According to Lenny Wells, UGA Pecan Specialist, we have had one of the largest Desirable drops this year. This variety is well known to drop 40-60% of its crop in June most years. Many want to chalk this up solely to pollination (which does contribute in some years) and think we can get around it with one or another foliar spray. Still, the fact of the matter is that this is deeply ingrained in the genetics of this variety. Most varieties express alternate bearing by not putting on a crop at all the year after a heavy crop. The drop seems to be Desirable’s way of expressing its alternate or irregular bearing. The trees know what they can handle, and Desirable puts them on and then drops them in June if it needs an off year. I have also seen and heard about a reasonably significant drop in Pawnee this year. Both of these varieties make up a substantial part of Georgia’s production.
From the pest standpoint, this is perhaps the worst year for phylloxera. We see both leaf and stem phylloxera almost everywhere in the state. Black aphids are beginning to rear their heads. I would not spray this early generation unless you see nymphs on the leaves. If all you see are winged adults, keep an eye on them, but more than likely, they will simply move in and out. Black aphid nymphs should be sprayed at any time. Don’t sleep on hickory shuckworms. Mid-July and again mid-August will be the time to treat them. Pawnee probably needs an earlier treatment.
The other topic brought up by the dry conditions is irrigation. Given the drought and excessive heat, do I need to apply extra water right now? The answer is no. The current irrigation schedule UGA developed and recommends for mature trees has been studied, used, and proven in conditions exactly like those we are seeing, and it works very well to size the nuts. You need to be at 36-40% (about 1400 gal/acre/day) of full capacity in June and bump it up to 45% (1620-1800 gal) of full capacity in July with drip and microsprinkler. Solid set sprinklers should be 80% in June and 90% in July because they lose more to evaporation than drip and microsprinkler. Pecan trees function very well in hot, dry conditions as long as water is available. They are incredibly efficient at taking that water up in June and July but less so in August and September. If you over-water now and size the nuts too large, you are setting yourself up for problems with kernel filling in August/September if conditions remain dry.
Scab is out there from the wet weather of a few weeks ago, though it does not seem to be severe in most orchards. The current dry spell is helping us with scab, and I for one, would rather see a dry June and July as long s the wells are capable of running. Despite the dry conditions, do not extend spray intervals for Desirable and Pawnee beyond 2 weeks. We still have enough night-time humidity to drive scab on susceptible varieties. You may have the opportunity to extend it for more moderately susceptible varieties, but I do not like to gamble this time of year. The nuts will be at their most vulnerable point from now through July. To play it safe stick to a 2 week maximum interval during this time. If you choose to stretch it, watch the weather carefully and get in and spray before it rains when needed.