Texas Chilli Thrips Update

There has been a lot of questions and concerns regarding chilli thrips over the last year. I thought this would be a good time to provide an update. The good news is that we have only been able to confirm one infestation in Texas. Last fall a homeowner in Houston submitted a sample from plants in her yard that were being damage. It turned out that the damage was caused by chilli thrips. The unusual damage caused by this thrips to the plant's foliage is the easiest methods to detect this pest (see photo).

There are no indications that any greenhouse or nursery producers in Texas are infested. One of the most important ways of keeping your facility clean is to properly inspect all incoming plant material.

If there is any good news about this pest, it is that at this time there appears to be a number of insecticides that will kill it. Almost any insecticide that is label for thrips control will kill chilli thrips. Abamectin, chlorfenapyr, pyridalyl, spinosad and systemic insecticides (acephate, acetamiprid, clothianadin, dinotefuran, imidacloprid, thiamethoxam) applied as a foliar sprays have been shown to be effective in efficacy testing.

For more information on chilli thrips in Texas visit http://chillithrips.tamu.edu/.

Excluding Weed Seed from Containers

Weed management often suffers when there is a labor shortage. Good cultural and sanitation practices will reduce the number of weed seeds infesting containers and increase herbicide effectiveness in preventing weed germination and development.

The goal of a successful weed management program is to prevent weeds from germinating and competing with the crop by using a combination of cultural and chemical control tactics within an integrated management approach.

Weed free growing areas can be created with a good drainage system, gravel, concrete, weed-barrier (geotextile) or other organic or inorganic mulch. Exclude weeds by using weed-free growing substrates and preventing establishment of seeds carried by wind, irrigation water, equipment and tools. Cover stored substrate materials to prevent weed contamination. Substrates harboring weed seeds may be treated with heat or chemicals before use. Install and maintain filters or treat recycled and surface irrigation water to eliminate seeds. Clean plant debris and spilled potting-mix and avoid excess irrigation and standing water. All of these create habitat and favorable conditions for many weed species. Some weeds can germinate and grow in container drainage holes and directly compete with the plant for water and nutrients.

Maintaining weed-free non-crop areas is probably the easiest and the most effective sanitary practice for reducing weed seed numbers in your containers. Many weeds can project seeds over a large area (bittercress and oxalis); it is important to keep these plants from establishing in and around growing beds. Regular mowing of roadways, drainage ditches, areas between nursery beds, etc., will drastically reduce weed seed number and improve weed control.

Herbicides provide an effective means of managing weed in hard to mow locations. Post-emergence herbicides can be used to eliminate existing weeds and pre-emergence herbicides used to prevent weed germination and re-growth. Water quality and quantity may affect herbicide effectiveness. High water pH and dissolved organic compounds may reduce herbicide performance. Avoid herbicide leaching and runoff by limiting irrigation water after herbicide applications. Always read and follow directions on pesticide labels.

Western Flower Thrips

Western flower thrips are out in full force. If you have sensitive crops it is important not to let your thrips population get out of hand.

Growers were provided a brief relief from western flower thrips when Conserve SC was labeled for ornamental crops. Unfortunately, there are cases being reported of western flower thrips not responding to Conserve label rate applications.

This developing tolerance may be a result of some growers not following the label instructions. The Conserve SC label states “no more than three consecutive applications should be used, nor should there be continuous use for more than 30 days. Consider rotating to a different active ingredient with a different mode of action or use no treatment for the next generation" and "Regardless of the crop or pest being treated (excluding leafminers, spider mites and/or diamondback moths), do not apply Conserve SC more than 10 times in a 12-month period inside a greenhouse or a structure that can be altered to be closed or open”.

Due to the intense nearly year-round thrips pressure some growers face, they are exceeding the three consecutive applications and the 10 total applications per year. One common mistake growers make is applying Conserve repeatedly for thrips and then again for caterpillars, mites, or leafminers. This causes them to exceed the number of total applications that can be made in a year. It is critical to follow the label instructions to reduce the development of resistance in western flower thrips to Conserve.

The recent labeling of Pylon for western flower thrips control provides greenhouse growers (not labeled for outdoor use) a highly effective rotation partner to use with Conserve. As with Conserve it is important to follow the resistance management component of the Pylon label to lengthen the period of efficacy of this product for thrips management.

There are a number of other insecticides that can be used in rotation for thrips management. These include, but are not limited to, Avid, Azain XL, BotaniGard, Enstar II, Pedestal, Mesurol and Orthene.

I am currently working on a project to monitor the tolerance level of western flower thrips to Conserve in East Texas. I will report more on this when the project is completed.

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