Alfalfa
Be sure to begin sampling for pea aphid and alfalfa weevil. When sampling for aphids and weevils, collect a minimum of 30 random stems throughout a field and place them top first in a white bucket. For aphids, you want to count the number present per plant as well as any that have dislodged from the stem into the bucket. As a general guideline, you should consider a treatment in alfalfa less than 10 inches tall if you find 40-50 aphids per stem. The treatment threshold for alfalfa 10 inches or taller in height is 75-100 per stem. Although beneficial insects can help to crash aphid populations, the recent cool temperatures have slowed their activity. As a general rule, you need one beneficial insect per every 50-100 aphids to help crash populations. For alfalfa weevil, you will want to record the number of weevil larvae per stem. The following thresholds, based on the height of the alfalfa, should be used as a guideline when making a treatment decision: up to 11 inches tall – 0.7 per stem; 12 inches tall – 1.0 per stem; 13 – 15 inches tall – 1.5 per stem; 16 inches tall – 2.0 per stem and 17 – 18 inches tall – 2.5 per stem
Field Corn
During our sampling for slugs this past week, we have observed low levels of adult marsh and grey garden slugs. We have not yet seen any signs of grey garden slug egg hatch. In general, the grey garden slug causes the majority of damage in our corn fields. Therefore, scouting for eggs and watching for egg hatch will help identify potential problem fields. For more information on scouting for slugs eggs, please watch the following video from Ohio State University: http://oardc.osu.edu/ag/pageview3.asp?id=2087
To help you keep track of Bt corn traits, efficacy, and refuge requirements for the 2015 season, Chris DiFonzo, Field Crops Entomologist from Michigan State University, has updated the Handy BT Corn Trait Table: http://msuent.com/assets/pdf/28BtTraitTable2015.pdf