Venom Approved for BMSB in Some Fruit

David Owens, Extension Entomologist, owensd@udel.edu and Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

A Section 18 label for Venom (dinotefuran) has been approved for use on Delaware stone and pome fruits for brown marmorated stink bug management. This chemical has lower risk to beneficial insects. Maximum size of fruit orchard treated with Venom is 415 acres. There is a 12 hour REI, 3 day PHI.

Guess the Pest! Week #9 Answer: Plum Curculio

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Congratulations to Sylvie Childress for correctly identifying the ovipositioning scar and larva in the photos below as plum curculio and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Click on the Guess the Pest logo to participate in this week’s Guess the Pest challenge!

Guess the Pest Week #9 Answer: Plum Curculio

The plum curculio is a pest of apples, peaches, plum, and other stone fruit. The adult beetles are about ¼” in length, dark brown with patches of white, and have a protruding snout. They belong to the weevil family, commonly referred to as the snout beetles.

Adult Plum Curculio

The primary damage to fruit is caused by the ovipositioning or egg laying behavior of the female plum curculio. The females lay eggs in the developing fruit and cut a crescent shaped slit beneath each egg to prevent the rapidly growing fruit from crushing the egg. As the fruit continues to grow, the slit the female beetle cut below the egg develops into the classic, crescent shaped scar that you see in the photo above. These scars are usually only cosmetic. However, if the egg hatches, the larva will bore into the fruit, which will usually cause the fruit to drop from the tree. After a couple weeks of feeding on the fruit, the larva will exit the fruit to pupate in the soil.

In addition to the crescent shaped ovipositioning scars and fruit drop, the adult beetles will also feed on fruit, creating numerous round puncture holes in the fruit skin. It has been estimated that a single beetle will average over 100 feeding and/or puncture wounds during its lifespan.

Fun Entomology Fact: The family Curculionidae (true weevils), are the largest family of insects with the most species described worldwide.

False Spring Concerns – Again

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

Some peaches, nectarines, plums, and apricots have started to bloom — four weeks ahead of normal. Other fruits such as strawberries may be blooming ahead of schedule in plasticulture systems. These fruit crops are at great risk of losses due to freeze events. Other fruits such as pears, cherries, and blueberries may also flower early and be at risk.

The expected temperatures near 20°F at the end of this week will damage many of these flowers. The long range outlook for March and April shows a return to more seasonable weather which will slow bloom. However, crops already in bloom will be exposed to the potential of freezing temperatures throughout the rest of March and April.

Peach in various stages of flowering including open bloom, the most susceptible state to freeze damage on March 2, 2017.

Open nectarine flower on March 2, 2017.

Plum with high percentage of open flowers on March 2, 2017

Pluot in full flower on March 2, 2017.

Normally, the average date of the last frost in Delaware is somewhere between April 20-25. We still have seven 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. Open blooms are damaged at 32-34° F. Blooms prior to opening have higher cold tolerance as do small fruit. For most fruits, critical temperature for losses after fruits have formed is 28-30° F.

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.

Radiation (or radiant) 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 radiation freezes too. Other options are over the top sprinklers, ground sprinklers, and heaters.

Over the top sprinkling is commonly used for frost protection but it has to be done properly. How this works is that as clear ice forms on plants heat is released. For frost production, overhead sprinkler systems are designed to deliver 0.1 to 0.2 acre-inches of water per hour. This method is used for radiant freeze or frost protection when wind speeds are low and temperatures 24°F or above. 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 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. In orchards, under-tree sprinklers can also be used to release heat (hot air then rises, protecting blooms).

Heaters that are placed throughout an orchard will add heat. Large numbers of small heaters are preferred (40 per acre). This is accomplished with fuel oil fired heaters, gas/propane heaters, or burn barrels using wood or other fuel (check with regulatory agencies before using open burning in barrels). Heaters are much more efficient and less are required if they are used in conjunction with wind machines.

