Page 43 - Volume 6, Issue 1, January 2013

Laboratory of Agronomy, Faculty of Crop Science, Ag-

ricultural University of Athens, 75, Iera Odos St., GR-

11855 Athens, Greece

*

Corresponding author:

travlos@aua.gr

Hellenic Plant Protection Journal

6:

41-48, 2013

Interference between silverleaf nightshade (

Solanum

elaeagnifolium

Cav.) and alfalfa (

Medicago sativa

L.) cultivars

I.S. Travlos

*

, A. Gatos and P.J. Kanatas

Summary

Alfalfa (

Medicago sativa

L.) is the most widely grown forage legume in Greece and other

Mediterranean countries. The successful establishment of the crop is crucial for its overall productivi-

ty. Weed infestations are a common problem, especially in spring-seeded alfalfa, with silverleaf night-

shade (

Solanum elaeagnifolium

Cav

.

) being one of the most noxious weeds. The main objective of the

field experiment conducted in Greece in 2010 and 2011 was to evaluate the differences among three

alfalfa cultivars (Gea, Dimitra and Hyliki) regarding their competitiveness against silverleaf nightshade

and their forage yield during the first crucial year of crop establishment. Moreover, density and fresh

weight data of

S. elaeagnifolium

were also recorded. Our results showed that the presence of this weed

caused an annual yield loss ranged from 8 to 26%, depending on the year and the cultivar. In particular,

Hyliki was the most productive cultivar, while even with the presence of nightshade it produced signifi-

cantly higher biomass than the other cultivars (up to 28%). Furthermore, Hyliki was the cultivar with the

highest regrowth rate after each cutting. Weed density and biomass were also significantly reduced in

the case of Hyliki, while Gea was the less competitive cultivar. The results of the present study confirm

that the competitive ability of the alfalfa cultivars might have a substantial range and can be a helpful

weed management tool for the growers, especially against noxious species such as

S. elaeagnifolium

.

Additional keywords

: alfalfa cultivars, integrated weed management, noxious weeds, regrowth, competition

Introduction

Alfalfa or lucerne (

Medicago sativa

L.),

the most widely grown forage legume

in Greece, could play a key role in organ-

ic crop-livestock systems, owing to its suit-

ability to low input, rainfed conditions, its

positive effects on soil fertility and nitrogen

balance, and the high protein content and

quality of its forage (Entz

et al

., 2001; Kara-

manos

et al

., 2009). The successful estab-

lishment of the crop is crucial for its overall

productivity (Stout

et al

., 1992). Established

stands of alfalfa are fairly competitive with

weeds. However, new alfalfa seedlings are

less competitive and more susceptible to

weed invasion (Annicchiarico and Pecet-

ti, 2010). In fact, weed competition is one

of the most limiting factors during crop es-

tablishment and early growth (especially in

spring-seeded alfalfa), since the emerging

crop plant is not a vigorous competitor and

weeds emerging shortly after seeding can

reduce alfalfa productivity (Pike and Stritz-

ke, 1984; Fischer

et al

., 1988; Zimdahl, 2004).

The ability of several alfalfa cultivars to sup-

press weed growth may allow crop produc-

ers to reduce total costs (Ominski

et al

., 1999;

Arregui

et al

., 2001; Dillehay

et al

., 2011).

During the last years, there have been

complaints from several regions of Greece

for reduced efficacy of herbicides or in-

creased competitiveness of many alien or

recently problematic species (Travlos, 2009;

Travlos and Chachalis, 2010). Silverleaf night-

shade (

S. elaeagnifolium

Cav

.)

is one of these

species, already present for many years in

the country (Economidou and Yannitsaros,

1975), with an ongoing dispersal in Greece

especially during the last decade, accord-

ing to extensive weed surveys (Travlos

et

al

., 2011; Travlos, 2013). Silverleaf nightshade

has spread in many arid regions of the world