Have some nice Rhodendums that have come into bloom lately, and look like
they are being eaten (but hard to tell for sure)..
Live outside of Boston, and have Deer and Wild Turkeys in my area.
Are either of these known "eaters" of Rhododendums ?
Leaves chewed on edges is a symptom of chewing insects. Most are
nocturnal feeders and can be found at night with a flashlight. The most
prominent chewing insects on rhododendrons and azaleas are the Black
Vine Weevil, Otiorhynchus sulcatus, Strawberry Root Weevil, Otiorhynchus
ovatus, or Twobanded Japanese Weevil, Callirhopalus bifasciatus. Adult
weevils feed on the leaves at night except the Twobanded Japanese Weevil
which feed during the day. Specimens may be collected during the day or
at night for identification depending upon the weevil. The major damage
is caused by weevil larvae which girdle the roots and kill the plant.
Larvacidal drenches may be used to kill them but are of limited
effectiveness. Foliar sprays are very effective at controlling adult
weevils when leaf notching starts. Foliar sprays must be repeated until
no adults emerge. Twobanded Japanese weevils are apparently resistant to
carbaryl (Sevin), diazinon, and malathion. Orthene gives good control
when applied as a foliar spray and drench. Since weevils can't fly and
spend part of each day in the soil and part of each day feeding, you can
paint the trunks with Tanglefoot to stop them, but make sure no branches
are touching the ground.
If the leaves are being ripped off, then it is deer. They are
especially bad in winter, but can be a problem all year long in areas
where they have developed a taste for rhododendrons.
Entire leaves being eaten by caterpillars is an indication of an
infestation of caterpillars such as the Red-headed Azalea Caterpillar,
Datana major. These caterpillars are black with rows of white or pale
yellow spots, reddish brown legs, head and neck area and are 2 1/2
inches when mature. Preferred host plants are azaleas, but they may also
attack witch hazel, sumac, apple, red oak and andromeda. The
caterpillars feed together when young and disperse as they mature.
Branches or entire plants may be defoliated. Damage occurs in late
summer and fall. Look for caterpillars when defoliation damage occurs,
and if only a few caterpillars are present, pick them off by hand. If
needed, spray shrubs with B.t. (Bacillus thuringiensis ), a microbial
insecticide that is specific for caterpillars. It is sold under various
trade names including Caterpillar Attack, Thuricide, Dipel, etc. Apply
sprays when caterpillars are numerous and less than 3/4 of an inch long.
Larger caterpillars must be sprayed with a registered residual
insecticide such as carbaryl (Sevin 50WP) or cyfluthrin (Bayer Advanced
Garden Multi-Insect Killer).
Leaves with crescent shaped holes. The Cranberry Rootworm, Rhadopterus
picipes, chews holes in the leaf, some of which are crescent shaped.
Other chewing insects include caterpillars, leaf rollers, sawflies (moth
larvae), cut worms, and loopers. The larvae of several species of
insects can cause damage as the result of chewing on new foliage. These
pests hatch as the new growth is forming, and often eat out large areas
of the soft growth. They may also roll the leaf with a white web. Damage
only occurs on soft growth. To control, use Orthene, Malathion, or
Chewed flowers and new leaves can be a sign of slugs and snails. These
pests feed on soft new growth and on flowers. To control, use
Metaldehyde baits or sprays
Hope this helps.
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