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August Is The Most Critical Month For Pecans

Pecan production, like any type of farming, is a continuous battle, but it doesn’t matter how much hard work a grower puts into growing pecans if they slack off in August and allow the many stresses that plague the trees to get ahead of them. Many of these stresses will affect the following year’s crop moreso than the current year crop. This is the time of year that flower induction occurs. This means that as I write this, the tree is programming its cells to produce vegetative or reproductive buds next year. While this is driven primarily by the effect of crop load on the tree, additional stresses like drought, insects, disease, sunlight, etc. in August can significantly reduce the following year’s crop. The trees should be kept as stress-free as possible at this time.

 

I am seeing signs of a number of stress factors pop up in orchards right now. The most common are black aphids, mites, shade and drought. In my last post I discussed the need for vigilance when managing black aphid susceptible varieties like Schley, Sumner, Gloria Grande, and Oconee. You have to pull the trigger on this pest before it builds to easily noticeable levels and the population gets out of hand as it did in the photos below. This can happen very rapidly if growers do not pay close attention to populations this time of year.

Black Aphid Damage

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Mites are a little tougher to know when to pull the trigger on. They can be found in the orchard throughout much of the year and normally don’t reach population levels that do harm. The trees can tolerate them to a point. But, like certain diseases that lay in wait until the right conditions are found. When it gets hot and dry in late July/August and you see a strong mite population on the leaves, they can explode rapidly just as black aphids do, causing severe scorching and defoliation. This normally occurs following a spray with chlorpyrifos or other broad spectrum insecticides but that’s not always the case. I have seen this in orchards where no broad spectrum insecticides were used. Therefore, growers should be vigilant of mites and watch for signs of early scorching which begins along the midrib of the leaflets. Portal is a good option but has shown signs of weakening in some orchards where it has been used exclusively for a couple of years for mite control. The same could be said of Acramite. If you have aphids and mites, Nexter at the 6.6 oz rate is a good option. It provides quick knockdown and works well on both pests. Envidore is a good option for mites, providing excellent residual control but does not provide a quick knockdown so it would need to be used before mite populations reach damaging levels. These miticides are expensive at over $20-over $25 per acre so you want to be sure that there are mites present before spraying. There are many things out there that can scorch leaves and a grower can waste a lot of money spraying scorched leaves rather than mites.

Mite Damage and Defoliation

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I see leaves falling in a number of orchards at the moment that are simply turning yellow and falling. With black aphids you can see distinct spots that may appear to stay within the margins of leaf veins. When the yellowing occurs in a more uniform pattern in the leaf, as you would expect to see when the leaves change in the fall, you are simply seeing early senescense of these leaves. More often than not this occurs in the inner canopy and is brought about by shading. It can also occur in crowded orchards on the outside of the canopy. Drought or failing to provide adequate water at this critical time of year can also contribute to this problem.

Shading/Drought/Early Senescence

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Any of these stress factors and others can significantly affect the pecan crop. This is especially true for its effect on next year’s return crop. If there is a light load or no crop on the tree, these stresses, while having some effect, usually won’t completely eliminate next year’s crop. If there is a heavy crop load and the trees suffer from the various stresses that occur this time of year, the trees will almost certainly respond with little or no return crop. Its management in August that separates good pecan growers from average ones. Its all about timing.

 

 

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About Lenny Wells

I am a Professor of Horticulture and Extension Horticulture Specialist for pecans at the University of Georgia. My research and extension programs focus on practical cultural management strategies that help to enhance the economic and environmental sustainability of pecan production in Georgia.