Could a Cherry Tree Tent be the Answer?

 We've posted before about a huge threat to backyard cherry trees in our area: the cherry maggot, also known as the Spotted Wing Drosophila. SWD is responsible for the little worms that backyard gardeners are starting to find in their cherries, and to a lesser extent in raspberries, strawberries and blueberries. An experiment conducted at the Fair Oaks Horticulture Center this past year by Sacramento County Master Gardeners may provide an answer to this growing problem throughout the West.

This was originally published in the Sacramento County Master Gardener Newsletter of Sept. 2012.
 
The problem: Spotted wing drosophila (SWD), is a gnat-sized fruit fly first found in 2008 damaging fruit in many California counties. Unlike the common vinegar fly that attacks rotting and fermenting fruit, the SWD infests ripening, undamaged cherries as well as ripening raspberry, blackberry, blueberry, and strawberry crops – especially in coastal areas.
 
Prior to 2011, no SWD damage was found on the multi-grafted cherry tree at the Fair Oaks Horticulture Center. In 2011, the early varieties escaped damage, but the later varieties were totally infested. In an attempt to prevent fruit loss in 2012, and to demonstrate to homeowners a possible cultural means of preventing infestation, the orchard group decided to tent the tree.
 

The tent: Mary Kay Ryan and Patty Peterson designed a structure to cover the tree while still allowing the harvest of seven varieties of cherries ripening at different times. The tree was pruned to just under 10 feet. Mary Kay and Patty used 1” schedule 40 PVC to create a large box frame anchored to the ground at the corners. The tent itself – 13.6 feet wide, 13.6 feet long, and 10 feet high – was sewn by Patty using 30-weight Agribon row cover and included a 110” sleeping bag zipper to allow easy entry. Diagonal guy wires and PVC clamps ensured the tent would not slip or be pulled due to winds. The bottom edge of the tent was weighted down. The tent was erected 4 weeks prior to the first harvest. The cost of the tent: approximately $200.
 
Traps: One SWD trap was placed outside the tent, and one trap inside the tent to monitor activity. A few male SWDs (with distinctive wing spots) were found in the outside trap during the season, but an exact number of SWD males was not determined, as there were many similar small insects in the trap. No SWD males were caught inside the tent.
 
Temperature observations: Because we were concerned about heat build-up in the tent, two recording thermometers were placed in the canopy of the cherry tree at 6 feet height under the Agribon from May 14 through June 19. Two additional thermometers were placed at the same height in an uncovered fig tree of similar size.
The low (nighttime) temperatures were on average 3 degrees cooler in the tree under the Agribon than in the uncovered tree (see graph). The high (daytime) temperatures under the Agribon were on average 2 degrees warmer than the uncovered tree. On days over 90F, temperatures under the Agribon were still only 2.5 degrees warmer, but during one 3-day period, temperatures averaged 8 degrees warmer.
 
Harvest: While harvest was a bit challenging (quickly entering/exiting the tent as well as moving ladders during harvest in a cramped space), overall it was a success with a full crop of undamaged, delicious cherries!
 
Other issues/drawbacks: The size of the tent required a number of us, with ladders, to assist in its assembly. The tent did suffer some damage near the bottom – we believe from a raccoon or similar creature. Several tears appeared overnight but were quickly repaired. Additionally, the tent suffered some wind damage along the bottom edge. We originally used 2’x4’s to secure the tent bottom, switching to soil to prevent further tears. On the plus side, we were able to disassemble the tent relatively quickly and store the parts for next season.
 
Conclusion: While our experiment was certainly not scientific, we do think of it as successful in that we avoided fruit damage of any kind on a fairly large tree with varying harvest periods. It does provide another option for homeowners who may be dealing with SWD. Although expensive initially, the cover should be reusable for possibly several years. In January 2013, we will espalier a cherry tree, and when the tree begins bearing we will secure row cover over it in the spring. This will provide demonstrations of both training and pruning on a trellis and a practical method of controlling SWD, since covering an espalier tree should be much cheaper and easier than a large tree.
—Tracy Lesperance, Cathy Coulter, and Chuck Ingels


For more information about the Sacramento County Master Gardener Program, including links to their wonderful 2013 Gardening Guide and Calendar, click here.

Droopy Leaves on a Hot Day. Water...or Not?

Do your plants have droopy leaves on a hot afternoon? 

 

There are two schools of thought.

One school says plants conserve moisture on a hot afternoon by allowing their leaves to sag.

