Wednesday, May 11, 2016

Results from Two Years of Organic Cucurbit Trials in Western NC

This article was written by Dr. Luping Qu, research specialist in our Alternative Crops and Organics Program in the Department of Horticultural Science at NC State University. This project is funded by USDA Grant number: 2012-51300-20006 with the project name  Organic Cucurbit Research: Critical Pest Management Challenges. The project is led by Dr. Michael Mazourek, Cornell University. These are preliminary results from the western North Carolina location. this study will continue for another growing season in 2016. A full report for all the sites and papers will be published later. You can follow this project on eOrganic here. 
 

Cucurbit downy mildew (CDM), the striped cucumber beetle (SCB) and aphid vectored viruses can cause significant damage and limit cucurbit production on organic farms. The Eastern Sustainable Organic Cucurbit Project (ESO-Cuc) addresses the three universal pest and pathogen challenges. This research project  approaches the management of these issues through disease forecasting, seed and variety choice, and production techniques such as trap cropping, row covers, and high tunnels. ESO-Cuc, the Eastern Sustainable Organic Cucurbit Project is a collaboration between Cornell University, North Carolina State University, Auburn University, and the Organic Seed Alliance.

Started in 2014 and continued in 2015, we conducted replicated field trials for this project at the Mountain Research Station in Waynesville, NC.  Trialed crops include cucumber, melon, and summer squash/zucchini.  For each crop eight open pollinated (OP) and hybrid cultivars that were either widespread standard cultivars or novel sources of disease resistance were planted in the field in each year following a randomized complete block experimental design with three replications. Seeds were greenhouse started in 50-cell flats. Melons were transplanted in the field on June 4 and cucumbers and summer squash were transplanted on June 20.   Field preparations included raised beds, black plastic mulch, and drip irrigation. Between row spacing was 9 x 9 feet (center to center) and in row spacing was 2 feet for melon and summer squash and 1 food for cucumber.  Row cover was used as a physical barrier for two weeks after transplanting for protecting young plants from damage by cucumber beetles in 2014. In 2015, row cover was applied for melons for 4 days after transplanting and had to be removed because the weather was too warm to keep it on without causing damage to the plants. Between row weed control was done by hand, cultivator, and laying straw.  No disease control was practiced. 

Cucumber beetles were observed in the filed in 2014 during the later stage of plant growth and the population was too small to cause visible plant damage. In 2015, these beetles showed up a few days after transplanting and damaged the young plants to some degree but plants outgrew the damage. Whether the beetle effect at young plant stage caused any fruit yield reduction was not assessed.   
CDM cause significant damage to death to cucumber plants and less significant damage to melon and summer squash.  At our site in both years, CDM was first observed on cucumber on about July 24 on the most susceptible cultivar Boston Pickler and the plants could be killed by the disease in three weeks. The most CDM resistant cucumber cultivar was DMR–NY 264. This cultivar fruits late and CDM caused insignificant damage to the plants at late growth stage.

Powdery mildew was observed on melons in 2014 and on summer squash in 2014 and 2015. Virus disease was not observed/screened at our trial site.   

DISEASE
Cucumber
Downy mildew was first observed on cucumbers on 7/25/2014 starting with the variety Boston Pickler. The disease developed quickly. There were no symptoms on 7/23, but by 7/28 this variety had been severely damaged by the disease. Progression of the disease was recorded by photo images as shown in the figure below of the variety Boston Pickler.
Downy mildew had developed on all other varieties except DMR-NY 264 by 7/28/2014. Downy mildew was first noticed on DMR-NY 264 on 8/20/2014. Leaf samples were taken on 9/2/2014 and downy Mildew was confirmed by the NCSU Plant Disease and Insect Clinic.  
Melon
Downy mildew was first noticed on Earlichamp melons on 7/28/2014 and it developed fast. The melons of this variety ripened quickly, too. It was difficult to differentiate the diseased leaves from natural senescence.  The disease developed on other varieties a few days later.

Summer squash
Powdery mildew was first noticed on Black Beauty, Gentry, and Multipik on 8/1/2014. Gentry and Multipik appeared to be more susceptible to this disease. Downy mildew occurred later and was obviouson 8/13/2014. Because the presence of powdery mildew, downy symptoms were not readily easy to visualize. 
HARVEST RESULTS

Cucumber
Cultivar
Days to maturity from
Fruit #/Plant
Type

Seeding
Transplanting


DMR-NY 264
60
44
32.1 ±  7.4  A
slicer
Alibi
48
32
21.3 ± 2.5    B 
pickler
Boston Pickler
48
32
8.0 ± 1.5      C
pickler
Marketmore 76
52
36
7.2 ± 2.5      C
slicer
Marketmore 97ff
50
34
6.7 ± 3.5      C 
slicer
MM80BW
50
34
6.7 ± 0.9      C 
slicer
Straight 8
48
32
2.8 ± 0.8      C  
heirloom
Diva
48
32
1.8 ± 0.9      C
beit alpha

Melons
Cultivar
Days to maturity from
Fruit #/Plant
Type

Seeding
Transplanting


Wrangler
75
56
7.6 ±  0.8  A
muskmelon
Athena
78
59
5.8 ± 0.3   B  C
muskmelon
PMR Delicious 51
78
59
6.4 ± 1.0   A   B   C
muskmelon
Hannah’s Choice
78
59
7.2 ± 0.4   A   B  
muskmelon
Superstar
75
56
5.4 ± 0.0   C 
muskmelon
Diplomat
73
54
5.9 ± 0.6   B   C 
Galia
Earlichamp
73
54
6.1 ± 0.3   B   C  
muskmelon
PI124112
80
61
6.6 ± 0.2   B   C
Wild

Summer squash/zucchini

Days to maturity from


Cultivar
Seeding
Transplanting
Fruit #/Plant
Type
Multipik
41
25
34.9 ± 3.8  A
Straightneck summer squash
Gentry
43
27
34.9 ± 0.6  A
Crookneck summer squash
Success PM
47
31
27.7 ± 2.8   B
Straightneck summer squash
Zucchini Elite
41
25
19.6 ± 2.1   C
Green zucchini
Dunja
41
25
13.9 ± 1.0   C  D 
Green zucchini
Romulus
56
40
12.9 ± 1.3   D
Green zucchini
Black Beauty
43
27
12.2 ± 2.6   D
Green zucchini
Golden Zucchini
41
25
10.5 ± 1.9   D
Golden zucchini