Today I sprayed 4 different materials for EHS control. I applied the materials with a backpack mistblower, using about 100 gallons to the acre. I treated 40 trees each with either:
- Safari @ 8 oz/100 gallons
- Movento @ 10 oz/acre + Liberate (an adjuvant) @ 2 pts/100 gallons
- Lorsban @ 1 qt/acre
- Dimethoate @ 16 oz/100 gallons + Asana @ 10 oz/100 gallons
The population was ready for control. I collected a sample and looked at the percentage of individuals that were either males (the easiest to kill), nymphs, or females (the hardest to kill). Only 14% of the population were females with 24% as males and 62% as nymphs. I'll come back in a month or so to see what kind of controls I got.
The field I treated was part of a study to see how quickly the scales spread. On July 14, 2008, Bryan Davis and I evaluated 361 trees to see which ones had scales. We flagged infested trees and made a map. At that time, about 1/2 of the trees had scale, though most of it was only a shoot. Only 4% of the trees had moderately heavy scale.
We couldn't go back last year because the grower had put lime on the trees, and it was too hard to tell what was lime and what was scale. But I went back yesterday before treating today.
Now 95% of the trees have scale and 40% have it pretty bad. But even on trees that have had scale heavy for two years or more, they don't look that bad (one is pictured at the end of this blog along with a photo of the field). I do think the trees that have had scale heavy have weaker bottoms, but they are still growing well.
So how much does EHS really damage trees? The jury is still out. I think we can keep the scale "beat back" though never eliminating it completely. For most growers who aren't shipping to California or another country, that will probably be good enough.