Saskatoon Sawfly & Saskatoon Bud Moth
POSTED IN For Growers ON 5/19/2016
First Documentation of Saskatoon Sawfly in Michigan – May 13, 2016
Late last week I observed saskatoon sawfly (Hoplocampa montanicola) for the first time in Michigan, at the Northwest Michigan Horticultural Research Center in Leelanau County. I had suspected that some fruit injury seen at this site in 2015 was due to this insect, and growers had previously reported injury of a similar nature, but this was the first time the insects have actually been found.
Adult saskatoon sawfly
Adults of the saskatoon sawfly were plentiful (more than ten on a bush at some times) and very actively flying amongst the flower clusters (plants were at approximately 50% bloom at the time). Although I observed the sawflies for some time, I was not able to actually see one attempt to lay eggs. Based on what I have gathered from Canadian references, the egg laying behavior might not start until the flower ovaries start to swell after fruit set. Good pictures of the egg laying scars, larva and fruit damage can be seen at http://www.prairie-elements.ca/saskatoon/11.2-insects1.pdf. The potential threat for fruit losses in Michigan has not been determined, but this pest is an important one in Alberta and Manitoba.
Saskatoon sawfly is not listed in the 2016 Saskatoon Berry Pesticide Recommendations that I released earlier this spring. Based on recommendations made for a related pest of apples in Ontario, sprays of Assail, Altacor or Exirel at petal fall would be the best choice. These are all toxic to bees, so it is important that all bee activity be completed before the application.
Larvae of Saskatoon Bud Moth Now Active
On the same date and location I also noted the first larvae of saskatoon bud moth (Epinotia bicordana) for the season. Small larvae, a little over 0.25 inches in length, were feeding inside nests of tender leaves they had webbed together with silk. They must have been active here much earlier, as their first feeding of the year occurs as they bore into the bases of swelling buds. They were not numerous, so the early feeding on buds would likely have been very hard to detect. According to Canadian literature, the development and feeding of the larvae is
completed by the time of petal fall; the early season feeding inside buds is the damaging time as it can kill entire buds or injure some of the flowers. The later feeding on leaves is of no consequence to production. The importance of saskatoon bud moth to production in Michigan is uncertain. It is too late this year for sprays to reduce bud injury or fruit loss.
Leaves tied together by saskatoon bud moth larvae (left), and close up of a larva (right).
Duke Elsner, Small Fruit Educator, Michigan State University Extension firstname.lastname@example.org