Budworms Are Hatching, but It Pays to Wait Until They Reach Threshold to Treat

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Small tobacco budworm larva inside bud. Note black "frass", or insect droppings, near the larva and the small feeding holds. As the leaf grows, these holes may expand, although new damage is not occurring. Photo: Demetri Tsiolkas

Small tobacco budworm larva inside bud. Note black “frass”, or insect droppings, near the larva and the small feeding holds. As the leaf grows, these holes may expand, although new damage is not occurring. Photo: Demetri Tsiolkas

We observed our first budworm of the season this week in our research at the Upper Coastal Plain Research Station near Rocky Mount, and I’ve also gotten word from agents that growers are noticing larvae in their fields. At this point, budworm populations are very low, and I caution growers not to jump the gun with respect to making foliar insecticide applications.

We do not see a benefit from making foliar treatments for tobacco budworm before they reach threshold. In fact, treating too early for tobacco budworm can actually result in more, rather than less, insecticide applications. Our foliar insecticides in tobacco can only be expected to have residual activity on the treated leaf. They do not move to new leaves following an application. This means that as plants continue to grow, new leaves (the ones most attractive to egg-laying moths) will not be protected by too early insecticide applications.

It is not uncommon for prolonged budworm flights to occur where moths lay eggs over several weeks. It is better to time applications to threshold-level budworm populations than to hedge bets with an early application because you are more likely to hit a larger number insects with your treatment.

Physically observing plants via regular scouting is necessary to determine if tobacco budworm populations have reached the 10% treatment threshold. Just because moths are flying does not necessarily means that larvae are present in tobacco fields because budworms may feed on many different plants and predators may attack and kill large numbers of larvae feeding on tobacco.

More information

Tobacco budwormTobacco Growers Information

Tobacco budworm scoutingTobacco Growers Information