|
Project Leader: Meg McGrath, Dept. of Plant Pathology, Riverhead
Cooperators:
Ted Blomgren, Vegetable Specialist, Capital District Vegetable Program
Alan Erb, Vegetable Specialist, Lake Plains Vegetable Program
Julie Kikkert, Vegetable Specialist, CCE Ontario-Wayne-Yates Counties
Joseph Sieczka, Dept. of Fruit & Vegetable Science, Ithaca
Dale Moyer, Vegetable/Potato Specialist, CCE Suffolk County
George Moriarty, Dept. of Plant Breeding, Ithaca
Molly Kyle Jahn, Dept. of Plant Breeding, Ithaca
Bill Johnson, plant breeder, Seminis Vegetable Seeds, Inc., California
Type of grant: Pest-resistant crops; allelopaths
Project location: National application
Abstract:
Powdery mildew is an important disease of winter squash and other cucurbit
crops. It occurs throughout New York every year. Management is usually
needed to avoid a reduction in yield. Application of fungicides has
been the main practice. Several winter squash varieties with resistance
to powdery mildew are now commercially available. The source of this
gene for resistance is CornellŐs Department of Plant Breeding. Growers
need to know how well these resistant varieties perform compared to
horticulturally-similar, fungicide-treated susceptible varieties, and
whether there are benefits to an integrated program with reduced fungicide
inputs (fungicides applied every 14 days compared to the standard 7-day
interval). Two experiments were conducted to evaluate acorn and butternut
squashes. Growing varieties with resistance to powdery mildew was shown
to be an effective and economic means to manage powdery mildew. Powdery
mildew was managed better with chemical control than with heterozygous-based
genetic control (resistance from one parent): fungicide-treated susceptible
Taybelle had less powdery mildew than non-treated resistant Taybelle
PM. However, homozygous-based genetic control (resistance from both
parents) was more effective than chemical control: non-treated resistant
Autumn Delight and resistant Bugle had less powdery mildew than fungicide-treated
susceptible Table Ace and susceptible Waltham, respectively. Efficacy
of chemical control, however, was likely compromised by the presence
of pathogen strains that were resistance to the two main groups of systemic
fungicides used. Resistance to QoI fungicides was very common when assessed
on 31 Aug, one month after fungicide applications were started on the
susceptible varieties, and most of the pathogen population also was
moderately insensitive to DMI fungicides. Control of powdery mildew
was improved significantly by applying fungicides to the resistant acorn
squash varieties but not to the resistant butternut variety. Regardless
of disease control benefit, an integrated program is recommended to
reduce selection pressure for new races of the pathogen able to overcome
the resistance in these varieties and for new strains of the pathogen
that are able to tolerate the fungicides. A reduced-sprays fungicide
program with a 14-day spray interval was as effective as the conventional
program with a 7-day interval when applied to resistant varieties but
not when applied to susceptible varieties. The greater cost of seed
of Bugle, $48.50/lb versus $15.15/lb for Waltham, is offset by the additional
fungicide applications needed to affectively control powdery mildew
in Waltham. It will cost about $16 more to grow an acre of Waltham sprayed
seven times than an acre of Bugle sprayed thrice. Although seed of Taybelle
PM and Autumn Delight is priced slightly higher than seed of Taybelle
and Table Ace, overall production costs are lower because of the cost
difference between a 7- and 14-day fungicide program and because fungicide
treatment is needed earlier in susceptible varieties. It will cost about
$109 less to grow an acre of Autumn Delight sprayed thrice compared
to Table Ace sprayed seven times and $131 less for Taybelle PM compared
to Taybelle. The resistant varieties evaluated are commercially available,
thus growers can implement an integrated program (fungicides applied
on a reduced schedule) for managing powdery mildew now.
|
