1. Q. The pecans are falling from my tree. Why?
A. There are numerous causes of premature pecan drop. Some varieties such as 'Desirable' shed naturally. Poor pollination results in a drop from June through July. Planting several varieties helps reduce the poor pollination drop problem. A small insect known as the pecan nut casebearer is the cause of pecan shedding at three different periods of the year; mid-May, July and on rare occasions in late August. This drop is easy to identify because there is a small hole in the base of the pecan. Water stress can also result in pecan drop. Ideally pecans should be watered every two weeks. Three weeks without water is the maximum. Nutritional problems from shallow soil or poor fertilization can cause pecans to shed throughout the year. Water stage in later July and early August is the most common form of pecan drop. As the nuts move from size development into kernel formation the pecan sheds very easily. Any stress received by the tree at this stage can result in major fruit drop. Some trees can lose up to one half of its crop if not properly managed during water stage. My guess is that even though you have been watering your grass during hot, dry periods, you have not deep watered your pecan trees. Watering grass is not enough for watering trees - slowly soak the tree's root system at the dripline of the tree and not at the trunk.
2. Q. I know that you are not going to believe this, but the squirrels are eating my pecan tree! They are not eating the nuts but the bark off of limbs. What can I do?
A. I have an excellent recipe for squirrel stew, and there is no legal season for squirrels in Texas. I understand that neighbors will complain if your zeal for revenge involves the use of a shotgun and buckshot. This squirrel-eating-bark phenomenon is not uncommon. It seems that during dry summers, squirrels strip the bark from limbs to get moisture. Try watering the grass at the base of the trees early in the morning (squirrels lick dew off of grass blades). This has worked before.
3. Q. My small pecans and some leaves are falling off. What can I do?
A. Many people have the same problem. Pecan nut and leaf drop in late summer is caused by water stress or injury by insects and/or disease. Young nuts are very sensitive now and will abort at the onset of any stress. Water slowly and deeply and control insects and disease with a Malathion-benomyl spray.
4. Q. Some of the large limbs in my pecan tree are drying and breaking off. This has been occurring for several months - - even before they were weighted with a heavy pecan load. What could cause this?
A. this is usually caused by shading out. Pecan limbs need to receive full sunlight to prevent tis problem. Usually this happens when trees are planted too close and become crowded. The best solution is to remove some of the trees. Q: Are pecan leaves toxic when used as a mulch?
A: No. They make excellent compost material.
5. Q: Why didn't my pecan tree produce this year?
A: Pecans tend to produce on alternate years. The better the management program the less the alternate bearing characteristic. This usually amounts to applying nitrogen fertilizer and watering. Zinc sprays and a pest management program are beneficial as well. Trees need to hold their leaves until about November 15 every year in order to insure a crop the next year.
6. Q: How large do pecan trees need to be in order to graft?
A: Inlay grafting can be done on 1 inch to 4 or 5 inch diameter branches. Four flap grafting can be done on 3/8 to 3/4 or 1 inch maximum branches. Small pencil sized whips can be patch budded.
7. Q: Can fertilizer spikes be used around pecan trees?
A: Fertilizer spikes are not recommended. You have too much fertilizer in one area and not enough in another. Roots can also be burned. Use 21-0-0 and spread uniformily around the tree at the drip line.
8. Q: When do you fertilize pecan trees and with what?
A: Broadcast applications of nitrogen fertilizer in the dripline zone are considered optimum. Apply in late winter or early spring before pecan buds begin to break. It is best to use half the recommended amount before bud break and the second half in May. In heavy crop years a third application would be beneficial.
9. Q: Will a zinc spray hurt new pecan trees?
A: No, however be careful not to burn the trees. The zinc sprays can be applied every 2 weeks from April 15 to August 15. Only continue to spray if the trees continus to put on new growth.
10. Q: What are the long 'structures' or 'growths' coming out of the buds on the pecan trees?
A: Catkins, the pollen producing or male flowers.
