Farm #1: Georgetown-1A

May 26, 2021- Update

Growing Degree Day Accumulation: 646

Description

  • 1st cutting was made on 05/19/21
  • Alfalfa weevil feeding has slowed tremendously. As pictured below, numerous net-like cocoons were foound within the field indication that the weevils are advancing to their adult form. Adult wevils do very little damage to the alfalfa. In fileds that were harvested earlier, continue to watch for feeding on regrowth. 
  • What's next? Be on the look out for Potato Leaf Hopper. We will post updates and findings as we have them. Find more details about scouting and management at https://ohioline.osu.edu/factsheet/ENT-33

aa

a

May 10, 2021 - update

Growing Degree Day: 434

Description: 45 larvae were collected. Damgae continued to progress. As pictured below - No damage (top) vs damged (bottom).

Aa


Date: May 7, 2021

Growing Degree Day Accumulation (GDD): 419

Pest: Alfalfa Weevil

Description: Alfalfa plants had moderate to high levels of defoliation in the upper canopy. 30 stems were collected and a total of 31 weevil larva were found. Ranging from 1st instar to 3rd instar.

FoliarImage B

Management: This field's average plant height was 14" tall. When using the chart below, the 14'' height and the average of 1 insect per plant, there is no immediate control needed. GDD accumulation is ahead of our average Souther, Ohio. Weevil damage is commonly kept at lower levels by parasitic wasps and a type of fungal pathogen. Sevre damage is also normally closer to harvest and an early harvest can be used to reduce further damage. Producers should watch the regrwoth very closely for weevil feeding.

In this situtation the level of defoliation was higher than expected for this early in the season. Therfore, we will collect samples from this field again in 3 days and if defoliation increases, a rescue treatment of an insecticide may be warranted. 

Alfalfa Weevil Thresholds

More Information: 

  1. More information about scouting, managment, and lifecycles can be found at: Alfalfa Weevil on Alfalfa| Ohioline Fact Sheet
  2. Specific chemical control options can be found at: Control of Insect Pests of Field Crops | PDF

 

 

 


2. Farm Name & Location: Russellville-1A

Growing Degree Day Accumulation (GDD): 419

Pest: Alfalfa Weevil

Description: Alfalfa plants had low to high levels of defoliation in the upper canopy. 30 stems were collected and a total of 45 weevil larva were found. Ranging from 1st instar to 3rd instar. Overall, more quantity of early instart weevils and less foliar damage as compared to Georgetown-1A.

foliarweevil

Management: This field's average plant height was over 16 " tall. When using the chart below, the 16'' height and the average of 1 insect per plant, there is no immediate control needed. GDD accumulation is ahead of our average Southern Ohio. Weevil damage is commonly kept at lower levels by parasitic wasps and a type of fungal pathogen. Severe damage is also normally closer to harvest and an early harvest can be used to reduce further damage. Producers should watch the regrwoth very closely for weevil feeding.

We will collect samples from this field again in 3 days and if defoliation increases, a rescue treatment of an insecticide may be warranted. 

Alfalfa Weevil Threshold

More Information: 

  1. More information about scouting, managment, and lifecycles can be found at: Alfalfa Weevil on Alfalfa| Ohioline Fact Sheet
  2. Specific chemical control options can be found at: Control of Insect Pests of Field Crops | PDF