Oh, fruit tree pests, sometimes you're the bane of my existence.
For a few years, I tried treating my fruit tree pests with spray bottles of Neem, insecticidal soap, and horticultural oil, with mixed results. I'd spray, see a slight reduction in pests (notably aphids, mealybugs, and scale). But wait a short period of time, and the bugs would come back with a vengeance, causing particular damage when my citrus trees were brought inside during the winter months.
After going through bottle after bottle of the sprays, which can run north of $10 per bottle for a pre-mixed solution, I went apoplectic on one plant one day that had a mealybug infestation. Squirt after squirt (after squirt), I sprayed them as much as I possibly could, using most of a single bottle, and something interesting happened- I noticed a bigger reduction in the pests than I had before.
It was here that I had a lightbulb moment- it wasn't the sprays themselves that were the problem, but rather that I was likely not applying them nearly liberally enough (or possibly even frequently enough) to make a dent on the pests.
So I tossed the squirt bottles aside, upgraded to an industrial pump sprayer, bought some Neem and horticulture oil concentrates, and really blasted my trees with a good dousing.
The pest population dropped dramatically.
So in this one, let's talk about why squirt bottles may not be getting you all the way there and why upgrading to a proper sprayer is a better option- both for effectiveness and cost.