Biological control is widespread in management of greenhouse sweet pepper crops. Several species of predatory mites, bugs, and parasitoids are used against a wide range of pest species. However, biological control of particular pests like aphids, caterpillars, and the tobacco whitefly, Bemisia tabaci Gennadius, remains problematic. Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a generalist predatory bug which is used on a large scale in Western European tomato greenhouses. It has already been demonstrated that M. pygmaeus is a valuable biocontrol option in sweet pepper crops, but it has yet to find its way into common practice. Macrolophus pygmaeus should be introduced at the start of the growing season and determining an optimal release strategy is a key step in this process. In tomato crops, M. pygmaeus requires supplemental food releases to reach sufficient population numbers and dispersal levels. In this study, the need for food supplementation in sweet pepper is investigated. Three strategies were tested: (1) no food supplementation, (2) local food supplementation, and (3) full field food supplementation. Both population numbers and dispersal rates of the second generation were higher under the third strategy. Macrolophus pygmaeus oviposits near food sources, therefore dispersal rates are higher when food is more spread out. Pest control was achieved in all treatments, but faster and at lower pest levels under the full field strategy.

Key message• Generalist and specialist beneficials are used in greenhouse crops to control pests.• Predator-prey population models can be used to predict pest outbreaks and prevent pesticide applications. Currently, no such models are on the market for decision making.• Simple, logistic regression models were built for three economic important pests and their predators in tomato crops.• The predicted population dynamics are in line with generalist and specialist predator ecology• The models were validated and deemed satisfactory for practical guidance in biocontrol actions.

Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a generalist natural enemy that is used to control multiple pest species in a variety of horticultural crops. The bugs are released at the start of the crop cycle to allow them to establish and build up a population in the crop that can control pest infestations later in the season. To facilitate population growth and dispersal in protected sweet pepper crops, Capsicum annuum L. (Solanaceae), food should be supplemented in a full‐field fashion during the first 6–8 weeks after introduction. To reduce the costs of food supplementation, we investigated whether fewer applications could produce similar results in terms of population growth and dispersal within the greenhouse. First, a cage experiment was carried out in which a weekly and biweekly application rate was tested for three food sources: cysts of brine shrimps Artemia spp. (Anostraca: Artemiidae), eggs of the Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), and a commercial mix of the two. Artemia spp. cysts resulted in the largest M. pygmaeus populations. There was no difference in population size between the two application rates for any of the food sources. Second, a greenhouse experiment was set up to test both application rates for Artemia spp. cysts under conditions mimicking commercial practice. Again, no difference in population size was observed between a weekly and a biweekly application rate. This insight is good news for growers, as they can use the least expensive food source and they need fewer applications to successfully introduce M. pygmaeus in protected sweet pepper crops.

Yellow sticky traps (YSTs) are commonly used in greenhouse crops to monitor flying pest species. Whiteflies like Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) and Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) are typically monitored using YSTs in tomato and sweet pepper crops. By counting the whiteflies on a YST, growers get an idea of the pests density in space and time in the greenhouse and can take pest control measurements accordingly. The downside is that manual counting of whiteflies on a YST is very time‐consuming and thus costly. A protocol to semi‐automate counting and identification of whiteflies on YSTs using image analysis software was developed to speed up the monitoring process. Bemisia tabaci is on average smaller than T. vaporariorum and by discriminating by size based on the amount of pixels in digital images, ratios of both species in a mixed population on YSTs could be estimated accurately. At low densities, the countings of different YSTs should be pooled till a 200 density threshold is reached in order to get accurate ratio estimates of both species. This study provides a protocol to reliably count and identify whiteflies semi‐automatically on standardized pictures. More research is required to develop alternative techniques to make standardized pictures in the field (e.g., with smartphone).

BACKGROUND: Aphids (Hemiptera: Aphididae) are a problematic pest in global sweet pepper cultivation. Control of aphids often relies on insecticides, leading to widespread resistance. Biological control of aphids is mainly based on releasing specialist natural enemies, but they often fail to control outbreaks. Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a zoophytophagous generalist which attacks several sweet pepper pests, including aphids. Previous research showed that M. pygmaeus is capable of strongly reducing aphid populations in sweet pepper, but complete control was seldom achieved. Sweet pepper plants continue to grow during the season, reaching > 3 m high in Belgian and Dutch greenhouses. Dense foliage and large vertical distance from the flowers to the lower leaves impede the search efficiency of the predator. Leaf pruning may improve aphid predation by M. pygmaeus by increasing the probability of encountering prey. RESULTS: Four and five treatments (foliage range: 100 cm to full length) respectively were tested in a semi-commercial sweet pepper greenhouse in 2017 and 2018. Aphid populations in pruned treatments grew more slowly than in the control and M. pygmaeus was eventually able to control aphids in all pruned treatments in 2018. There was no difference in aphid control between the pruned treatments. Sweet pepper production was lower in the treatments with the shortest foliage lengths. CONCLUSION: Leaf pruning up to 160 or 190 cm foliage length improves aphid control by M. pygmaeus in sweet pepper without affecting production.