Downy mildew in lettuce

Downy mildew was found in a lettuce field in the Valley this week by Erika Bent (APM Agricultural Pest Monitoring Cons. Ltd.).  We don't always see lettuce downy mildew (Bremia lactucae Regel), but it can be very destructive. Spores are spread via splashing water or wind.  Air currents can carry spores several kilometers.  Cool temperatures (between 15' and 21' Celsius) are conducive to disease development, especially under wet conditions.  This includes heavy dew set in the mornings and overhead irrigation. 

Infection usually starts in the older leaves and travels inward.  Pale green or yellow areas will become apparent on the upper surface of the leaves, often having an angular appearance, with sporulation occurring on the underside.  This infection can spread very quickly, especially under favourable growth conditions, so be sure to check your fields often!

Fields that have been recently harvested are ideal locations for disease buildup to get out of hand, so be sure to plow down lettuce residue.

There are numerous fungicide options, which can be found on the Perennia Lettuce Management Schedule. Downy mildew can build up resistance to pesticide group modes of action very quickly, so be sure to rotate between pesticide groups at every application. While there are varieties that have been bred to be resistant to downy mildew, due to the quickly evolving nature of this disease, varieties may not be resistant to all strains of downy mildew.

Wind Meters

Perennia's Caitlin Congdon using the wind meter

Here at Perennia we've recently acquired a wind meter that can attach to a phone.  The small fan-like attachment plugs into the headphone jack and works in sync with a free app called Wind Meter established by the company, WeatherFlow.  The wind meter itself costs about $50 (CAD), which is comparable to a similar product from Weatherhawk, although the Weatherhawk version is not yet available for Android.

The wind meter and app will measure wind speed in either kilometers per hour or miles per hour and displays the real time wind speed, gusts, and lulls, and also track the average and report wind direction. Readings can be stored or sent via email and text, or viewed on a map.

Perennia's Research Technician Caitlin Congdon has been using the wind meter when we spray our trials to minimize drift. She has compared the app and phone plugin with our handheld model and has found it to be very accurate. This type of gadget is small enough to be carried in your pocket with your phone, and is an easy way to provide specific on-site information.

There are several portable wind and weather meters on the market at a wide range of price points and levels of detail. Some work through apps, either through an attachment to your phone, or via Bluetooth. The Bluetooth devices generally give more information, such as temperature, humidity, barometric pressure, etc. and sell for anywhere from $50-$250 (CAD).

This post was written in part by Caitlin Congdon, Perennia's Agriculture Research Technician.