Late July- Pest News for WNC Fruit and Vegetable Growers

FRUIT AND VEGETABLES

From: Hannah Burrack, Extension Entomologist

End of Harvest Concerns in Blueberries

As blueberry harvest nears the end in some areas of North Carolina, a few important insect related issues require some attention.  

Spotted wing drosophila in processing fruit

Rainfall makes spotted wing drosophila (SWD) management more challenging (http://strawberries.ces.ncsu.edu/2013/05/swd_in_rain/), as growers have discovered in the last two months.  As we move into the end of blueberry harvest, fruit being picked for processing is at higher risk for SWD infestation for several reasons: It is often softer than fruit picked for the fresh market and SWD prefer soft fruit (http://news.ncsu.edu/releases/wms-burrack-suzukii-2013/). Processing fruit may be harvested less frequently than fresh market fruit, increasing the time ripe berries are exposed to SWD. Finally, because processing fruit is often machine harvested, all the fruit in the field (good and bad) may be picked.

There are some strategies that growers can employ post harvest to decrease the likelihood that SWD infested fruit will be sent off for processing:

1. Hold fruit at cool temperatures. Work in our lab suggests that SWD eggs and larvae cease development at temperatures less than 41F. They will not necessarily die at cool temperatures, but they likely will not cause further damage to the fruit. The longer fruit are stored and the cooler the temperature of storage, the more likely that small SWD larvae will die. Holding fruit at cooler temperatures also give growers the added benefit of determining how significant the infestation, as large larvae will exit fruit as it cools.

2. Sort out soft fruit. Soft fruit is the most likely to be infested with SWD for two reasons – egg laying SWD are more attracted to soft fruit and blueberries become softer as SWD feed. If growers can remove soft fruit before sending fruit for processing, this will further decrease risk of infestation being present. I suspect our aggressive soft sorting standards for fresh market blueberries are one of the reasons that SWD has been a less significant issue in this crop than some other hosts.

3. Sample collection timing. When receiving fruit, processors can either collect samples before or after fruit are sorted/de-stemmed. Samples collected before fruit has been soft sorted are not necessarily representative of the status of the fruit that will be processed. Samples of fruit after chilling and sorting, prior to processing/freezing, are likely more representative.

Post harvest leafhopper treatments

Treatments to manage sharpnosed leafhopper (http://ipm.ncsu.edu/small_fruit/hopper.html) vectors of blueberry stunt disease typically begin post harvest (http://pemaruccicenter.rutgers.edu/assets/PDF/Blueberry/iSharp-nosed_Leafhopper.pdf). Blueberry stunt disease is caused by a phytoplasma, and symptoms include "bushy" growth due to short, stunted branches and yellowed leaving during the growing season which may prematurely turn red and fall off in late summer. Most importantly, plants infested with stunt-causing phytoplasma do not produce. 

Aerial applications of ULV (ultra low volume) malathion has been used in the past for leafhoppers due to effectiveness and ease of application. However, many growers have also used this material for SWD management during the season, and careful attention must be paid to label restrictions on the number of applications that can be made of materials when selecting tools to manage sharpnosed leafhopper. Application limits apply to the entire growing season, not just harvest season, so label limits on the number of applications also apply to leafhopper treatments. Application limits apply to the amount of active ingredient, not the trade names of those active ingredients. Sources for updated labels with current use restrictions include CDMS (http://www.cdms.net/Home.aspx) and Agrian (http://www.agrian.com/home/label-lookup/overview).

Alternatives to malathion that are effective against sharpnosed leafhopper include Assail (acetamiprid) and Asana (esfenvalurate).  Imidaclorprid and thiamethoxam are also options for sharpnosed leafhopper. The North Carolina Agricultural Chemicals Manual (http://ipm.ncsu.edu/agchem/agchem.html) has recommendations for the use of these materials. It's important to note, however, that all these materials pose some risks to pollinators. While blueberries are not in bloom, some of our most efficient blueberry pollinators (http://repository.lib.ncsu.edu/ir/handle/1840.16/7822) are ground nesting bees that may remain near fields after bloom. Therefore, any insecticide treatments should be timed to leafhopper flights, ideally determined through trapping, to provide maximum efficacy against target pests and limit unnecessary applications. See http://ncsmallfruitsipm.blogspot.com/2011/04/practicing-what-we-preach-implimenting.html for information on trapping and the following for images, http://ipm.ncsu.edu/small_fruit/hopper.html, to aid in sharpnosed leafhopper identification.

From: Lina Quesada-Ocampo, Extension Plant Pathologist

Cucurbit Downy Mildew Moves Towards Western North Carolina

Cucurbit downy mildew has been reported in Haywood, Polk, Ashe, Henderson and Chatham counties (http://cdm.ipmpipe.org/scripts/map.php) during this past week. Now that cucurbit downy mildew is present in several regions of North Carolina and surrounding states, it’s important that growers scout for the disease and keep up with preventive sprays to protect their crop and avoid yield loses.

If you are not familiar with cucurbit downy mildew symptoms on different cucurbits please see our previous alert (http://plantpathology.ces.ncsu.edu/2013/07/do-you-know-how-to-diagnose-cucurbit-downy-mildew-in-different-cucurbit-crops/) to assist you in diagnosing this foliar disease. If you think you have cucurbit downy mildew in your cucurbits please contact your local Extension agent (http://www.ces.ncsu.edu/local-county-center/) and send photos and/or physical samples to the Plant Disease and Insect Clinic (http://www.cals.ncsu.edu/plantpath/extension/clinic/submit-sample.html).

For more information about the disease and how to control it, see our factsheets in English and Spanish (http://projects.cals.ncsu.edu/veggiepathology/disease_factsheets). Control recommendations are also available in the cucurbit downy mildew IPM pipe website (http://cdm.ipmpipe.org/index.php), where you can also register to receive text, e-mail and/or phone alerts when new disease outbreaks are reported. We have also compiled previous cucurbit downy mildew alerts athttp://plantpathology.ces.ncsu.edu/tags/cdm/.

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