Wind machines or frost protection fans above an orchard or vineyard mix the warmer air above the inversion layer with the colder air at ground level to protect against radiation frosts. These large fans can be permanently installed and will cover as much as 10 acres. Another type of fan is placed at ground level and pushes the cold air upward, again achieving mixing. Portable fans are also available.

The following is a good factsheet on frost protection on berry crops: http://www.fruit.cornell.edu/berry/production/pdfs/frost%20protection%20tips%20techniques.pdf

Section 18 Label for Brown Marmorated Stink Bug (BMSB) Management in Stone and Pome Fruit

We just received the notice that our Section 18 request for the use of two dinotefuran products (Trade Names: Venom from Valent U.S.A. Corporation; and Scorpion 35SL from Gowan Company, LLC) to control BMSB on stone and pome fruits has been approved by EPA. This use expires on Oct 15, 2016. You must have a copy of the label in your possession before making an application. The labels contain information on use rate, restrictions, PHI and REI as well as information on pollinator protection. Please see this link for the Sect 18 label for Scorpion 35SL from Gowan Company LLC. Please contact either Christopher Wade at the Delaware Department of Agriculture (Christopher.Wade@state.de.us) or Joanne Whalen (jwhalen@udel.edu) for more information.

Section 18 for Brown Marmorated Stink Bug (BMSB) Management on Apples, Peaches and Nectarines Approved

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

Our Section 18 request for the use of three bifenthrin products (Brigade WSB – FMC Corporation; Bifenture EC and Bifenture 10DF – both from United Phosphorus) to control BMSB on apples, peaches and nectarines has been approved by EPA. This use expires on Oct 15, 2016. You must have a copy of the label in your possession before making an application. Please contact either Chris Wade at the Delaware Department of Agriculture (Christopher.Wade@state.de.us) or Joanne Whalen (jwhalen@udel.edu) for more information.

Revisiting Fruit Losses Due to the Late Freeze and Fruit Drop in Tree Fruits

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu and Emmalea Ernest, Associate Scientist – Vegetable Crops; emmalea@udel.edu

Losses in tree fruits due to the late freeze are now more obvious. As one grower put it “a light crop becomes even lighter”, that is, the damage is not fully known for several weeks. Fruits that seemed to be set often do not develop because the embryos have been damaged.

Plum, pluot, plumcot, and apricots have 80-100% losses. Peaches and nectarines are more variable depending on location and variety. In discussions with growers, some orchards are carrying only a 20% (or less) crop, others are in the 40-60% crop range. However, certain varieties, such as Redhaven and White Lady, and later flowering varieties are carrying a heavier (near full) crop. What remains to be seen is if there is hidden freeze damage to existing fruit leading to continued drop.

Fruit drop is a result of unfertilized or poorly fertilized seeds, freeze damage to buds and flowers (as in this year 2016), competition between fruits, or shading. In other years, fruit drop may be due to poor pollination as a result of cold, rainy weather during bloom in self-fertile fruits such as peaches, or poor insect pollinator activity during flowering in insect pollinated fruits such as apples. In stone fruit, some fruit that is not fertilized will remain on the plant for 25-50 days after bloom and then will drop before pit hardening starts. This is what we are seeing now in cold damaged peaches and nectarines.

Another cause of fruit drop is cloudy weather during the period 5 to 7 weeks after bloom. A continuous 4 day period of cloudy days during this period will cause fruit to drop. In addition, defoliation due to disease such as peach leaf curl, chemical injury such as copper fungicide damage, or severe storms can cause fruit drop during this critical period.

Another wave of natural fruit drop occurs in late May or early June. This fruit drop is due to competition between fruit for sugars stored and produced by the tree. A tree can only carry a certain load of fruit and will naturally drop smaller and weaker fruit during this period. With the light crops in 2016, competitive drop should be minimal. However, when there are large differences in timing of fruit set (late set fruit on the same twig near to earlier set fruit), the larger fruit will become a sink for resources and the smaller fruit will abort leading to further crop reduction.

