Cucurbit Genetics Cooperative Report 3:5-6 (article 3) 1980
Screening Cucumbers for Resistance to the Vegetable Leafminer
Gwendolyn Eason, G.C. Kennedy, and R.L. Lower
North Carolina State University, Raleigh, NC 27650, University
of Wisconsin, Madison, WI 53706
Effective chemical control of the pickleworm and
cucumber beetle has reduced natural populations of wasp
species which formerly kept the vegetable leafminer, Liriomyza
sativae Blanchard, under biological control (2,3,4).
Host plant resistance to the leafminer was deemed more desirable
than the use of additional chemicals to control leafminers
on cucumber crops.
Greenhouse and controlled environment chamber (ca. 27°C,
55% RH) experiments were used to develop seedling screening
techniques and to evaluate a collection of breeding lines,
cultivars, and plant introductions for resistance (1). More
mature plants (ca.3 leaves) were evaluated in the greenhouse
Both angle and height of the cotyledons were found to affect
leafminer response to cucumber seedlings. Seedlings with
revolute cotyledons received fewer mines than seedlings
with cotyledons which were flat and parallel to the ground
plane. In seedling tests conducted directly beneath a light
source, taller seedlings had more mines than short seedlings.
When seedling experiments were blocked against a light source,
seedling height interacted with distance to the light source
to affect leafminer choice. Consistent results among seedling
experiments were obtained only when all cotyledons within
each experiment were adjusted to a uniform distance above
the ground plane. Because light reflection and distribution
among seedlings may be affected by both height and angle
of the cotyledons, the importance of both of these plant
factors in resistance screening may be explained by the
positive phototactic nature of the leafminer.
When cotyledon heights were adjusted within seedling experiments,
similar results could be obtained in the controlled chamber
and in the greenhouse. Greenhouse experiments with mature
plants had similar results when plant samples within the
experiments were of uniform development. Seedling response
in the chamber or greenhouse did not predict the response
of some lines in the more mature plant stage; cotyledon
resistance apparently is not contingent on the same factor(s)
as mature plant resistance.
Of the screened materials, PI 200815 and PI 279465 appeared
to have the most potential as sources of resistant germplasm.
These plant introductions were resistant in both seedling
and in later stages. 'Gy 2,' a gynoecious breeding line,
was resistant only in the seedling stage. 'Addis' and 'Spartan
Salad', pickling cucumber cultivars, and PI 271327 were
consistently susceptible at all plant stages.
Field experiments will be necessary to evaluate the resistance
levels of PI 200815 and PI 279465 outside the greenhouse.
- Eason, Gwendolyn. 1980. Procedures in Screening Cucumis
sativus L. for Resistance to the Vegetable Leafminer,
Liriomyza sativae Blanchard. M.S. Thesis. North
Carolina State University, Raleigh, NC.
- Hills, O.A. and E.A Taylor. 1951. Parasitization of
dipterous leafminers in cantaloupe and lettuce in the
Salt River Valley, Arizona. J. of Econ. Entomol. 44:759-762.
- Michelbacher, A.E., W.W. Middlekauff, O.G. Bacon, and
J.E. Swift. 1955. Controlling melon insects and spider
mites. California Agric. Expt. Stn. Bul. 749, 46p.
- Wolfenbarger, D.O. 1958. Serpentine leafminer: brief
history an summary of a decade of control measures in
southern Florida. J. of Econ Entomol. 51:357-359.