FORSKNINGSNYTT • Nr 3-4 • 2007
Are carrots able to tolerate some carrot
psyllid feeding without considerable
yield loss? Is it possible to develop an
ecological control method of carrot psyllid
based on push-pull strategy? This was recently investigated in a Finnish study.
Looking for ecological control of carrot psyllid
O
verwintered adult carrot
possibility of developing an ecological
cotyledon stage reduced the carrot yield
psyllids (Trioza apicalis) start
control method of carrot psyllid based
at harvest on average 35 % whereas th-
phloem-feeding on carrot im-
on a push-pull strategy*.
ree psyllids feeding for three days was
mediately after entering carrot fields, and
needed to cause significant yield loss at
the damage symptoms (curled leaves,
Difficult to monitor
the one-leaf stage. Yellow, purple and
stunted growth) become visible on ave-
In Finland carrot psyllid flight is mo-
bronze discolouration appeared in leaves
rage in two days. The migration flight
nitored by yellow sticky traps changed
over one month after the psyllids were
from conifers to carrot fields continues
once a week. However, conventional
removed. Therefore, a part of the symp-
for several weeks in June-July. Therefore,
farmers complain that a week is a too
toms could be caused by a plant disease,
crop covers are the only effective method
long monitoring period, resulting
such as phytoplasma infection.
to protect the yield in organic farming.
delayed application of control measu-
in
res. Another problem is to define the
An attractive cultivar was found
In conventional farming several insec-
beginning of the flight of carrot psyllid.
Carrot psyllids preferred an old yellow-
ticide treatments are used annually to
Several Trioza-species are caught in the
rooted cultivar over Splendid (hybrid
control carrot psyllids in the main car-
traps in May-June. The most difficult
cultivar) in a two-choice egg laying test.
rot cultivation areas. Even after control
species to distinguish from Trioza apicalis
For four cultivars, Splendid, Parano,
measures were applied 3–18 % of carrots
is T. anthrisci, which lives on cow parsley
Panther, and Napoli, a negative linear
were moderately or seriously damaged
(Anthriscus sylvestris) and apparently
correlation was found between numbers
(leaf damages exceeding 15 %) in con-
does not damage carrot.
of eggs-laid and limonene concentration
ventional carrot fields in 2005–2006 in
of leaf essential oils. However, in larger
Finland. The aims of this study were to
Carrots are vulnerable at
data concerning 15 cultivars (majority
determine if carrots are able to tolerate
early growth stages
non-hybrids) and wild carrot, no cor-
some carrot psyllid feeding without con-
One gravid carrot psyllid female feeding
relation was found. Possible trap crops
siderable yield loss, and to assess the
for three days on a carrot seedling at
were searched among carrot cultivars
8
FORSKNINGSNYTT • Nr 3-4 • 2007
since carrot psyllids prefer cultivated car-
results will be published later on.
rot among Apiaceae-species. Non-hybrid
with possible repellent compounds, such
as winter host volatiles, will be needed
cultivars were studied since they would
Conclusions
to develop an efficient ecological control
be economical as a trap crop owing to
The results suggest that a one-week trap
method for this species.
cheaper seeds. In addition to trap crop,
replacement period, which is the current
the use of repellents could help preven-
practise in carrot psyllid monitoring,
Anne Nissinen
ting the carrot psyllids damage. Howe-
is too long at the early growth stages
E-mail: [email protected]
ver, the repellent effect of limonene or a
of carrot. Regardless of the oviposition
mixture of limonene and carvone was not
(laying of eggs) preference for a certain
Anne Nissinen is researcher at MTT Agri-
shown in greenhouse experiments, even
carrot cultivars, the possibility of a func-
food Research Finland, Plant Production
though it was previously observed in the
tional push-pull control strategy based
Research. Her special competences are in
field in Swedish experiments.
on limonene seems unlikely, since the
chemical ecology, ecological pest management
repellent effect of limonene could not be
and organic production,
High light intensity
verified. However, reliable behavioural
attracts carrot psyllids
assays with carrot psyllid turned out to
One possible reason to the failure to
be difficult to conduct in laboratory or
show repellent effect of limonene in
greenhouse conditions, since this spe-
greenhouse was that carrot psyllids
cies reacts to very small changes in light
were strongly attracted to higher light
intensity. Therefore, further field studies
■
* Push-pull strategies involve the behavioral
manipulation of insect pests and their natural
enemies via the integration of stimuli that act
to make the protected resource unattractive
or unsuitable to the pests (push) while luring
them toward an attractive source (pull) from
where the pests are subsequently removed.
intensity in laboratory. The effect of light
intensity on host plant selection of carrot
psyllids was studied, since carrot psyllid
behaviour varied from experiment to
experiment in different laboratory and
greenhouse assays. The strong attraction
Nytt svenskt projekt
om näring till ekotomater
make up the migrating cohort in nature.
I
inte i första hand på brister i jorden utan
eventuell ökning av fosfortillgänglighe-
Another explanation is that the continu-
på att frigörelsehastigheten är låg. En
ten påverkar upptaget av zink, koppar,
ous rearing of carrot psyllid on summer
anledning till lågt fosforupptag trots god
järn och mangan.
host only may alter their behaviour.
tillgång i marken kan vara fastläggning på
Therefore, I recommend conducting the
grund av stigande pH. Brist på fosfor kan
I växthusförsök studeras även hur halm
behavioural assays of carrot psyllid in
i sin tur ge upphov till kvävebrist genom
påverkar tillgången på kväve och fos-
the field.
störningar av proteinsyntesen i plantan.
for. Vid tillförsel av halm uppförökas
especially of virgin individuals to higher
light intensity may be connected to their
migratory behaviour, since virgin adults
ekologiska tomatodlingar är ofta
oxalsyra. Vidare undersöks om sänkt pH
kväve- och fosfornivån i plantorna
ökar fosforupptaget och höjer kvävekon-
låg. Bristen i plantan beror troligen
centrationen i tomatplantan och om en
markens mikroflora och efterhand som
Research on carrot injuries
I ett tvåårig projekt inom SLU:s forsk-
mikrofloran omsätts frigörs uppbunden
continues
ningsprogram ”Ekoforsk” undersöks
växtnäring. Samtidigt frigörs organiska
During the season 2007, the effect of a
hur stor påverkan på pH några vanliga
syror som momentant sänker pH och
three-day feeding period of carrot psyl-
jordförbättrings- och gödselmedel har.
bildar stabila kelat med aluminium,
lids on carrot seedlings at one-, two- and
Projektet utgår från förhållandena i tre
kalcium och järn vilket minskar fastlägg-
four-leaf stage was studied on carrot
odlingar med olika gödslingsstrategier.
ningen av fosfor. Även kväve immobili-
yield. The discolouration symptoms
seras i mikrofloran vid tillförsel av halm
were also observed in these experiments
I odlingarna följs tillgången på kväve och
men då kväve i motsats till fosfor inte
and the possible phytoplasma infection
fosfor i jorden och upptaget i växten. I
fastläggs i svåromsättbara föreningar
is being investigated. Major sugars and
inkubations- och växthusförsök jämförs
kan nettoeffekten av halmtillförsel för
phenolic compounds were analysed from
pH-sänkningen vid tillförsel av okalkad
kvävets del förväntas bli negativ.
damaged and healthy roots to assess
torv, urin, ensilage, kiserit och blodmjöl
the internal quality of the carrots. These
med pH-sänkningen vid tillförsel av
■
Kontakt: [email protected]
9