In 2016, Asian pears and European pears had some flower losses due to the freeze but still have good crops. Most apples were minimally affected by the freeze.

Sweet cherries in the open have high losses; however, those in high tunnels have full crops if they were covered early. Sour cherries have a much reduced crop. One of the issues with sweet cherries is that cross pollination is needed for many varieties. If a pollinator variety suffered damage, the varieties dependent on the pollinator will have reduced crops, compounding the freeze damage.

Marginally hardy fruits such as figs were killed to the base and persimmons were also damaged.

Strawberries also had some fruit losses in both plasticulture and matted row systems and have a higher than normal amount of deformed berries in early pickings. Brambles (raspberries and blackberries) have more tip dieback this year than usual. Early flowering blueberry varieties (mostly Southern highbush) have some freeze loss in our trials at Georgetown, but it will be difficult to estimate yield loss until closer to harvest.

Assessing Freeze Damage in Fruit

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

On Wednesday, April 6, I evaluated a mixed orchard for damage from several freeze events below 25 over the last 3 weeks. Apricots and Pluots were in the post bloom stage and had greater than 90% loss. Plums were also in the post bloom stage and while significant freeze losses of 50% or more are evident, final fruit load is still uncertain. Peaches and nectarines have severe losses but because they flower at very high numbers, final fruit load is still uncertain; however, the early flowering peaches and nectarines that were inspected showed the most damage and are expected to have very light fruit loads or no fruit. All early flowers on cherries were killed. Asian pears in bloom had over 70% losses (see photo below). Apples are pre- bloom and damage is expected to be low.

FreezeDamageAsianPear

Freeze damaged Asian pear flowers. Note the black centers of flowers that have been killed by freezing.

Flowers and young fruit that are dead will be discolored (yellow, brown, black) or shriveled and often will pull off easily from the tree. Viable flowers and fruit will have green ovaries inside and out. You may have to cut open the ovaries with a razor blade to see if they have been damaged.

Freezes, Frost and Frost/Freeze Protection

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

Fruits and fruit flowers are damaged by temperatures below 28°F and by frost. Temperatures in Delaware reached 21°F or lower on April 6. Another freeze is predicted for Saturday, April 9. The term freeze means that temperatures dropped below 32°F. Frost is the formation of ice crystals on crops and occurs when the dew point is near or below freezing. You can have a freeze without frost and a frost without a freeze. Both are damaging to plant tissue.

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.

Fruits and Freeze Damage During Flowering

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

Tree fruits are ahead of schedule on bloom in March this year and as a result there has been a greater risk of freeze damage. Plasticulture strawberries are also in bloom and subject to freeze injury. We had temperatures in the mid 20s (F) last week and on March 30 temperatures dropped as low as 25°F in parts of Delmarva.

Plums and apricots are past full bloom, peaches are in full bloom, and cherries are in pre-bloom stage. Research has shown that when stone fruits are in the First Pink Stage (flower petals coming out of bud but not open), the temperatures required to cause 10% and 90% kill at this bud development stage were 25°F and 15°F, respectively. At First Bloom, the temperatures required to cause 10% and 90% kill were 26°F and 21°F, respectively. At Full Bloom Stage the temperatures required to cause 10% and 90% kill were 27°F and 24°F, respectively and at Post Bloom Stage the temperatures required to cause 10% and 90% kill were 28°F and 25°F, respectively.

For strawberries the critical temperature during bloom at the blossom level is 28°F. Below 28°F, there is a progressively higher risk of flower damage, and below 26°F most blooms will be damaged or killed. Flowers that are not open and just emerging from the crown can tolerate temperatures down to 22°F and once fruit has formed temperatures down to 26°F can be tolerated for short periods of time. Flower acclimation is also important. Plants with flowers exposed to several cold days before a frost will be more tolerant than those exposed to warm days before a frost. In addition, not all flowers in a field will have equal risk of damage. Flowers under leaves or near the soil will often be warmer than those higher on the plant or those more exposed.

