Lebanon Crop Management Video


19 May 2016

Slug Management and Options-

 Del Voight Penn State Extension
SLUG RESOURCES  Slug Resources

There are numerous pests of corn and as the plants emerge it is important to scout to determine if there any insect issues that need to be addressed.  There are two pests that are active that we have received calls this week regarding leaf feeding  those being slugs and cutworms.
Right of center with residue and 1 stage earlier than left of center with vertical tillage graphic difference in level of slug injury no yield difference at the end of the season.

 Slugs – Slugs are active and small the gray garden slug is measuring about ¼ but can be found easily now under surface residue… They  can severely impact the development of corn if prolonged wet weather is occurring. If we get dry windy weather the slug issue will go away as quickly as it emerged with the exception of side wall compaction when they feed under the soil line and are not subject to weather.  My experience with slugs is that leaf feeding is not a huge issue provided dry weather returns,  however,  if the slugs attack the seed due to sidewall compaction they can kill plants and set seedlings back weeks before recovering. To avoid this pest here are some methods.
Avoid sidewall compaction
Utilize Starter and trash cleaners
Check in the fall and the spring for activity

Step up field visits when wet prolonged weather exists.
Monitor populations
An open slit with sidewall compaction ideal for the worst injury from slugs in the row with the seed.
If one looks closely about 2 inches below my finger you will see two grey garden slugs huddled together on a windy day they will seek moisture and no air movement.
Treatments  - There are numerous methods to deal w
An example of field with sidewall compaction and tremendous slug population that is feeding right in the row with the seed
ith slugs and results will vary in control.  Likewise the cost of these materials and methods can impact the management option.
Trash cleaners, zone tillage
Deadline MP or other baits in row under severe infestation. Cost - @$2.20/lb would require 10lb if banded and 40 lbs if broadcast.($22-84/acre)
Broadcast or band over the row as rescue.  Here is what Galen Dively found in his work from the early 90’s.
Liquid UAN half and half sprayed at night. (Growers report success when the slugs are visible during application). Cost - @2.00/gal at 10 gallon per acre= $20/acre
Galen Dively from University of Maryland did some experimenting with this tactic and this is what he found many years ago.

Tillage – this practice disrupts hiding places and also allows the soil to dry. Replanting is required so this would be the most expensive. Below are some preliminary reports from Joanne Whalen related to slug management and trends in tillage.
Tillage Demonstration to Determine the Impacts of Various Tillage Treatments on Corn Plant Feeding Injury from Slugs
      Tillage demonstration plots were established with one cooperator in two different fields near Middletown, Delaware to evaluate the impacts of various tillage treatments in reducing corn injury from slug feeding.  Tillage has been used as a control or management strategy to reduce the risk and severity of slug damage to crops.  To determine the effectiveness of tillage in reducing slug damage, demonstration plots were established by dividing a field into thirds and performing three different tillage treatments prior to planting including; 1) no-Till, 2) disking and 3) chisel plowing and disking.  Prior to performing the tillage treatments, three shingle traps 1’ x1’ were randomly placed in each of the plots to establish an estimate of slug densities within the plots.  Using line transect methods, the percentage of crop residue remaining on the soil surface was also estimated prior to performing the tillage treatments.  The percent of plants with slug feeding injury was estimated by dividing each tillage treatment plot into four quadrants and evaluating 5 consecutive plants for a total of 20 plants in each of the plots.  The presence or absence of slug feeding injury and a damage rating was assigned for each plant on a scale of 0-4.  The percentage of damaged plants and average plant injury rating was then calculated for each plot.

Chart 9.  Pretreatment Slug Counts, Plot A

Chart 10. Pretreatment Slug Counts, Plot B

Chart 11. Slug Damage Evaluations: Percent of Damaged Plants for Plot A & Plot B, 3 Leaf Corn
Chart 12.  Slug Damage Evaluations: Average Damaged Rating for Plot A & Plot B, 3 Leaf Corn
Conclusions: The pre-treatment slug counts varied greatly across the tillage plots for both locations by slug species and in the presence of adults and juveniles.  This variability is consistent with what has typically been found in crop production fields.  Despite this variability, as expected, there does appear to be a trend of a higher percentage of plants with slug feeding injury in the no-till plots compared to the disked and chisel plowed plots for both locations.  The average damage rating for each plot also follows the same trend in that the no-till treatment plots exhibited more severe feeding injury that the disked and chisel plowed plots.     
The use of Lannate insecticide is another option however it comes with some baggage related to beneficial insect reduction and is the last resort option at this time.
Visual Slug Counts, Feeding Injury Percentages and Shingle Trap
Treatment Timing
5/21 (2 Days After Treatment)
5/25 (5 Days After Treatment)
Grey Garden Slugs
Marsh Slugs
% of Plants with Slug Feeding Injury
Shingle Trap Slug Counts
# of Grey Garden Slugs
# of Marsh Slugs
Early Evening - 6:55 PM
Lannate LV (2.4 SL)
1.5 pt
Late Evening - 9:40 PM
Lannate LV (2.4 SL)
1.5 pt
Early Morning - 5:15 AM
Lannate LV (2.4 SL)
1.5 pt
Untreated Check
<Means in the same columns followed by the same letter are not significantly different (Tukey’s; P=0.05)
<Conclusions:  At two days after treatment, there were significantly fewer grey garden slugs in each of the treatments compared to the untreated. However, there were no significant difference between the treatments and the untreated check for the marsh slugs.  At five days after treatment, there were no significant differences between the treatments and untreated check for the percentage of plants with slug feeding injury and slug counts under the shingle traps for either the grey garden slug or the marsh slug.  Overall, grey garden slugs appeared to be the most prominent species causing damage to the corn plants and the marsh slug densities were low based on visual observations at night.  The level of control that was obtained 2 days after treatment is promising; however, additional studies will need to be conducted to determine the efficacy of Lannate (methomyl) to control slugs in field corn. Additional information is also needed to determine the best time of application and the length of control.

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