Monday, June 04, 2012

High Tunnel Crop Talk Notes June 4, 2012

 High Tunnel Crop Talk Notes June 4, 2012

Summary: Peppers in experimental trials at Meigs Farm are blooming; possible nutritional problems observed in red raspberries; white druplets seen in blackberries; blossom end rot and zippering of tomatoes observed; pests observed on tomatoes include aphids, cabbage loopers, yellow striped armyworm, and stink bug (eggs only).

Join us again on June 18, 2012. 12:30–1:30 p.m. Eastern/11:30-12:30 Central. Point your web browser to and click on the phone icon to be dialed in to the call, or just dial 1-866-492-6283.
Dr. David Conner from Univ. of Vermont will join us to discuss results of his economic research on high tunnel production in Michigan. You might be interested in reading some of the information in advance. See 'Model Business Plan for Season Extension with Hoophouses' at, and 'Hoophouse Contributions to Farm Profitability and Food System Sustainability: Lessons from Michigan' at There is also an abstract ' Determinants of Hoophouse Profitability: A Case Study of 12 Novice Michigan Farmers' available at

Adams County: No major changes since two weeks ago. It is a little cooler now; in particular there have been some cool nights.

DeKalb County: Last week saw 0.1 to 0.3 inches of rain, the first in 3 weeks. It is very dry. First cutting of hay has been taken.

South Central Indiana: Researching tunnel type to purchase with a NRCS grant. The 'nicer' tunnels seem to cost more than NRCS grants provide.
Question: Does anyone have an opinion on the different sizes of pipe? Another grower I talked to said the 14 gauge pipe we were looking at from a certain company may not be great. (Readers, if you have an opinion, please write a comment, or send it by email to emaynard(at)

Throckmorton PAC, Meigs Horticulture Research Facility:
Sweet peppers transplanted May 3 into black plastic mulch are flowering. These are part of an experiment to look at how organic fertility amendments are mineralized in the soil. There are two organic fertility treatments (green manure (hairy vetch) plus alfalfa meal or composted chicken manure), a conventional fertility treatment with urea as the nitrogen source, and a 'control' treatment with no added nutrient source. Each treatment has 8 plants and is about 5.5 ft. by 10.5 ft. Treatments are replicated in the tunnel and also in adjacent plots out of the tunnel.
For the green manure treatment, hairy vetch was seeded at 35 lb./acre as a cover crop in November 2011. Vetch didn’t grow much in winter, but took off in Feb. and March. This photo was taken in late March and shows the vetch and other treatments. The next photo shows nodules on the roots of hairy vetch. It is in these nodules that the symbiotic nitrogen-fixing bacteria live and convert nitrogen from the air into forms used by the bacteria and the plant.
Hairy vetch in high tunnel. Photo by M. Rudisill.
Nodules on roots of hairy vetch. Photo by M. Rudisill.
Hairy vetch plots after incoporation. Photo by M. Rudisill.
Vetch was incorporated April 18. Since this is an experiment, hairy vetch was pulled up, weighed, and then tilled in - quite a difficult process. It was incorporated 2 wks prior to planting. The photo shows the plots after incorporation.
Peppers shortly after transplanting on May 3. Photo by M. Rudisill.
The final photo shows peppers shortly after transplanting.
Blooms present on peppers at transplanting were removed, as well as any flowers in the first two or 3 weeks after transplanting.
No insect pests have been noticed in the tunnel. Peppers planted outside about two weeks ago have noticed whiteflies. (Matt Rudisill)

Southwest Indiana: Red (Joan J.) and black (Mac Black) primocame-fruiting raspberries in tunnel are showing interveinal chlorosis and/or bronzing. It is probably a nutritional disorder. The problem is severe enough on black raspberries that fruit will not ripen properly. See the photos below. 
'Joan J' red raspberries showing internveinal chlorosis and
bronzing. Photo by B. Bordelon.

These are very large plants. They were planted last year, on raised beds, on plastic mulch.
If it is a nutritional disorder, it is possible that the vigorous growth in high tunnels combined with the limited rooting volume (only in the portion of the soil wet by drip irrigation) has contributed to the problem. In an outdoor situation, blackberries rarely have nutritional problems. Red raspberries more commonly have such problems in a field situation.
'Mac Black' black raspberries showing inteveinal chlorosis
and necrosis. Photo by B. Bordelon.

