Editor’s Note: The following research involving muskmelon (Cucumis melo ‘Sweet Granite’) and powdery mildew (Podosphaera xanthii) and Alternaria leaf blight (Alternaria solani) was performed and reported here by Purdue’s D. Egel, S. K. Saha, S. Johnson, S. Monroe, D. Nowaskie, and M. Restrepo.

On May 20, muskmelon seedlings were transplanted to a field at the Southwest Purdue Agricultural Center in Vincennes, Indiana, which was managed for the fifth consecutive year organically. Individual row plots consisted of 30 ft rows on 6-ft centers. Muskmelon was seeded in the greenhouse on April12 using polystyrene transplant trays filled with OMRI (Organic Materials Research Institute) approved Sunshine soilless mix (Sun Gro Horticulture Ltd., Bellevue, WA 98008). Muskmelon seedlings were transplanted 3-ft apart with 10 plants per plot. Each row was mulched with 4 ft wide x 0.16 in. black plastic (Visqueen 4020). The experimental design was a randomized complete block with four replications. Treatment plots were separated in the row by 10-ft unplanted buffers. K+Neem was applied on June 7 for aphid control. OMRI listed fungicides were applied weekly from June 12 to July 29 with CO2 backpack sprayer with 4 flat fan nozzles Tee-Jet 8002VS spaced 19 inches apart applying 10 gal per acre at 30 psi. A Horsfall-Barratt ratings system was used to evaluate severity of powdery mildew and Alternaria leaf blight on muskmelon leaves on July 13, 23, 29, and August 6. Muskmelon fruit were harvested July 14, 16, 19, 21, 23, 26, and 28. Rainfall totals for June, July and August were 4.79, 10.67 and 1.54 inches respectively.

Both powdery mildew and Alternaria leaf blight spread into the plots naturally and were first observed on July 13. No significant differences in yield were observed in any harvest date or in total yields. The only significant differences in disease severity levels are shown below. Muskmelon plants treated with Champ DP or Milstop had significantly lower levels of powdery mildew than plants treated with Serenade Max. All products tested except Oxidate had significantly lower levels of Alternaria leaf blight than the untreated check.

Treatment, rate/Az	Disease severity 23 Jul (%)y		Number of muskmelon/A
	Powdery mildew	Alternaria leaf blight
Serenade Max 3 lbs. . . . . . .	13.4 a x	2.9 b	5,639
Oxidate 90 fl ozw. . . . . . . . .	6.4 ab	4.1 ab	5,518
Untreated check. . . . . . . . . .	6.4 ab	7.7 a	4,792
Milstop 2 lbs. . . . . . . . . . . .	4.7 b	3.5 b	5,155
Champ DP 3 lbs. . . . . . . . . .	4.1 b	2.3 b	4,792
P-value	0.0719	0.0496	0.6375

^z Fungicides were applied approximately weekly from 12 Jun until 29 Jul, except Oxidate which was applied twice weekly. 

^yPlots were rated for severity of powdery mildew using the Horsfall-Barratt scale and converted to percent using the ELANCO tables.

^x Means within each column with a letter in common are not significantly different (Fisher’s Protected LSD), P=0.1 for powdery mildew and 0.05 for Alternaria leaf blight.

^wOxidate was mixed in a dilution of 1:100 with water, the resulting rate per A appears above.