2008 small fruit insect summary

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

Insects have continued to give grape, blueberry, strawberry, and raspberry growers some challenges in 2008. Spring rains and windy conditions made control of some early season insects difficult, especially if timing of application was critical. Some vineyards had frost damage that led to low cropload and so some vineyards have had a minimal pest management program this year. This season was slower than 2007, but more like an average year in terms of weather and crop development, although there was a long dry spell in mid-summer that held back populations of some pests. Overall, 2008 has seemed like an average year for insect pests in Michigan’s small fruit crops.

Blueberry

This year the Guthion phaseout started to restrict the use of this key insecticide, and so blueberry growers have been testing alternatives for fruitworm control including Intrepid during bloom and Imidan, Asana, and Sevin applied after bloom. The insect growth regulator Intrepid was registered early in 2008, and this was used widely during bloom in place of Confirm. All indications from our research and from talking with growers during the season are that the 12 oz rate of Intrepid was very effective against cranberry fruitworm, and we expect this product to replace Confirm. Growers who used this product during bloom had superior control of fruitworms compared with those that did not. The alternatives to Guthion mentioned above that were used after bloom also worked well for cranberry fruitworm if applications were timed correctly. We have also conducted trials at grower cooperator farms with Assail and Delegate, two new insecticides registered for blueberry. A program with Intrepid in bloom followed by Assail and then Delegate after bloom was as effective at controlling cranberry fruitworm as a standard Confirm followed by two Guthion sprays.

The Achilles heel of fruitworm control programs in 2008 seemed to be accurate timing. Some fields did not get protected in time for various reasons, and the result was seen a few weeks later as fruitworm infestation became visible. Reports of cherry fruitworm infestation were more common this summer, and this is a pest where the early activity of this insect is catching growers by surprise. Understanding the monitoring and early activity of cherry fruitworm is part of an ongoing research project at MSU and we will focus on reporting about our results on fruitworm management this winter at grower meetings. Another big challenge to good insect management this spring was Mother Nature. A few 80°F days coupled with windy and rainy conditions made fields in bloom quickly move through petal fall, leaving fruit exposed to cranberry fruitworm egglaying, but not suitable weather for growers to apply protective sprays. Depending on the stage of development of the varieties, this caused some fields to experience higher fruitworm infestation this season.

Blueberry maggot activity was variable across blueberry fields this year as usual, but we did see a long and high level of activity at some of the non-managed farms that we trap flies at. In particular, traps at the Trevor Nichols Station in Fennville trapped very high numbers and continued catching flies much later than usual. A potential explanation is that the dry 2007 summer caused flies to stay in the ground for an additional season (blueberry maggot has the flexibility to do this), leading to a higher and longer emergence this year. Growers following a good IPM program that are monitoring and responding to fly activity should have been able to achieve high control of this pest.

As usual, Japanese beetle activity started in early July and continued through into September. Growers have learned the host spots on their farms over recent years and know what products work the best to prevent this beetle from being present at harvest time. We have also seen more fields using the combined system of bare ground in summer, to remove egglaying sites for beetles, followed by a winter rye cover crop. Seeding this after harvest gives it time to grow through the fall and provide soil stability in winter and spring before mowing and tilling again the next year.

A new pest that has been growing in abundance over the past few years is Putnam scale. This insect creates a small brown scale, one to two millimeters in diameter, over itself for protection and moves onto leaves, stems and fruit in mid-late summer. A few processing sheds and fields visited during August had infestations with one or more scales on berries, and reposts of this insect over the past few years have come from across the main production region in west Michigan. For photos of this pest, see the MSU blueberry website www.blueberries.msu.edu/scales.htm. This is a pest that growers and consultants should be monitoring for, and if fields have been infested in 2008, a spring application of oil to suffocate the overwintering scales should be planned for early 2009. Coupled with an active pruning program, this can go a long way to minimizing the activity of scales in blueberry.

Grape

The season started off with frost damage hitting some vineyards during the flea beetle and cutworm activity period. This cold weather cut back populations of these pests and also took away their food in some sites. By the time secondary buds pushed, the danger from these pests was largely over. We also observed grape cane gallmaker and banded grape bug (see a photo at www.grapes.msu.edu/bandedbug.htm) early in the year, but levels of these pests were below economic thresholds.

Potato leafhopper moved into Michigan this spring on the rain fronts, but most of the pressure dropped off quickly, with little reinfestation. Consultants reported scouting vineyards and seeing such low numbers that insecticides weren’t warranted, while for others a single treatment prevented this pest for the season.

Grape berry moth populations started lower this year in the first generation, perhaps because of the low survival in late 2007. Despite the slow start, populations have caught up through the season and this is now close to the average level of infestation we have monitored over the past five years. Vineyards in the Traverse City area are reporting more infestation from this insect, and this insect will require attention next year in some sites to prevent the berry splitting and associated diseases that can use the holes to enter berries. We have been testing Grape berry moth control programs on-farm this season and have seen good activity from eight oz/acre of Intrepid applied to high risk vineyards in mid-July to cover the long period of egglaying by this pest. Additional studies testing two new products from DuPont, Altacor and Avaunt, applied for berry moth control have looked as good as the conventional program, though pre-harvest samples remain to be taken in these Concord vineyards.

Japanese beetle pressure in vineyards was not as high in some previous years, though some growers needed to protect their vines with insecticides to prevent leaf damage. This was especially true in some winegrape vineyards with susceptible varieties or small vineyards with low leaf area. Berry moth sprays were also timed to catch Japanese beetles and we heard variable opinions on levels of this pest from “not too bad” to “much worse this year.” Populations of this pest are usually very variable, and the level you experience will depend on where your vineyard is located, how good the local landscape is for supporting Japanese beetle (was there moist grassy land nearby last year?) and the weather conditions this year. In the northwest growing region, Japanese beetles have been seen in very low numbers, but it is clear that these beetles are getting established in this region.

Over the past few weeks, a few reports have come in of mite bronzing on labrusca vines and high grape leafhopper infestations in some vineyards around Lawton. This emphasizes the need to remain vigilant in scouting vineyards and planning an IPM program for your 2009 season that can prevent these problems next season.

Strawberry

Potato leafhopper populations were moderate, but still caused leaf curling symptoms on fields, especially young ones, that did not get protected. During harvest, sap beetle populations were high in some sites, with reports this summer of growers being forced to close U-pick farms. Cyclamen mite was found this year too, emphasizing the need to purchase plants from reputable nurseries that minimize the chance of you bringing this pest into your farm.

Finally, a big thank you to all the growers who provided research sites for our on-farm projects and also opened their farms for extension meetings this summer. See you in 2009!

Dr. Isaacs’s work is funded in part by MSU‘s AgBioResearch.

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