Young Trees
Pecan Budmoth – Adults overwinter under bark scales then start laying eggs in the Spring. Eggs hatch in about 6 days and the larvae then feed on buds and leaves. The tips of the leaves may look necrotic or burned. They stay in larvae stage for 2 weeks, it takes about a month to complete a generation. They can have 5 or 6 generations in a year. This maybe why we had so much damage last year. They seemed to keep hammering young trees over and over. They can damage an old tree, but first year trees are what they need to be worried about. They can kill a first year tree for sure.
What do they need to do? The best thing is scout for them first. Once you see or confirm damage from budmoths, apply insecticide. Tiny larvae will be cream colored and mature larvae will be yellow-green and have brown head. Terminals and tips of leaves look burned up.
What insecticide to use? Worm materials better than Lorsban if you catch it early. We used Lorsban a lot last year because the problem got so bad, we needed a quick knock-down. If you catch early, I would do:
- Intrepid
- Intrepid Edge
- Dimlin
- Minecto Pro
The main difference is with Minecto Pro or anything containing the cyantraniliprole family, Dr. Hudson says has a long residual. Could be a month? It is more expensive though. I think catching them early, Dimlin and Intrepid is fine.
Photo of budmoth caterpillar from Ben Reeves last year. 2nd is photo of damage.
Asian Ambrosia Beetle – Though numbers are not high this year, just communicate with growers that they tend to have two spikes: 1) Feb/March then again April/May. Most important on first year tree.
Photo of adult AAB trying to get in a trap and exit hole from a trap I took last Friday.
Mature Trees
Pecan Leaf Phylloxera – These are tiny, aphid-like insects that cause the warts on the leaves. Usually they are found in orchards that are a lot older. There are 3 or so species. Some cause the warts on the leaves and others cause the warts on the stems. Since I have been in Extension, they generally say the stem phylloxera is worse and may hurt yield. Leaf phylloxera isn’t as serious, but if left unchecked does get worse. So overall, a grower needs to do something for it.
Control – They must be sprayed for at budbreak, and imidacloprid is what we use. The reason we spray at budbreak is eggs hatch now and young go straight to the buds to feed. Their feeding forms those galls, which encapsulates them. Once the galls form, insecticide cannot penetrate. Sometimes this gets difficult when you have multiple varieties that have this issue but budbreak at different times. While an agent in Thomas County, Dr. Hudson and I tried drenching imidacloprid at the base of trees in Dec, Jan, Feb and March with the idea that it would take up the insecticide for budbreak. It never worked. So budbreak spray is the only thing we can do.
Pecan leaf phylloxera
Scab – On this subject, the growers are going to do what they do and that’s fine. I wanted to share some thoughts on this mostly to newer agents with pecan interest.
Where I started as ANR agent in Thomas County, growers began fungicide spray at budbreak simply because all they have is Desirable, Stuart and Pawnee (High susceptible cultivars) and a very low elevation. They have been burned by scab so much, they start this early. With that being said, Dr. Wells would tell me that they don’t have to start that early and can wait until leaves unfolded some. This is because the fungicide must contact leaf surface. And..You really don’t know how many catkins are breaking bud with leaves either. If we get fungicide on more catkins than leaves, it’s pointless since the tree will shed catkins.
In light of the greater use phosphite fungicides now, I spoke with Dr. Brenneman today on this exact issue. I asked if there has been a difference in leaf scab (or nut scab) if a grower cuts out his ‘budbreak spray’ and begins at parachute stage. Tim said it all depends on rain. The last 2 years, our Springs were dry. So, a grower could almost wait until nut sizing to begin scab sprays and be okay. When it is raining, however, there may be a difference in a budbreak spray on a susceptible cultivar (Desirable, Pawnee, Cunnard, and Byrd) and waiting another 2 weeks. We know that scab on nuts has a direct effect on kernel quality and yield. What about leaf scab? If leaf scab gets out of control, nut scab control becomes more difficult. Bottom line, you can’t let leaf scab get out of hand.
Back to the phosphites – what we know is that they translocate much further in a tree. In older trees, they will translocate into the stem. In young trees, phosphites can translocate to the roots. Your Group 11 and Group 3 are systemic, but mostly stay close to where they touch the leaf. Therefore, with phosphite, an early spray WILL get into the leaves and trees MORE and really could be beneficial in a rainy season.
Here is a picture I took in 2017 in Thomas County of (Left) parachute stage and (right)