Potato bugs: distinguish soil damage from foliage pests
Potato bugs damage the tuber, the roots or the foliage, and the organism differs in each case. If you find bugs in potatoes, keep the damaged tuber and any insect you recovered together with the lot identity. Before choosing a spray, establish which organism is present and whether the damage affects the tuber, roots or foliage.
Wireworms in potatoes: examine the larva and field history
Wireworms are soil-dwelling click-beetle larvae. They feed on potato seed pieces, roots and tubers. Keep the larva alongside the damaged material when you investigate the field.
During establishment, wireworms injure seed pieces and young roots. Later feeding leaves holes in developing tubers. The larvae are slender, cylindrical and hard-bodied, with yellowish to brown colouring. Adults are click beetles. Photograph the larva's shape and body surface beside the damaged tissue.
For wireworm control in potatoes, the field is examined before planting, when management opportunities are greatest. Check for wireworms by observing the field during ploughing or discing, or by baiting; where they are present, soil samples show whether treatment is needed. Write down the field's previous crops and infestation history next to those findings.
Wireworms bore into the tuber perpendicularly or diagonally to a depth of up to 0.5 inch (about 1.3 cm), but do not tunnel all the way through.
For establishment failure, inspect the seed piece and roots. For a harvested tuber, photograph its exterior and cut surface next to the recovered larva.
Sweet potato weevil: preserve the specimen and trace the affected material
Before discussing a treatment for sweet potato weevil, identify the specimen and the damaged root or stem. Keep sweet-potato material apart from potato tubers. Photograph the whole insect, its snout and the affected root or stem before you cut anything open, and tell an empty gallery from one that holds a concealed larva.
Cylas formicarius adults have thin bodies, long legs and an ant-like outline. Look at the slightly curved snout and the contrasting body colours; photograph the long snout, antennae, thorax, abdomen and wing covers, together with a whole-insect image. Pale, legless larvae burrow into sweet-potato roots or stems after hatching.
Females lay eggs singly in cavities in sweet-potato roots or stems, often near their junction. The sealed cavities conceal the eggs. Adults also reach roots through soil cracks. Look at the junction and the interior as well as the root surface.
Larvae make tunnels and then pupal chambers within roots or stems. Pupae resemble adults with the head and wing covers bent underneath, and darken during development. Adults chew exit holes but can remain inside and continue feeding. Write down the stage you find in each cavity.
Infested roots become riddled with cavities, darkened and spongy. Vine yellowing may appear only with heavy infestation, so look at root condition as well as foliage.
Reduce carryover of sweet potato weevil
Use planting slips or cuttings free of weevils. Locate new crops away from previous sweet-potato plantings and storage facilities where practicable. Rotate fields between crop cycles. Remove discarded and unharvested roots, which support large populations, and control alternate Ipomoea weed hosts.
Dry soil cracks give adults access to developing roots. Appropriate irrigation limits cracking, and the root–stem junction is worth checking during inspection. Keep old-crop waste and storage residues away from healthy planting stock, and note the source lot of incoming material so an infestation can be traced.
Infestations are aggregated in the field. Pheromone traps monitor adults, while examination of vines and roots detects concealed stages. Compare trap locations with patches of internal damage. Larval feeding also opens routes for soil-borne pathogens, and even low feeding levels can cause a bitter taste and terpene odour in roots.
American potato beetle larvae: recognise the Colorado potato beetle
The Colorado potato beetle, Leptinotarsa decemlineata, is the insect people also search for as the American potato beetle. Older names include ten-lined potato beetle and potato-bug. Potatoes are its preferred host, and it also feeds on other nightshade-family plants such as eggplant and tomato.
Keep your spray records in one place. Free to start.
Potato bug larvae of this beetle are plump, reddish and about 1/2 inch (1.3 cm) long when mature, with two rows of black spots down the sides. Females glue orange eggs in clusters of 5 to 100 to the underside of leaves, so turn the leaves over when you inspect. The larvae feed almost continuously on the leaves; there are four larval stages, together lasting about 21 days. Mature larvae burrow 2–5 cm into the soil to pupate, so a plant stripped of leaves with no larvae left on it does not mean the pest has gone.
False potato beetle: check an overseas identification against the specimen
False potato beetle, Leptinotarsa juncta, occurs mainly in the eastern United States. Its pale larvae have one lateral row of dark markings; Colorado potato beetle larvae have two. Compare the lateral markings and the host plant of your specimen.
Compare beetle body markings under magnification
False potato beetles and Colorado potato beetles are closely related leaf beetles with striped wing covers. For larvae, compare the lateral rows of dark spots rather than relying on the striped adult outline. Photograph the head, legs, underside and back markings without crushing the specimen, and note the host plant for every insect collected from a damaged plant.
Before choosing the best insecticide for flea beetles: inspect seedlings
A flea beetle control insecticide or any vegetable insecticide is allowed only for the crops listed in its Maltese authorisation; the authorisation guide shows how to read the entry. Name the vegetable crop first, and only then compare products. A flea beetle enquiry should show the living beetle, the crop establishment stage and fresh feeding.
High flea-beetle populations stunt or kill cole-crop seedlings. Older plants generally tolerate feeding better. Write down the establishment stage next to the fresh injury.
Adult beetles move from nearby hosts into new crops, so weeds along field margins matter. Inspect young brassicas and seedlings, mark the adjacent vegetation on a parcel sketch, and separate direct-sown areas from transplants when you compare damage.
Adult flea beetles are shiny and hard-bodied, with enlarged hind-leg femora for jumping. Larvae are pale and slender. Adult feeding makes small pits and irregular holes, often from the underside. Photograph the insect from the side next to a damaged and an intact leaf.
Seedlings face the greatest economic risk from flea-beetle feeding. Check cotyledons, first true leaves and growing points separately, and compare cotyledon survival, remaining leaf area and new feeding across the affected patch.
Flea-beetle larvae can mine leaves or feed on roots. Adults occur especially in weedy fields and along weed-covered boundaries, so inspect the boundary plants as well as the centre of the planting.
Before choosing an insecticide for grasshoppers: inspect crop-edge damage
Before asking for the best insecticide for grasshoppers, photograph the nymph or adult and the crop edge.
On a small crop area, row covers can exclude the pest physically; edges are sealed and holes repaired. Plan access for crop work and pollination, and check that the cover material suits the size and behaviour of the identified pest.
An insecticide for grasshoppers is identified by its Maltese authorisation reference; the product-register guide shows commercial identity, formulation, status and uses. Give your supplier or adviser the pest, the crop, the site and the proposed application method, and ask for the exact product label and the Maltese authorisation reference.
Grasshopper nymphs resemble small, wingless adults. As they develop, they move from hatching areas into adjacent vegetation. When you map crop-edge feeding, record nymphs and winged adults separately.
Grasshoppers feed irregularly at leaf edges; larger insects remove more tissue. Tell fresh bites from old torn margins, missing leaves and damaged growing points, and photograph the animal next to its feeding site.
Grasshopper numbers change with weather, predators, parasites and pathogens. Compare small nymphs in hatching areas with larger insects already feeding in the crop, and note movement from the surrounding vegetation when edge damage continues.
Next step
Send the specimen photographs, the crop stage and the parcel history to your adviser. Check any proposed product through the Malta authorisation guide.