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 ------------- 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.