Postharvest Biology and Technology 20 2000 295 – 302
Mortality of eggs and third instar larvae of Anastrepha ludens and A. obliqua with insecticidal controlled
atmospheres at high temperatures
Elhadi M. Yahia , Dora Ortega-Zaleta
DIPA, Facultad de Quı´mica, Uni6ersidad Auto´noma de Quere´taro, Quere´taro
76010
, Mexico Received 15 November 1999; accepted 18 June 2000
Abstract
The in vitro mortality of eggs and third instar larvae of Anastrepha ludens and A. obliqua was determined after exposure to 21 treatments of air or controlled atmospheres CA at high temperatures and 50 RH. Air at 44°C for
160 min caused very low mortality, which increased significantly by CA. Higher temperatures caused a more rapid kill. One hundred percent mortality was achieved for third instar larvae of both species in air or CA at 48°C for 220
min. A 100 mortality of eggs of A. ludens was achieved in air at 51°C for 240 min or in CA at 52°C for 240 min, and 100 mortality of eggs of A. obliqua was achieved in air or in CA at 55°C for 240 min. A. obliqua was slightly
more tolerant than A. ludens, and eggs were more tolerant than third instar larvae in both species. CA had a synergistic effect at B 50°C, but was slightly less effective than air at higher temperatures. Low O
2
concentrations were more effective than high CO
2
levels. The mean estimated temperatures for 50, 99 and 99.9968 mortality LT
50
s, LT
99
s, LT
99.9968
s of eggs of A. obliqua the most tolerant exposed to 0 kPa O
2
+ 50 kPa CO
2
for 240 min were 49.4, 54.8 and 60.9°C, respectively. We conclude that dry hot air at ] 44°C and 50 RH in CA 0 kPa O
2
+ 50 kPa CO
2
, for 160 min or longer, is effective in increasing mortality of eggs and third instar larvae of A. ludens and A. obliqua.
© 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Postharvest; Heat; Insects; Fruit fly; Disinfestation; Quarantine; Hot air www.elsevier.comlocatepostharvbio
1. Introduction
Mango in Mexico can be infested with fruit flies, the most important being Anastrepha ludens
Loew and A. obliqua L.. A disinfestation treat- ment may be required when fruit is transported to
national or export markets free of the fly. For example, all mango fruit exported to USA and
Japan are treated with hot water the only autho- rized treatment, that consists of 46.1°C for 65, 75
or 90 min depending on fruit weight. This treat- ment, especially for longer periods, accelerates
ripening and causes fruit injury Campos and Yahia, 1991. Modified MA or controlled atmo-
spheres CA can be lethal to some insects and yet
Corresponding author. Tel.fax: + 52-42-156867. E-mail address
:
yahiasunserver.uaq.mx E.M. Yahia. 0925-521400 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 5 - 5 2 1 4 0 0 0 0 1 4 0 - X
beneficial for preserving the postharvest quality of several fruits Yahia, 1998. The lethal MACA
effects on insects and beneficial effects on com- modity is stimulating research interest to develop
these treatments as quarantine systems for differ- ent insects in different crops. Some mango culti-
vars such as ‘Keitt’ are tolerant to insecticidal extreme atmospheres 0.1 – 0.5 kPa O
2
andor 50 – 80 kPa CO
2
for up to 5 days at 20°C Yahia, 1993, 1994, 1998; Yahia and Tiznado-Hernandez,
1993; Yahia and Vazquez-Moreno, 1993; Yahia and Paull, 1997; Yahia et al., 1989. Several in-
sects can be killed by heat andor by insecticidal atmospheres Armstrong, 1994; Hallman, 1994.
The time required for mortality varies with species and is affected by the life stage, the climatic
conditions temperature, relative humidity, and the atmosphere composition. Mortality is usually
higher at higher temperatures Armstrong, 1994. Short periods of elevated temperatures in combi-
nation with CA are effective in controlling insect pests Yahia, 1998; Yahia and Paull, 1997; Yahia
et al., 1997. Insect mortality by CA and MA is faster at higher temperatures Hallman, 1994.
Whiting and Van Den Heuvel 1995 have shown that CA at 40°C significantly reduced the dura-
tion of exposure required for 100 mortality of Tetranychus urticae Koch. Carbon dioxide at 50
kPa for 4 h and 100 kPa for 7 h at 23°C caused only 6.0 and 6.9 mortality of the Caribbean
fruit fly A. suspensa Loew larvae, respectively, and 100 kPa N
2
killed 7.4 of larvae Benschoter et al., 1981. Sixty hours of exposure to 100 kPa
N
2
were required to kill all the larvae. From a practical
standpoint, a
quarantine treatment
should be accomplished in a shorter period of time. Mango fruit is fairly tolerant to heat Yahia
et al., 1997, and thus quarantine treatments have been developed based on the use of hot water or
hot air Heather et al., 1997. Soderstrom et al. 1991 have shown that CA is more effective for
the control of Cydia pomonella L. when com- bined with high temperatures. Whiting et al.
1991 have shown that lower concentration of O
2
1 kPa at high temperatures increased the mortal- ity of several insects. The use of high levels of
CO
2
60 – 90 kPa and low levels of O
2
1 kPa decreased the mortality time of Tribolium casta-
neum Herbst. when combined with high temper- ature 42°C Soderstrom et al., 1992. Mortality
of third instar larvae of A. ludens was significantly higher at 44°C in 1 kPa O
2
than in air Shellie et al., 1997. A 100 mortality of third instar larvae
of A. ludens was accomplished in 3.5 h in 1 kPa O
2
at 44°C Shellie et al., 1997. The most heat resistant life stage of A. ludens Loew. was re-
ported to be the third instar stage Shellie et al., 1997. In a preliminary study Yahia et al., 1997
we reported that 0 kPa O
2
+ 50 kPa CO
2
at 44°C for 160 min caused 100 mortality of eggs and
third instar larvae of A. ludens and A. obliqua. This atmosphere for 120 min caused 100 mor-
tality of larvae, but only 62 – 72 mortality in eggs of A. ludens.
The objective of this study was to evaluate the in vitro mortality of eggs and third instar larvae
of A. ludens and A. obliqua at high temperatures 44, 48, 51, 52, 54 and 55°C, in air or in CA O
2
concentration as low as 0 kPa and CO
2
concentra- tion as high as 50 kPa, for 80, 160, 220 or 240
min.
2. Materials and methods
