With the heavy crop load that most of us are seeing during 2007, there are major factors that producers need to consider this time of year. In the majority of orchards that I've been in during this summer, scab, a fungal disease, is a major problem. With all the rain this year, scab has appeared on trees that haven't been previously affected.
If you have scab in your orchard, you must make the decision whether to spray or not. There are two types of scab that we are concerned with on pecans, leaf scab and nut scab. Leaf scab we can tolerate a little more because it will most likely affect next year's crop more than this year's, unless it is so bad that the trees lose their leaves early. Nut scab, on the other hand, affects this year's crop and is the problem that I have been seeing in the orchards. Nuts that are less than 30 percent covered with scab should still open at harvest. If nuts have more than 50 percent damage, they will not open at shuck split. The range between 30 and 50 percent is a gray area as to whether it is feasible to spray or just walk away from this crop. I have been recommending that growers scout their orchards and spray only the trees that have the least damage. The fungicides that we spray will not reduce the amount of damage, it will only stop or slow down the amount of infection that has already occurred.
Weevil is the other big concern this time of year. It is very important to know when weevils are in your orchard. To determine this, use weevil traps to capture weevils climbing the trunks of the trees. When your threshold is met, then it is time to spray. The threshold set by entomologists is 0.3 weevils per trap, if two traps are used per tree and 10 trees are monitored, for a total of 20 traps. For the producers that use fewer traps, emergence needs to be monitored and, once you see an increase in emergence, then it may be time to spray. Continue to monitor the traps until shuck split. Weevil can and do emerge and cause damage to pecans up to and through shuck split.
A study conducted at the Noble Research Institute showed wildlife damage on native groves ranged from 73 to 755 pounds per acre. Average damage on six different grove sites was higher than the amount harvested from the groves. Therefore, timely harvest is critical. You have spent all year producing this nice crop of pecans and, now that it is time to harvest them, you have to fight all the predators. Squirrels start damaging pecans as they are sizing in late July/early August and throughout harvest. They can damage half a pound of pecans per day. Birds are equally as damaging, normally starting their damage at shuck split until harvest. For example, crows can be very devastating on your pecan crop as they normally travel in flocks and can consume and damage half a pound to one pound of pecans per day per crow. Blue jays will consume about half as much as the crows. Other predators that can affect your pecan crop are raccoons, possums, mice, hogs and cattle. Also, do not forget the numerous insects that can cause damage to the pecans after they have fallen from the trees (ants, stinkbugs, etc.).