Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is among the most devastating pests worldwide of solanaceous plants, particularly of tomato (Solanum lycopersicum L.). Since its recent introduction into sub‐Saharan Africa, it has become an additional widespread tomato pest throughout the region. When no control measures are taken, yield losses caused by T. absoluta larvae can reach 100%. Chemical control remains the primary management option despite its many adverse effects and increasing inefficiency due to the species’ endophytic habits and ability to develop insecticide resistance. Safer and more effective alternatives are therefore urgently required. Here, we investigated the effectiveness of two bioinsecticides compared to that of a widely used deltamethrin‐based synthetic insecticide, in preventing damage caused by T. absoluta larvae to tomato leaves and fruits, thereby affecting tomato yield. A field trial was conducted in 2018 and 2019 in northwestern Senegal using a randomized complete block design. Damage caused by T. absoluta affected approximately 65% of total leaf area and 3–24% of the fruits. Damage to the leaves caused by other insect species or other factors was less significant. At the dose applied, the chemical insecticide did not significantly reduce the surface area of leaflets affected by T. absoluta or other causal agents, the number of T. absoluta mines on the leaflets, or the proportion of fruits damaged. In contrast, the azadirachtin and Bacillus thuringiensis (Bt) formulations rapidly and significantly reduced damage to both leaves and fruits. The proportion of fruits damaged was reduced by a factor two and the total tomato yield was improved, particularly when the Bt formulation was used. In addition to their effectiveness in reducing damage caused by T. absoluta larvae to tomato leaves and fruit, and increasing the yield of marketable fruits, the viability of these organic alternatives was shown. The scope of our results is discussed in the context of T. absoluta control, in particular in integrated pest management programmes for tomato crops.

Tomato yellow leaf curl disease (TYLCD) caused by tomato yellow leaf curl virus (TYLCV) and a group of related begomoviruses is an important disease which in recent years has caused serious economic problems in tomato (Solanum lycopersicum) production worldwide. Spreading of the vectors, whiteflies of the Bemisia tabaci complex, has been responsible for many TYLCD outbreaks. In this review, we summarize the current knowledge of TYLCV and TYLV-like begomoviruses and the driving forces of the increasing global significance through rapid evolution of begomovirus variants, mixed infection in the field, association with betasatellites and host range expansion. Breeding for host plant resistance is considered as one of the most promising and sustainable methods in controlling TYLCD. Resistance to TYLCD was found in several wild relatives of tomato from which six TYLCV resistance genes (Ty-1 to Ty-6) have been identified. Currently, Ty-1 and Ty-3 are the primary resistance genes widely used in tomato breeding programs. Ty-2 is also exploited commercially either alone or in combination with other Ty-genes (i.e., Ty-1, Ty-3 or ty-5). Additionally, screening of a large collection of wild tomato species has resulted in the identification of novel TYLCD resistance sources. In this review, we focus on genetic resources used to date in breeding for TYLCVD resistance. For future breeding strategies, we discuss several leads in order to make full use of the naturally occurring and engineered resistance to mount a broad-spectrum and sustainable begomovirus resistance.

Tomato yellow leaf curl disease (TYLCD) caused by tomato yellow leaf curl virus (TYLCV) and a group of related begomoviruses is an important disease which in recent years has caused serious economic problems in tomato (<i>Solanum lycopersicum</i>) production worldwide. Spreading of the vectors, whiteflies of the <i>Bemisia tabaci</i> complex, has been responsible for many TYLCD outbreaks. In this review, we summarize the current knowledge of TYLCV and TYLV-like begomoviruses and the driving forces of the increasing global significance through rapid evolution of begomovirus variants, mixed infection in the field, association with betasatellites and host range expansion. Breeding for host plant resistance is considered as one of the most promising and sustainable methods in controlling TYLCD. Resistance to TYLCD was found in several wild relatives of tomato from which six TYLCV resistance genes (<i>Ty-1</i> to <i>Ty-6</i>) have been identified. Currently, <i>Ty-1</i> and <i>Ty-3</i> are the primary resistance genes widely used in tomato breeding programs. <i>Ty-2</i> is also exploited commercially either alone or in combination with other <i>Ty</i>-genes (i.e., <i>Ty-1</i>, <i>Ty-3</i> or <i>ty-5</i>). Additionally, screening of a large collection of wild tomato species has resulted in the identification of novel TYLCD resistance sources. In this review, we focus on genetic resources used to date in breeding for TYLCVD resistance. For future breeding strategies, we discuss several leads in order to make full use of the naturally occurring and engineered resistance to mount a broad-spectrum and sustainable begomovirus resistance.

