The Lygus Bug (Lygus hesperus) is a common pest on a wide variety of plants, including berries, cotton, and beans. They can be very challenging to control, and different insecticide products may target different life cycle stages (eggs, nymphs, adults) and not affect the pest at the other life cycle stages. For this reason, predicting when different life cycle stages will occur, based on current observations and weather data, can be very helpful. Researchers have developed a growing degree day model for Lygus Bug to help predict when different life cycle stages will occur.

Calculating Growing Degree Day Units

There are several different models for Lygus Bug growing degree days, depending on the host. The Pest Prophet app offers models for alfalfa, strawberries, green beans, and safflower, which is used as part of the safflower-cotton complex, to predict when the lygus bug will move into cotton. Each model uses different temperature thresholds. The growing degree day units can be calculated from daily maximum and minimum temperatures using these thresholds, or by using the Pest Prophet app, which features this model and is easy to set up and use.

Setting the Biofix date

In order to begin growing degree day accumulation, first a “biofix” date must be set which is the first date, after which growing degree day units will begin to accumulate. In the Pest Prophet app, the biofix date can be adjusted for any observed life cycle stages.

For Lygus bug, the biofix is typically when the first adult is observed in the field. The model can then be used to predict when nymphs will be present, as well as the next generation of adults. For the safflower model, as part of the safflower-cotton complex, April 1st can be used as biofix date, to predict adult emergence on safflowers.

Sources:

Sevacherian, V., V. M. Stern, and A. J. Mueller. 1977. Heat accumulation for timing Lygus control measures in a safflower-cotton complex. J. Econ. Entomol. 70: 399-402.

Ben C. Simko, OSU, Agricultural Extension Agent, and Dani Jo Kriegh, Student Assistant, Lygus Summit, 28 November 2000. Visalia, CA, University of CA Division of Agriculture and Natural Resources.

Champlain, R. A., and G. D. Butler, Jr. 1967. Temperature effects on development of the egg and nymphal stages of Lygus hesperus (Hemiptera: Miridae). Ann. Ent. Soc. Amer. 60: 519-521.

Pickel, C., N. C. Welch, and D. B. Walsh. 1990. Timing Lygus sprays using degree-days in Central Coast Strawberries. Santa Cruz County Agricultural Extension Publication.