Udea profundalis Packard Lepidoptera Pyralidae

The Bitcoin Greenhouse

Build Your Own Greenhouse

Get Instant Access

Natural History

Distribution. Celery leaftier, also known as "greenhouse leaftier," is found throughout the United States. Its distribution is favored by its adaptability to both indoor- and outdoor-plant cultivation. As a celery pest, it has proved to be numerous, and destructive, in all major celery-growing regions including California, Florida, Michigan, and New York. It is known to cause damage in the field in southern Ontario, but in most of Canada it is known only as a greenhouse pest. This insect also occurs in Central and South America.

False celery leaftier, which occurs only on the Pacific Coast from British Columbia to California, is a much less important pest, and is poorly known. It closely resembles celery leaftier.

Host Plants. In the field, celery leaftier is principally a pest of celery, but also has damaged sugarbeet and lettuce, and feeds on bean, beet, cabbage, cauliflower, kale, parsley, and probably other crops. In the greenhouse, its host range is quite large, and includes ageratum, anemone, calendula, carnation, cineraria, cucumber, dahlia, daisy, geranium, lettuce, sweetpea, snapdragon, rose and violet, but chrysanthemum is most important. Plants in the family Compositae seem preferred. A long list of greenhouse hosts was given by Weigel et al. (1924). However, neither the flowers nor the vegetables are usually attacked under field conditions, and Ball et al. (1935) suggested that the luxuriance of the forced, greenhouse-grown plants was the most important factor in allowing larvae to develop on these plants.

Weeds are important hosts. In Florida, key elements in celery leaftier biology are redroot pigweed, Amar-anthus retroflexus, and spiny amaranth, A. spinosus. These species and to a lesser extent several other weed hosts are important in maintaining the leaftiers through the celery-free summer period. Other known hosts are plantain, Plantago spp.; wild lettuce, Lactuca spp.; cowslip, Caltha palustris; tickweed, Verbesina vir-ginica; and water hemp, Acnida sp. In California, sugar-beet similarly provides a suitable host during the celery-free summer months. Essig (1934) reported that false celery leaftier fed extensively on hawksbeard, Crepis sp.

Natural Enemies. Studies in Florida documented the importance of several insect parasitoids of celery leaftier (Ball et al., 1935), though the most important was an egg parasite, Trichogramma sp. (Hymenoptera: Trichogrammatidae). It could account for 70-90% mortality, but was only effective during warm weather. During the summer months the egg parasites also use Amaranthus-infesting webworms as hosts. Of lesser importance were the larval parasitoids, Casanaria infesta Cresson (Hymenoptera: Ichneumonidae) and Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae). These normally accounted for less than 5% mortality.

Ball et al. (1935) provided unusually good documentation on the importance of birds as predators of celery leaftier in Florida. They contended that during the spring northward migration, birds faced difficulty in finding adequate food supplies. Thus, celery leaftier and celery looper, Anagrapha falcifera, which can be abundant in celery during the spring months, are a prime food source. Small fields were often maintained free of caterpillars by birds, principally palm warbler, Dendroica palmarum, and tree swallow, Tachycineta bicolor.

Life Cycle and Description. Under ideal conditions the celery leaftier may complete its life cycle in a month, and this occurs under greenhouse conditions. Under field conditions, development is delayed, depending on weather. In California, a generation requires one month in the summer, two months in the spring and autumn, and over three months during the winter. Thus, five to six generations occur annually, with three to four during the period of June-December and two during the remainder of the year (Campbell, 1927). In Illinois, four generations occur under field conditions.