11. Q. I saw your pecan tree shaking story on television - - I hope you and the squirrels have recovered from being dislodged from that limb. I have a unique problem; the pecans won't fall from the tree. Even if I shake the limbs severely, the pecans won't dislodge. What can I do to correct this situation?
A: Unfortunately, there is nothing to do to readily correct the sticking shuck problem of this year's pecan crop. No one is sure about what caused the problem. More than likely, the major cause was the severe drought.
It could have also been caused by hickory shuckworm. A small white worm which tunnels in the shuck. This tunneling causes the nuts to be poorly filled and the shuck adheres tightly to the nut.
A better water management program and 1 to 2 sprays in mid to late August should overcome the problem in future years.
The environmental elements should begin to work on the stick shucks ultimately resulting in their breakdown with the nuts eventually falling to the ground. They probably will have little or no kernel.
This problem should not be confused with the similar symptoms of sticky shuck fungus which must be sprayed for in late summer. Sticky shuck fungus causes the pecan hull to adhere tightly to the pecan shell but the pecan meat is black and inedible when cracked.
12. Q: Can pecans be grown in the Medford area of southwest Oregon? What variety would you suggest?
A: Pecans will survive in your part of the world; the big question is whether you have a sufficiently long growing season to mature the nuts. They require a growing season of at least 210 and preferably 240 to 280 days. A mean temperature for the three hottest months, June through August, above 80 degrees F. A heat-unit accumulation, using a base temperature of 50 degrees F, of above 5000 units for the 7 month period from April through October. A mean temperature for the three coldest months, December through February, between 45 degrees F and 55 degrees F, with at least 400 hours of temperatures at or below 45 degrees F. Medium rainfall and humidity with facilities for irrigation during the dry periods and/or especially at nut fill (August, September and October). And finally a deep, well-drained but water-retentive, fertile soil.
Varieties you might want to try include: Pawnee--a tree was planted on the capital grounds in Washington D.C. It supposedly is doing well. It is a vigorous, upright growing tree which matures its nuts in about 160 to 170 days. Osage--a smaller pecan but one which matures even before Pawnee. And finally, Giles, a northern variety which matures early but has fair quality.
13. Q: Concerning Powdery Mildew on pecan trees; I had a serious problem with this in the Fall of 1995. For best results, when do I spray, before or after the mildew appears? Also do you have a product recomendation?
A: Powdery mildew is usually not a problem where growers make 2 - 3 fungicide applications a year. So normally we do not see the problem unless we don't spray. Also, usually only the nuts on the lower limbs are affected. If I were you I would make a fungicide application with my casebearer spray. This will probably take care of the problem, but if you see some show up later make another application. Products containing Benomyl are most effective.
14 Q: I am having nut drop with my five year old grafted pecan tree (rootstock=8yrs gscion=5yrs). Rootstock is a stuart and scion is a chocktaw. This is the fourth year it has beared. I followed the recomendations from our county etension agent (Texas A&M published material) for fertilzing, watering, and spraying winter and spring and may spraying for casebearers. The only spraying I ommited was for pecan husk scab. The nuts that drop do show some scab on them but look healthy and have plenty of moisture in them. I have not had a pecan harvest yet! Four straight years of premature nut drop! I have a water well 19 and a half feet deep. Could the taproot be in the underground aquafier and actually allowing the tree to receive too much water? I don't think so since we live in such a hot climate.
A: Sounds like you have a pollination problem. Pecans require cross pollination in order to set and mature pecans. Are there other pecan trees within 200 feet of your tree? If not, you will need to get another tree or graft another variety into your tree. The latter will be faster and Desirable would be a good candiate.
If there are other trees nearby, you may have another variety, such as Stuart which takes a long time to come into production.
Disease and insect damage will cause some nut drop, but rarely is it the whole crop. However, any damage to the shuck prior to shell hardening will cause the nuts to drop. Water stress will also cause nuts to drop. The deep water you mentioned helps the tree survive dry times, but does little to fill out the nuts.
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