Unfortunately the July rain has brought the leaf spot pain. Watching another storm roll in as we rated our apple trials this afternoon, it seems like the start of August is giving Western NC apple growers no break in fungicide applications in the midst of commencing the harvest season. At the Research Station in Mills River, 7.4 inches of rain fell in July, and unfortunately these were brief showers where you'd get less than 1.25 inches of rain at time, given you the freedom to "cover up" if needed. For example, July 7-10 brought 1.4 inches of rain; July 18-19, 2.9 inches, and July 23-26, 3.0 inches. If you did not followup with a fungicide application, even if you had sprayed 7-10 days earlier, you likely may have some GLS symptoms showing up.

Although I haven't crunched the data yet, just based on my observations, treatments where we started tightening our fungicide applications at bloom or petal fall had considerably less GLS that treatments where we tightened our intervals later in the season (e.g. 2nd-5th cover). The good news is that so far while we have been observing an increase on leaf spots such as Glomerella and Marssonina, fruit are relatively clean with strong fungicide programs, even in blocks where GLS and bitter rot are historically established.

In regards to fungicide sprays for this week I'd consider the following as the risk of storms continues throughout the week:

• For cultivars being harvested in the next week and no resistance to the strobilurins (FRAC 11): Merivon or Cabrio or Pristine + 2.5 lb/A Captan 80WDG
• For cultivars being harvested in the next week but resistance to the strobilurins (FRAC 11): Topsin (or generic equivalent) + 2.5 - 5 lb/A Captan 80WDG
• For cultivars within 30 days of Harvest: Aprovia (7 fl oz) + 2.5 lb Captan 80WDG OR 4 lb Ziram
• For all other cultivars within 30 days of Harvest: Topsin (or generic equivalent) + 2.5 lb Captan 80 WDG OR Omega (or generic equivalent) + 2.5 lb Captan 80 WDG

Today I also heard that Necrotic Leaf Blotch (NLB) was beginning to develop on 'Golden Delicious' throughout the county. Remember, NLB is a deficiency in zinc and not a disease. Historically occasional applications of Ziram have worked fairly well to manage NLB; however with the Ziram shortage this year and last, you may need to consider adding liquid zinc to your program. Glomerella leaf spot and NLB look quite similar so for the remainder of this post, I'm going to briefly compare both leaf spot issues.

• GLS: All cultivars with 'Golden Delicious' parentage. Severity of symptoms is generally the same across all cultivars
• NLB: Symptoms are usually observed first and are most severe on the 'Golden Delicious' cultivar. Symptoms may be observed on other cultivars (particularly those with Golden parentage) but do not tend to be as severe.
• If you have a block (or row) of 'Golden Delicious' with leaf spots and premature defoliation and another cultivar susceptible to GLS adjacent to that 'Golden' block, take a look at the other cultivar for leaf symptoms. If you've sprayed identical fungicide programs in both cultivars, and only the 'Goldens' have leaf symptoms, this evidence points more towards NLB than GLS.

• GLS: A fungal pathogen: Colletotrichum spp. It is a disease of apple.
• NLB: Cause is unknown but is believed to be associated with a zinc deficiency. It is a physiological disorder of apple.

• GLS (above photo): Symptoms usually begin in early to mid summer as small purple flecks on leaves and rapidly expand into irregular concentric lesions with purple borders. Lesions can be located anywhere on leaves, but are not usually observed on leaf margins or initiating from the leaf mid-vein.
• NLB: Symptoms (see earlier photo) are most often observed later in the summer and can appear suddenly. I have not observed early "purple fleck" symptoms with NLB. Mature leaf lesions/blotches are in general larger than GLS (though not always the case) and appear more like chemical burn. Lesions lack the concentric ring appearance.

• GLS: Warm/hot + humid weather.
• NLB: Symptoms most often appear during a period of hot, dry weather that follows a period of humid, rainy weather.