  1. Celery leaftier eggs are about 0.8 mm long and 0.6 mm wide, spherical, and slightly flattened. The eggs are shiny, and whitish initially, growing darker as they mature. The eggs are deposited on the underside of leaves singly or in small groups of up to 12. As is common with pyralids, the eggs overlap one another. The incubation period is usually about six days (range 4-10 days). Most eggs are deposited just below the outer layer of plant canopy.
  2. The larvae are pale yellowish-white and measure only about one mm long initially, but soon become pale green, with a single dark green line dor-sally and bordered on each side by a broad whitish band. This striped pattern persists throughout the larval period. The color of the ventral surface of the larva tends toward yellow. The head, thoracic shield, and thoracic legs are pale, though the shield bears a dark, oval spot on each side. The larvae are sparsely covered with long hairs. Larvae feed on the lower surface of leaves, often rolling leaves or webbing them together. In most respects, larvae behave like other webworms, including the tendency to retreat into their webbed shelter or to wriggle violently and spin down from the plant on a strand of silk if disturbed. At maturity, the larvae measure only about 17-19 mm long. There are five larval instars, each requiring 2-5 days for completion. The total development time of the larval stage averages about 21 days (range 15-30 days). Head capsule widths for the instars are about 0.20, 0.27, 0.40, 0.67,1.05 mm, respectively.
  3. Pupation normally takes place in a thin, whitish silk cocoon amongst folded leaves. The pupa is smoky brown, and measures 8.5-9.0 mm long. Dura-

»

r

>1

fi

é

t>

er

Ä

•y

V

k

0

A

*

0

9>

3. «Í

N ?!

p

<5,

ñ

Celery leaftier larva.

tion of the pupal stage averages 10 days (range 6-16 days).

Adult. The moth of celery leaftier is small, the wingspan measuring only 15-21 mm. The front wings are light-brown, suffused with reddish-brown, and are irregularly marked with black lines. The hind wings are grayish, becoming brown distally. The outer margin of the fore and hind wings are marked with a row of small, dark spots. Adults live for several days; males tend to survive about 4-5 days and females 9-10 days. They are nocturnal, and remain hidden during the daylight hours. Mating occurs almost immediately upon adult emergence, and oviposition begins within 24 h of emergence. Eggs, which tend to be deposited principally during the first few days of adulthood, are deposited at night.

The eggs, larvae, pupae, and moths of false celery leaftier are not easily differentiated from celery leaf-tier, and in nearly all respects the biology is the same. Munroe (1966) gave characters to distinguish the moths. False celery leaftier averages slightly larger than celery leaftier, the wingspan ranging from 1925 mm. The larvae also are slightly larger. Mean head capsule widths for the five instars are 0.23, 0.34, 0.54, 0.82, and 1.23 mm, respectively.

The field ecology of celery leaftier was best described by Ball et al. (1935); developmental biology was provided by Fletcher and Gibson (1901) and Weigel et al. (1924). False celery leaftier is poorly studied; Tamaki and Butt (1977) gave the only substantive biological information on this insect.

Damage

Larvae feed mostly on the underside of foliage. Depending on the thickness of the plant tissue they may eat the entire leaf, only the lower surface, or leave the foliage skeletonized. They also cover the leaves with a thin layer of silk. The silk webbing may be used to draw portions of the leaf together. Celery leaftier larvae may work their own way down to the youngest tissue, the "heart" of celery, and feed on both leaves

Adult celery leaftier.

and petioles (Stone et al., 1932). Jones and Granett (1982) indicated that false celery leaftier also damaged the heart of celery in California.

Management

Moths of celery leaftier are attracted to phenyl-acetaldehyde, and this chemical may be useful with some types of traps for population monitoring (Cantelo et al., 1982). They also come to light traps. Foliar insecticides are applied for leaftier suppression, and growers are encouraged to target the young larvae for control because they are easier to kill. This insect is only occasionally threatening, however.

Was this article helpful?

0 0
Building Your Own Greenhouse

Building Your Own Greenhouse

You Might Just End Up Spending More Time In Planning Your Greenhouse Than Your Home Don’t Blame Us If Your Wife Gets Mad. Don't Be A Conventional Greenhouse Dreamer! Come Out Of The Mould, Build Your Own And Let Your Greenhouse Give A Better Yield Than Any Other In Town! Discover How You Can Start Your Own Greenhouse With Healthier Plants… Anytime Of The Year!

Get My Free Ebook


Post a comment