I have found a legal notice about not spraying plants when they are in flower or part flower:
It is on page 37 (section 58) of the Hazardous substances (Hazardous Property Controls) Notice 2017. The link to this notice is below:
This notice is issued by the Environmental Protection Authority (the Authority) under sections 75 and 76 of the Hazardous Substances and New Organisms Act 1996 (the Act). It is issued in accordance with section 76C of the Act, having had regard to the matters specified in section 76C(2).
The objective of this notice:
This notice prescribes requirements to ensure that hazardous substances are stored and used in a manner that protects the environment, and people in places other than workplaces to which the Health and Safety at Work Act 2015 applies.
Excerpt of Section 58 of the notice:
58. Protection of invertebrate pollinators
(1) This clause applies to an agrichemical that is applied to a plant if the agrichemical—
(a) has the hazard classification hazardous to terrestrial invertebrates; and
(b) is in a form that non-target invertebrate pollinators are likely to be exposed to either during, or after, its application.
(2) A person who applies the agrichemical must ensure the application plot does not include any—
(a) bees that are foraging; or
(b) plants (including trees and weeds) that—
(i) are likely to be visited by non-target invertebrate pollinators; and
(ii) are either—
(A) in flower or part flower; or
(B) likely to flower within the period specified by the Authority as an additional control for the substance.
(3) Subclause (2) does not apply if the application plot is indoors, and the agrichemical is contained within the facility.
(4) In this clause, invertebrate pollinator means an invertebrate agent that moves pollen from the male anthers of a flower to the female stigma of a flower, including (without limitation): bees, pollen wasps, ants, hoverflies, butterflies, moths and flower beetles.