Introduction:

Western flea beetle is a significant pest on broccoli and other brassicas in Colorado and precludes direct seeding of these crops, especially under organic production systems. Alternatively transplanted crops allow the plant to survive early flea beetle infestation. In this experiment, direct seeding with floating row cover intended to exclude early infestation by flea beetle on the broccoli plants was compared with the common practice of using transplants.

Methods:

On May 25, 2005, Packman and Premium Crop broccoli seeds were planted in the greenhouse and in the field. The direct seeded crop was immediately covered with floating row cover (1/2 oz./yard weight). At three-leaf stage the greenhouse grown transplants were transplanted to the field on June 22, 2005. The direct seeded plants emerged and grew at the same rate as the transplants. Flea beetles were effectively excluded from the field planted broccoli. Both treatments were planted double rows per bed with a single drip line used for irrigation. The transplanted treatment was blind cultivated before transplanting. Approximately 6 weeks after direct seeding, the floating row cover was removed.

As seen in the photo, weed emergence and growth coincided with the direct seeded broccoli emergence, resulting in significant weed pressure. Weeds were hand removed and the broccoli thinned to 10″ spacing. At this point the development of the broccoli in both treatments was similar. Time to development and yield under both treatments were similar.

Project Leader: Tom Doherty, Colorado West Sweet Corn Market Order, Olathe, CO

Technical Advisor: Robert Hammon, CSU Western Colorado Research Center, Fruita, CO

Project Years: 2002, 2003

2002 Project Summary

Dusky sap beetles are a significant concern to commercial sweet corn growers in western Colorado. Sap beetles have been in Colorado sweet corn since it was first planted, but it has increased each year, with the greatest impact in 2001. The goal of this research program is to develop a research based management program to keep sap beetle contamination at low levels without increasing production costs and insecticide use.

The most common insecticides will be investigated, using different spraying schedules to see what works best. Sap beetle pheromone traps, which have only been used for research in the past, will also be investigated.

The treatments of insecticides are:

• Asana XL, 3 day interval from 1 st silk to brown silk, followed by 2 day interval until harvest
• Asana XL, 2 day interval throughout
• Warrior ZT, 3 day interval from 1 st silk to brown silk, followed by 2 day interval until harvest
• Warrior ZT, 2 day interval throughout
• Untreated

Sap beetle pheromones and co-attractants will be placed at the center of each plot to attract sap beetles and ensure enough pest pressure to make sampling meaningful.

Conclusions

• Sap beetle adults invade sweet corn shortly after pollen shed, but do not begin to lay eggs until about one week before the field is harvest ready.
• The time from egg laying until larvae can be seen with the naked eye can be as short as 3 days at temperatures in the high 90s.
• Early season spray schedules play no role in preventing sap beetle infestations.

The data and conclusions from these experiments were incorporated into a spray program which was used by Olathe Spray Service during late July and August. It was obvious that spraying every other day in the two weeks before harvest reduced sap beetle larval infestations, but did not eliminate them entirely. This program was successfully used on several fields, and became a standard treatment during mid and late August, with no failures.

At CSU’s Plant Environmental Research Center (PERC), the Specialty Crops Program manages three quonset hut greenhouses for blueberries, papayas, salad mix, strawberries, and vegetable starts. Common insect pest problems currently include aphids, two-spotted spider mites, and fungus gnats.

Aphids can be controlled with insecticidal soap, ladybird beetles, and lacewings. We tried introducing adult lacewings but had very poor results. They didn’t lay eggs as we had hoped, and so we resorted to introducing adult ladybird beetles which are presently dropping the aphid population quickly and laying eggs. Parasitoids have not been introduced at this time because they usually appear naturally and will help to maintain aphid levels after control is gained by the ladybird beetles.

Feltiella acarisuga, a predatory midge was introduced to the papaya greenhouse. It has successfully established and is providing good biological control of two-spotted spider mites. Phytoseilius persimilis, a predatory mite has also been introduced to control two-spotted spider mites and is widely used for this purpose.

Hypoaspis miles, a predatory mite, was introduced to control fungus gnat larvae in the potting media and is maintaining fungus gnats at low levels. The rove beetle (Atheta sp.), also a soil dwelling predator of fungus gnats and shore flies, is established in our potting medium and was not introduced.

