Temperature Thresholds and Degree-Day Model for Marmara gulosa (Lepidoptera: Gracillariidae)

Abstract

The developmental thresholds for Marmara gulosa Guillén & Davis (Lepidoptera: Gracillariidae) were investigated in the laboratory by using 17, 21, 25, 29, and 33 degrees C. The lowest mortality occurred in cohorts exposed to 25 and 29 degrees C. Other temperatures caused >10% mortality primarily in egg and first and second instar sap-feeding larvae. Linear regression analysis approximated the lower developmental threshold at 12.2 degrees C. High mortality and slow developmental rate at 33 degrees C indicate the upper developmental threshold is near this temperature. The degree-day (DD) model indicated that a generation requires an accumulation of 322 DD for development from egg to adult emergence. Average daily temperatures in the San Joaquin Valley could produce up to seven generations of M. gulosa per year. Field studies documented two, five, and three overlapping generations of M. gulosa in walnuts (Juglans regia L.; Juglandaceae), pummelos (Citrus maxima (Burm.) Merr.; Rutaceae), and oranges (Citrus sinensis (L.) Osbeck; Rutaceae), for a total of seven observed peelminer generations. Degree-day units between generations averaged 375 DD for larvae infesting walnut twigs; however, availability of green wood probably affected timing of infestations. Degree-day units between larval generations averaged 322 for pummelos and 309 for oranges, confirming the laboratory estimation. First infestation of citrus occurred in June in pummelo fruit and August in orange fruit when fruit neared 60 mm in diameter. Fruit size and degree-day units could be used as management tools to more precisely time insecticide treatments to target the egg stage and prevent rind damage to citrus. Degree-day units also could be used to more precisely time natural enemy releases to target larval instars that are preferred for oviposition.

Predicting adult emergence of Dakota skipper and Poweshiek skipperling (Lepidoptera: Hesperiidae) in Canada

“…Ideally, the development threshold would be calculated by subjecting immature stages of the study species to various constant temperatures in a laboratory, measuring the development rate of the insects at each of these temperatures, and fitting a linear or nonlinear line to the data points. The temperature at which the line intersects the point of zero development is then taken as the lower threshold temperature (Bryant et al 1997;Johansen 1997;Han et al 2000;Mironidis et al 2010;O'Neal et al 2011). Future studies should therefore examine methods for rearing these species in captivity and measuring development thresholds for the various population centers across the North American range for each species.…”

“…They have been widely used to increase the precision of insecticide applications, and to improve integrated pest management techniques for insect pests, both invasive and endemic (Sanders 1975;Gerber and Howlader 1987;Régnière 1987;Malinoski and Paine 1988;Hébert and Cloutier 1990;Johansen 1997;McBrien and Judd 1998;Han et al 2000;Kim et al 2000;Senanayake et al 2000;Doerr et al 2002;Baek et al 2008;Mironidis et al 2010;O'Neal et al 2011;Thöming and Saucke 2011;Son et al 2012). Fewer studies of this sort have been conducted on non-pest species of Lepidoptera.…”

“…However, a single threshold temperature has often been used for several larval instars, or several different developmental stages of the same species (Régnière and Turgeon 1989;Bryant et al 1997;O'Neal et al 2011;Son et al 2012). Upper threshold temperatures, the point at which development slows due to excessive heat, can also be determined and used in degree day calculations (Malinoski and Paine 1988;Han et al 2000;O'Neal et al 2011;Son et al 2012). However, it is often the case that the use of an upper threshold temperature has a negligible effect on the number of heat units accumulated, especially near the beginning of the growing season when temperatures are relatively cool in temperate climates.…”

“…In reality, the relationship between these two variables is usually nonlinear, especially near the upper and lower developmental thresholds (Weber et al 1999;Kim et al 2000;Régnière et al 2012;Son et al 2012). However, linear degree-day models have been demonstrated to work well enough for practical purposes, such as timing of insect life stages for pest control (Johansen 1997;O'Neal et al 2011; University of California Agriculture and Natural Resources 2012), and Selby has successfully used a linear model to predict the flight periods of Minnesota populations of Dakota skipper and Poweshiek skipperling for the past 10 years (G. Selby, personal communication, 2013).…”

“…This model [(max temp -min temp/2) -LTT] has been used to predict the number of generations per year of the citrus peel miner (Marmara gulosa Guillén and Davis) in California (O'Neal et al 2011). It has also been used to predict the adult emergence dates of insects such as the pea moth (Cydia nigricana Fabricus) in northern Germany, and Gillette's checkerspot butterfly (Euphydryas gillettii Barnes) in the western United States (Thöming and Saucke 2011;McInnis and Gibson 2012).…”