Rolling into this weekend, there looks to be some potential stormy weather approaching in western NC. While no day appears to be a washout, If you haven't applied a fungicide in the past 10 days, make sure you get your trees covered prior to the rain rolling in. Regardless as to when you last sprayed, if it rains about 1.5 inches or more, I'd strongly advise you to reapply as soon as you're able to next week. At this point Captan should be the backbone of your fungicide program. With the predicted rain, you may want to consider some of the following options:

• Merivon, Cabrio, Pristine, Luna Sensation, or Flint Extra. These are your strobilurins. If you have resistance to any of these fungicides listed under this bulleted point, you have resistance to all the fungicides listed under this bulleted point. Apply no more than 4 of any of these aforementioned fungicides in a season.
• Aprovia
• Omega or Orbus 4F. These formulated fungicides have the same active ingredient.
• Topsin

If you apply any of these fungicides listed above, it'll give you a bit more time to go out and reapply Captan. Again, since there are consecutive days of rain currently in the forecast, I'd strongly encourage the addition of one of these fungicides at their highest labeled rate for apples from the list above in addition to Captan.

As we were conducting our first GLS rating last week, I also observed some frogeye leaf spot and early symptoms of Marssonina leaf blotch in our 'Gala' block. In our 'Rome Beauty" block, frogeye was fairly prevalent. Thus, I'll spend the rest of this post with my annual reminder of how to distinguish these different leaf spots.

• Pathogen: Botryosphaeria obtusa (same pathogen that causes black rot on fruit and cankers in woody tissue in older apple trees)
• Symptoms: Begins as small purple flecks (early symptoms) advancing to circular lesions with purple margins with a dark spot in the center. Sometimes lesions might merge together (see blue arrow above. The purple flecks in that photos are actually early Marssonina blotch symptoms). As lesions advance, they may become more gray in color. If symptoms are severe, leaves will be become chlorotic and abscise prematurely.
• Cultivars most affected: To my knowledge all cultivars commonly grown here are susceptible, but there are varying degrees of susceptibility. An overwintering location of the black rot pathogen are fruit mummies so those that tend to retain mummies more, such as Fuji, often are regarded as more susceptible.
• When to start scouting: Usually around petal fall but I’ve seen symptoms during the early bloom period.
• When to spray: No later than tight cluster. Continue throughout the season
• Effective fungicides: Captan, Luna Sensation, Flint Extra, Merivon, Cabrio, Pristine, Topsin (thiophanate-methyl). My preference is to include Topsin with mancozeb and scab fungicides (DMIs and/or SDHIs) until you start spraying strobilurins (FRAC 11) or Captan for GLS/bitter rot.

The pathogen that causes frogeye leaf spot can also cause black rot on apple fruit .

• Pathogen: Diplocarpon coronariae
• Symptoms: Early symptoms of MLB are diffuse purple specks (left photo), which quickly expand throughout the leaf (middle). As the disease progresses, lesions remain diffuse, and are brown and irregular in appearance.
• Cultivars most affected: All, but varying levels of susceptibility. ‘Rome Beauty’ seems to be a poster child in NC, perhaps likely due to the fact they are less intensely managed with fungicides compared to cultivars highly susceptible to GLS and bitter rot.
• When to start scouting: Early to mid-July in NC
• When to spray: Based on our research in NC, applications targeting MLB should begin around petal fall and continue through fourth cover (~ on an ~ 7-14 day interval. After the 4th cover application, continue biweekly fungicide applications of a multi-site protectant (e.g. captan) through harvest.
• Example effective fungicides: Cevya (only fungicide in USA labeled for this disease), Merivon, Sercadis/Tesaris, Inspire Super, Indar 2F

• Pathogen: Colletotrichum chrysophilum; Colletotrichum fructicola
• Symptoms: Small purple flecks (see left photo) that expand into irregularly shaped lesions with wavy or concentric rings. Leaves become chlorotic (middle photo) and premature defoliation may occur if not managed properly (right photo-July 2020)
• Cultivars most affected: Cultivars with ‘Golden Delicious’ parentage (e.g. Gala, Pink Lady, Golden Delicious, Jonagold) and ‘Granny Smith’
• When to start scouting: As early as the end of May in NC
• When to spray: Applications targeting GLS should commence around petal fall/first cover. In years with cooler springs, no later than 2nd cover.
• Effective fungicides: Mancozeb, captan, ziram, and fungicides containing a strobilurin/FRAC 11 fungicide. (e.g. Luna Sensation, Flint Extra, Merivon, Cabrio, Pristine) Aprovia (FRAC 7), Omega, Orbus, Topsin. MUST APPLY ON A 7 to 10 DAY INTERVAL.