How Can I Control Thrips?

Do you want to control thrips using the biological control method?

Do you want to control thrips by pruning?

Do you want to control thrips using low-risk (organic) insecticides?

Do you want to control thrips using synthetic insecticides?

Do you want to use residual, foliar sprays?

Predatory thrips, green lacewings, minute pirate bugs, mites, and certain parasitic wasps help to control plant-feeding thrips. To conserve and encourage naturally occurring populations of these beneficial insects, avoid creating dust and consider periodically rinsing dust off of small plants, avoid persistent pesticides, and grow a diversity of plant species. There is little research-based information on the effectiveness of releasing thrips natural enemies in gardens and landscapes. Releasing purchased natural enemies, in most situations, is unlikely to provide satisfactory thrips control.

Prune and destroy injured and infested terminals when managing a few small specimen plants in the landscape. Avoid shearing plants, which is the clipping of dense foliage to maintain an even surface on formal hedges or creating specific shapes (topiary). Shearing stimulates thrips-susceptible new growth. Prune by cutting plants just above branch crotches and nodes instead of shearing off terminals.

Contact insecticides that do not leave persistent residues can be effective for greenhouse thrips and other species that feed openly on plants. These include azadirachtin, insecticidal soaps, narrow-range oil, neem oil, and pyrethrins. To be effective, contact sprays must be applied to thoroughly cover buds, shoot tips, and other susceptible plant parts where thrips are present. On plants with a history of unacceptable damage, begin treatment early when thrips or their damage is first observed. Unless directed otherwise by the product label, periodically repeat the application as long as pest thrips and susceptible plant parts are both present.

Avoid foliar sprays of organophosphate insecticides (e.g., malathion), carbamates (carbaryl), or pyrethroids (e.g., bifenthrin, cyfluthrin, fluvalinate, and permethrin). These materials are highly toxic to natural enemies and pollinators, can cause spider mite outbreaks, and are not particularly effective against most thrips. Because their use in landscapes and gardens can run or wash off into storm drains and contaminate municipal wastewater, these insecticides are being found in surface water and are adversely affecting nontarget, aquatic organisms.

Systemic insecticides are absorbed by one plant part and moved to other plant parts. Trunk spray or injection of an effective, systemic, neonicotinoid insecticide can provide relatively rapid control. With soil drench or injection, there is a long time delay between neonicotinoid application and insecticide action. Neonicotinoids have a low, moderate, or severe adverse impact on natural enemies and pollinators varying with the product, situation, and the species and life stage of invertebrate. Delay systemic insecticide application until after plants have completed their seasonal flowering, unless the product label directs otherwise.

Row covers, hot caps, and other types of cages with a fine mesh can exclude thrips and other insects from vegetables and other young herbaceous plants. Apply row covers before crops emerge or to pest-free plants during planting. Any type of covering that excludes insects but allows light and air penetration can be used. With sturdy crops that do not grow too tall, floating row covers (vented polyethylene, spun-bonded polyester, point-bonded polypropylene) can be placed on top of beds with no frames or hoops.