What is a herbicide? Types of weed killers and how to pick one

What is a herbicide?

A herbicide is a plant protection product that controls weeds. A weed is any plant you did not plant but that grows in the same field and competes with your crop for water, light, and nutrients. A herbicide kills those weeds or stops their growth so the crop comes through the competition unharmed.

In Turkey, herbicides are one sub-group of Bitki Koruma Ürünleri (plant protection products, abbreviated BKÜ). For an agronomist, herbicides come up as often as insecticides or fungicides, because weed pressure exists in nearly every field.

The problem is not small. Weeds cause an average 34% loss of crop yield worldwide, higher than any single uncontrolled pest group. The right herbicide choice directly affects what a grower harvests at the end of the season.

How are herbicides classified?

Two questions describe a herbicide in practice: what it kills and when it is applied.

What it kills is about selectivity. A selective herbicide targets a specific weed group and leaves the crop largely intact. For example, a product used against broadleaf weeds in wheat clears mustard and pigweed without harming the wheat itself. A non-selective herbicide kills most green tissue it touches. These are usually used to clean a field before planting, between rows in orchards and vineyards, or along roadsides.

When it is applied is about emergence timing. Pre-emergence herbicides go onto the soil before weed seeds germinate and stop the seedling as it comes up. Post-emergence herbicides act through the foliage once the weeds are up and actively growing.

A further distinction is mode of action. Contact herbicides burn only the tissue they touch; they work fast, but if the root survives the weed can regrow. Systemic (translocated) herbicides move inside the plant and reach the root, which is the deciding factor on perennial, deep-rooted weeds.

These classes also read historically. 2,4-D, the first selective herbicide, came out in the 1940s at the end of World War II and is still one of the most widely used active ingredients against broadleaf weeds worldwide. Its arrival mattered because before it, weed control was mostly mechanical hoeing; a selective chemical made it possible to clean a field without uprooting the crop. The best-known systemic example, glyphosate, was registered in 1974 and went on to become the most heavily applied weed killer in the history of agriculture.

For an agronomist, these four axes (selectivity, emergence timing, mode of action, and active ingredient) are the basic facts that describe a product. Two products can be registered for the same weed, but one is a pre-emergence soil treatment and the other a post-emergence foliar spray; which one you recommend depends on the current state of the weeds in the field.

What is BKÜ GPT?

BKÜ GPT is a free lookup tool for plant protection products in Turkey. It covers the insecticides, fungicides, acaricides, and herbicides an advisor recommends every week, and is built for agronomists, dealer technicians, and field advisors. You can write a query in Turkish or English and get the same products back.

The index covers 5,619 registered products at last count and keeps growing as new products are registered; herbicides are only one part of that list. You reach bku gpt at bkugpt.com on web, iOS, and Android.

For herbicides specifically, the value is this: a grower's problem in the field is rarely a single weed. The advisor wants to see, on one screen, which weed can be controlled in which crop with a registered product, what the dose is, and the pre-harvest interval. bkü gpt runs that query against the currently registered products in one step.

Which crops use herbicides most in Turkey?

Weed pressure differs by crop, so herbicide need does too. The widest herbicide use in Turkey is in cereals, which have the largest planted area. In wheat and barley, broadleaf weeds and grass weeds such as wild oat are managed with separate product groups, so the advisor usually identifies the weed type first.

In summer crops like maize and cotton, pre-emergence soil treatments are common, because the window before the rows close is the best time to handle weeds. In vineyards, hazelnut groves, and orchards, non-selective products are often chosen to manage weeds between rows, where the aim is to keep the ground clean without touching the trees or vines.

In every case the same constraint holds: the product used has to be registered for that crop and that weed. Using a herbicide that works in one crop on another crop not on its label leaves the grower exposed to possible crop damage and residue problems in export markets.

How do I list only herbicides on BKÜ GPT?

Open the BKÜ lookup tool. On the results screen, the category filter splits products into groups: Acaricides, Biological, PGR, Fungicides, Insecticides, Herbicides, Nematicides, and Other. Pick the Herbicides group and the list narrows to weed killers only; everything else drops off the screen.

From there you keep narrowing. Pick maize from the crop field, check a specific molecule under active ingredient, or set an upper bound on the pre-harvest interval. In a few taps, a question like "herbicides registered for maize in Turkey that can be used with fewer than 30 days to harvest" becomes a short list on screen.

Here is a concrete example: a wheat grower sees a lot of wild oat in the field and asks what you can write. You pick the Herbicides group, check wheat under crop, and type the relevant molecule into the active ingredient field. The remaining list is the products registered against that weed in wheat in Turkey. Tap one and you see the registered dose, the pre-harvest interval, and the trade names on one page; if the first option is not in stock at the dealer, you move to an alternative from the same list.

This is the practical way to work without flipping through a paper catalogue or opening dozens of labels side by side. For a fuller walkthrough of the same workflow, see find registered pesticides fast. For the abbreviation itself and what counts as a BKÜ, see what is BKÜ?.

What is the difference between a herbicide and other pesticides?

In everyday speech they are all called "spray," but the categories do different jobs. An insecticide targets an insect, a fungicide a fungal disease, an acaricide a mite. A herbicide manages a competing plant rather than a living pest. That difference changes timing too: you spray a fungicide once disease symptoms appear, while you apply a pre-emergence herbicide to the soil when no weeds are visible yet.

The practical result is that a single field can use products from all four groups in one season, and all of them fall under BKÜ. The main reason an advisor thinks about herbicides separately is resistance management. Using a herbicide with the same site of action for years in a row can lead to an application that no longer works on that weed. According to 2024 data, 267 weed species have evolved resistance to 21 of the 31 known sites of action. This is why advisors rotate active ingredients and sites of action.

What does an advisor check before recommending a herbicide?

The filter narrows the list to registered herbicides; the final call is still the advisor's. Before writing a recommendation, the checks are similar each time.

First, the crop and weed match. The product has to be registered for that crop and the weed group you are targeting. Then emergence timing: is the product on hand pre-emergence or post-emergence, and does that fit the current state of the weeds in the field. After that, dose and pre-harvest interval, confirmed against the current label on the package. Labels get revised; the version on a five-year-old can may not match today's.

bkugpt helps you find the right product fast, but it does not replace the label. However wide the index is, the final dose and conditions depend on the label on the package in your hand.

Frequently asked questions

What does herbicide mean? A plant protection product that kills or stops the growth of weeds. In Turkey it is one sub-group of the BKÜ category.

What is a selective herbicide? A herbicide that targets a specific weed group while leaving the crop largely unharmed. Example: products used against broadleaf weeds in wheat.

What is the difference between pre-emergence and post-emergence herbicides? A pre-emergence product is applied to the soil before weeds germinate. A post-emergence product acts through the foliage once weeds are up and growing.

How do I list registered herbicides in Turkey? Open bkügpt at bkugpt.com, pick the Herbicides group in the category filter, then narrow by crop or active ingredient.

Is a herbicide the same as a pesticide? No. A herbicide is the weed-control sub-group of pesticides. The term pesticide also covers insecticides, fungicides, and acaricides.

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BKÜ GPT is informational. Verify every value against the current product label before issuing a recommendation, and growers should follow their licensed agronomist's instructions before applying any pesticide.