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.