At the Horticulture Research Center (HRC), common insect pests include flea beetles, cucumber beetles, squash bugs, and various species of caterpillars.

The use of transplants and floating row covers are preventive measures that can protect plants against flea beetles damage. Cabbage looper, Imported cabbage moth, and diamondback moth were present and controlled with Bt.

The Bt (Bacillus thuringiensis) should be sprayed in the evening since sunlight can break down the active ingredient. CSU Cooperative Extension has more information about Bacillus thuringiensis information on their website. We used a motorized, 3-gallon, backpack mounted mist blower to spray Bt on our sweet corn silks and the non-motorized backpack sprayer for the cole crops.

Other Sources of Information About Biocontrol and Integrated Pest Management

The Mountain West IPM Network is a pest management information network for Colorado and Wyoming. High Plains Integrated Pest Management has a website which provides current effective management options for insect and other arthropod pests, and for plant pathogens affecting all major field crops grown in Colorado, Montana, Wyoming, and Western Nebraska. See the University of California Statewide Integrated Pest Management Website for IPM research, educational resources, and pest management techniques. Cornell University also has an informative website called Biological Control: A Guide to Natural Enemies in North America.

Specialty Crop Program Grower Grants that involve integrated pest management include Biology and Management of Sap Beetle in Sweet Corn and Japanese Beetle Eradication from Palisade, Colorado.

At the HRC, we laid down a 1.1 millimeter thick black plastic mulch with a tractor and mulch layer. The soil has to be in very good condition before laying the mulch down (fine, small particles, not big clods). A very level field is also helpful. The mulch layer lays a line of drip tape down the center of the bed, and then the plastic over the top of it while creating trenches on the sides of the plastic. Discs in the back of the mulch layer then push soil onto the sides of the plastic to keep it snug and secure. Planting transplants into plastic mulch involves checking for the drip tape and then poking or burning a hole into the plastic (cutting is not advised as it will begin a tear that will continue). For the melons which were planted in peat pots, we used a bulb planter to create a hole in the plastic and open a space in the soil for the transplant.

Black plastic mulch aids in warming the soil earlier, retains moisture, and decreases weed pressure, all of which contribute to higher yields, especially for warm season crops like tomatoes, peppers, eggplant, and melons.

The use of plastic mulches does create waste, so there is indeed a question of sustainability. There is currently research being done into biodegradable and more natural “plastics” as well as aspen mulch mats, etc. We will undoubtedly see more advances in this field in the years to come. Another difficulty is that when a grower is lucky enough to have rainy growing season like we did in 2004, they must still water the beds under plastic.

Other Sources of Information About PlasticultureA major source of research involving plasticulture is the Penn State University Center for Plasticulture. Several of the Specialty Crops Grower Grants have investigated the use of plasticulture including Using Row Covers and Plasticulture to Produce Earlier Harvest and Greater Yields, and Growing Seedless Watermelon in the Arkansas Valley.

Project Leader: Wyatt Barnes, Red Wagon Organic Farm, Lafayette, CO

Technical Advisor: Kerri Badertscher, Boulder County Extension Office, Longmont, CO

Project Year: 2004

Project Summary

The goal of this project is to determine whether earlier harvests and greater yields could be achieved by planting early using row covers and plasticulture to protect plants and enhance growth. This research tested heat-loving plants such as tomatoes, melons, peppers, and eggplant.

The effects of red and black plastic mulch with and without row cover were compared to soil without row cover for tomatoes, melons, peppers, and eggplant. Three cultivars of tomato, eggplant, and pepper were used and two cultivars of melons. The crops were transplanted in mid-May, after putting down the red and black plastic mulch. Five 365 foot rows of tomatoes and melons were planted and ninety-one feet of peppers and eggplant each were planted. Each cultivar of each crop was trialed on red mulch, red mulch with row cover, black mulch, and black mulch with row cover. Bare soil was used as a control for comparison. Once the transplants were in the ground, the row covers were put over the plants that required that treatment.

