apple maggot % emerge [cherry, apple]
 Type:                              insect
 Model source/other links:          Jones etal 89
 Calculation method:                single sine
 Lower threshold:                   44 degrees Fahrenheit
 Upper threshold:                   113 degrees Fahrenheit
 Directions for starting/BIOFIX:    initialize at first emergence from traps
 No starting/BIOFIX date, set to:   default date  6 15
 No ending date, set to:            default date  12 31
 Model validation status:           testing
 Region of known use:               UT and OR
 ==============================EVENTS TABLE================================
 1.  318 DD after 1st emerge 5% fly emerge
 2.  541 DD after 1st emerge 25% fly emerge
 3.  797 DD after 1st emerge 50% fly emerge
 4. 1046 DD after 1st emerge 75% fly emerge
 5. 1252 DD after 1st emerge 95% fly emerge
 6. 1694 DD after 1st emerge 99% fly emerge

For years we have researched and chosen varieties of these popular fruits that are the most insect and disease resistant. Unfortunately, these popular fruits are susceptible to some degree of insect damage if precautions are not taken. Our choice for guarding against damaged fruit is Surround crop protectant. Surround is a clay-based product used by organic growers. Surround works very well, preventing insects from damaging fruits by the physical dust.

In the spring after the petals of the flowers of your fruit tree have fallen, aphids, codling moths, leafhopper and plum curculios (east coast) are attracted to the very small fruits. Insect pressure varies year to year. With monitoring -visual inspections- we may choose to spray Surround at petal fall and keep the fruit covered with the kaolin clay product for at least 5 weeks to control these insects. Surround can be purchased from Skipley Farm.

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Home Apple William’s Pride Apple
William’s Pride Apple
Tags: Apple
William’s Pride Apple
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$36.00

Vendor: The Original Edible Landscaping
SKU: ap-wp-d01
Availability: In Stock
Malus spp Early maturing attractive, dark red apple with excellent aromatic fruit quality and immunity to apple scab as well as apple maggot. Its also very resistant to cedar apple rust and fire blight. For an out-of-hand apple this is the best…

Early maturing attractive, dark red apple with excellent tart fruit quality and immunity to apple scab. Extremely resistant to cedar apple rust and fire blight. For an out-of-hand apple this is the best for so early in the season. It blooms over a long span and produces annually. Zones 4-8.

For years we have researched and chosen varieties of these popular fruits that are the most insect and disease resistant. Unfortunately, these popular fruits are susceptible to some degree of insect damage if precautions are not taken. Our choice for guarding against damaged fruit Surround crop protectant. Surround is a clay-based product used by organic growers. Surround works very well. Preventing insects from damaging fruits.

In the spring after the petals of the flowers of your fruit tree have fallen, various species of aphid, codling moths, leafhopper and plum cuculios are attracted to the very small fruits. We spray Surround at petal fall and keep the fruit covered with the Surround for at least 5 weeks to control these insects. Read on for Apple Maggot Surround can be purchased from vendors in the area as well as Skipley Farm.

Apple Plum Curculio Damage is from a weevil that occurs east of the Rockies.

Keep the young fruits covered with Surround, spraying at 7-14 day intervals for the first four weeks after petal fall. Coverage can have advantages for longer periods up to harvest. In June and early July the Apple Maggot (Rhagoletis pomonella) lays their eggs on the fruit – Red sticky (Tanglefoot) balls or bright yellow boards covered with tanglefoot are hung in the trees to monitor- trapping the apple fly adults. If conditions warrant it, gardeners may widen the spray interval to 14-21 days, so long as good film coverage is maintained.Surround will control this insect also. Surround also reduces sunscald where this is a problem – especially desert areas.

Surround does not control diseases, however when used in combination with Lime-sulfur, it provides excellent suppression of powdery mildew, scab as well as late season sooty blotch and fly speck though flavor may be tainted with sulfur. Potassium bicarbonate is an excellent late season spray with fungicidal properties. Lime-sulfur is an excellent dormant spray that kills over wintering scale, insect eggs and mites and is used alone at that time. Lime-sulfur is hard on soil life so warrants minimal use. There are many apple varieties resistant to powdery mildew, scab and fire blight. There are many apple varieties that are resistant or immune to scab grown and sold at Skipley Farm.