Relation between plant water status and Macrosiphum euphorbiae (Hemiptera: Aphididae) population dynamics on three cultivars of tomato

Abstract

Abstract. Deficit irrigation scheduling is used to increase the efficiency with which water is used in many crops including tomato, however a water deficit is predicted to favour phloem feeding insects. We tested if and how different cultivars of tomato grown under water deficit conditions affect the population growth of the aphid Macrosiphum euphorbiae. Three tomato cultivars (Scintilla, Beefmaster and Rio Grande) were used in the experiments. The results for three watering regimes were compared with those of a control, which was well watered every three days: stressed plants received one third of the water supplied to the control over each three-day interval (experiment 1); stressed plants received a gradually decreasing amount of water (100% at the first watering and then 80%, 60%, 50%, 40% and 20%) every three days (experiment 2); stressed plants received the same amount of water as the control but at longer intervals, that is when evident signs of wilting appeared (experiment 3). The results showed that water stress either enhanced, had an adverse effect or had no effect on aphid population growth, depending on the cultivar and watering regime. No difference was recorded in the population dynamics of M. euphorbiae feeding on Beefmaster tomato plants subjected to different levels of water stress. In the case of the cultivar Scintilla, live aphids were less abundant on stressed plants than on well watered ones in experiment 1 and 3 but not in experiment 2. The highest variability in aphid population dynamics on the plants grown under the different water stress protocols was recorded on the cultivar Rio Grande. In experiment 1, the initial peak in aphid numbers was higher on the water stressed plants than on the control and then decreased to lower numbers than on the control. In experiment 2, there were no differences in the numbers of aphids infesting stressed and control plants. In experiment 3, there were fewer aphids on stressed than on control plants after six days, as in experiment 1, but there was no initial peak in aphid numbers.

Reproduction of an arboreal aphid pest, Elatobium abietinum, is altered under drought stress

“…White (1969)'s 'plant stress hypothesis' (PSH) stated that, under drought, host stress improved the nutritional quality of the host by increasing the availability of nitrogen for consumption by herbivorous insects, leading to increased reproduction and survival rates, inducing an outbreak of the insect population. Support for the hypothesis was originally provided by field observations that phytophagous insect populations often increased after drought events (Mattson and Haack 1987), although evidence for negative effects of sustained, severe water deficit was widely reported (Kennedy et al 1958;Inbar et al 2001;McVean and Dixon 2001;Huberty and Denno 2004;Rivelli et al 2013). The original hypothesis was modified in White (2009) to specify the PSH's relevance to senescence-feeding insects under moderate drought.…”

“…; McVean and Dixon ; Huberty and Denno ; Rivelli et al. ). The original hypothesis was modified in White () to specify the PSH's relevance to senescence‐feeding insects under moderate drought.…”

Drought-stressed tomato plants trigger bottom-up effects on key mite pests

“…Tomato (Solanum lycopersicum L) is a major vegetable crop grown all over the world in outdoor fields and greenhouses, and it is also one of the most water demanding. Thus, it needs to be cultivated under irrigation in most growing areas (Rivelli et al, 2013). Its cultivation is mainly concentrated in semiarid zones, where drought events associated with climate change are expected to be more frequent (Nankishore and Farrell, 2016).…”

“…The resulting performance of phytophagous arthropods on drought-stressed plants will then depend on the balance of plant nutrients and defenses, which may vary from plant to plant, depending on the plant species and genotype and in response to the intensity and the mode of the imposition of stress (Huberty and Denno, 2004;White, 2009). For instance, different tomato cultivars and different drought stress levels have positive, negative or no-effect on the aphid Macrosiphum euphrobiae (Rivelli et al, 2013).Nevertheless, the consequences of water stressed plants are not equivalent for different feeding guilds, since in general they have positive responses for borers, negative responses for gallformers, and inconsistent responses for free-living species and leaf miners (Inbar et al, 2001;Huberty and Denno, 2004). Another important factor is the grade of specialization of the General Introduction │CHAPTER 1 23 herbivore, polyphagous species being expected to be more affected than specialists by droughtmediated alterations in plant defenses (Gutbrodt et al, 2011).…”

“…The resulting performance of phytophagous arthropods on drought-stressed plants will then depend on the balance of plant nutrients and defenses, which may vary from plant to plant, depending on the plant species and genotype and in response to the intensity and the mode of the imposition of stress (Huberty and Denno, 2004;White, 2009). For instance, different tomato cultivars and different drought stress levels have positive, negative or no-effect on the aphid Macrosiphum euphrobiae (Rivelli et al, 2013).…”