Results

The highest yields of crops were found in the red mulch with row cover and the black mulch with row cover. In some cases, these treatments produced yields double and triple the amount produced on soil. Some plants had more vigorous growth with these treatments, as well. The tomatoes grew so large and close together that it was difficult to find a place to step while harvesting. The summer of 2004 was cooler and wetter than regular summers, which may have affected the yield of the hot weather crops that were used in the experiment. The plastic mulch also reduced costs associated with weeding by over 30%. A lot of the melons cracked on the red mulch, however, this may have been due to the irrigation in the final stages of ripening. The best treatments to use will vary for each user depending on the importance placed on factors such as earliness, overall yield, or cost of materials.

• Click here for the full text of the 2004 Annual Report (Word document).
• Click here for the Yield Data from this project (Excel spreadsheet).
• Click here for the Graphs for this project (Excel spreadsheet).
• Click here for the Appendix for this project (Excel spreadsheet).

Floating row cover is a spun-bound polyester which can be purchased on large rolls and lets water, air, and most of the sunlight through. The row covers keep in warmth and humidity and exclude insect pests. They also reduce shock for newly transplanted plants. We have been experimenting with different types of support for the floating row covers. Sturdy plants like garlic do not need support, but more fragile plants like tomato and pepper seedlings need something to keep the row cover from bruising or breaking them when battered about by strong Colorado winds.

In 2004 we cut 3/4″ irrigation tubing to make support hoops. It already had a curved shape, is inexpensive, and lightweight. Eight or 10 gauge wire can also be used for support hoops. We used 18 grams/sq meter weight row cover to cover the eggplant, tomatoes, peppers, and artichokes. We also used it in the fall to cover the pumpkins and protect them from frost damage.

It can take time and labor to lay out row cover but the advantages to the crop can be great and worth the effort. For the warm weather crops, we held the row cover down using #2 plastic pots filled with field soil. The pots worked very well and held the row cover in place even in high winds. It is easy to dump the soil and store the pots in the off-season, and easy to add more pots later on. By not putting the soil directly on the row cover, it preserves it and makes it easy to uncover and cover again. Some growers use sandbags but these can be heavy to transport and take space to store.

Other Sources of Information About Row Covers

Several of the Specialty Crops Grower Grants involve research with row covers such as Increasing the Marketing Period for Melons Using Row Covers and Using Row Covers and Plasticulture to Produce Earlier Harvests and Greater Yields.

Flower Trellis System
We trellised the flowers using plastic netting. Initially we were going to use electric fence posts but then switched to cut 3/4″ plastic tubing which we were using as row cover supports. It supported the trellis nicely.

Bean Trellising
We put t-posts at 20 foot intervals and strung electric fence wire at the top and bottom of the posts. Baling twine was strung in zig-zag fashion between the top and bottom wires and the bean plants were trained to it.

The Florida Weave – Tomato Trellising System
The Florida weave trellising system is used for tomatoes. T-posts were used at both ends of the row for extra support, but wooden stakes were used for the majority of the trellis system. The 2″x2″ stakes (which we found for free as waste wood from a local lumber company) were cut and pounded into the soil using a t-post pounder. Plastic tomato twine and baling twine was used to trellis the tomato plants. Sisal twine stretches and therefore is not recommended.

The twine is tied to the t-post at the end, and then weaved between the tomato plants to the first wooden stake. At that stake, the twine is wound around it, pulled taut, and then continued down the line. As the plant grows, additional lines of twine are added about every 8″ up the stakes (see photos below). It is important to keep the twine very tight otherwsie the plants sag down and the benefit of the trellis is lost. Here’s a great tool to make the job easier: an 18″ piece of 1″ pvc pipe – which the twine is strung through before tying to the end post- gives your arm an extension to reach between the plants. Tomato twine comes in a small box which can be put on your belt, freeing both hands to handle the twine.

After the first few times the plant is “twined”, it is not necessary to do a “figure-8″ around each plant. The idea is that the plant is supported by the twine on either side of it. We did some pruning of the lower stems during trellising. The trellis was effective, however we found that we needed posts taller than 6′ aboveground for the vigorous indeterminate types like heirlooms and that thicker posts driven farther down into the soil would have also been more sturdy. Our salvaged 2″x2″ stakes (which were often 1″x1”) were not strong enough to withstand high winds and many broke.