Fruit trees should only be sprayed when they have a severe infestation or infection that cannot be handled by other means, or when they have a history of disease or insect infestation. When you spray your citrus trees, only use organic, food-safe sprays if you intend to eat the fruit that your tree produces. And never apply those sprays when the tree is flowering. This may kill bees or other pollinators and ruin next year's crop.
Spray your citrus tree at the right time which will be dictated by the type of spray that you are using. It is best to follow the manufacturer's instructions. However, the general rule is that dormant oil sprays go on in winter when the citrus tree is dormant and all of the leaves have dropped. And fungicides should be sprayed before flower buds open, and once again after they have dropped.
Wait until conditions are right to spray. A good day for spraying is windless, has low humidity levels (well under 80%), temperatures between 40 and 70 degrees Fahrenheit (do not spray if temperatures exceed 100 degrees), and no rain or forecasted rain in the near future.
Cover any nearby plants or trees with tarps or other protective covering.
Put on gloves, protective goggles and a breathing mask before handling the spray.
Determine the appropriate amount of citrus tree spray to apply. The amount will depend on several factors: the type of spray, the size of your tree and the type of sprayer that you are using. Read the manufacturer's instructions carefully for guidelines.
Load the pump sprayer. Fill it halfway with water, add the chemical and then finish filling the sprayer with water. Shake the sprayer thoroughly before using it.
Spray the tree. Stand far enough away from the tree so that none of the spray drips down onto you (the exact distance will be dictated by the sprayer's manufacturer). Start by spraying the center of the tree's canopy. Then work upward and outward until all of the nooks, branches and leaves (top and underside) are covered. Then move to the trunk and any surface roots. If the spray drips from the leaves, then you have applied it too heavily.
Wait until the tree is dry before removing the tarp from the protected plants.