Aculops lycopersici

Aysan, Elif & Kumral, Nabi Alper, 2018, Tritrophic relationships among tomato cultivars, the rust mite, Aculops lycopersici (Massee) (Eriophyidae), and its predators, Acarologia 58 (8), pp. 5-17 : 8-11

Aculops lycopersici population development

The mean numbers of A. lycopersici mobile stages differed significantly among the six tomato cultivars under controlled conditions ( Table 1 , F5,48 =9.21, P<0.01). Similarly, the mean mite numbers differed significantly among both the abaxial and adaxial surfaces of the six tomato cultivars (F5,48 =7.77, P<0.01, F5,48 =9.31, P<0.01), and the mean mite number for Jana was significantly higher than the other cultivars. Although the H2274 cultivar had fewer mites, the difference was not significant compared with the other tomato cultivars.

The A. lycopersici density among the six tomato cultivars varied remarkably throughout the entire growing season under natural conditions ( Table 2, F5,409 =2.93, P= 0.0013). Aculops

2015.

lycopersici on M1103 had a significantly higher population density, followed by the Etna and

Jana cultivars, respectively. Similar to the controlled condition results, mean mite numbers were significantly lower on the Grande and H2274 cultivars than the others. Mean mite numbers significantly differed on both the lower and upper surfaces of these tomato cultivars ( Table 2, F5,409 =2.50, P= 0.03, F5,409 =3.59, P= 0.0034). The population trends and densities of A. lycopersici on the six tomato cultivars under natural conditions for 2015 are shown in Figure 2A. The mite density increased in early August and peaked in late August. The highest A. lycopersici density was significant on 24 August for Jana and H2274 and on 31 August for the M1103, Dora, Grande and Etna cultivars (P<0.01). The population density gradually decreased from mid-September to mid-October.

Population development of predator mites

In the present study, 5 predator species belong to Phytoseiidae were obtained from the six tomato cultivars under natural conditions. These species were Neoseiulus barkeri Hughes , Euseius finlandicus (Oudemans) , Typhlodromus (Anthoseius) recki Wainstein , Typhlodromus (Typhlodromus) athiasae Porath and Swirski and Phytoseius finitimus Ribaga ( Acari : Phytoseiidae ). In addition, two species were detected from Tydeidae and Iolinidae , Tydeus kochi Oudemans and Pronematus ubiquitus (McGregor) , which have varied feeding habits including predatory.

Tydeus kochi density varied significantly among the six tomato cultivars throughout the entire growing season under natural conditions ( Table 3, F5,409 =2.28, P= 0.046). The highest significant density of T. kochi was found on the H2274 and Grande cultivars. In contrast to the A. lycopersici results, mean mite numbers were significantly lower on the Jana and Dora cultivars than the other cultivars ( Table 3). T. kochi population trends and densities on the six tomato cultivars under natural conditions for 2015 are shown in Figure 2B. Similar to the A. lycopersici trend, T. kochi was first observed in late July to early August and peaked significantly twice on 31 August and 20 September (P<0.01). The T. kochi population trend was positively correlated with that of A. lycopersici on all tomato cultivars ( Table 4, r= 0.22

to 0.59, P<0.01 or <0.05). In addition, although the P. ubiquitus densities varied significantly among the six tomato cultivars, they were not significantly correlated with the A. lycopersici population trend ( Table 3 and 4, Figure 2C, F5,409 =2.79, P= 0.017, r= -0.11 to 0.12, P> 0.05). However, although phytoseiid were observed between early August and early September, these population trends were not correlated with those of A. lycopersici , and the difference in their population density among the six tomato cultivars was not significant ( Tables 3 and 4, Figure

2D, P> 0.05, r= -0.15 to 0.05, P> 0.05).

Predator insect population development

In this study, the mite predatory species, Macrolophus sp. (Heteroptera: Miridae ) was observed on all tomato cultivars under natural conditions ( Table 3 and Figure 2E), but the cultivar did not significantly affect the population density of the predatory insect (F5,409 =0.69, P= 0.63). The Macrolophus sp. density was slightly higher on the Grande, Etna and M1103 cultivars. Similar to A. lycopersici , the predator insect was first observed in early August (Figure 2E). In contrast, the highest significant population densities were seen on 16 September and 5 and 19 October

(P<0.01); however, these were not positively correlated with the A. lycopersici population density ( Table 4, r=-0.24 to -0.02).

Trichome density and its effect on pest and predator densities

Non-glandular (types II and V) and glandular trichome (type VI) densities on the tomato leaves under natural conditions differed significantly ( Table 5, type II F5,24 =8.91, P<0.01, type V F5,24 =57.55, P<0.01, type VI F5,24 =19.13, P<0.01). While trichome density was higher on the abaxial surface for all cultivars, their densities on both surfaces differed significantly among the six tomato cultivars (type II F5,24 =9.99, P<0.01, F5,24 =5.97, P<0.01, type V F5,24 =26.99, P<0.01, F5,24 =63.57, P<0.01, type VI F5,24 =7.53, P<0.01, F5,24 =32.07, P<0.01). The trichome densities of non-glandular type II, and especially type V, on both surfaces were highest on Jana, followed by H2274 and Dora. The lowest trichome densities were detected on Grande ( Table 5). Similarly, glandular type VI trichomes were high for Jana and low for Grande ( Table 5).

Multivariate analysis results for the glandular and non-glandular trichome densities of the six tomato cultivars versus A. lycopersici and its predator densities under natural conditions are shown in Table 6. Although the A. lycopersici density showed a significant positive correlation with type V non-glandular and type VI glandular trichome densities, type II non-glandular and type VI glandular trichome densities were negatively correlated with the predator, T. kochi . Similar negative correlations were found for both P. ubiquitus and Macrolophus sp. vs. type V.