The major issues, with links to great answers
- Scale insects,
- leaf spot,
- holly leaf miner and
- winter damage (dessication)
are the problems holly growers might have to deal with.
Standard procedures applies: Keep the plant healthy and it will
resist problems on its own, but "shake hands" with the plant
regularly. Saying hello every few weeks focuses your attention so
you can see signs of any trouble in early stages when they are most
Cottony camellia scale on holly:
Below: Cottony camellia scale on a holly.
Don't wait until the scale population is so heavy as what
you see here (above). Watch for early signs, such as the sooty mold
that grows where the sticky liquid excrement from scale insects
coats leaf surfaces and twigs. Sooty mold is what has made those
interior leaves so dark.
Note: "Spine spot" can be mistaken for a fungal leaf spot. If
you see small gray spots with purple halos, put spine spot on your
suspect list. It's caused by the piercing of a leaf by adjacent
Below: This is not a variegated holly but one that suffered
drying wind. The tiny wounds are spine spot, caused by that same
wind which rattle nearby leaves so their tips pierced this blade.
This damage cannot be reversed. Leaves do not heal, but hang
in until they are too damaged to support themselves. This leaf
still has 75% of its surface, so it's only lost 25% of its energy
production capacity. Protect the plant from future wind, prune to
encourage new growth at all depths, and clean new foliage will
Winter damage. Dessication from wind in any
season. Photo above, and see the problem-round-up below.
For an overall holly problem round-up:
And one "How 'bout that, now!" item, look what you find here if
you read all the way into the "Damaging Agents" section: Midges making the berry stay green