Tatters, oak tatters, hackberry tatters or something else?
By Ed Hayes
What is tatters and what do we currently understand about the condition?
Tatters is a symptom that describes the appearance of emerging leaves. Affected leaves appear lacy or malformed at a time when they should be fully developed, hence the name "tatters". Tatters was first reported during the 1980's in Iowa, Indiana and Ohio, but has been observed in many states in the last ten years including Minnesota, Michigan, Wisconsin, Illinois, and Missouri. In Minnesota during 2002, tatters was observed in the central region of the state, a region that previously have remained unaffected. However, as is a common pattern with tatters, the symptoms did not repeat in the central region this year.
Over the last several years there has been a history of wide spread outbreaks of tatters in several Mid-western states. Hardwoods affected included white oaks, a few other oaks species and hackberries. During the 2001 season in Minnesota, more acres of hackberry were affected across a wide swath of southwestern Minnesota than were all acres of all oak species combined. Additionally, the southwest Minnesota outbreak on hackberry did not repeat in the following two field seasons.
There are several known factors about tatters, and many more unknown factors. Let's review what we know and what we do not know.
What we know about tatters.
1. Symptoms. The symptoms first appear at the time of leaf emergence, generally in middle to late May. Newly emerging leaves have reduced interveinal tissues, which gives leaves a lacy, skeletal, or tattered appearance. From a distance trees may appear to be light in color or undeveloped in comparison to other trees. The damage is often evenly distributed throughout the entire crown, but sometimes may be greater in the lower crown. Within a few weeks, trees will begin to produce a second flush of leaves that are generally free of tatters symptoms. The new foliage may be smaller and lighter in color than normal leaves. Tatters may affect all sizes and ages of trees and whole stands of same species in woodlands or urban areas. However, adjacent trees of the same species may remain unaffected.
2. Host Range. We know what the host range looks like. In the several states where tatters has been observed, trees in the white oak group have been most affected. The species include bur, eastern white, and swamp white oaks. Red oaks are occasionally affected. The other major host appears to be hackberry.
What we don't know.
1. The cause. Current observations implicate weather as a major factor and more than one cause may exist. Tatters can be easily associated with the symptoms of herbicide injury, frost, or a fast moving early season leaf disease. Other possible causes include insect activity or some combination of the preceding factors.
2. From year to year we do not know on which species or when the symptoms are likely to repeat or what portions of the landscape will be affected.
3. We do not know the long-term impacts, if any.
Insights from symptoms
Examining the pattern of symptoms that occur from year to year across the landscape can provide some in-sight into the possible causes. They are worth examining and discussing.
1. Frost. Scattered frosts have occurred in the years and in areas associated with tatters symptoms. However, tatters can be consistently seen in both lowland and upland areas both with and without association with frosts.
2. Insect activity. The symptoms of tatters are somewhat consistent with what could be expected from an outbreak of thrips that would infest the buds at the time of leave emergence. However, the pattern is inconsistent with an insect infestation since it does not repeat in the same areas each year and more than one tree species in involved. In addition, no thrips have been identified from collected foliage.
3. Leaf disease. No fungi have been associated with tatters symptoms.
4. Herbicides. Given the variability of where symptoms develop each year and the pattern of species affected it would seem inconsistent with what might be expected if herbicides were the only cause. If the use of herbicides were responsible it would indicate a rather dramatic landscape impact that should be easy to research and explain through a change of the products being used and or how they are applied. Broader landscape patterns would not favor patterns consistent with herbicide application. In addition, most often the tatters symptoms do not repeat on the second flush of foliage. This is inconsistent with what we would expect to see if herbicides were involved.
There may be long-term impacts as a result of many repeated early season defoliation events. Small losses over time can add up over the years, and lead to long-term impacts, such as diebacks and declines. Trees currently affected by tatters should to be maintained in good over all health. Other existing stresses, such as grazing, should be evaluated and corrected. Water trees during dry periods, mulch where possible, avoiding wounds, soil compaction, and any type of construction injury.
What's the good news?
The timing of defoliation is in the early summer. Early defoliation has the advantage of time for refoliation and for the opportunity to rebuild valuable food reserves. So far, tatters appears to have had little impact on tree vigor.
Report observations of suspect tatters to local tree care professionals. Follow approved tree care practices.