Some formulations of iron chelate can be applied to the foliage, but this approach is usually not as permanent as soil applications. Follow the manufacturer's recommendations for application rate. Tree implants containing iron chelates are also available for treating chlorosis. Implantation eliminates the problem of spraying, requires less time and equipment than soil applications and is less troublesome. Medicap implants are available at most garden centers.
Different sizes are available and kits contain the appropriate drill bit.
Implants will usually correct chlorosis for two to three seasons. There is some concern amongst arborists that drilling holes could lead to decay, and this issue is not completely resolved because many factors are involved. However, if chlorosis is severe, prompt correction is needed, and implants will be the best approach. Hopefully, soil treatment procedures will alleviate the chlorosis before more implants are required. The procedure for installing the encapsulated iron involves drilling a hole into the tree trunk and inserting the capsule with the head recessed through the bark and slightly into the wood.