Protect your crops
vegetable weevil, the bean seed maggot, and sawflies.
Vegetable weevil The vegetable weevil (Figure 1) originated in Brazil. The adult beetles are 8 to 10 mm in length, greyish brown (mostly dull in colour) with a pale, short “V” on the elytra. The body may also be covered with tan or grey scales and scattered hairs. Adults may be gregarious at times, hiding or feeding in small groups. Diedrich Visser, ARC Vegetable and They only feed at night and hide unOrnamental Plants, Pretoria der debris or clods during the day. They seldom fly, even if provoked, but rather feign death or walk away to safety. The vegetable weevil is a cool-weather pest, being active from late autumn until early summer. They are dormant in the warm summer months (aestivation). Females lay eggs on plants or the soil near plants. They are legless, but manage to move up on stems using Photo: pixabay.com ventral and lateral ridges or protrusions on their bodies. Young larvae have a creamy-white colour, while older larvae may be yellowish or green and can grow up to 14 mm in length. When mature, larvae pupate in the soil, down to a depth of five centimetres. Only a single generation occurs per year. The beetles are parthenogenetic; only females are known, and mating is therefore not needed to reproduce. Adults and larvae both feed on foliage Figure Figure1 1The Theadult adultvegetable vegetableweevil. weevil. Figure Figure2:2:The Theadult adultbean beanseed seedmaggot maggotisis and roots. They may move down to the aasmall smallfly flyofofonly onlyfive fivemillimetres millimetresinin root zone in crops like carrot and beet. length. length. Adults also feed on stem tissue, sometimes causing damage similar to Figure 1: The adult vegetable Figure 2: The adult bean seed Figure 1 The adult vegetable weevil. 2: The2:adult is that of Figure 1 The adult vegetable weevil. FigureFigure Thebean adultseed beanmaggot seed maggot is cutworms. Most vegetables that weevil. maggot is a small fly of only five a small fly of only five millimetres in are grown during the cooler months a small fly of only five millimetres in millimetres in length. are attacked. length.
against cool weather vegetable pests this winter
length.
Bean seed maggot The bean seed maggot (Delia platura) is the larva of a small fly, five millimetres in length (Figure 2). Crops planted in freshly worked and well-composted soils are especially vulnerable. It is a cosmopolitan species also known as the seedcorn maggot. Bean seed maggots usually only infest young seedlings and sprouting seeds; they do not attack plants past the seedling stage. Crops grown in the cooler months may be attacked by the maggots. Females lay eggs in groups of up to ten near decaying or sprouting seeds. Figure 3: Atypical typical Athalia sawfly, Figure 4:AAsawfly sawfly larva with seven Figure3:3: Athalia sawfly, withits its Figure Figure4:4: larva with seven pairs Figure AAtypical Athalia sawfly, with A sawfly larva with seven pairs Poor quality seed and seedbeds with with its distinctive black and orange pairs of prolegs (caterpillars have a distinctive blackand andorange orange colouration. prolegs (caterpillars haveaamaximum maximum distinctive black colouration. ofofprolegs (caterpillars have rotting seeds and rotting plant material colouration. maximum of five pars or prolegs). fivepairs pairsororprolegs). prolegs). ofoffive attract females to lay their eggs nearby. Larvae may burrow into the soil down to a depth of eight centimetres. ost vegetable pests prefer warm, These pests increase their metaboWhen seeds are in short supply, they dry conditions to thrive. The lism when the temperature drops, and may develop on other rotting materioptimum temperatures under which stop feeding under hot and dry condiFigurethe 3: important A typical Athalia sawfly, Figure 4: Alatter sawfly with pairs als, including compost. The flies and pests inflict the with mostits tions. The is larva referred toseven as aestidistinctive black and orange colouration. of prolegs (caterpillars have a maximum maggots damage range from sawfly, 23 to with its vation, also known as oversummering. Figure 3: usually A typical Athalia Figure 4: A sawfly larva with seven pairs prefer cool weather; the optimal ambient temperatures for the 33°C. There are,and however, a few pests "overwintering" is used for a maximum ofThe fiveterm or prolegs). distinctive black orange colouration. ofpairs prolegs (caterpillars have growth of larvae are between 21 and that are adapted to develop below the opposite phenomenon. of five pairs or prolegs). 23°C. Development of the maggots these temperatures, and they prefer to Vegetable pests that are more active stops during the summer months. attack winter crops. during the cooler months include the
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