Abstract
The effectiveness of augmentative biological control using parasitoids often depends on their physiological state and the pest population density at the time of release. Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) is a primary host-feeding parasitoid of a serious invasive pest Bactericera cockerelli (Šulc) (Hemiptera: Triozidae). Here we investigated the effects of adult diets (honey, water, yeast, and hosts) and timing of their provision on T. triozae fitness and oviposition patterns, providing knowledge for enhancement of its biological control potential. Adults fed with honey for four days with no access to hosts or with water or yeast for one day followed by host feeding for three days had similar longevity and lifetime pest killing ability. Adults fed with only water for one day before release had significantly greater intrinsic rate of increase, shorter doubling time, and higher daily fecundity peak. Adults fed with honey or yeast for one day followed by host feeding for three days significantly flattened their daily oviposition curves. These findings have several implications for augmentative biological control using T. triozae. First, honey diet may allow at least four days for successful shipment of host-deprived adults without compromising biological control effectiveness. Second, the release of host-deprived adults with one-day water feeding may achieve rapid pest suppression when the pest population density is high. Finally, releasing host-deprived adults with one-day honey or yeast feeding followed by three-day host feeding can increase their establishment success and reduce the risk of massive removal of hosts when the pest population density is low.
Highlights
Augmentative release of natural enemies, parasitoids, is one of the most widely used approaches to pest biological control in annual crops and greenhouses
We developed two Gaussian functional models according to Archontoulis and Miguez (2015): y = a e(−0.5{[(x−c)−(x0−c)]∕b}2) to fit the daily host feeding and y = a e(−0.5{ln[(x−c)∕(x0−c)]∕b}2) to fit the daily oviposition and daughter production for each treatment, where x is the age of female wasps, a is the peak at time x0, b is the coefficient controlling the width of the peak, and c is the period before the females were exposed to hosts (i.e., c = 1 and 4 days for the + Host and − Host treatments, respectively)
Like other synovigenic parasitoids (e.g., Giron et al 2004; Liu et al 2015; Gebiola et al 2018), adult feeding on honey and/or hosts was essential for the survival of T. triozae because carbohydrates in these diets provided energy to prolong their longevity (e.g., Jervis et al 2008; Picciau et al 2019)
Summary
Augmentative release of natural enemies, parasitoids, is one of the most widely used approaches to pest biological control in annual crops and greenhouses (van Lenteren and Bueno 2003; Hoy 2008; Amadou et al 2019; Bueno et al 2020; Kazak et al 2020). When the pest population density is low, we may want to delay their oviposition peaks and flatten their oviposition curves (Stahl et al 2019) where the released parasitoids are expected to spread their oviposition and host feeding more evenly or move these activities toward their later life It is not clear how alteration of timing and type of diets provided for adult parasitoids before release can change their life history traits towards our advantage. It is unclear whether such manipulation would compromise their overall pest killing ability in terms of fecundity and host feeding. This knowledge is crucial for the development of successful augmentative biological control programs using parasitoids
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