Hi Selma –
Flower-eating bugs can be difficult to control and have a big impact on your garden. Properly identifying your garden’s pests and understanding their biology will help decide the proper course of action. Use yellow sticky traps around your garden to identify your pests and to provide a visual gauge for the efficacy of control measures.
First and foremost, pests more easily infect unhealthy or stressed plants. Keep plants health with appropriate watering and fertilizing schedules reduce infestations. Moreover, follow sunlight preferences when planting, as plants receiving incorrect levels of sunlight are twice as likely to develop infestations. Remove leaf litter and weeds from beds to prevent infestations from the ground up. Also, remove diseased leaves and deadhead flowers for additional pest control. Remove infested plant materials from your yard as soon as possible and avoid composting, which will spread infestations. Avoid over-pruning or fertilizing with infestations, as soft, new growth is susceptible to pests. Proper plant spacing improves air circulation and reduces intensity of pest infestations. Furthermore, certain plant varieties have resistances to certain pests, so choose appropriately for your garden.
Understanding the life history of your pests will allow for a tailored plan of attack. For example, diatomaceous earth is effective against crawling pests, such as earwigs, ants, slugs, and cutworms. Sprinkle diatomaceous earth, made from fossilized algae, around plants and beds; pests dehydrate and die when walking through it. Reapply after rain.
Planting certain flowers among your garden also helps naturally deter pests. Nasturtiums are attractive to many pests, which choose to eat these flowers instead of your ornamental flowers. Prune and destroy infected leaves and flowers to control pest populations. Chrysanthemum naturally contains pyrethrum, an insecticidal compound that repels insect pests. Clover, lavender, and marigold also contain compounds that repel pests; plant throughout your garden and benefit from a natural pest deterrent.
Predatory and beneficial insects are effective at controlling pests and have low impacts on pollinators. Treat soil-dwelling life stages, such as thrip pupa or fungus gnat larvae, with predatory mites or nematodes, beneficial insects that live in the soil and prey on these pests. Treat plant-dwelling life stages, such as aphids, scale insects, and azalea plant bugs with green lacewings or ladybug beetles. Controlling all life stages of the pest is the most effective way to minimize infestations.
Care should be used when selecting chemical treatments for pest infestations, as even natural and organic insecticides and repellants can negatively affect pollinators. Insecticidal soaps and horticultural oils are effective at controlling both adults and newly hatched pest larvae, when applied directly to pests. Horticultural oils smother eggs, which pests imbed into plants, making control difficult. Apply these products at dusk to thoroughly dry before coming into contact with pollinators.
Neem oil is natural produced from an Indian species of evergreen and effectively controls pests. Neem’s active ingredient, azadirachtin is a hormone disrupter, appetite suppressant, growth regulator, and repellant for insects. Even though neem is marketed safe for pollinators, research found neem to lower body weight and affect activity levels of bees. Therefore, care should be used when applying to flowers, where pollinators can directly ingest neem.
Pyrethrum from chrysanthemum flowers effectively controls pests, including aphids, thrips, and certain beetles. Pyrethrum can also treat soils, controlling soil-dwelling pests. Pyrethrum is relatively short-lived and may need to be applied several times to effectively control pests. Some pyrethrum products may contain piperonyl butoxide, enhancing the toxicity and duration of the compound. Pyrethrum is toxic to pollinators, and should be applied at dusk.
Spinosad is a relatively new pest control compound. Isolated from soil bacterial, spinosad is effective at managing specific caterpillars, beetles, and thrips for up to a month. Spinosad is mildly toxic to birds and humans and highly toxic to pollinators; apply at dusk.
Bacillus thuringiensis, B.t. for short, is also a compound isolated from soil bacteria that is effective against dipteran pests, such as mosquitos, fungus gnats, and black flies. A short-lived pesticide (i.e., lasting only 1-2 days), B.t. has not been found to negatively impact pollinators and can be sprayed when pollinators are present.
To protect pollinators, mechanical and biological pest control is best. If these methods are not producing desired results after proper application, B.t. is the safest pest control compound on the market, but will require frequent and repeated applications. A multi-pronged approach to managing garden pests may be needed: using different methods to control life stages will knock back pest populations and reduce damage to flower beds.
Hope it helps!