Fungicide costs, like seemingly everything, have gone up a little this year. Some, like the tin products, have gone up dramatically. When I checked a couple weeks ago, Tin was at $120/gal. This may lead many growers to look for other options aside from Tin when the time comes. However, a word of caution on that. Tin offers great nut scab control when used in combination with Elast. But, you are getting more than just scab control out of using Tin in your program.
We currently have 7 classes of chemistry labeled for fungicide use in pecan (8 if you count tea-tree oil). We are still heavy on the group 3 materials because we often use at least 1 group 3 early in combination with a group 11 and we also use them later for nut scab as one of the components of Miravis Top or Miravis Prime. Using too many group 3 materials is dangerous because resistance (or at least insensitivity) has developed quickly in the past to some group 3’s like propiconazole and tebuconazole in places when used too often. That doesn’t necessarily mean the same will occur with difenconazole or mefentrifluconazole, but the history of the class of chemistry should be considered. This is why I am hesitant to replace Tin with another group 3 spray in the program when we are already using 3 or 4 group 3 sprays in the season. It could be done but you need to be careful.
Preservation of our fungicide chemistry is of paramaount importance and along with efficacy should be your top consideration when designing your fungicide program. In short, a combo spray of 25 oz Elast and 6 oz Tin is still only around $15/acre, which is a couple dollars more than the average fungicide spray cost this year but I feel the rotational value is worth that. Many do not like using the lowest labeled rate for fear of resistance development and loss of efficacy. When used alone I would agree but application as a tank mix -especially when rotating with other fungicide classes around it -is an effective method of preserving efficacy. Yes, there are places (ex. Albany area) where the 25 oz and 6 oz rates have become questionable over the years because of repeated consecutive use with these materials and if you have an orchard with a history of Tin insensitivity, then you may not want to use the 6 oz rate, but for most areas where the chemistry has not been abused in the past, the 25 oz Elast + 6 oz Tin rates still work well in combination when rotated with Miravis Top for nut scab sprays and are probably less of a risk long -term than rotating in another group 3 in that spot. If you don’t feel comfortable with the 25 +6 oz combo of Elast and Tin, then a full rate (48 oz) of Elast may be a better option in that spot but it will be around $18/acre.
All that being said, the fungicide schedule we suggested last year works well and I see no reason to change it. You can find that here.
I’ve had a lot of questions about when to start spraying this week. Some are already giving it a go but especially for anything but Desirable and other super scabby varieties, I would not even consider it until next week or the week after. There’s not much foliage out on most varieties yet and you don’t have much tissue to cover. The last 3 years, we’ve started here around April 20 and had no problems from the “later” start. This year we may need to go a week earlier with the earlier budbreak. The foliage will be growing fast and if you spray today, there will still be a lot of unprotected tissue there 2 days from now. You have to pick a time to get started and I prefer to wait until there is more there to spray. If you are itching to go ahead and spray you may want to consider an airplane spray for the first spray. With the sparse foliage an airplane spray early can penetrate all the way through the canopy and provide effective coverage. Once the canopy closes, you only get the top with an airplane.
Another common question at the moment is “should I use 50 GPA or 100 GPA”? 100 GPA has been the standard for a long time but Dr. Clive Bock with USDA in Byron has being doing some exceptional work in this area and has several years of compelling data to support using 50 GPA. From what I can see, it really comes down to coverage. For the heights your sprayer can reach, 50 GPA works great. Your droplets are more concentrated and, as always, where you get good coverage you get good efficacy. For hedged trees and trees 40′ or less, it is a no brainer that 50 GPA is a good way to go. The argument can be made that above that height you need 100 GPA but honestly, above that height you are not getting very good coverage with 100 GPA either, so does it make much difference? Maybe not, but honestly, I’m not quite ready to go there just yet on big trees aorund 60′ tall. But, we’ve got to look for creative ways to save some money growing pecans, and the 50 GPA application volume may offer a tool to chip away at that cost of production.
