Scorch is caused by an infection by phytoplasm, a type of bacteria without an outer shin. It can only live inside vessels inside plant and in saliva gland of sucking insects. The insects are the transmitting vector.
A recent suggestion for cure of scorch involves heating the plant to 104 degrees F. for a few days. This seems to kill the scorch, leaving the plant unharmed. This can be done with a covering over the plant, but care must be taken that the temperature doesn't get too hot and cook the plant.
This what borer looks like early in season
A closer look
At this time (during blooming season) the borer is very small
And even closer
Only about 1/16". They gradually eat their way down stem and enter rhizome where they continue to grow. Reaching about 1.5" in length. Matur borer is pinkish. They then go into pupa stage, about mid to end of August in my ag zone 4 garden. The warmer the climate, the earlier they reach maturity. .
As moth, hatch in early Sept-October to lay eggs for next season in my ag zone 4. The warmer the climate, the earlier this happens.
Once you know what to look for , hand removal is not that hard , or theat time consuming. But early in season, before they rech rhizome and do major damage.
This is an annoying and unsightly condition involving small brown spots on the leaves. This is a fungus that, though unsightly, does little damage to the plant. A spray of Benelate (or other fungiside) early in the season can help with this, although it is often necessary to repeat several times in the season. Often the easiest way to deal with it is to just remove the unsightly leaves and dispose of them (but not by putting them in the compost). An increase of nitrogen in the fertilizer can often be helpful, but too much nitrogen can make the plant more susceptible to soft rot.
This is seen more often in older clump where there are a number of factors at work. With the crowding, there is less air circulation between leaves. There is less nutrients available to each fan. Heavy rains can wash out nitrogen. With the plant being less healthy, the plant is more susceptable to diseases.
The fungus spores are in the soil. They are more prevelant if infected leaves are left over winter. So a clean up of infected leaves in fall can help reduce amount of fungus spores present.If there are major problems, a mulch around base of plant can help. DON'T place mulch at base of plant , leave it at least 3" awaw from rhizome.
In following pictures, various pictures of infected plants. This includes a badly infected plant, a dead leaf, and close up of an infected spot.
This fungus has been called by several names. "Mycosphaerella macrospora" seems to be current name, but it has also been called "Didymellina macrospora", "Cladosporium iridis", " Heterosporium gracile", and "Heterosporium iridis"
This fungus, by whatever name you use, can also be hosted on Hemerocallis (daylies). This year (2012) there has been reported a problem with dayliles reffered to as "Midwest Malaise". it very well could be same fungus, burt shows slightly differernt as it is on a diferernt species. I suspect that it is worse this year because of weather conditions. A wet sprin with lots of rain can leach out nitrogen in soil, placing plant under stress. Then infection takes advantage of the weakened plant. The fungus doesn't need to transfer directly from iris. It can have been present on the daylilies for a number of years, but only causing mnor problems, that have not been paticularly noticed. So fungus is present, waiting to take advantage of conditions, such as wet spring, followed by hot weather.
Remove and dispose of infected foliage. DON'T compost. Have mulch around base of plant to prevent splashing of fungus spores onto leaves. Giving plant some nitrogen will help streanth plant. You could try a foliage fertilizer. But remove infected leaves first. Avoid overhead watering if you can. If you do have to water via overhead, be sure to remove all infected foliage first.