TREE FRUITS AND NUTS
Problems Common to Many Trees Bearing Fruits and Nuts
SYMPTOMS POSSIBLE CAUSES CONTROL AND COMMENTS
Premature fruit drop -Natural thinning -Many trees produce more
fruit than they need and
thin themselves naturally
-Spring frost -Frost often kills developing
fruits or buds
-Poor pollination -Tree may require other trees
nearby to pollinate it; be
careful not to kill bees with
insecticides
-Environmental stress -Drought, cold, or heat can
cause fruit drop
-Disease stress -See controls under specific
diseases
-Use of Sevin -Sevin causes some fruit thin-
insecticide ning; do not misuse
-Various insects -Submit insect for laboratory
identification
Poor fruit -Poor pollination -Tree may require other trees
development (small nearby to pollinate it; be
number of fruit on careful not to kill bees with
tree insecticides
-Biennial bearing -Apples, pears, and pecans can
overbear one year followed by
few fruit the next year if
not properly thinned.
-Improper pruning -Do not prune off fruit-
bearing wood during the
dormant season; consult
pruning manual for proper
instructions on pruning
-Frost injury
Fruits too small -Failure to prune -Peaches, nectarines, plums,
and apples tend to produce
many small fruits if not
pruned; consult pruning
manual for proper pruning
-Poor soil fertility -Soil test
Many small twigs -Squirrel damage -Squirrels girdle branches
broken off -Wind breakage which then die back and blow
out
Oozing sap on -Natural gummosis -Cherries, plums, apricots,
branches or trunk and peaches naturally ooze
sap
-Environmental stress -Drought or waterlogging can
cause fruit trees to ooze
excessively
-Mechanical injury
-Disease or insect -See section on specific
damage diseases
-Holes in limbs and -Borer damage; use registered
trunks with tunneling insecticides
beneath
Large areas of -Freeze cracks -Freeze can split tree trunks
split bark; no decay if sap in trunk expands; use
evident tree-wrap to protect bark
from sun to prevent extremes
in temperature
-Sunscald -Thin-barked trees, e.g. young
ones, split when exposed to
intense sunlight; use tree-
wrap or block sun with board
on bright days
-Mechanical injury, -Dig up grass around trunk
e.g. lawnmower and replace with mulch to
avoid mowing too closely
to base of tree
-Lightning injury
Large areas of -Secondary decay of -No adequate controls; remove
split bark; decay any of the wounds loose bark; water and ferti-
evident in wood described above lize tree when necessary
Gray-white powdery -Powdery mildew (fungal -Use registered fungicide
growth on leaves; disease)
leaves and fruit may
be distorted
Black, sooty growth -Sooty mold (fungus -Identify insect then control
on leaves, stems, that grows on honeydew with registered insecticide
and/or fruit substance secreted by
aphids and other
insects
Brown dead areas on -Leaf scorch, caused -Water tree deeply during
leaf margins insufficient trans- dry periods; scorch is
port of water to usually caused by hot, dry
leaves weather, but root rots or
other root damage can also
be involved
-Cold injury -Do not fertilize late in
season
Tree wilted and -Dry soil -Water deeply during drought
may have poor -Root rot (fungal -Improve drainage
color disease) -Submit soil sample for
-Root knot or root nematode analysis
feeding nematodes
-Various fungal, -Submit sample for laboratory
bacterial, or viral diagnosis
diseases
-Water-logged soil -Improve drainage
Interveinal yellowing -Nutrient or mineral -Soil test
of leaves; no wilting deficiency
-Water-logged soil, -Improve drainage
resulting in poor
transport of
nutrients to leaves
Large, corky galls -Crown gall (bacterial -Some galls can be pruned
at base of tree and disease) out, but it is best to
on roots consult an arborist; trees
may live for many years
inspite of galls
Young leaves curled -Aphids -Use registered insecticide;
and distorted; thorough coverage of under-
cluster of insects on sides of leaves is necessary
underside of leaves
Silk tents in branch -Tent caterpillar -Physically remove tents or
crotches use registered insecticide
when caterpillars are small
Silk tents on ends -Fall webworm -Same as for tent caterpillar
of branches
Crescent-shaped scars -Plum curculio -Use registered insecticide
on fruit; whitish, on a regular schedule
legless grubs with
brown heads present
Leaves with tiny -Spider mites -Use registered miticide
white spots, often
dirty with webbing
Bark encrusted with -San Jose scale -Use a dormant oil spray
tiny, slightly or treat with registered
raised bumps; apples insecticide when eggs are
may have red spots hatching
with white centers
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Access to the newsgroup may be a problem. I'm helping friends in Minnesota
who run a small research farm to acquire net access -- they're doing
fascinating work by selecting hazelnuts and chestnuts for woody
agriculture (using local native stock from target areas is the goal,
and crossing in strains with good commercial behavior such as
- being fire-adapted so growing as bushes, harvestable like blueberries,
and able to grow back from stumps every four or five years
- nuts in first year
- ease of mechanical (US) or hand=harvesting (Pakistani and Chinese
researchers
are working with them)
Plus the gamut of other commercially-interesting traits.
Their numbers indicate that their strains of hazelnuts can be as profitable
as corn or soybeans in food value, plus harvesting wood, plus having
the plants in the ground year-round to get spring and fall sunlight and
control erosion (in snowy areas, to act as snow fences to capture water too).
Til they find a net connection, you can find a summary of their work in an
article titled "Reducing Earth's Greenhouse CO2 Through Shifting Staples
Production to Woody Plants" - December 1988, Proceedings of the Second
North American Conference on Preparing for Climate Change; from the Climate
Institute, 316 Pennsylvania Avenue SE Ste 402, Washington DC 20003.