White druplet disorder was observed on blackberries in a high tunnel. This disorder is relatively common in hot years. It has been attributed to UV light, heat, and possibly stink bug. In this case, UV light seems unlikely as a cause since the plastic should block UV light. Stink bug also seems unlikely because injury is only observed on druplets on the upper side of the fruit. (Bruce Bordelon)

White druplets on blackberry. Photo by B. Bordelon.
West Central Indiana:
Interveinal chlorosis is visible on one lower leaf
at right center; otherwise plants look good.
Photo by D. Egel.

Close view of interveinal chlorosis on lower tomato leaf.
Photo by D. Egel.
Interveinal chlorosis was noted on lower, older leaves of tomato plants that otherwise looked healthy. No disease, insects, or mites were observed. 
Yellowing of older leaves is a common symptom when nitrogen or other mobile nutrients (magnesium, potassium) are moved from older leaves to younger leaves. Interveinal chlorosis is a classic symptom of magnesium deficiency; marginal chlorosis is typical of potassium deficiency. When restricted to older leaves, the symptoms don't necessarily mean that the plant needs more fertilizer. Regular tissue testing of recently mature leaves is the preferred way to monitor nutritional status of the plant. If this type of leaf yellowing is observed, it makes sense to look on the back side of the leaves to see whether there is any disease or pest. 
Aphids and cast exoskeletons on tomato leaf. Photo by D. Egel.

Aphids were also observed on tomatoes, see photo. These are probably potato aphids. A number of materials are labeled for control. Biocontrol may also be possible with the predatory wasp, Aphidius colemani, illustrated in the image below. 

This tiny wasp lays an egg in the aphid, the egg hatches and the wasp larva feeds inside the aphid, eventually emerging as an adult wasp. A parasitized aphid turns grey or tan and takes on a more spherical shape so it is readily distinguished with the naked eye. These wasps can be purchased and released, but there are also natural populations that can help to provide control. Specific studies on their use under Indiana conditions have not been conducted. The image also illustrates a parasitized grain aphid, a species that does not feed on broadleaf plants. This type of aphid was put on potted sorghum and placed in a greenhouse to build up a population of aphids as food for the predatory wasp. (Shubin Saha and Dan Egel)

Southwest Indiana, Southwest Purdue Ag Center:
Floral parts stuck to tomatoes can cause deformities in tomato fruit. A result of this can be a zipper scar, a dark narrow scar running from the stem scar towards the blossom end, with small horizontal crosshatches. 
Tomato fruit deformed and with flower parts attached.
Photo by S. Saha.

Double tomato fruit from fused flowers. Photo by S. Saha.

Tomato with zipper scar and hole into locule. Photo by S. Saha.
Sometimes in addition to the there is a hole into the locule. At SWPAC these are showing up on the first and second flower clusters. In some cases flowers have fused and two tomatoes develop stuck together. These tomatoes are probably not marketable.

Small fruit on a normally large-fruited tomato can be a symptom
of poor pollination or fertilization. Photo by S. Saha.

Inside of fruit shows reduce seed development on one side.
Photo by S. Saha.
Poor pollination or fertilization has also been observed. The tomatoes in the images above look like roma tomatoes, but they are a beefsteak (large, round) variety. The small fruit can be related to poor pollination or fertilization of ovules. These are from the first cluster.
Blossom end rot on tomato fruit, cross-section. Photo by S. Saha.

Blossom end rot on tomato fruit, external view. Photo by S. Saha.

Blossom end rot has also shown up on tomato fruit, as shown in the photos above.. The tan or brown sunken area at the blossom end often extends into the fruit. This is associated with insufficient calcium at a particular time, which is often due to insufficient water. These tomatoes experienced temperatures over 100° on some days when it wasn't possible to keep the tunnel cool enough.
Other pests Shubin has observed at SWPAC include: stink bugs in the egg stage, cabbage looper, and yellow striped armyworm. All of these have been managed in the experimental trials by hand removal. Yellow striped armyworm has also been quite common in field plantings. (Shubin Saha)

Spider mites have been observed on tomatoes in tunnels in north central Indiana.
A problem on red raspberries was tentatively identified as phytophthora. But it doesn't really look like phytophthora does on vegetable crops. It looks somewhat like images of manganese deficiency in vegetable crops. Tissue samples sent in three weeks ago looked good.
Bruce Bordelon recommends sending a sample of the root system to the Plant and Pest Diagnostic Lab They can quickly test for phytophthora, which is a fairly common problem in wet areas of fields. To test for nutrient deficiencies, follow recommendations in The Midwest Small Fruit Pest Management Handbook

Notes by L. Maynard. Please get in touch with corrections or additions, or just post a comment.

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