The following refers to trap counts taken on June 2 of Drosophila suzukii, previously (incorrectly) identified in this post as Drosophila biarmipes.
Several raspberry fields have fairly high counts of D. suzukii now. One in the vicinity of Peckham Rd and another on Riverside Rd have counts in excess of 50 D. suzukii males (identified by the spots on the back of each wing) per trap, numbers which would be consistent with some fruit damage. Another raspberry planting on Thompson Rd also has seen an increase to 28 male flies found in one trap. It is recommended in these cases to start a program of control.
Two farms which have been applying GF 120 fruit fly bait since the end of March/ beginning of April have seen sharp reductions in the numbers of D. melanogaster and D. suzukii trapped. While this is not a controlled study with an untreated check, it does suggest that consistent, weekly applications of GF 120 fruit fly bait are useful in reducing numbers of this pest.
Another point of interest is that one raspberry plantation that had increasing numbers of vinegar flies (both D. melanogaster and D. suzukii) made a series of 3 applications of Entrust (which contains the same active ingredient as GF 120 fruit fly bait) over a two week period to control leaf rollers. The last trap reading had a single vinegar fly found, again suggesting some effect of this pesticide on the vinegar fly population. However, this is not a trial with an untreated control, so this evidence should be understood as being anecdotal only.
To date, blackberry fields have had very few flies trapped.
It is very important to know that what has been identified in this blog as Drosophila biarmipes in this post is actually Drosophila suzukii. From this point on, all posts referring to the new species of vinegar fly will refer to Drosophila suzukii.
Lately there has been some concern about leafrollers in raspberries, so it is important first for growers to know how to identify what a leafroller looks like in order to make correct pest management decisions.
Leafrollers are generally true to their name, meaning they will roll leaves up to form a shelter with a whitish webbing. They will also form shelters between several leaves, growing points of plants, developing flowers and fruit. This is a sure way to distinguish leafroller larvae from other larval pests in the caneberry field.
The leafroller larvae themselves in raspberries are green in color and will move about vigorously (if healthy) when disturbed. This compares to other larval pests found in caneberries which are either sluggish to respond or a distinct method of movement, such as the looper described below.
It is important to note that it is almost impossible to distinguish leafroller species from one another in the field. Generally, identification of leafrollers needs to be done under a microscope or through DNA analysis, and indeed this has been the case lately with light brown apple moth.
Please be aware that the Monterey Bay Academy Field Day will take place this coming June 19. Click the link below to access the agenda:
Don't miss this one!