Thistles Are A Host For Leaffooted Bugs
By Les Harrison, Wakulla County Extension Director
With the turn of the year and the noticeably lower temperature readings, most of Wakulla County’s residents turn their attention to activities that do not require exposure to the outdoor elements.
Recovering from the holidays, paying for the holidays, and preparing income tax filings all take precedence over the events forecast to be occurring when the weather warms again.
Even with the frosty mornings of late, the initial link for next summer’s insect problems are already making an appearance by way of a host plant. This is prime time for thistles to start growing and become established for the pleasant spring days which will arrive a few months from now.
Wakulla County’s thistles are now actively emerging while many other plant species are dormant. Only a relatively few local plants react positively to the unforgiving cold nights by getting a botanical jumpstart on their competition.
The head start gives the thistles a major advantage for colonizing new ground and pushing out competitor plants when the warmer season arrives. The Cirsium species, as thistles are botanically known, also serve as a host for a local horticultural pest and disease vector.
The leaffooted bug, Leptoglossus phyllopus, is a widely distributed and common pest of many kinds of crops, including fruits, vegetables, grains, nuts and ornamentals. It has been identified as a major pest for anyone attempting to produce citrus either commercially or as a hobby
At maturity, this native insect will target ripening fruit which causes premature color break and fruit drop. Large scale infestations do not occur often, but a large proportion of the citrus fruit may be lost when they have a population explosion.
Adults have been observed all months of the year, depending of environmental condition, but populations attain peak numbers during the warmer months. This coincides with the ripening cycle on local citrus trees where the leaffooted bug uses its piercing mouth parts to ruin the fruit.
There are at least nine different species of thistle in Florida which include tall thistle, Lecontes thistle, swamp thistle, Nutalls thistle, purple or yellow thistle, bull thistle, Virginia thistle. They are distinguished by their flower’s color and the general shape of the plant, but several are rare and not commonly seen.
All Florida thistles are biennials, with the exception of Lecontes thistle which is a perennial. Biennial plants are those growing from seed in the first year and which produce seeds the second year.
There are three distinct life stages pertaining to all native thistles. During the first year the plant will grow as a rosette, a taproot with a cluster of leaves on or near the soil surface. The rosette growth stage occurs primarily during the winter months in Wakulla County.
During the second year, a stalk with a bloom bud will elongate from the rosette, which is referred to as bolting. Bolting frequently begins in late January and goes through July, depending on the species and environmental conditions.
Once the biennial plant flowers, it can produce up to 4,000 seeds per plant. The tiny seed are dispersed by wind with the aid of thistledown, a soft feathery material easily moved on the breeze. As the seed are scattered the biennial thistles are dying.
The aggressive thistles give little warning to their colonizing efforts. Once established, they spread by the thousands and grow while others are asleep. The leaffooted bugs will show soon afterwards.