Posts Tagged ‘tree fruit’

Weather Worries for Fruit Growers

Thursday, March 29th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Peaches, plums, and apricots have bloomed, several weeks ahead of normal. Strawberries have been blooming for weeks in plasticulture systems. These fruit crops are at great risk of losses due to freeze events. Other fruit may also flower early and be at risk. For example, pears are in bloom now and cherries and blueberries are starting to bloom.

Normally, the average date of the last frost in Delaware is somewhere between April 20-25. We still have four weeks of worry ahead for our fruiting crops.

For all these fruit crops the most susceptible stage of injury is when flowers have just opened. Closed buds have higher cold tolerance as do small fruit. For most fruits, critical temperature for losses after fruits have formed is 28° F.

 Plasticulture strawberries blooming 3- 29-2012.

Frost and freeze protection methods vary with fruits and the type of freeze expected. Advective freezes occur with freezing temperatures and high winds. This is the most difficult to protect against. For strawberries, two layers of floating row covers may be the most effective strategy for advective freezes. Double covers have been shown to be more effective than single heavy covers in this case. Irrigation along with double covers can provide even more protection if done properly.

Radiational freezes occur on cold, still nights. In this case cold air is near the ground and warmer air is above. Wind machines and helicopters have been successfully used to stir the air and raise the temperatures in orchards in this case. Row covers in strawberries will protect against radiational freezes too.

Irrigation has also been successfully used for frost protection but it has to be done properly. How irrigation works is that as ice forms on plants heat is released. The key is to keep ice formation occurring through the night and continue through melt in the morning. Remember that initially, until ice starts forming, there will actually be evaporative cooling of the plant. The latent heat of fusion (water freezing) will release heat (approximately 144 BTUs/lb of water), whereas evaporative cooling will absorb heat from the plant (absorbing approximately 1,044 BTUs/lb of water) and lower plant temperatures. Therefore, irrigation must start well above critical temperatures. Also, the volume of water needed needs to be matched with the expected temperature drop and wind speed. In addition, uniformity of water application is critical. This is difficult to do in high wind situations.

This past week temperatures dropped below freezing in parts of Delaware on three nights, with some areas in the mid-twenties. NOAA has predicted an increased risk for lower than normal temperatures in the Mid-Atlantic region for the next 2 weeks.

Be Sure to Monitor for Spotted Wing Drosophila in Strawberry and Brambles This Year

Friday, March 2nd, 2012

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

By now everyone should know that the newest invasive pest, the spotted wing drosophila (SWD), is here in the mid-Atlantic. It was found heavily infesting blackberries and raspberries in central Maryland this past summer and fall. Just about everywhere we trapped for it (I am still trapping adults in February in brambles, SWD overwinter as adults) we have found it on the western shore. We know it is on the eastern shore through trapping efforts by the University of Delaware. What we do not know about the eastern shore is how bad SWD infestations might be this coming season. The first crop that may get hit is strawberries. Information from Oregon and Michigan shows that their strawberries are not attacked to any great extent, but we DO NOT know what the fly may do to our strawberry crop. That is why it would be prudent to put SWD traps out and monitor for the adult flies. Males have a spot at the end of their wings (Photo 1), females do not (Photo 2), but the females do have a strong ovipositor they use to saw into non ripe fruit and lay their eggs—which is why they are such a devastating pest.

Most growers we visited did not think they had SWD on their farm and yet we found it everywhere we looked. The damage is often mistaken for early rotting berries or fruit (Photo 3). Early control is essential, if this fly is allowed to build its population through the summer into the early fall it will be very difficult to control and will be present on your farm basically forever. There are several web sites you can use to build your own traps (just Google spotted wing drosophila traps), or you could ask for help from me or your Extension educator about trapping. The key is to use a very common, inexpensive product as bait in the traps – apple cider vinegar. Traps should be placed in the field within the plant canopy, out of the sun if possible, and checked once a week for flies. Some traps should be located near the edge of the strawberry field and others along a woods edge. There will be many fly species in the trap, if you are not sure you have SWD take it to your local Extension educator for identification.

Photo 1. SWD adult male

Photo 2. SWD adult female

Photo 3. SWD damage to blackberries

Spotted Wing Drosophila Verified in Delaware

Friday, March 2nd, 2012

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

We finished our 2011 SWD monitoring activities in late September in a commercial vineyard and we did not detect any SWD adults in our traps. However, traps that were set out near the Milford area from September through December did collect flies which were verified by a USDA identifier in January 2012 as SWD. During the 2011 season, this pest made its way to Virginia, Maryland, Pennsylvania and New Jersey, so it was only a matter of time before their presence was confirmed in Delaware. As you start the season you will need to consider this pest when making management plans.

These flies can infest and cause a great deal of damage to ripening fruit, as opposed to the overripe and fallen fruit that are infested by most other Drosophila species. Females damage fruit by slicing through the skin with their knife-like ovipositor, and inserting eggs that develop into small white larvae. These cuts can also be a pathway for fungal pathogens, leading to greater reductions in fruit quality. Therefore, monitoring for SWD is important to avoid economic loss. This insect is a pest of most berry crops, cherries, grapes and other tree fruits, with a preference for softer-fleshed fruit. In areas where it has been detected, it is has become an important pest of cherries, raspberries, blackberries, blueberries, strawberries, grapes, peaches, and plums.

For more information on monitoring, identification and control of this insect pest, please check the following links:
http://www.ncipmc.org/alerts/drosophila.cfm
http://swd.hort.oregonstate.edu/

Update on Brown Marmorated Stink Bug on Tree Fruit – August 12, 2011

Friday, August 12th, 2011

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Please refer to the most recent update from Tracy Leskey, USDA-ARS regarding BMSB activity in tree fruit at: http://agdev.anr.udel.edu/weeklycropupdate/wp-content/uploads/2011/08/BMSB-Tree-Fruit-Update-8-8-11-2.pdf.

The photo above, courtesy of Gordon Johnson, is of BMSB damage to peach fruit.

Section 18 for Brown Marmorated Sting Bug (BMSB) Management on Stone and Pome Fruit Approved

Friday, July 1st, 2011

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

This week we received the letter from EPA that they approved our Section 18 request for the use of dinotefuran (Trade Names: Venom from Valent U.S.A. Corporation; Scorpion from Gowan Company, LLC) to control BMSB on stone and pome fruits. This use expires on Oct 15, 2011. Please refer to http://agdev.anr.udel.edu/weeklycropupdate/wp-content/uploads/2011/07/DinotefuranSec18.pdf for more information on use rates and restrictions. Both labels are also available so please contact either David Pyne at the Delaware Department of Agriculture (David.Pyne@state.de.us) or Joanne Whalen (jwhalen@udel.edu) for more information.