Spring 2016 field crop insect issues update for southwest Michigan

Timely scouting is a critical component to a good insect pest management program.

Michigan State University Extension field crop entomologist Christina DiFonzo presented timely information on insect pests of field crops at an integrated pest management (IPM) meeting on May 31, 2016, in St. Joseph County. DiFonzo answered several questions from participants on a wide range of topics and insect species, including corn rootworm, soybean aphid, alfalfa weevil, western bean cutworm, corn borer and even ticks. However, the overall emphasis was placed on careful scouting, particularly if pest pressure has been high in a given field or if regional reports warrant local investigation.

As DiFonzo noted in “Weeds, wet weather and cutworms” in early May, true armyworm and black cutworm moth captures were very high in Indiana in late-April with peak flight occurring the week of April 21–27 in Whitley and LaPorte counties, according to Purdue University Pest and Crop Newsletter, Issue 8. True armyworm and black cutworm moth captures appear to have peaked around mid-May in East Lansing, Michigan, this spring according to “Armyworm and black cutworm trap catches for May 2016” by DiFonzo.

During the meeting, DiFonzo noted that since St. Joseph County lies approximately halfway between the northern Purdue University sites and the MSU campus, peak moth flight times for black cutworm and armyworm were likely in early May. This estimation agrees with moth capture counts in traps located in St. Joseph County this spring (Table 1). Incidentally, the very high weekly trap catches at Purdue University sites cannot be directly compared with those from MSU trap counts as the types of traps were different. However, relative numbers can be used to estimate peak flight times in each area.

As DiFonzo noted previously, scouting for crop damage in corn from the larvae of black cutworm and armyworm should generally begin 300 degree-days after a significant moth capture. According to MSU Enviro-weather station data from south central Michigan, all station locations had received more than this many heat units during the month of May (Table 2). Begin scouting fields now, particularly if you have fields that had green vegetation (live cover crops, winter annual weeds, grasses) when significant moth captures were recorded in the area.

Table 1. True armyworm and black cutworm moth captures at three locations each (weekly totals in bold) in St. Joseph County, Michigan. Moths were trapped using pheromone lures and wing traps with sticky trays.

Week 1: Apr 29-May 6

Week 2: May 6-13

Week 3: May 13-20

Week 4: May 20-27

True armyworm

15

1

1

0

16

0

0

0

24

8

4

0

55

9

5

0

Black cutworm

8

1

0

1

7

8

1

0

35

3

1

1

50

12

2

2

 

Table 2. Number of growing degree-days (base 50 F, maximum 86 F) from May 1–31, 2016 at several Enviro-weather stations in south central Michigan.

Station

Growing degree-days (86-50)

Coldwater

330

Hastings

344

Leslie

346

Charlotte

359

Kalamazoo

363

Constantine

370

Mendon

377

The St. Joseph County IPM Breakfast Series is organized by the MSU Extension field crops team in southwest Michigan. The meetings run through the end of June and are held on Tuesdays at the Royal Café in Centreville, Michigan, beginning at 7 a.m. Each meeting includes an update of the major field crops grown in the region, including a crop and pest report, followed by a presentation from a guest speaker on a topic important to crop production. Participants can order breakfast and eat during the meeting.

The speaker for June 7 will be MSU plant pathologist Martin Chilvers who will address the topic, “Field Crop Disease Issues.” The meeting will be sponsored by Mike Schrock with Advanced Farm Supply, Inc. in Burr Oak, Michigan, and CEU and RUP credits will be available. Meetings are open to the public. For more information on this breakfast meeting series, contact Eric Anderson at the MSU Extension St. Joseph County office at 269-467-5511.

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