In Taiwan, numerous crops are threatened by Xanthomonas diseases such as citrus bacterial canker caused by X. citri subsp. citri and tomato bacterial spot mainly caused by X. euvesicatoria pv. perforans. Foliar sprays of copper-based bactericides have been frequently used for control of plant bacterial diseases. However, in Taiwan not much attention was paid on copper-resistant (CuR) Xanthomonas spp. and their impact on disease control efficacy of copper-based bactericides. In this study, CuR Xanthomonas isolates were collected from citrus and tomato in Taiwan. Compared with the pronounced effect on the copper sensitive isolate, spraying of copper hydroxide at the recommended rate of 0.5 kg/ha could not protect tomato plants against bacterial spot caused by the CuR isolate. Phylogenetic analysis of concatenated copper resistance genes, copL, copA, and copB, indicate that the Taiwanese CuR isolates belong to the worldwide clade. In addition to the three previously reported variants of the copB gene, analysis of complete copB sequences from xanthomonads associated with citrus and solanaceous hosts revealed the other three variants of copB and their global distribution. Copper-resistant Xanthomonas isolates from Taiwan have the two unreported variants of copB genes which differ from the other three previously reported types in the sizes and structures. The information provided here reveals the necessity to develop and include alternative measures rather than relying on foliar sprays of copper bactericides for sustainable control of tomato bacterial spot in Taiwan.

In Taiwan, numerous crops are threatened by Xanthomonas diseases such as citrus bacterial canker caused by X. citri subsp. citri and tomato bacterial spot mainly caused by X. euvesicatoria pv. perforans. Foliar sprays of copper-based bactericides have been frequently used for control of plant bacterial diseases. However, in Taiwan not much attention was paid on copper-resistant (CuR) Xanthomonas spp. and their impact on disease control efficacy of copper-based bactericides. In this study, CuR Xanthomonas isolates were collected from citrus and tomato in Taiwan. Compared with the pronounced effect on the copper sensitive isolate, spraying of copper hydroxide at the recommended rate of 0.5 kg/ha could not protect tomato plants against bacterial spot caused by the CuR isolate. Phylogenetic analysis of concatenated copper resistance genes, copL, copA, and copB, indicate that the Taiwanese CuR isolates belong to the worldwide clade. In addition to the three previously reported variants of the copB gene, analysis of complete copB sequences from xanthomonads associated with citrus and solanaceous hosts revealed the other three variants of copB and their global distribution. Copper-resistant Xanthomonas isolates from Taiwan have the two unreported variants of copB genes which differ from the other three previously reported types in the sizes and structures. The information provided here reveals the necessity to develop and include alternative measures rather than relying on foliar sprays of copper bactericides for sustainable control of tomato bacterial spot in Taiwan.

In Taiwan, numerous crops are threatened by Xanthomonas diseases such as citrus bacterial canker caused by X. citri subsp. citri and tomato bacterial spot mainly caused by X. euvesicatoria pv. perforans. Foliar sprays of copper-based bactericides have been frequently used for control of plant bacterial diseases. However, in Taiwan not much attention was paid on copper-resistant (Cu^R) Xanthomonas spp. and their impact on disease control efficacy of copper-based bactericides. In this study, Cu^R Xanthomonas isolates were collected from citrus and tomato in Taiwan. Compared with the pronounced effect on the copper sensitive isolate, spraying of copper hydroxide at the recommended rate of 0.5 kg/ha could not protect tomato plants against bacterial spot caused by the Cu^R isolate. Phylogenetic analysis of concatenated copper resistance genes, copL, copA, and copB, indicate that the Taiwanese Cu^R isolates belong to the worldwide clade. In addition to the three previously reported variants of the copB gene, analysis of complete copB sequences from xanthomonads associated with citrus and solanaceous hosts revealed the other three variants of copB and their global distribution. Copper-resistant Xanthomonas isolates from Taiwan have the two unreported variants of copB genes which differ from the other three previously reported types in the sizes and structures. The information provided here reveals the necessity to develop and include alternative measures rather than relying on foliar sprays of copper bactericides for sustainable control of tomato bacterial spot in Taiwan.