Tobacco budworm

The tender growing tips, buds and young leaves at the top of the plant look chewed and ragged, with small holes. Soon comes the giveaway sign: a round hole bored into a flower bud, a tomato or pepper, or a cotton boll, usually plugged with frass - the caterpillar's droppings, which look like damp sawdust - at the entrance.

, and bored fruit and bolls rot or hollow out from the inside. Because the caterpillar hides inside, you will often see the damage before you ever see the pest itself.

is up to about 4 cm long - the length of your little finger - but its colour is not fixed: it can be green, cream, pink, tan or reddish-brown, always with pale stripes running lengthwise down each side. Its head is brownish, and the body feels rough and prickly, covered in tiny bumps and spines, when you rub it between your fingers. Look for it tucked head-first into a bud, a flower, or the hole it has bored.

are laid one at a time (not in fuzzy clusters), tiny and dome-shaped with fine ridges, whitish then turning brown, dotted on and around the top growing tips, buds and flowers.

the tobacco budworm looks almost exactly like the cotton bollworm / tomato fruitworm and behaves the same way - the good news is the control below works for both, so do not lose sleep over which one it is. What matters is to separate these borers from surface leaf-eaters: armyworms and loopers chew leaves from the outside and never drill into buds or fruit, and a looper is smooth and 'loops' or inches as it crawls. If you see a clean hole bored into a bud, boll or fruit with frass at the mouth, it is the budworm type - not a leaf-eater.

and keep going right through flowering and early fruit- and boll-set - this is exactly when the moth lays eggs on the tender tips and when the caterpillars can ruin the parts you sell. A 'square' is the young flower bud of cotton. Scout harder in warm weather (around 20-32 degrees C) and whenever earlier or neighbouring fields are already flowering.

Walk a big "W" across the whole field twice a week, so you cover the four corners and the middle - not just the edge nearest the path. Make about 10 stops, and check 10 plants at each stop (100 plants in all).

At every plant, look at the top of the plant - the growing tips, the flower buds and squares, the open flowers, and any young fruit or bolls. Search for single eggs, tiny caterpillars on the tender new growth, and fresh bore-holes with moist frass. Gently part the growing tip and turn the buds over; the pest hides where two surfaces meet.

Old, dry frass with no caterpillar is a past attack; do not spray for that.

Hang a pheromone trap - a trap baited with the scent of the female moth, which lures and catches the male moths - to tell you when the moths start flying. When the catches climb, scout harder and time any spray to egg-hatch, before the caterpillars bore in.

• just a handful of plants in your sample. Keep this trigger low: once the caterpillars bore inside buds, bolls and fruit, no spray can reach them, so it is far better to act a little early than a day too late.

, ideally together with your neighbours, so your buds, flowers and fruit form and firm up before moth numbers build to their peak later in the season. A budworm that arrives to find hard, setting fruit does far less harm than one that arrives to soft new buds.

As soon as you finish picking, pull up and destroy the old stalks, host weeds and 'volunteers' (self-sown plants that sprout on their own from last season's dropped seed) - on tobacco, cotton, tomato, pepper and beans alike - because the budworm keeps breeding on any of these between crops. Harvest promptly and do not leave a ragged, flowering field standing.

Tiny parasitic wasps, predatory bugs and lacewings attack its eggs and young caterpillars for free. Do not wipe them out with broad, harsh poisons sprayed 'just in case' - they are your first line of defence.

• Bacillus thuringiensis, a natural bacterium that sickens only caterpillars and is safe for you, for bees and for the helpful insects - onto the tips and buds in the cool of the day, timed to egg-hatch. A natural caterpillar virus (NPV) works the same way. Pick off and crush any caterpillars and egg-dotted tips you spot. Remember: Bt and NPV only reach caterpillars that are still exposed - they are useless once the pest has bored inside.

Spinosad is a contact-and-stomach poison - it must land on the caterpillar or be eaten by it - so it too only works before the pest bores in; time it to egg-hatch and small caterpillars. Safety: cover your skin, eyes, nose and mouth; spray in the cool of morning or evening with the wind behind you; keep it off food, off drinking and washing water, and away from children and animals; spinosad kills bees while it is still wet, so spray late in the day and never onto open flowers the bees are working; and respect the pre-harvest interval (PHI - the number of days you must wait between your last spray and picking or eating the crop; read the label). Wash yourself, your clothes and the sprayer afterwards.

The tobacco budworm has already survived many older insecticides, so never spray the same chemical group twice in a row: rotate to a different group (the 'mode of action' - the way the poison kills) each time, and lean on Bt and the cultural steps above so you do not wear out spinosad as well. Spraying needlessly, or spraying when the caterpillars are already inside, only speeds up resistance and kills your helpful insects.

when fresh bore-holes and dropped buds keep appearing after you spray, the caterpillars are already inside the buds, bolls and fruit where nothing can reach them - stop wasting spray on them. Instead, keep picking off and destroying every bored, rotting bud, fruit and boll (with the caterpillar still in it) to cut off the next generation, protect the clean fruit that is left, and bring your harvest forward if the crop is nearly ready. When a block is too far gone - most of the fruit already bored and rotting - cut your losses: clear and destroy it quickly, then pull and burn or bury every residue and volunteer so the budworm cannot carry over into your next crop.