Jeninah Karungi

Oviposition preference and offspring performance of Crocidolomia pavonana (Lepidoptera: Pyralidae) on different host plants

The cabbage head caterpillar Crocidolomia pavonana (Fabricius) (Lepidoptera: Pyralidae) is an increasingly devastating pest on white cabbage (Brassica oleracea var. capitata) in Uganda. Screen house and field trials were used to assess oviposition preference and offspring performance of C. pavonana on six hosts in the genus Brassica: kale (B. oleracea var. acephala), cauliflower (B. oleracea var. botrytis), broccoli (B. oleracea var. italica), Chinese cabbage (B. campestris spp. pekinensis), Indian mustard (B. juncea (L.) Czern.) and white cabbage (B. oleracea var. capitata). To assess oviposition preference, the hosts were offered to C. pavonana in multiple‐choice (all six); two‐choice (cabbage with each of the other hosts) or cabbage‐only situations. After specified oviposition periods, egg numbers on individual plants were recorded. To determine C. pavonana offspring performance on the six hosts, whole plants were placed in individual cages, where larvae were monitored for development time, pupal weight and foliage consumption. Results of the choice tests indicated that C. pavonana preferred Chinese cabbage and broccoli for oviposition. In two‐choice arrangements, all the tested host plants were able to greatly reduce oviposition on white cabbage (69–100%) when compared with the monocrop. Chinese cabbage was the most suitable host with regard to C. pavonana offspring performance as demonstrated by the shortest development time and highest pupal weight. Chinese cabbage and broccoli can be used as traps for the pest but the resulting larvae should be destroyed regularly to prevent accumulation in the system.

Seedling protection and field practices for management of insect vectors and viral diseases of hot pepper (Capsicum chinense Jacq.) in Uganda

The focus of this study was on nursery and field management of seed and insect vectors of viruses on hot pepper. Seedlings raised from hypochlorite-treated seeds under a net tunnel nursery were compared with seedlings raised from untreated seeds in an open nursery. The two groups of seedlings were used to evaluate field practices in a split plot randomized controlled block design: (i) weekly foliar applications with dimethoate; (ii) close plant spacing of 60 cm × 50 cm); (iii) 1.5-m high net perimeter screen; (iv) transparent plastic mulch; (v) untreated control. Whiteflies were the vectors most affected by the treatments, showing 28%, 38%, 43% and 36% reductions in occurrence by seedling protection, net screens, transparent plastic mulch and close plant spacing, respectively. Aphids were only responsive to close plant spacing and chemical treatments, with a reduction in incidence of up 43% by the former. The lowest virus disease incidence (12%) was on plants raised unprotected in the nursery but grown under the close plant spacing in the field. Plants from protected seedlings had a marginally higher fruit yield (2.1 kg/plant) compared with plants from unprotected seedlings (1.7 kg/plant)

Cover cropping and novel pesticide usage in the management of pests of hot pepper (Capsicum chinense)

In a bid to develop technologies that serve grower needs for economic management of pests and diseases of hot pepper (scotch bonnet) while protecting public health and the environment, a study to assess the potential of cover cropping and/or less-risk pesticide usage in the management of pests and diseases of hot pepper was conducted for two consecutive seasons in Uganda. A split-plot randomized complete block design with three replications was used with cropping system (main plots) and pesticide treatment (sub-plots) as the factors. There were two cropping systems: the hot pepper + cowpea system vs. a hot pepper monocrop and five pesticide treatment options: (i) prophylactic treatment of plots at transplanting with granular carbofuran; (ii) weekly sprays of a neem-based formulation; (iii) combination of the prophylactic carbofuran treatment and neem; (iv) sulphur sprays at 10-day intervals (season 2 only); and (v) the untreated control. Data were collected on population dynamics of aphids, whiteflies, thrips, mites, nematodes and on plant performance parameters of branching and fruit weight. Results indicated that the hot pepper + cowpea system greatly lowered infestations of aphids and nematodes on hot pepper, but did not decrease thrips and whiteflies; and brought about a yield penalty on hot pepper. Prophylactic applications of carbofuran and/or sprays of a neem-based formulation lowered populations of aphids and whiteflies on hot pepper to varying extents; and increased yield of pepper.

Assessing the potential of trap cropping in the management of different insect taxa on white cabbage

This study set out to explore the influence of trap crops designated for the management of Crocidolomia pavonana (Fab.) on two other frequent pests of cabbage: diamondback moth [Plutella xylostella (L.) and cabbage aphid (Brevicoryne brassicae (L.)]. The three pests were offered six hosts in the genus Brassica: kale (B). oleracea var. acephala), cauliflower (B. oleracea var. botrytis), broccoli (B. oleracea var. italica), Chinese cabbage (B. campestris L. ssp. pekinensis), Indian mustard (B. juncea (L.) Czern.), and white cabbage (B). oleracea var. capitata) in multiple (where all the six were offered at the same time) and two-crop trials (where each of the different hosts was paired with cabbage, including a control of cabbage in monoculture) in field trials. Oviposition was considered as a measure of preference for C. pavonana and P. xylostella while colonization and reproduction were measures of preference for B. brassicae. The treatments were arranged in a complete randomized block design with four blocks. The experiment was carried out in the field in 2007 and 2008. The results indicated that C. pavonana oviposition on cabbage was consistently lowered in trap crop treatments when compared with monoculture. The results for P. xylostella and B. brassicae were not as consistent and there was a great deal of variation. It was clear, however, that trap cropping for the control of C. pavonana would not worsen pest problems with the diamondback moth or the cabbage aphid.

IPM Vegetable Systems in Uganda

Smallholder famers in Sub-Saharan Africa (SSA) have been encouraged to produce horticultural crops as an agricultural and rural development strategy to enhance incomes and improve household nutrition. In Uganda, intensified production of marketed vegetable crops has led to changing agricultural practices, including crop and input-intensification, a changing set of pests, and increased use and reliance on synthetic pesticides to manage these pests. Beginning in 2002, the IPM CRSP team in Uganda implemented a participatory IPM program with smallholder farmers to develop and disseminate alternative pest management strategies for managing priority pests and reducing pesticide usage on tomato. The major pest constraints addressed were late blight, bacterial wilt, viruses, bollworm, aphids, thrips and white flies. Baseline farmer surveys indicated that farmers were spraying a variety of pesticides 12–24 times per growing season. The component technologies developed into a package and disseminated to farmers included a bacteria wilt resistant tomato variety MT56, mulching, staking, and a minimum spray schedule of 3–4 pesticide sprays per season. Impact assessments indicated that yields were 40 % higher when the package was used and reduced production costs (by reducing the number of sprays) that led to higher net revenues for IPM-practicing tomato farmers. Use of MT56 and mulching led to a 21 % reduction in production costs and led to an internal rate of return of 250 % if adopted. Use of tomato variety MT56 reduced production cost by 21 % with a Benefit: Cost ratio of 770. Other IPM technologies developed included grafting using bacterial wilt resistant rootstocks; seedling production using low tunnel systems for pest/vector exclusion; and good nursery management practices.