The Honeydew Moth (Cryptoblades gnidiella) is an important pest on citrus, and other crops in some regions. Overwintered Honeydew Moth larvae typically emerge in late winter/ early spring and the first adults may be seen soon after. There can be up to 6th generations in a year, depending on the weather.  The Honeydew Moth Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to predict egg hatch based on adult trap catches and field-specific temperature data.

Initiating the Biofix

To properly use the model, the biofix must first be set. This is the date that will serve as the starting point for growing degree day accumulation. For Honeydew Moths, this biofix is usually set to January 1st for the Northern Hemisphere. Once adult moths have been trapped for a few weeks in a row, the date of the first catch can be used to reset the biofix, and improve accuracy of later predictions.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 50F and an upper threshold of 95F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. The first adults from overwintered larvae will occur at about 221 GDD (F) and peak at approximately 344 GDD. Adult moth Flight for the second generation will begin at approximately 2255 GDD after the Jan. 1 biofix date. The third generation will begin adult moth flight at approximately 3211 GDD after the first biofix. Traps and mating disruption pheromones should be placed to coincide with adult moth flight stages.

Adjusting Biofix for Each Generation

For best results after the second generation of Honeydew moths in a given season, the biofix should be reset when new pheromone traps have successfully capture adult moths in late spring/ early summer.  Trap placement and treatments should then coincide with the first generation of adults, following the adjusted biofix date. This will be improve accuracy of later life cycle stage predictions.

Source:

Avidov, Z. and S. Gothilf. 1960. Observations on the honeydew moth (Cryptoblabes gnidiella Milliere) in Israel. I. Biology, phenology and economic importance. Ktavim. 10:109-124.