Planting resistant summer squash and zucchini gives you the opportunity to harvest a late-season squash crop when wholesale prices for this commodity tend to be higher. There are now many varieties with resistance to one or more of the diseases that affect the late-season supply (and thus price) of squash. In 1997, we conducted a couple of small trials at UConn to compare yields between some of the virus/powdery mildew resistant squash varieties that are on the market, or soon will be.

Most of the varieties tested, resist or tolerate 1-3 of the 5-6 important mosaic virus diseases that may infect squash (table 1and table 2). Therefore, until breeders stack resistant genes to all of the common viruses within a single variety there is still a chance of late-season virus problems.

Powdery mildew (PM) is another important late-season disease of squash which can now be combated with resistant varieties. General Patton, a straightneck summer squash from Asgrow, and a numbered zucchini variety being developed by Rogers Seed Company (ZS-23) proved to have a good degree of PM tolerance. Both varieties produced the most fruit per plant for their respective trials.

We made a single late-season planting (16 July) of 10 zucchini and 5 summer squash varieties at the University of Connecticut’s Plant Science Research Farm. Despite planting two to three seeds per hill, one variety in each trial failed to germinate. The two trials (zucchini and summer squash) utilized three plants per plot and were replicated three times in a randomized complete block design. Plants were spaced every two feet in rows four feet apart. The plots received a broadcast application of 1000 pounds of 5-10-10 (N-P-K) and were sidedressed on 5 September-1997 with 30 pounds of nitrogen. All marketable-size fruit were harvested every three to four days, for a total of eight times, between 2 and 26 September. No fungicides or insecticides were used.

The fruit quality, shape and color of all the varieties that emerged met marketable standards; producing relatively straight, smooth, glossy squash. Tigress was slightly lighter, while Jaguar was darker in color than the other zucchini tested. All of the squash trialed were straightneck varieties. Virus symptoms occurred on only two plants in the entire experiment (no symptoms on any fruit), and thus severity of infection was not rated. Plants were rated for the degree of PM infection on the final day of harvest.

Table 1
Resistant Zucchini Trials 1997

Variety	Resistance1	Company	#Fruit/Plant	Wt(lbs)Plant	Powdery Mildew2 Disease Rating
Revenue	ZYMV,WMV,CMV	Rogers	6.00 a	3.75 a	3.3 ab
ZS-23	PM	Rogers	6.3 a	3.63 a	1.1 d
Jaguar	ZYMV,WMV	Harris Moran	5.17 a	3.34 ab	3.1 ab
1776	ZYMV,WMV	Asgrow	4.78 bc	3.22 ab	3.0 bc
ACX34		Abbot & Cobb	3.34 c	2.70 bc	3.3 ab
Dividend	ZYMV,WMV,CMV	Rogers	5.00 ab	2.63 bc	3.8 a
Puma	SQMV	Harris Moran	3.55 bc	2.16 c	3.2 ab
Tigress	ZYMV,WMV	Harris Moran	3.00 c	2.06 c	3.3 ab
1814	ZYMV,WMV	Asgrow	3.11 c	1.98 c	3.3 ab

LSD:5%
1Resistance: PM = powdery mildew, ZYMV = zucchini mosaic virus, WMV = watermelon mosaic virus, CMV = cucumber mosaic virus, SQMV = squash mosaic virus
2Disease Rating: 0 = no disease, 1 = lower leaves infected, 2 = lower, mid-leaves and stems infected, 3 = whole plant infected (light), 4 = moderate to severe infection, 5 = dead or dying

Table 2
Resistant Summer Squash Trials 1997

Variety	Resistance1	Company	#Fruit/Plant	Wt(lbs)Plant	Powdery Mildew2 Disease Rating
General Patton	PM, Prec.	Asgrow	10.34 a	2.95 a	1.5 b
Precious II	Prec.	Abbot & Cobb	8.00 ab	2.66 ab	2.2 a
Multipik	Prec.	Harris Moran	7.55 ab	2.22 ab	2.2 a
Superpik	Prec.	Harris Moran	0.77 b	1.63 b	2.3 a

LSD:5%
1Resistance: PM = powdery mildew, Prec. = Precocious gene masks fruit color breaks caused by cucumber mosaic virus (CMV) and watermelon mosaic virus (WMV).
2Disease Rating: 0 = no disease, 1 = lower leaves infected, 2 = lower, mid-leaves and stems infected, 3 = whole plant infected (light), 4 = moderate to severe infection, 5 = dead or dying

By: Jude Boucher, IPM Program Leader, Vegetable Crops and Gianna Nixon, IPM Program Assistant, University of Connecticut. Reviewed 2012.

Published: Grower, New England Vegetable and Small Fruit Newsletter vol. 98-4, April 1998.

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