Research Reports

Bob Precheur, Thom Harker, Mac Riedel, Celeste Welty, Brad Bergefurd, Paulette Pierson, Mary Stuart, Becky Lyon and Mandy Wilson. Dept. of Horticulture and Crop Sci., Pl. Pathology, Entomology and Alternative Agri-Enterprise Center, OSU Columbus.

All the varieties tested in 1996 were evaluated for powdery mildew resistance on two dates. The results are in the Tables below.

Powdery Mildew Review

Powdery Mildew lesions on leaf, (see red arrow), appear as white talcum-like powdery fungal growth. They can appear on both leaf surfaces, stems and petioles. Symptoms usually develop first on older leaves.	Mildew on leaves and vines in advanced stage. Lesions cover entire leaf turning it white in color. Some infected areas of the leaf appear as yellow spots. The next stage will be necrosis or death of the leaf which will turn brown.
Powdery Mildew on handles (see red arrow). Usually occurs in late August and early September.	A closer view of mildew damage on handle (Look for yellow spots caused by mildew, see red arrow). Left uncontrolled, mildew can damage handles and become an entry point for other disease organisms some of which can cause secondary fruit and handle rots.

Powdery Mildew Resistance In Pumpkin Cultivars - 1996

Summary Of Results

At Hillsboro, 22 cultivars from different size categories were evaluated. The best large varieties, with an average fruit size of 17-22 pounds or higher, were Gold Rush and Appalachian, each producing 23 tons per acre. In the 15 to 20 pound fruit size category, both Pro Gold 500 and Pro Gold 510 produced 19 tons per acre with an average fruit size of 15 pounds. In the smaller 10 pound size, RWS 525 produced 27 tons per acre. Some of the best small varieties were HMX 2690, 4695 & 4696.

See the complete Hillsboro Yield Table file plus pictures.

On 25 September, varieties with good powdery mildew tolerance in Hillsboro, (Table 1 below), were HMX 5683, HMX 6686 and RWS 525.

In Columbus, 18 cultivars were evaluated for yield and quality. Half of the 4 replications were sprayed with a standard chemical disease control program and the other half received no fungicide sprays. Yield, across all varieties in sprayed plots, Table 3, averaged 7.6 tons per acre and significantly higher than the average of 5.4 tons per acre in no disease control plots, Table 2. One of the best overall varieties was Gold Strike producing 8 tons per acre with an average fruit size of 14 pounds in both sprayed and unsprayed plots. Some of the better varieties were Gold Rush, Jumpin Jack and Howden Biggie.

Powdery Mildew development on the foliage was rapid and severe after the first week of Aug in no disease control plots, Table 2. Varietal reactions to Powdery Mildew differed in the no disease control trials. On 23 Aug, in no disease control plots, variety HMX 4693 had significantly less Powdery Mildew development than all other varieties except Pro Gold 510, RWS 525, HMX 4694 and HMX 5680. Also, RWS 525 had significantly less Powdery Mildew on foliage than varieties Howden, Pro Gold 300, Oz, HMX 2690 and Gold Strike. By 19 Sep, HMX 4694 had significantly less necrotic leaves from Powdery Mildew than all other varieties except Gold Rush, RWS 525, and HMX 5680. Varieties RWS 525 and HMX 5680 had significantly less foliage death than Howden, Pro Gold 300, Pro Gold 500, RWS 523, HMX 4693, Wizard and Gold Strike. Only Pro Gold 510 had significantly less Powdery Mildew development on fruit handles than other varieties. In the standard disease control plots, Powdery Mildew development was effectively controlled on the foliage of all varieties except RWS 523. Powdery Mildew developed on the handles of all varieties except Howden, Howden Biggie, Appalachian and Pro Gold 300. Yield of marketable orange fruit was higher in standard disease control plots.

An explanation of the rating system for the presence of mildew on foliage and fruit handles, is at the bottom of each table.

II. No Disease Control

III. Standard Chemical Disease Control