Hi Jaclyn, 

There are a number of diseases that can cause leaves to whither, and branches to die on a redbud. Stress caused by too little, or too much water, and leaf sucking insects can make a tree more susceptible. You don't say how old your redbud is, they are not especially long lived trees - 20 years is a typical life span.  

From your description of onset Verticillium Wilt is the closest match:

Verticillium Wilt is caused by the fungus verticillium albo-atrum. It is characterized by the yellowing and eventual browning of leaves. Typically, the tree will die branch by branch, sometimes over a period of years. Drought exacerbates the process. Sadly, there is no chemical/fungicidal treatment available, but trees will sometimes recover if 1) the affected branches are removed (follow cautionary procedures outlined above), 2) debris is kept cleared from beneath the tree; dispose like you would removed branches, 3) fertilizer is applied as recommended for this type of tree (be sure to not over-fertilize) and 4) the tree receives adequate water, generally an inch per week of rain or irrigation (don’t overwater).

If you remove the affected branch, look for a tell-tale discoloration in the sapwood. These articles from MSU Extension and Wisconsin Horticulture might help you with diagnosis.

This article from Piedmont Master Gardeners is a useful tool for diagnosing redbud diseases.

To make a more definite diagnosis it would help if you could answer some questions, and for me to have more close up pictures of individual leaves, front and back, and pictures of healthy, yellowing/spotted/ damaged leaves, and those that are already dead. Would you be able to take some additional pictures for me?

Do all the leaves on your tree have the white masses on them? 

Have you noticed any insect activity, or gray, lumpy masses on the branches and trunk? 

Has any sticky stuff dripped off the leaves or branches?

I've listed descriptions of other common disease, and included links to additional information sources below.

From the Ohio Department of Natural Resources fact sheet

"Planting Requirements - Redbud prefers deep, moist, organic, well-drained soils, but adapts to many less-than-favorable soils of either acidic or alkaline pH as long as they are not wet. It grows most rapidly and flowers most prolifically in full sun if adequate moisture is available during the heat of summer, but it is often found in partial sun to partial shade in nature. It can grow in zones 4 to 9, but occurs naturally in zones 5 to 9.

Potential Problems - Redbud grows rapidly and often lives about twenty years before it begins to decline or die, especially in urban situations where poorly drained, heavy clay soils predominate.

Trunk canker is a serious disease of Redbud and is evident as sunken depressions in the bark of large branches or trunks, which often begin to heal before the tree eventually dies. Verticillium wilt and root rot are two additional, serious pathogens that affect the roots often due to wet soils but become evident as entire branches rapidly die. Some pests such as scales may also cause problems, but the tree diseases cited above wreak havoc on Redbud and limit its lifespan."

OtherCommon Diseases of RedBud

Redbud Canker (botryosphaeria ribis) is a fungus that causes a canker and is the most serious illness in Redbud trees. It also affects more than 50 other trees. To diagnose, check the limb that is affected and see if there are dark, circular, sunken spots. This would be an indicator of cankers. You can remove the affected branches which might save the remaining trunks if the fungus has not spread to them. Be sure to dispose of the branches carefully; do not compost them or leave them where the fungus might spread. And be sure to thoroughly clean your tools, such as pruners, loppers or saws with soap and water or rubbing alcohol between cuts to prevent reinfection.

Leaf Spot, aka leaf anthracnose usually occurs in very wet conditions and is characterized by spots on the leaves, as the name suggests. Missouri Botanic Garden Fact Sheet

Ohio State University Fact Sheet

Kind Regards,

Hi Jaclyn, 

Thank you for the additional photos, and information they were a big help.  The vascular system of the tree looks all right - none of the streaking associated with verticillium wilt. Seeing more leaves in different stages of collapse presents that this is a very bad case of leaf scorch, aggravated by some aphid damage, and possibly some other leaf piercing insects. You mentioned seeing assassin bugs - they feed on aphids, and other leaf damaging pests - so you're getting some free pest control.

Watering your tree deeply, until the top six inches of soil are wet, using a soaker hose or a sprinkler on a low setting near the drip line (outer most line of branches from tree) and then waiting until the soil is back to a normal, moist state is a better way to support the health of your tree than more frequent, shallow waterings.  A layer of mulch, no more than two inches deep, and  eight inches away from the tree trunk, will help the soil hold moisture.  

As a precaution gather up and dispose of all fallen leaves, twigs, and branches in Fall. In Winter water the tree once a month if there has been no rain or snow previously. Keep an eye on the tree in Spring, remove any branches that do not leaf out.

Kind Regards,