Most Delmarva growers are using floating row covers for frost and freeze protection in platiculture strawberries. Row covers reduce temperature loss by cold winds, radiational cooling, convection, and evaporative cooling. With row covers, temperatures drop more slowly under the cover and therefore the nighttime temperatures will be higher than in uncovered areas. This will usually give you 2-8 degrees of protection depending on the thickness of the row cover and weather conditions. Monitoring temperatures under the row covers can verify this. In freezing, windy conditions where outside temperatures are expected below 23°F, additional protection may be needed. This can be done by double covering the strawberries or by sprinkler irrigation over the row covers during the night.

Site Selection for Fruit Plantings

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

There has been an increase in interest in planting fruits in Delaware. This is a positive trend that matches the interest in buying local and can also provide local fruit to the steady influx of visitors in the region.

Success with tree fruits, blueberries, grapes, brambles, and other long-term perennial fruits begins with selecting a proper site. I have visited too many sites in the past 10 years where growers have lost expensive planting material because of poor locations and poor planning. Landowners most often are not buying properties with fruit planting in mind and many properties just are not suitable for fruit.

The most common issue with planting fruit is that of high seasonal water tables. When water rises in winter, it can saturate part of the root zone of the fruit plant and roots will then die due to lack of oxygen. Roots injured by waterlogging are also then more susceptible to root rot pathogens. Fruit plants with water damaged roots also have fewer effective roots which can make them more susceptible to other plant stresses such as drought. In the end, these fruit plants will die prematurely, have shorter life spans or will be less productive.

The best time to evaluate a site for the height of the seasonal water table is in late winter. Find the lowest elevation in the property being evaluated and dig a hole 6 feet deep using a posthole digger. If any free water is found in the hole then the site is not suitable for most deep rooted perennial fruits such as tree fruits and grapes. With brambles and blueberries water should not be found within 4-5 feet of the surface in these observation holes. Also examine the soil that comes out of the borings. If you see considerable amount of gray colored soil, this is an indication of water saturation. Do these borings throughout the property and map your site and avoid planting fruits on any areas with high water tables.

Another problem with water saturation and roots can be perched water tables. This is when an impervious soil layer does not allow water to drain and a saturated area develops above that layer. If perched water tables are found, the area is again not ideally suited for fruits. Subsoiling can fracture these layers if done properly but the layers may reform in a few years.

In high water table soils, it may be possible to grow some fruits such as brambles or blueberries by creating high mounds to grow on. In this case, the growing area is elevated 2-4 feet by moving soil to create a mounded ridge where fruit is planted. While this is possible, it is expensive and must be done in such a way that water does not collect between the mounds.

Another issue with fruit siting is air drainage. Our last 2 winters have had sub-zero conditions which can cause problems with winter kill in some grapes and brambles and bud damage in some tree fruits. Lower areas where cold air drains to also are more susceptible to late frost damage to flowers in the spring, particularly in peaches, nectarines, apricots, and plums. All sites should be evaluated for air drainage by doing elevations on the property. Fruit should be planted on the highest elevations and frost pockets should be avoided. Frost pockets are easily seen by looking where frost is found during late spring frost events. On Delmarva, an issue we have is that some areas are just completely flat, with low elevation. These areas will not allow for air to drain and can also have issues with cold air accumulating.

Soil pH is an issue with blueberry establishment. Blueberries require a soil pH of 4.5-4.8. Most of our soils have much higher pHs and the soil must be acidified before blueberries can be planted. This can take 1-2 years using sulfur as the acidifying agent.

Sites should also be evaluated for nematodes, soil pests that can be damaging to fruit roots, before planting.