The other school says: don't believe them. Drooping leaves are usually indicative of a lack of water from the root zone. "Large, thin leaves, common in many of ornamental, annual and vegetable species, do not conserve water," writes Washington State University Horticulture Professor Linda Chalker-Scott. "Tomatoes, zucchini and black-eyed Susans...are not water conservers. Chronic wilting of these and others can eventually cause leaf tip and margin necrosis (or tissue death). It also reduces growth, so that your yield of tomatoes, zucchini and black-eyed Susans will be decreased."
She advises applying a layer of mulch around those plants to help conserve water.

Also, check the moisture at the root level before watering.
To determine the amount of water at the root level:

• A day or two after watering, dig down 8 to 10 inches with a trowel or small shovel, near the drip line (outer canopy) of the plant. Doing this in two or three spots would be more helpful.

• At that depth, grab a handful of the soil. Squeeze that handful. If it is muddy and watery, reduce your watering for plants that require regular (but not frequent) irrigation. If it is so dry you cannot form a clod in your hand (it turns to dust instead), increase your watering (for those plants that require moderate amounts of water).

• If you can form a dirt clod in your hand, yet break it apart with a little effort, that is probably the correct soil moisture for your plant.

• Steve Zien, owner of the Citrus Heights-based organic landscaping consulting service, Living Resources, recommends the use of a soil sampling tube to determine the moisture at root level. "Just press the tube down six to eight inches into the soil after you are done watering," says Zien. "When you bring it back up, the open slot along the side of the tube will let you see if the soil at that depth is wet, moist or dry. Adjust your watering time so that the soil sample is moist, not too wet or dry."

• An easier, but more unreliable way to measure the water content of the soil: purchase an inexpensive (under $10) moisture meter, available at most nurseries. Test its accuracy by putting its probe into a glass of water. If the probe does not read "wet", choose another. Expect it to function for only a year or so.

• Battery operated moisture meter probes may set you back a few more dollars, but in my experience - with proper care (clean them after each use, don't leave them outdoors) - they will last many years.

• Extended, infrequent, slowly applied irrigation is the most efficient watering method. Soaker dripline or drip irrigation systems work best. Here in the Central Valley, foothills and Bay Area, run them for 3 to 6 hours at a time, twice a week, in the summer. This is only a guideline to get you started. Adjust that timing to your particular soil type and plants.

• And, don't forget: add more drip emitters and drip lines as the plant grows, especially for trees and shrubs. Make sure to get water to the outer canopy of the plant (and beyond) where the roots travel.

Improper watering is the number one cause of plant failure. Knowing how wet the soil is at the root level can help you keep your plants healthy.

Keep in mind: different plants have different watering needs. Learn those needs, then group plants together with similar watering requirements when designing your landscape. The Sunset Western Garden Book is a good source for that information.

Signs of not enough water at the root level of plants:
Wilted leaves in the morning. Wilted leaves in the afternoon.
Wilted leaves in the evening.
Red-brown margins of leaves.
Premature fall color of leaves.
Growth reduction.
Leaf drop.
Branch dieback.

Signs of too much water (also called aeration deficit) at the root level of plants:
The soil has a foul smell, like rotten eggs.
Soil is a blue-gray color.
Yellowing, wilting and/or dropping of leaves.
Limited new growth.
Small, corky outgrowths on the undersides of leaves.

Be warned, though: sometimes, symptoms of overwatering and underwatering can be the same (such as leaf wilting). And, symptoms of soil water problems may actually be another problem...that was caused by your watering regimen! Root rots, for example, thrive in saturated soils.

Frequent, light watering leads to shallow rooting, increasing the chances of plant problems.

How much water does your lawn need?

Some tips from the UC Integrated Pest Management Website:


• Avoid planting turf species that require frequent watering, such as bluegrass or ryegrass.
• Design your landscape to minimize water runoff onto hard surfaces and into storm drains.
• To reduce runoff, install non-irrigated buffer areas, which include water-efficient plants or permeable features, next to sidewalks or on slopes.
• Aerate heavy or compacted soils, so water can easily move down to reach grass roots.
• Install an irrigation system that you can adjust to properly water areas of your landscape that have different requirements.
• Water only when your lawn needs it.
• Water requirements vary according to turf species, location, and month of the year.
• Most lawns need water when the top 2 inches of soil have dried out.
• Shady and sunny areas and different soil types will have different water requirements.
• Deeper, less frequent watering is best for most lawns. Water only 2 to 3 times a week.
• Make sure your sprinkler system isn’t producing runoff, especially on slopes. If you see runoff, use shorter watering times and repeat the cycle to allow time for the water to move into the soil.
• Water early in the morning when evaporation and wind are minimal.
• Adjust your watering schedule seasonally, and shut off your irrigation system during rainy weather.