After a long delay due to low temperatures for the most part of April, this week’s daily temperatures are rising up and crops are starting to develop. Current weather conditions in west central Michigan are characterized by an average minimum temperature of 51 degrees Fahrenheit and a maximum temperature of 73 F.

Precipitation accumulated from Jan. 1 until May 8 is 8.09 inches, with an accumulation for the past five days of 0.7 inch in some areas around west central Michigan. Based on current weather conditions, growing degree-day (GDD) accumulations so far is 122 GDD base 50. The six-day advanced weather forecast indicates temperatures similar to the ones already reported with chances of rain between 66 and 72 percent May 9 to 13.

Lack of enough rain over the past 25 days is compelling growers to start providing supplemental irrigation. However, due to the low temperatures that prevailed over the last few weeks and the moisture accumulated in the soil, drought conditions are not evident yet in blueberry fields. Also, at this time of the year, the demand for water by the plant is still minimal.

Regarding plant phenology, blueberry varieties are at different developmental stages depending on the location and variety. In Ottawa County, Draper and Bluecrop are at the tight cluster stage with vegetative buds at 0.5 inch green. In Allegan County, Bluecrop is in the early pink stage and Bluetta is already in the pink stage. Meanwhile, Elliott and Jersey are in the tight cluster stage with 0.5 inch green. The beginning of bloom is expected by the end of this week and the beginning of next week in Allegan and southern counties.

Although the lack of rain may represent a problem for growers with fields on sandy soils, dry conditions have allowed growers to conduct early season disease management without much delay. Most growers have already applied the first fungicide application against mummy berry and Phomopsis. There are some blueberry fields that show bacterial blight that can be easily taken for Botrytis twig blight. On those fields, applications of fungicides may have limited effect. This infection only responds well to copper-based fungicides.

For early applications against mummy berry and Phomopsis, look for alternatives to Indar. There are other systemic fungicides with similar efficacy such as Tilt and Quash that could be a lot cheaper. For dose and other alternatives, consult the 2018 Michigan Fruit Management Guide, Michigan State University Extension bulletin E0154.

For early insect problems, the current GDD accumulation base 50 F since March 1 for west central Michigan is approximately 200 GDD. This accumulation is a good indication of needing to deploy pheromone traps for fruitworm management.

MSU Enviroweather’s cherry fruitworm predictive model indicates that on average, cherry fruitworm adults emerge around 238 ± 30 GDD and the egglaying period starts at 432 ± 15 GDD base 50 accumulation after March 1. These values are a biofix point to start the forecast of the cherry fruitworm population dynamics. For adults, the biofix is 238 ± 30 GDD base 50. For egglaying, the biofix is 431±30 GDD base 50.

To successfully use the Enviroweather cherry fruitworm predictive model, deploy pheromone traps at this time in order to establish with accuracy the beginning of the adult overwintering moths to initiate the calculation for predicting the time for insecticide applications against eggs and first instar cherry fruitworm.

See the Enviroweather cherry fruitworm predictive model to get the most accurate information for your location.

Advanced IPM training for Hispanics

On May 12, 2018, MSU Extension, Michigan Food & Farming Systems and Very Blue Farms will host a special workshop for Hispanic/Latino blueberry growers. This training is to prepare underserved blueberry growers to better manage spotted wing Drosophila in 2018. 2018 Spotted Wing Drosophila/Integrated Pest Management Training for Hispanic/Latino Blueberry Growers will take place from 9 a.m. to 4 p.m. at Very Blue Farms LLC, 76749 38th Ave, Covert, MI 49043.

Growers attending the training will receive four recertification units (RUP) for the renewal of their Pesticide Applicator License.

There is a $25 fee that includes materials and refreshments. This training is in Spanish, but limited English translation will be provided upon request to accommodate Hispanics or non-Hispanic growers with language barriers.

For the training agenda and to register online, go to 2018 Spotted Wing Drosophila/Integrated Pest Management Training for Hispanic/Latino Blueberry Growers. You may also pre-register by calling Jesus Barajas at 269-764-0084 or Filiberto Villa at 269-830-2309.

This educational program is possible thanks to the collaboration and economic support from the Michigan Food and Farming Systems, the Michigan Blueberry Advisory Council, the Michigan State Horticultural Society and the packing/shipping company Very Blue Farms LLC from Covert, Michigan.