With much of our cotton planted for 2018, Louisiana is beginning to experience insect issues in seedling cotton. Based on our thrips species surveys, the breakdown appears to be a 50-50 mix of western flower and tobacco thrips. However, I have received reports of almost 100 percent western flower thrips or 100 percent tobacco thrips, depending on the location.

Tobacco thrips adults are black, while western adults are amber to yellow in color. Immature thrips are small versions of adults that lack wings. Immature thrips from both species appear yellow to orange.

Thrips species can dictate how well an insecticide seed treatment holds up. Westerns are still susceptible to Cruiser (thiamethoxam) while tobacco are resistant. Both species are susceptible to imidacloprid. Avicta Elite seed treatment contains thiamethoxam, imidacloprid and abamectin (abamectin is for nematodes). Aeris contains imidacloprid and thiodicarb. Aeris is a consistent performer in our insecticide seed treatment efficacy trials, and Avicta Elite is performing well in 2018.

I expect to see Avicta Elite hold longer in areas where the primary species present is western and Aeris to perform well where tobacco thrips are the primary species. However, both treatments are satisfactory where we have mix of both species. Depending on species present and environmental conditions, insecticide seed treatments have held well in many places but needed an over-spray in others. Once cotton reaches the four-true-leaf stage, thrips are no longer a cause for concern.

Related:National Cotton Council supports registration of new nematicide

Spider mites

Two-spotted spider mites are appearing in much of the cotton in northeast Louisiana. Spider mite infestations often originate from incomplete spring burndown applications, tree lines and turn rows. Post-emergence herbicide applications and hot, dry weather create an ideal environment for mite proliferation. Mites move the greatest distances by wind and mechanical movement, which often create hot spots in different parts of fields.

Spider mite infestations in seedling cotton usually do not warrant applications for an entire field. Spot treatments where severe injury and stand loss are occurring may be warranted. If fields are questionable on treatment and rain is in the forecast for the near future, it may be prudent to wait on dedicated miticide applications. Rainfall, especially on seedling cotton, will often dislodge spider mites, effectively reducing populations.

If an application is warranted, rotate modes of action if further applications are needed later in the season. Abamectin resistance in two-spotted spider mites has been documented in Louisiana, and high label rates should be used.

Related:Cotton blue disease – aphid-transmitted virus

An unconventional option is to use glufosinate (Liberty, Cheetah, etc.) for post-emergence weed control. The LSU AgCenter has documented miticidal activity of glufosinate in cotton. Glufosinate is not labeled as an insecticide or miticide. However, this compound has the utility of controlling two-spotted spider mites that may be on weeds or cotton when an application is made. Glufosinate works on contact and has no efficacy on eggs.

Finally, immature thrips are voracious predators of spider mite eggs. Thrips are an economic pest in cotton from the one- to four-true-leaf stages, but once cotton reaches the four-true-leaf stage, thrips are an important natural control agent that will help keep mite populations in check.